Merge pull request #2206 from ehuss/bump-version

Update to 0.4.35

.github/ISSUE_TEMPLATE/bug_report.yml

@@ -0,0 +1,45 @@
+name: Bug Report
+description: Create a report to help us improve
+labels: ["C-bug"]
+body:
+  - type: markdown
+    attributes:
+      value: Thanks for filing a 🐛 bug report 😄!
+  - type: textarea
+    id: problem
+    attributes:
+      label: Problem
+      description: >
+        Please provide a clear and concise description of what the bug is,
+        including what currently happens and what you expected to happen.
+    validations:
+      required: true
+  - type: textarea
+    id: steps
+    attributes:
+      label: Steps
+      description: Please list the steps to reproduce the bug.
+      placeholder: |
+        1.
+        2.
+        3.
+  - type: textarea
+    id: possible-solutions
+    attributes:
+      label: Possible Solution(s)
+      description: >
+        Not obligatory, but suggest a fix/reason for the bug,
+        or ideas how to implement the addition or change.
+  - type: textarea
+    id: notes
+    attributes:
+      label: Notes
+      description: Provide any additional notes that might be helpful.
+  - type: textarea
+    id: version
+    attributes:
+      label: Version
+      description: >
+        Please paste the output of running `mdbook --version` or which version
+        of the library you are using.
+      render: text

.github/ISSUE_TEMPLATE/feature_request.yml

@@ -0,0 +1,28 @@
+name: Enhancement
+description: Suggest an idea for enhancing mdBook
+labels: ["C-enhancement"]
+body:
+  - type: markdown
+    attributes:
+      value: |
+        Thanks for filing a 🙋 feature request 😄!
+  - type: textarea
+    id: problem
+    attributes:
+      label: Problem
+      description: >
+        Please provide a clear description of your use case and the problem
+        this feature request is trying to solve.
+    validations:
+      required: true
+  - type: textarea
+    id: solution
+    attributes:
+      label: Proposed Solution
+      description: >
+        Please provide a clear and concise description of what you want to happen.
+  - type: textarea
+    id: notes
+    attributes:
+      label: Notes
+      description: Provide any additional context or information that might be helpful.

.github/ISSUE_TEMPLATE/question.yml

@@ -0,0 +1,24 @@
+name: Question
+description: Have a question on how to use mdBook?
+labels: ["C-question"]
+body:
+  - type: markdown
+    attributes:
+      value: |
+        Got a question on how to do something with mdBook?
+  - type: textarea
+    id: question
+    attributes:
+      label: Question
+      description: >
+        Enter your question here. Please try to provide as much detail as possible.
+    validations:
+      required: true
+  - type: textarea
+    id: version
+    attributes:
+      label: Version
+      description: >
+        Please paste the output of running `mdbook --version` or which version
+        of the library you are using.
+      render: text

.github/workflows/deploy.yml

@@ -3,26 +3,46 @@ on:
   release:
     types: [created]
 
+defaults:
+  run:
+    shell: bash
+
+permissions:
+  contents: write
+
 jobs:
   release:
     name: Deploy Release
     runs-on: ${{ matrix.os }}
     strategy:
       matrix:
-        os: [ubuntu-latest, macos-latest, windows-latest]
+        target:
+          - aarch64-unknown-linux-musl
+          - x86_64-unknown-linux-gnu
+          - x86_64-unknown-linux-musl
+          - x86_64-apple-darwin
+          - x86_64-pc-windows-msvc
+        include:
+          - target: aarch64-unknown-linux-musl
+            os: ubuntu-20.04
+          - target: x86_64-unknown-linux-gnu
+            os: ubuntu-20.04
+          - target: x86_64-unknown-linux-musl
+            os: ubuntu-20.04
+          - target: x86_64-apple-darwin
+            os: macos-latest
+          - target: x86_64-pc-windows-msvc
+            os: windows-latest
     steps:
     - uses: actions/checkout@master
-    - name: Install hub
-      run: ci/install-hub.sh ${{ matrix.os }}
-      shell: bash
     - name: Install Rust
-      run: ci/install-rust.sh stable
-      shell: bash
-    - name: Build and deploy artifacts
+      run: ci/install-rust.sh stable ${{ matrix.target }}
+    - name: Build asset
+      run: ci/make-release-asset.sh ${{ matrix.os }} ${{ matrix.target }}
+    - name: Update release with new asset
       env:
         GITHUB_TOKEN: ${{ secrets.GITHUB_TOKEN }}
-      run: ci/make-release.sh ${{ matrix.os }}
-      shell: bash
+      run: gh release upload $MDBOOK_TAG $MDBOOK_ASSET
   pages:
     name: GitHub Pages
     runs-on: ubuntu-latest
@@ -40,3 +60,14 @@ jobs:
         curl -LsSf https://raw.githubusercontent.com/rust-lang/simpleinfra/master/setup-deploy-keys/src/deploy.rs | rustc - -o /tmp/deploy
         cd guide/book
         /tmp/deploy
+  publish:
+    name: Publish to crates.io
+    runs-on: ubuntu-latest
+    steps:
+      - uses: actions/checkout@master
+      - name: Install Rust (rustup)
+        run: rustup update stable --no-self-update && rustup default stable
+      - name: Publish
+        env:
+          CARGO_REGISTRY_TOKEN: ${{ secrets.CARGO_REGISTRY_TOKEN }}
+        run: cargo publish --no-verify

.github/workflows/main.yml

@@ -1,10 +1,7 @@
 name: CI
 on:
-  # Only run when merging to master, or open/synchronize/reopen a PR.
-  push:
-    branches:
-      - master
   pull_request:
+  merge_group:
 
 jobs:
   test:
@@ -30,14 +27,15 @@ jobs:
             os: windows-latest
             rust: stable
           - build: msrv
-            os: ubuntu-latest
-            rust: 1.39.0
+            os: ubuntu-20.04
+            # sync MSRV with docs: guide/src/guide/installation.md and Cargo.toml
+            rust: 1.66.0
     steps:
-    - uses: actions/checkout@master
+    - uses: actions/checkout@v3
     - name: Install Rust
       run: bash ci/install-rust.sh ${{ matrix.rust }}
     - name: Build and run tests
-      run: cargo test
+      run: cargo test --locked
     - name: Test no default
       run: cargo test --no-default-features
 
@@ -45,7 +43,24 @@ jobs:
     name: Rustfmt
     runs-on: ubuntu-latest
     steps:
-    - uses: actions/checkout@master
+    - uses: actions/checkout@v3
     - name: Install Rust
       run: rustup update stable && rustup default stable && rustup component add rustfmt
-    - run: cargo fmt -- --check
+    - run: cargo fmt --check
+
+  # The success job is here to consolidate the total success/failure state of
+  # all other jobs. This job is then included in the GitHub branch protection
+  # rule which prevents merges unless all other jobs are passing. This makes
+  # it easier to manage the list of jobs via this yml file and to prevent
+  # accidentally adding new jobs without also updating the branch protections.
+  success:
+    name: Success gate
+    if: always()
+    needs:
+      - test
+      - rustfmt
+    runs-on: ubuntu-latest
+    steps:
+      - run: jq --exit-status 'all(.result == "success")' <<< '${{ toJson(needs) }}'
+      - name: Done
+        run: exit 0

.gitignore

@@ -8,6 +8,7 @@ guide/book
 
 .vscode
 tests/dummy_book/book/
+test_book/book/
 
 # Ignore Jetbrains specific files.
 .idea/

CHANGELOG.md

@@ -1,5 +1,490 @@
 # Changelog
 
+## mdBook 0.4.35
+[v0.4.34...v0.4.35](https://github.com/rust-lang/mdBook/compare/v0.4.34...v0.4.35)
+
+### Added
+- Added the `book.text-direction` setting for explicit support for right-to-left languages.
+  [#1641](https://github.com/rust-lang/mdBook/pull/1641)
+- Added `rel=prefetch` to the "next" links to potentially improve browser performance.
+  [#2168](https://github.com/rust-lang/mdBook/pull/2168)
+- Added a `.warning` CSS class which is styled for displaying warning blocks.
+  [#2187](https://github.com/rust-lang/mdBook/pull/2187)
+
+### Changed
+- Better support of the sidebar when JavaScript is disabled.
+  [#2175](https://github.com/rust-lang/mdBook/pull/2175)
+
+## mdBook 0.4.34
+[v0.4.33...v0.4.34](https://github.com/rust-lang/mdBook/compare/v0.4.33...v0.4.34)
+
+### Fixed
+- Fixed file change watcher failing on macOS with a large number of files.
+  [#2157](https://github.com/rust-lang/mdBook/pull/2157)
+
+## mdBook 0.4.33
+[v0.4.32...v0.4.33](https://github.com/rust-lang/mdBook/compare/v0.4.32...v0.4.33)
+
+### Added
+- The `color-scheme` CSS property is now set based on the light/dark theme, which applies some slight color differences in browser elements like scroll bars on some browsers.
+  [#2134](https://github.com/rust-lang/mdBook/pull/2134)
+
+### Fixed
+- Fixed watching of extra-watch-dirs when not running in the book root directory.
+  [#2146](https://github.com/rust-lang/mdBook/pull/2146)
+- Reverted the dependency update to the `toml` crate (again!). This was an unintentional breaking change in 0.4.32.
+  [#2021](https://github.com/rust-lang/mdBook/pull/2021)
+- Changed macOS change notifications to use the kqueue implementation which should fix some issues with repeated rebuilds when a file changed.
+  [#2152](https://github.com/rust-lang/mdBook/pull/2152)
+- Don't set a background color in the print page for code blocks in a header.
+  [#2150](https://github.com/rust-lang/mdBook/pull/2150)
+
+## mdBook 0.4.32
+[v0.4.31...v0.4.32](https://github.com/rust-lang/mdBook/compare/v0.4.31...v0.4.32)
+
+### Fixed
+- Fixed theme-color meta tag not syncing with the theme.
+  [#2118](https://github.com/rust-lang/mdBook/pull/2118)
+
+### Changed
+- Updated all dependencies.
+  [#2121](https://github.com/rust-lang/mdBook/pull/2121)
+  [#2122](https://github.com/rust-lang/mdBook/pull/2122)
+  [#2123](https://github.com/rust-lang/mdBook/pull/2123)
+  [#2124](https://github.com/rust-lang/mdBook/pull/2124)
+  [#2125](https://github.com/rust-lang/mdBook/pull/2125)
+  [#2126](https://github.com/rust-lang/mdBook/pull/2126)
+
+## mdBook 0.4.31
+[v0.4.30...v0.4.31](https://github.com/rust-lang/mdBook/compare/v0.4.30...v0.4.31)
+
+### Fixed
+- Fixed menu border render flash during page navigation.
+  [#2101](https://github.com/rust-lang/mdBook/pull/2101)
+- Fixed flicker setting sidebar scroll position.
+  [#2104](https://github.com/rust-lang/mdBook/pull/2104)
+- Fixed compile error with proc-macro2 on latest Rust nightly.
+  [#2109](https://github.com/rust-lang/mdBook/pull/2109)
+
+## mdBook 0.4.30
+[v0.4.29...v0.4.30](https://github.com/rust-lang/mdBook/compare/v0.4.29...v0.4.30)
+
+### Added
+- Added support for heading attributes.
+  Attributes are specified in curly braces just after the heading text.
+  An HTML ID can be specified with `#` and classes with `.`.
+  For example: `## My heading {#custom-id .class1 .class2}`
+  [#2013](https://github.com/rust-lang/mdBook/pull/2013)
+- Added support for hidden code lines for languages other than Rust.
+  The `output.html.code.hidelines` table allows you to define the prefix character that will be used to hide code lines based on the language.
+  [#2093](https://github.com/rust-lang/mdBook/pull/2093)
+
+### Fixed
+- Fixed a few minor markdown rendering issues.
+  [#2092](https://github.com/rust-lang/mdBook/pull/2092)
+
+## mdBook 0.4.29
+[v0.4.28...v0.4.29](https://github.com/rust-lang/mdBook/compare/v0.4.28...v0.4.29)
+
+### Changed
+- Built-in fonts are no longer copied when `fonts/fonts.css` is overridden in the theme directory.
+  Additionally, the warning about `copy-fonts` has been removed if `fonts/fonts.css` is specified.
+  [#2080](https://github.com/rust-lang/mdBook/pull/2080)
+- `mdbook init --force` now skips all interactive prompts as intended.
+  [#2057](https://github.com/rust-lang/mdBook/pull/2057)
+- Updated dependencies
+  [#2063](https://github.com/rust-lang/mdBook/pull/2063)
+  [#2086](https://github.com/rust-lang/mdBook/pull/2086)
+  [#2082](https://github.com/rust-lang/mdBook/pull/2082)
+  [#2084](https://github.com/rust-lang/mdBook/pull/2084)
+  [#2085](https://github.com/rust-lang/mdBook/pull/2085)
+
+### Fixed
+- Switched from the `gitignore` library to `ignore`. This should bring some improvements with gitignore handling.
+  [#2076](https://github.com/rust-lang/mdBook/pull/2076)
+
+## mdBook 0.4.28
+[v0.4.27...v0.4.28](https://github.com/rust-lang/mdBook/compare/v0.4.27...v0.4.28)
+
+### Changed
+- The sidebar is now shown on wide screens when localstorage is disabled.
+  [#2017](https://github.com/rust-lang/mdBook/pull/2017)
+- Preprocessors are now run with `mdbook test`.
+  [#1986](https://github.com/rust-lang/mdBook/pull/1986)
+
+### Fixed
+- Fixed regression in 0.4.26 that prevented the title bar from scrolling properly on smaller screens.
+  [#2039](https://github.com/rust-lang/mdBook/pull/2039)
+
+## mdBook 0.4.27
+[v0.4.26...v0.4.27](https://github.com/rust-lang/mdBook/compare/v0.4.26...v0.4.27)
+
+### Changed
+- Reverted the dependency update to the `toml` crate. This was an unintentional breaking change in 0.4.26.
+  [#2021](https://github.com/rust-lang/mdBook/pull/2021)
+
+## mdBook 0.4.26
+[v0.4.25...v0.4.26](https://github.com/rust-lang/mdBook/compare/v0.4.25...v0.4.26)
+
+**The 0.4.26 release has been yanked due to an unintentional breaking change.**
+
+### Changed
+- Removed custom scrollbars for webkit browsers
+  [#1961](https://github.com/rust-lang/mdBook/pull/1961)
+- Updated some dependencies
+  [#1998](https://github.com/rust-lang/mdBook/pull/1998)
+  [#2009](https://github.com/rust-lang/mdBook/pull/2009)
+  [#2011](https://github.com/rust-lang/mdBook/pull/2011)
+- Fonts are now part of the theme.
+  The `output.html.copy-fonts` option has been deprecated.
+  To define custom fonts, be sure to define `theme/fonts.css`.
+  [#1987](https://github.com/rust-lang/mdBook/pull/1987)
+
+### Fixed
+- Fixed overflow viewport issue with mobile Safari
+  [#1994](https://github.com/rust-lang/mdBook/pull/1994)
+
+## mdBook 0.4.25
+[e14d381...1ba74a3](https://github.com/rust-lang/mdBook/compare/e14d381...1ba74a3)
+
+### Fixed
+- Fixed a regression where `mdbook test -L deps path-to-book` would not work.
+  [#1959](https://github.com/rust-lang/mdBook/pull/1959)
+
+## mdBook 0.4.24
+[eb77083...8767ebf](https://github.com/rust-lang/mdBook/compare/eb77083...8767ebf)
+
+### Fixed
+- The precompiled linux-gnu mdbook binary available on [GitHub Releases](https://github.com/rust-lang/mdBook/releases) inadvertently switched to a newer version of glibc. This release goes back to an older version that should be more compatible on older versions of Linux.
+  [#1955](https://github.com/rust-lang/mdBook/pull/1955)
+
+## mdBook 0.4.23
+[678b469...68a75da](https://github.com/rust-lang/mdBook/compare/678b469...68a75da)
+
+### Changed
+- Updated all dependencies
+  [#1951](https://github.com/rust-lang/mdBook/pull/1951)
+  [#1952](https://github.com/rust-lang/mdBook/pull/1952)
+  [#1844](https://github.com/rust-lang/mdBook/pull/1844)
+- Updated minimum Rust version to 1.60.
+  [#1951](https://github.com/rust-lang/mdBook/pull/1951)
+
+### Fixed
+- Fixed a regression where playground code was missing hidden lines, preventing it from compiling correctly.
+  [#1950](https://github.com/rust-lang/mdBook/pull/1950)
+
+## mdBook 0.4.22
+[40c06f5...4844f72](https://github.com/rust-lang/mdBook/compare/40c06f5...4844f72)
+
+### Added
+- Added a `--chapter` option to `mdbook test` to specify a specific chapter to test.
+  [#1741](https://github.com/rust-lang/mdBook/pull/1741)
+- Added CSS styling for `<kbd>` tags.
+  [#1906](https://github.com/rust-lang/mdBook/pull/1906)
+- Added pre-compiled binaries for `x86_64-unknown-linux-musl` and `aarch64-unknown-linux-musl` (see [Releases](https://github.com/rust-lang/mdBook/releases)).
+  [#1862](https://github.com/rust-lang/mdBook/pull/1862)
+- Added `build.extra-watch-dirs` which is an array of additional directories to watch for changes when running `mdbook serve`.
+  [#1884](https://github.com/rust-lang/mdBook/pull/1884)
+
+### Changed
+- Removed the `type="text/javascript"` attribute from `<script>` tags.
+  [#1881](https://github.com/rust-lang/mdBook/pull/1881)
+- Switched to building with Rust Edition 2021.
+  This raises the minimum supported Rust version to 1.56.
+  [#1887](https://github.com/rust-lang/mdBook/pull/1887)
+- When hidden code is hidden, the hidden parts are no longer copied to the clipboard via the copy button.
+  [#1911](https://github.com/rust-lang/mdBook/pull/1911)
+- Various HTML changes and fixes to be more compliant with HTML5.
+  [#1924](https://github.com/rust-lang/mdBook/pull/1924)
+- The theme picker now shows which theme is currently selected.
+  [#1935](https://github.com/rust-lang/mdBook/pull/1935)
+
+### Fixed
+- Avoid blank line at the end of an ACE code block
+  [#1836](https://github.com/rust-lang/mdBook/pull/1836)
+
+
+## mdBook 0.4.21
+[92afe9b...8f01d02](https://github.com/rust-lang/mdBook/compare/92afe9b...8f01d02)
+
+### Fixed
+- Fixed an issue where mdBook would fail to compile with Rust nightly-2022-07-22.
+  [#1861](https://github.com/rust-lang/mdBook/pull/1861)
+
+## mdBook 0.4.20
+[53055e0...da166e0](https://github.com/rust-lang/mdBook/compare/53055e0...da166e0)
+
+### Fixed
+- Fixed a regression in 0.4.19 where inline code would have excessive padding
+  in some situations such as headings.
+  [#1855](https://github.com/rust-lang/mdBook/pull/1855)
+
+## mdBook 0.4.19
+[ae275ad...53055e0](https://github.com/rust-lang/mdBook/compare/ae275ad...53055e0)
+
+### Added
+- The `serve` command now supports HEAD requests.
+  [#1825](https://github.com/rust-lang/mdBook/pull/1825)
+
+### Changed
+- An error is now generated when a custom theme directory does not exist.
+  [#1791](https://github.com/rust-lang/mdBook/pull/1791)
+- Very wide tables now have independent horizontal scrolling so that scrolling
+  to see the rest of the table will not scroll the entire page.
+  [#1617](https://github.com/rust-lang/mdBook/pull/1617)
+- The buttons on code blocks are now only shown when the mouse cursor hovers
+  over them (or tapped on mobile). There is also some extra spacing to reduce
+  the overlap with the code.
+  [#1806](https://github.com/rust-lang/mdBook/pull/1806)
+- The first chapter always generates an `index.html` file. Previously it would
+  only generate the index file for prefix chapters.
+  [#1829](https://github.com/rust-lang/mdBook/pull/1829)
+
+### Fixed
+- `mdbook serve --open` now properly handles the case if the first chapter is a draft.
+  [#1714](https://github.com/rust-lang/mdBook/pull/1714)
+  [#1830](https://github.com/rust-lang/mdBook/pull/1830)
+- Very long words (over 80 characters) are no longer indexed to avoid a stack overflow.
+  [#1833](https://github.com/rust-lang/mdBook/pull/1833)
+
+## mdBook 0.4.18
+[981b79b...ae275ad](https://github.com/rust-lang/mdBook/compare/981b79b...ae275ad)
+
+### Fixed
+- Fixed rendering of SUMMARY links that contain markdown escapes or other
+  markdown elements.
+  [#1785](https://github.com/rust-lang/mdBook/pull/1785)
+
+## mdBook 0.4.17
+[a5fddfa...981b79b](https://github.com/rust-lang/mdBook/compare/a5fddfa...981b79b)
+
+### Fixed
+- Fixed parsing of `output.html.print` configuration table.
+  [#1775](https://github.com/rust-lang/mdBook/pull/1775)
+
+## mdBook 0.4.16
+[68a5c09...a5fddfa](https://github.com/rust-lang/mdBook/compare/68a5c09...a5fddfa)
+
+### Added
+- Added `output.html.print.page-break` config option to control whether or not
+  there is a page break between chapters in the print output.
+  [#1728](https://github.com/rust-lang/mdBook/pull/1728)
+- Added `output.html.playground.runnable` config option to globally disable
+  the run button in code blocks.
+  [#1546](https://github.com/rust-lang/mdBook/pull/1546)
+
+### Changed
+- The `mdbook serve` live reload websocket now uses the protocol, host, and
+  port of the current page, allowing access through a proxy.
+  [#1771](https://github.com/rust-lang/mdBook/pull/1771)
+- The 404 not-found page now includes the books title in the HTML title tag.
+  [#1693](https://github.com/rust-lang/mdBook/pull/1693)
+- Migrated to clap 3.0 which handles CLI option parsing.
+  [#1731](https://github.com/rust-lang/mdBook/pull/1731)
+
+### Fixed
+- Minor fixes to the markdown parser.
+  [#1729](https://github.com/rust-lang/mdBook/pull/1729)
+- Fixed incorrect parsing in `SUMMARY.md` when it didn't start with a title.
+  [#1744](https://github.com/rust-lang/mdBook/pull/1744)
+- Fixed duplicate anchor IDs for links in search results.
+  [#1749](https://github.com/rust-lang/mdBook/pull/1749)
+
+## mdBook 0.4.15
+[5eb7d46...68a5c09](https://github.com/rust-lang/mdBook/compare/5eb7d46...68a5c09)
+
+### Changed
+- Major update to expand the documentation located at <https://rust-lang.github.io/mdBook/>.
+  [#1709](https://github.com/rust-lang/mdBook/pull/1709)
+  [#1710](https://github.com/rust-lang/mdBook/pull/1710)
+- Updated the markdown parser with various fixes for common-mark compliance.
+  [#1712](https://github.com/rust-lang/mdBook/pull/1712)
+
+## mdBook 0.4.14
+[ffa8284...c9b6be8](https://github.com/rust-lang/mdBook/compare/ffa8284...c9b6be8)
+
+### Added
+- The 2021 Rust edition option has been stabilized.
+  [#1642](https://github.com/rust-lang/mdBook/pull/1642)
+
+### Changed
+- Header anchors no longer include any HTML tags. Previously only a small
+  subset were excluded.
+  [#1683](https://github.com/rust-lang/mdBook/pull/1683)
+- Deprecated the google-analytics option. Books using this option should place
+  the appropriate code in the `theme/head.hbs` file instead.
+  [#1675](https://github.com/rust-lang/mdBook/pull/1675)
+
+### Fixed
+- Updated the markdown parser which brings in a few small fixes and removes
+  the custom smart quote handling.
+  [#1668](https://github.com/rust-lang/mdBook/pull/1668)
+- Fixed iOS Safari enlarging text when going into landscape mode.
+  [#1685](https://github.com/rust-lang/mdBook/pull/1685)
+
+## mdBook 0.4.13
+[e6629cd...f55028b](https://github.com/rust-lang/mdBook/compare/e6629cd...f55028b)
+
+### Added
+
+- Added the ability to specify the preprocessor order.
+  [#1607](https://github.com/rust-lang/mdBook/pull/1607)
+
+### Fixed
+
+- Include chapters with no headers in the search index
+  [#1637](https://github.com/rust-lang/mdBook/pull/1637)
+- Switched to the `opener` crate for opening a web browser, which should fix
+  some issues with blocking.
+  [#1656](https://github.com/rust-lang/mdBook/pull/1656)
+- Fixed clicking the border of the theme switcher breaking the theme selection.
+  [#1651](https://github.com/rust-lang/mdBook/pull/1651)
+
+## mdBook 0.4.12
+[14add9c...8b4e488](https://github.com/rust-lang/mdBook/compare/14add9c...8b4e488)
+
+### Changed
+- Reverted the change to update to highlight.js 11, as it broke hidden code lines.
+  [#1597](https://github.com/rust-lang/mdBook/pull/1621)
+ 
+## mdBook 0.4.11
+[e440094...2cf00d0](https://github.com/rust-lang/mdBook/compare/e440094...2cf00d0)
+
+### Added
+- Added support for Rust 2021 edition.
+  [#1596](https://github.com/rust-lang/mdBook/pull/1596)
+- Added `mdbook completions` subcommand which provides shell completions.
+  [#1425](https://github.com/rust-lang/mdBook/pull/1425)
+- Added `--title` and `--ignore` flags to `mdbook init` to avoid the
+  interactive input.
+  [#1559](https://github.com/rust-lang/mdBook/pull/1559)
+
+### Changed
+- If running a Rust example does not have any output, it now displays the text
+  "No output" instead of not showing anything.
+  [#1599](https://github.com/rust-lang/mdBook/pull/1599)
+- Code block language tags can now be separated by space or tab (along with
+  commas) to match the behavior of other sites like GitHub and rustdoc.
+  [#1469](https://github.com/rust-lang/mdBook/pull/1469)
+- Updated `warp` (the web server) to the latest version.
+  This also updates the minimum supported Rust version to 1.46.
+  [#1612](https://github.com/rust-lang/mdBook/pull/1612)
+- Updated to highlight.js 11. This has various highlighting improvements.
+  [#1597](https://github.com/rust-lang/mdBook/pull/1597)
+
+### Fixed
+- Inline code blocks inside a header are no longer highlighted when
+  `output.html.playground.editable` is `true`.
+  [#1613](https://github.com/rust-lang/mdBook/pull/1613)
+
+## mdBook 0.4.10
+[2f7293a...dc2062a](https://github.com/rust-lang/mdBook/compare/2f7293a...dc2062a)
+
+### Changed
+- Reverted breaking change in 0.4.9 that removed the `__non_exhaustive` marker
+  on the `Book` struct.
+  [#1572](https://github.com/rust-lang/mdBook/pull/1572)
+- Updated handlebars to 4.0.
+  [#1550](https://github.com/rust-lang/mdBook/pull/1550)
+- Removed the `chapter_begin` id on the print page's chapter separators.
+  [#1541](https://github.com/rust-lang/mdBook/pull/1541)
+
+## mdBook 0.4.9
+[7e01cf9...d325c60](https://github.com/rust-lang/mdBook/compare/7e01cf9...d325c60)
+
+### Changed
+- Updated all dependencies and raised the minimum Rust version to 1.42.
+  [#1528](https://github.com/rust-lang/mdBook/pull/1528)
+- Added more detail to error message when a preprocessor fails.
+  [#1526](https://github.com/rust-lang/mdBook/pull/1526)
+- Set max-width of HTML video tags to 100% to match img tags.
+  [#1542](https://github.com/rust-lang/mdBook/pull/1542)
+
+### Fixed
+- Type errors when parsing `book.toml` are no longer ignored.
+  [#1539](https://github.com/rust-lang/mdBook/pull/1539)
+- Better handling if `mdbook serve` fails to start the http server.
+  [#1555](https://github.com/rust-lang/mdBook/pull/1555)
+- Fixed the path for `edit-url-template` if the book used a source directory
+  other than `src`.
+  [#1554](https://github.com/rust-lang/mdBook/pull/1554)
+
+## mdBook 0.4.8
+[fcceee4...b592b10](https://github.com/rust-lang/mdBook/compare/fcceee4...b592b10)
+
+### Added
+- Added the option `output.html.edit-url-template` which can be a URL which is
+  linked on each page to direct the user to a site (such as GitHub) where the
+  user can directly suggest an edit for the page they are currently reading.
+  [#1506](https://github.com/rust-lang/mdBook/pull/1506)
+
+### Changed
+- Printed output now includes a page break between chapters.
+  [#1485](https://github.com/rust-lang/mdBook/pull/1485)
+
+### Fixed
+- HTML, such as HTML comments, is now ignored if it appears above the title line
+  in `SUMMARY.md`.
+  [#1437](https://github.com/rust-lang/mdBook/pull/1437)
+
+## mdBook 0.4.7
+[9a9eb01...c83bbd6](https://github.com/rust-lang/mdBook/compare/9a9eb01...c83bbd6)
+
+### Changed
+- Updated shlex parser to fix a minor parsing issue (used by the
+  preprocessor/backend custom command config).
+  [#1471](https://github.com/rust-lang/mdBook/pull/1471)
+- Enhanced text contrast of `light` theme to improve accessibility.
+  [#1470](https://github.com/rust-lang/mdBook/pull/1470)
+
+### Fixed
+- Fixed some issues with fragment scrolling and linking.
+  [#1463](https://github.com/rust-lang/mdBook/pull/1463)
+
+## mdBook 0.4.6
+[eaa6914...1a0c296](https://github.com/rust-lang/mdBook/compare/eaa6914...1a0c296)
+
+### Changed
+- The chapter name is now included in the search breadcrumbs.
+  [#1389](https://github.com/rust-lang/mdBook/pull/1389)
+- Pressing Escape will remove the `?highlight` argument from the URL.
+  [#1427](https://github.com/rust-lang/mdBook/pull/1427)
+- `mdbook init --theme` will now place the theme in the root of the book
+  directory instead of in the `src` directory.
+  [#1432](https://github.com/rust-lang/mdBook/pull/1432)
+- A custom renderer that sets the `command` to a relative path now interprets
+  the relative path relative to the book root. Previously it was inconsistent
+  based on the platform (either relative to the current directory, or relative
+  to the renderer output directory). Paths relative to the output directory
+  are still supported with a deprecation warning.
+  [#1418](https://github.com/rust-lang/mdBook/pull/1418)
+- The `theme` directory in the config is now interpreted as relative to the
+  book root, instead of the current directory.
+  [#1405](https://github.com/rust-lang/mdBook/pull/1405)
+- Handle UTF-8 BOM for chapter sources.
+  [#1285](https://github.com/rust-lang/mdBook/pull/1285)
+- Removed extra whitespace added to `{{#playground}}` snippets.
+  [#1375](https://github.com/rust-lang/mdBook/pull/1375)
+
+### Fixed
+- Clicking on a search result with multiple search words will now correctly
+  highlight all of the words.
+  [#1426](https://github.com/rust-lang/mdBook/pull/1426)
+- Properly handle `<` and `>` characters in the table of contents.
+  [#1376](https://github.com/rust-lang/mdBook/pull/1376)
+- Fixed to properly serialize the `build` table in the config, which prevented
+  setting it in the API.
+  [#1378](https://github.com/rust-lang/mdBook/pull/1378)
+
+## mdBook 0.4.5
+[eaa6914...f66df09](https://github.com/rust-lang/mdBook/compare/eaa6914...f66df09)
+
+### Fixed
+
+- Fixed XSS in the search page.
+  [CVE-2020-26297](https://groups.google.com/g/rustlang-security-announcements/c/3-sO6of29O0)
+  [648c9ae](https://github.com/rust-lang/mdBook/commit/648c9ae772bec83f0a5954d17b4287d5bb1d6606)
+
 ## mdBook 0.4.4
 [4df9ec9...01836ba](https://github.com/rust-lang/mdBook/compare/4df9ec9...01836ba)
 

CODE_OF_CONDUCT.md

@@ -0,0 +1,3 @@
+# The Rust Code of Conduct
+
+The Code of Conduct for this repository [can be found online](https://www.rust-lang.org/conduct.html).

CONTRIBUTING.md

@@ -6,15 +6,23 @@ If you have come here to learn how to contribute to mdBook, we have some tips fo
 
 First of all, don't hesitate to ask questions!
 Use the [issue tracker](https://github.com/rust-lang/mdBook/issues), no question is too simple.
-If we don't respond in a couple of days, ping us @Michael-F-Bryan, @budziq, @steveklabnik, @frewsxcv it might just be that we forgot. :wink:
+
+### Issue assignment
+
+**:warning: Important :warning:**
+
+Before working on pull request, please ping us on the corresponding issue.
+The current PR backlog is beyond what we can process at this time.
+Only issues that have an [`E-Help-wanted`](https://github.com/rust-lang/mdBook/labels/E-Help-wanted) or [`Feature accepted`](https://github.com/rust-lang/mdBook/labels/Feature%20accepted) label will likely receive reviews.
+If there isn't already an open issue for what you want to work on, please open one first to see if it is something we would be available to review.
 
 ### Issues to work on
 
-Any issue is up for the grabbing, but if you are starting out, you might be interested in the
+If you are starting out, you might be interested in the
 [E-Easy issues](https://github.com/rust-lang/mdBook/issues?q=is%3Aopen+is%3Aissue+label%3AE-Easy).
 Those are issues that are considered more straightforward for beginners to Rust or the codebase itself.
-These issues can be a good launching pad for more involved issues. Easy tasks for a first time contribution
-include documentation improvements, new tests, examples, updating dependencies, etc.
+These issues can be a good launching pad for more involved issues.
+Easy tasks for a first time contribution include documentation improvements, new tests, examples, updating dependencies, etc.
 
 If you come from a web development background, you might be interested in issues related to web technologies tagged
 [A-JavaScript](https://github.com/rust-lang/mdBook/issues?q=is%3Aopen+is%3Aissue+label%3AA-JavaScript),
@@ -22,16 +30,16 @@ If you come from a web development background, you might be interested in issues
 [A-HTML](https://github.com/rust-lang/mdBook/issues?q=is%3Aopen+is%3Aissue+label%3AA-HTML) or
 [A-Mobile](https://github.com/rust-lang/mdBook/issues?q=is%3Aopen+is%3Aissue+label%3AA-Mobile).
 
-When you decide you want to work on a specific issue, ping us on that issue so that we can assign it to you.
+When you decide you want to work on a specific issue, and it isn't already assigned to someone else, assign the issue to yourself by leaving a comment with the text `@rustbot claim`.
 Again, do not hesitate to ask questions. We will gladly mentor anyone that want to tackle an issue.
 
 Issues on the issue tracker are categorized with the following labels:
 
 - **A**-prefixed labels state which area of the project an issue relates to.
 - **E**-prefixed labels show an estimate of the experience necessary to fix the issue.
-- **M**-prefixed labels are meta-issues used for questions, discussions, or tracking issues
+- **M**-prefixed labels are meta-issues regarding the management of the mdBook project itself
 - **S**-prefixed labels show the status of the issue
-- **T**-prefixed labels show the type of issue
+- **C**-prefixed labels show the category of issue
 
 ### Building mdBook
 
@@ -46,7 +54,7 @@ mdBook builds on stable Rust, if you want to build mdBook from source, here are
 0. Navigate into the newly created `mdBook` directory
 0. Run `cargo build`
 
-The resulting binary can be found in `mdBook/target/debug/` under the name `mdBook` or `mdBook.exe`.
+The resulting binary can be found in `mdBook/target/debug/` under the name `mdbook` or `mdbook.exe`.
 
 ### Code Quality
 
@@ -60,7 +68,7 @@ This will ensure we have good quality source code that is better for us all to m
 [rustfmt](https://github.com/rust-lang/rustfmt) has a lot more information on the project.
 The quick guide is
 
-1. Install it
+1. Install it (`rustfmt` is usually installed by default via [rustup](https://rustup.rs/)):
     ```
     rustup component add rustfmt
     ```
@@ -72,18 +80,15 @@ The quick guide is
    ```
    cargo fmt
    ```
-   When run through `cargo` it will format all bin and lib files in the current crate.
+   When run through `cargo` it will format all bin and lib files in the current package.
 
 For more information, such as running it from your favourite editor, please see the `rustfmt` project. [rustfmt](https://github.com/rust-lang/rustfmt)
 
 
 #### Finding Issues with Clippy
 
-Clippy is a code analyser/linter detecting mistakes, and therfore helps to improve your code.
-Like formatting your code with `rustfmt`, running clippy regularly and before your Pull Request will
-help us maintain awesome code.
-
-The best documentation can be found over at [rust-clippy](https://github.com/rust-lang/rust-clippy)
+[Clippy](https://doc.rust-lang.org/clippy/) is a code analyser/linter detecting mistakes, and therefore helps to improve your code.
+Like formatting your code with `rustfmt`, running clippy regularly and before your Pull Request will help us maintain awesome code.
 
 1. To install
     ```
@@ -94,15 +99,77 @@ The best documentation can be found over at [rust-clippy](https://github.com/rus
     cargo clippy
     ```
 
-Clippy has an ever growing list of checks, that are managed in [lint files](https://rust-lang.github.io/rust-clippy/master/index.html).
+### Change requirements
+
+Please consider the following when making a change:
+
+* Almost all changes that modify the Rust code must be accompanied with a test.
+
+* Almost all features and changes must update the documentation.
+  mdBook has the [mdBook Guide](https://rust-lang.github.io/mdBook/) whose source is at <https://github.com/rust-lang/mdBook/tree/master/guide>.
+
+* Almost all Rust items should be documented with doc comments.
+  See the [Rustdoc Book](https://doc.rust-lang.org/rustdoc/) for more information on writing doc comments.
+
+* Breaking the API can only be done in major SemVer releases.
+  These are done very infrequently, so it is preferred to avoid these when possible.
+  See [SemVer Compatibility](https://doc.rust-lang.org/cargo/reference/semver.html) for more information on what a SemVer breaking change is.
+
+  (Note: At this time, some SemVer breaking changes are inevitable due to the current code structure.
+  An example is adding new fields to the config structures.
+  These are intended to be fixed in the next major release.)
+
+* Similarly, the CLI interface is considered to be stable.
+  Care should be taken to avoid breaking existing workflows.
+
+* Check out the [Rust API Guidelines](https://rust-lang.github.io/api-guidelines/) for guidelines on designing the API.
 
 ### Making a pull-request
 
 When you feel comfortable that your changes could be integrated into mdBook, you can create a pull-request on GitHub.
 One of the core maintainers will then approve the changes or request some changes before it gets merged.
 
-If you want to make your pull-request even better, you might want to run [Clippy](https://github.com/Manishearth/rust-clippy)
-and [rustfmt](https://github.com/rust-lang/rustfmt) on the code first.
-This is not a requirement though and will never block a pull-request from being merged.
-
 That's it, happy contributions! :tada: :tada: :tada:
+
+## Browser compatibility and testing
+
+Currently we don't have a strict browser compatibility matrix due to our limited resources.
+We generally strive to keep mdBook compatible with a relatively recent browser on all of the most major platforms.
+That is, supporting Chrome, Safari, Firefox, Edge on Windows, macOS, Linux, iOS, and Android.
+If possible, do your best to avoid breaking older browser releases.
+
+Any change to the HTML or styling is encouraged to manually check on as many browsers and platforms that you can.
+Unfortunately at this time we don't have any automated UI or browser testing, so your assistance in testing is appreciated.
+
+## Updating highlight.js
+
+The following are instructions for updating [highlight.js](https://highlightjs.org/).
+
+1. Clone the repository at <https://github.com/highlightjs/highlight.js>
+1. Check out a tagged release (like `10.1.1`).
+1. Run `npm install`
+1. Run `node tools/build.js :common apache armasm coffeescript d handlebars haskell http julia nginx properties r scala x86asm yaml`
+1. Compare the language list that it spits out to the one in [`syntax-highlighting.md`](https://github.com/camelid/mdBook/blob/master/guide/src/format/theme/syntax-highlighting.md). If any are missing, add them to the list and rebuild (and update these docs). If any are added to the common set, add them to `syntax-highlighting.md`.
+1. Copy `build/highlight.min.js` to mdbook's directory [`highlight.js`](https://github.com/rust-lang/mdBook/blob/master/src/theme/highlight.js).
+1. Be sure to check the highlight.js [CHANGES](https://github.com/highlightjs/highlight.js/blob/main/CHANGES.md) for any breaking changes. Breaking changes that would affect users will need to wait until the next major release.
+1. Build mdbook with the new file and build some books with the new version and compare the output with a variety of languages to see if anything changes. The [test_book](https://github.com/rust-lang/mdBook/tree/master/test_book) contains a chapter with many languages to examine.
+
+## Publishing new releases
+
+Instructions for mdBook maintainers to publish a new release:
+
+1. Create a PR to update the version and update the CHANGELOG:
+    1. Update the version in `Cargo.toml`
+    2. Run `cargo test` to verify that everything is passing, and to update `Cargo.lock`.
+    3. Double-check for any SemVer breaking changes.
+       Try [`cargo-semver-checks`](https://crates.io/crates/cargo-semver-checks), though beware that the current version of mdBook isn't properly adhering to SemVer due to the lack of `#[non_exhaustive]` and other issues. See https://github.com/rust-lang/mdBook/issues/1835.
+    4. Update `CHANGELOG.md` with any changes that users may be interested in.
+    5. Update `continuous-integration.md` to update the version number for the installation instructions.
+    6. Commit the changes, and open a PR.
+2. After the PR has been merged, create a release in GitHub. This can either be done in the GitHub web UI, or on the command-line:
+   ```bash
+   MDBOOK_VERS="`cargo read-manifest | jq -r .version`" ; \
+    gh release create -R rust-lang/mdbook v$MDBOOK_VERS \
+        --title v$MDBOOK_VERS \
+        --notes "See https://github.com/rust-lang/mdBook/blob/master/CHANGELOG.md#mdbook-${MDBOOK_VERS//.} for a complete list of changes."
+   ```

Cargo.toml

@@ -1,63 +1,73 @@
 [package]
 name = "mdbook"
-version = "0.4.4"
+version = "0.4.35"
 authors = [
     "Mathieu David <mathieudavid@mathieudavid.org>",
     "Michael-F-Bryan <michaelfbryan@gmail.com>",
     "Matt Ickstadt <mattico8@gmail.com>"
 ]
-documentation = "http://rust-lang.github.io/mdBook/index.html"
-edition = "2018"
+documentation = "https://rust-lang.github.io/mdBook/index.html"
+edition = "2021"
 exclude = ["/guide/*"]
 keywords = ["book", "gitbook", "rustbook", "markdown"]
 license = "MPL-2.0"
 readme = "README.md"
 repository = "https://github.com/rust-lang/mdBook"
 description = "Creates a book from markdown files"
+rust-version = "1.66"
 
 [dependencies]
-anyhow = "1.0.28"
-chrono = "0.4"
-clap = "2.24"
-env_logger = "0.7.1"
-handlebars = "3.0"
-lazy_static = "1.0"
-log = "0.4"
-memchr = "2.0"
-open = "1.1"
-pulldown-cmark = "0.7.0"
-regex = "1.0.0"
-serde = "1.0"
-serde_derive = "1.0"
-serde_json = "1.0"
-shlex = "0.1"
-tempfile = "3.0"
-toml = "0.5.1"
+anyhow = "1.0.71"
+chrono = { version = "0.4.24", default-features = false, features = ["clock"] }
+clap = { version = "4.3.12", features = ["cargo", "wrap_help"] }
+clap_complete = "4.3.2"
+once_cell = "1.17.1"
+env_logger = "0.10.0"
+handlebars = "4.3.7"
+log = "0.4.17"
+memchr = "2.5.0"
+opener = "0.6.1"
+pulldown-cmark = { version = "0.9.3", default-features = false }
+regex = "1.8.1"
+serde = { version = "1.0.163", features = ["derive"] }
+serde_json = "1.0.96"
+shlex = "1.1.0"
+tempfile = "3.4.0"
+toml = "0.5.11" # Do not update, see https://github.com/rust-lang/mdBook/issues/2037
+topological-sort = "0.2.2"
 
 # Watch feature
-notify = { version = "4.0", optional = true }
-gitignore = { version = "1.0", optional = true }
+notify = { version = "6.0.1", optional = true }
+notify-debouncer-mini = { version = "0.3.0", optional = true }
+ignore = { version = "0.4.20", optional = true }
 
 # Serve feature
-futures-util = { version = "0.3.4", optional = true }
-tokio = { version = "0.2.18", features = ["macros"], optional = true }
-warp = { version = "0.2.2", default-features = false, features = ["websocket"], optional = true }
+futures-util = { version = "0.3.28", optional = true }
+tokio = { version = "1.28.1", features = ["macros", "rt-multi-thread"], optional = true }
+warp = { version = "0.3.5", default-features = false, features = ["websocket"], optional = true }
 
 # Search feature
-elasticlunr-rs = { version = "2.3", optional = true, default-features = false }
-ammonia = { version = "3", optional = true }
+elasticlunr-rs = { version = "3.0.2", optional = true }
+ammonia = { version = "3.3.0", optional = true }
 
 [dev-dependencies]
-select = "0.5"
-pretty_assertions = "0.6"
-walkdir = "2.0"
+assert_cmd = "2.0.11"
+predicates = "3.0.3"
+select = "0.6.0"
+semver = "1.0.17"
+pretty_assertions = "1.3.0"
+walkdir = "2.3.3"
 
 [features]
 default = ["watch", "serve", "search"]
-watch = ["notify", "gitignore"]
-serve = ["futures-util", "tokio", "warp"]
-search = ["elasticlunr-rs", "ammonia"]
+watch = ["dep:notify", "dep:notify-debouncer-mini", "dep:ignore"]
+serve = ["dep:futures-util", "dep:tokio", "dep:warp"]
+search = ["dep:elasticlunr-rs", "dep:ammonia"]
 
 [[bin]]
 doc = false
 name = "mdbook"
+
+[[example]]
+name = "nop-preprocessor"
+test = true

README.md

@@ -6,229 +6,15 @@
 
 mdBook is a utility to create modern online books from Markdown files.
 
+Check out the **[User Guide]** for a list of features and installation and usage information.
+The User Guide also serves as a demonstration to showcase what a book looks like.
 
-## What does it look like?
-
-The [User Guide] for mdBook has been written in Markdown and is using mdBook to
-generate the online book-like website you can read. The documentation uses the
-latest version on GitHub and showcases the available features.
-
-## Installation
-
-There are multiple ways to install mdBook.
-
-1. **Binaries**
-
-   Binaries are available for download [here][releases]. Make sure to put the
-   path to the binary into your `PATH`.
-
-2. **From Crates.io**
-
-   This requires at least [Rust] 1.39 and Cargo to be installed. Once you have installed
-   Rust, type the following in the terminal:
-
-   ```
-   cargo install mdbook
-   ```
-
-   This will download and compile mdBook for you, the only thing left to do is
-   to add the Cargo bin directory to your `PATH`.
-
-   **Note for automatic deployment**
-
-   If you are using a script to do automatic deployments using Travis or
-   another CI server, we recommend that you specify a semver version range for
-   mdBook when you install it through your script!
-
-   This will constrain the server to install the latest **non-breaking**
-   version of mdBook and will prevent your books from failing to build because
-   we released a new version.
-
-   You can also disable default features to speed up compile time.
-
-   Example:
-
-   ```
-   cargo install mdbook --no-default-features --features output --vers "^0.1.0"
-   ```
-
-3. **From Git**
-
-   The version published to crates.io will ever so slightly be behind the
-   version hosted here on GitHub. If you need the latest version you can build
-   the git version of mdBook yourself. Cargo makes this ***super easy***!
-
-   ```
-   cargo install --git https://github.com/rust-lang/mdBook.git mdbook
-   ```
-
-   Again, make sure to add the Cargo bin directory to your `PATH`.
-
-4. **For Contributions**
-
-   If you want to contribute to mdBook you will have to clone the repository on
-   your local machine:
-
-   ```
-   git clone https://github.com/rust-lang/mdBook.git
-   ```
-
-   `cd` into `mdBook/` and run
-
-   ```
-   cargo build
-   ```
-
-   The resulting binary can be found in `mdBook/target/debug/` under the name
-   `mdBook` or `mdBook.exe`.
-
-
-## Usage
-
-mdBook is primarily used as a command line tool, even though it exposes
-all its functionality as a Rust crate for integration in other projects.
-
-Here are the main commands you will want to run. For a more exhaustive
-explanation, check out the [User Guide].
-
-- `mdbook init`
-
-    The init command will create a directory with the minimal boilerplate to
-    start with.
-
-    ```
-    book-test/
-    ├── book
-    └── src
-        ├── chapter_1.md
-        └── SUMMARY.md
-    ```
-
-    `book` and `src` are both directories. `src` contains the markdown files
-    that will be used to render the output to the `book` directory.
-
-    Please, take a look at the [CLI docs] for more information and some neat tricks.
-
-- `mdbook build`
-
-    This is the command you will run to render your book, it reads the
-    `SUMMARY.md` file to understand the structure of your book, takes the
-    markdown files in the source directory as input and outputs static html
-    pages that you can upload to a server.
-
-- `mdbook watch`
-
-    When you run this command, mdbook will watch your markdown files to rebuild
-    the book on every change. This avoids having to come back to the terminal
-    to type `mdbook build` over and over again.
-
-- `mdbook serve`
-
-    Does the same thing as `mdbook watch` but additionally serves the book at
-    `http://localhost:3000` (port is changeable) and reloads the browser when a
-    change occurs.
-
-- `mdbook clean`
-
-    Delete directory in which generated book is located.
-
-### 3rd Party Plugins
-
-The way a book is loaded and rendered can be configured by the user via third
-party plugins. These plugins are just programs which will be invoked during the
-build process and are split into roughly two categories, *preprocessors* and
-*renderers*.
-
-Preprocessors are used to transform a book before it is sent to a renderer.
-One example would be to replace all occurrences of
-`{{#include some_file.ext}}` with the contents of that file. Some existing
-preprocessors are:
-
-- `index` - a built-in preprocessor (enabled by default) which will transform
-  all `README.md` chapters to `index.md` so `foo/README.md` can be accessed via
-  the url `foo/` when published to a browser
-- `links` - a built-in preprocessor (enabled by default) for expanding the
-  `{{# playground}}` and `{{# include}}` helpers in a chapter.
-
-Renderers are given the final book so they can do something with it. This is
-typically used for, as the name suggests, rendering the document in a particular
-format, however there's nothing stopping a renderer from doing static analysis
-of a book in order to validate links or run tests. Some existing renderers are:
-
-- `html` - the built-in renderer which will generate a HTML version of the book
-- `markdown` - the built-in renderer (disabled by default) which will run
-  preprocessors then output the resulting Markdown. Useful for debugging
-  preprocessors.
-- [`linkcheck`] - a backend which will check that all links are valid
-- [`epub`] - an experimental EPUB generator
-
-> **Note for Developers:** Feel free to send us a PR if you've developed your
-> own plugin and want it mentioned here.
-
-A preprocessor or renderer is enabled by installing the appropriate program and
-then mentioning it in the book's `book.toml` file.
-
-```console
-$ cargo install mdbook-linkcheck
-$ edit book.toml && cat book.toml
-[book]
-title = "My Awesome Book"
-authors = ["Michael-F-Bryan"]
-
-[output.html]
-
-[output.linkcheck]  # enable the "mdbook-linkcheck" renderer
-
-$ mdbook build
-2018-10-20 13:57:51 [INFO] (mdbook::book): Book building has started
-2018-10-20 13:57:51 [INFO] (mdbook::book): Running the html backend
-2018-10-20 13:57:53 [INFO] (mdbook::book): Running the linkcheck backend
-```
-
-For more information on the plugin system, consult the [User Guide].
-
-### As a library
-
-Aside from the command line interface, this crate can also be used as a
-library. This means that you could integrate it in an existing project, like a
-web-app for example. Since the command line interface is just a wrapper around
-the library functionality, when you use this crate as a library you have full
-access to all the functionality of the command line interface with an easy to
-use API and more!
-
-See the [User Guide] and the [API docs] for more information.
-
-## Contributions
-
-Contributions are highly appreciated and encouraged! Don't hesitate to
-participate to discussions in the issues, propose new features and ask for
-help.
-
-If you are just starting out with Rust, there are a series of issues that are
-tagged [E-Easy] and **we will gladly mentor you** so that you can successfully
-go through the process of fixing a bug or adding a new feature! Let us know if
-you need any help.
-
-For more info about contributing, check out our [contribution guide] which helps
-you go through the build and contribution process!
-
-There is also a [rendered version][master-docs] of the latest API docs
-available, for those hacking on `master`.
-
+If you are interested in contributing to the development of mdBook, check out the [Contribution Guide].
 
 ## License
 
 All the code in this repository is released under the ***Mozilla Public License v2.0***, for more information take a look at the [LICENSE] file.
 
-
 [User Guide]: https://rust-lang.github.io/mdBook/
-[API docs]: https://docs.rs/mdbook/*/mdbook/
-[E-Easy]: https://github.com/rust-lang/mdBook/issues?q=is%3Aopen+is%3Aissue+label%3AE-Easy
 [contribution guide]: https://github.com/rust-lang/mdBook/blob/master/CONTRIBUTING.md
 [LICENSE]: https://github.com/rust-lang/mdBook/blob/master/LICENSE
-[releases]: https://github.com/rust-lang/mdBook/releases
-[Rust]: https://www.rust-lang.org/
-[CLI docs]: http://rust-lang.github.io/mdBook/cli/init.html
-[master-docs]: http://rust-lang.github.io/mdBook/
-[`linkcheck`]: https://crates.io/crates/mdbook-linkcheck
-[`epub`]: https://crates.io/crates/mdbook-epub

ci/install-hub.sh

@@ -1,24 +0,0 @@
-#!/usr/bin/env bash
-# Installs the `hub` executable into hub/bin
-set -ex
-case $1 in
-  ubuntu*)
-    curl -LsSf https://github.com/github/hub/releases/download/v2.12.8/hub-linux-amd64-2.12.8.tgz -o hub.tgz
-    mkdir hub
-    tar -xzvf hub.tgz --strip=1 -C hub
-    ;;
-  macos*)
-    curl -LsSf https://github.com/github/hub/releases/download/v2.12.8/hub-darwin-amd64-2.12.8.tgz -o hub.tgz
-    mkdir hub
-    tar -xzvf hub.tgz --strip=1 -C hub
-    ;;
-  windows*)
-    curl -LsSf https://github.com/github/hub/releases/download/v2.12.8/hub-windows-amd64-2.12.8.zip -o hub.zip
-    7z x hub.zip -ohub
-    ;;
-  *)
-    echo "OS should be first parameter, was: $1"
-    ;;
-esac
-
-echo "$PWD/hub/bin" >> $GITHUB_PATH

ci/install-rust.sh

@@ -13,6 +13,17 @@ TOOLCHAIN="$1"
 rustup set profile minimal
 rustup component remove --toolchain=$TOOLCHAIN rust-docs || echo "already removed"
 rustup update --no-self-update $TOOLCHAIN
+if [ -n "$2" ]
+then
+    TARGET="$2"
+    HOST=$(rustc -Vv | grep ^host: | sed -e "s/host: //g")
+    if [ "$HOST" != "$TARGET" ]
+    then
+        rustup component add llvm-tools-preview --toolchain=$TOOLCHAIN
+        rustup component add rust-std-$TARGET --toolchain=$TOOLCHAIN
+    fi
+fi
+
 rustup default $TOOLCHAIN
 rustup -V
 rustc -Vv

ci/make-release-asset.sh

@@ -11,16 +11,21 @@ fi
 TAG=${GITHUB_REF#*/tags/}
 
 host=$(rustc -Vv | grep ^host: | sed -e "s/host: //g")
+target=$2
+if [ "$host" != "$target" ]
+then
+  export "CARGO_TARGET_$(echo $target | tr a-z- A-Z_)_LINKER"=rust-lld
+fi
 export CARGO_PROFILE_RELEASE_LTO=true
-cargo build --bin mdbook --release
-cd target/release
+cargo build --locked --bin mdbook --release --target $target
+cd target/$target/release
 case $1 in
   ubuntu*)
-    asset="mdbook-$TAG-$host.tar.gz"
+    asset="mdbook-$TAG-$target.tar.gz"
     tar czf ../../$asset mdbook
     ;;
   macos*)
-    asset="mdbook-$TAG-$host.tar.gz"
+    asset="mdbook-$TAG-$target.tar.gz"
     # There is a bug with BSD tar on macOS where the first 8MB of the file are
     # sometimes all NUL bytes. See https://github.com/actions/cache/issues/403
     # and https://github.com/rust-lang/cargo/issues/8603 for some more
@@ -30,7 +35,7 @@ case $1 in
     tar czf ../../$asset mdbook
     ;;
   windows*)
-    asset="mdbook-$TAG-$host.zip"
+    asset="mdbook-$TAG-$target.zip"
     7z a ../../$asset mdbook.exe
     ;;
   *)
@@ -39,9 +44,10 @@ case $1 in
 esac
 cd ../..
 
-if [[ -z "$GITHUB_TOKEN" ]]
+if [[ -z "$GITHUB_ENV" ]]
 then
-  echo "$GITHUB_TOKEN not set, skipping deploy."
+  echo "GITHUB_ENV not set, run: gh release upload $TAG target/$asset"
 else
-  hub release edit -m "" --attach $asset $TAG
+  echo "MDBOOK_TAG=$TAG" >> $GITHUB_ENV
+  echo "MDBOOK_ASSET=target/$asset" >> $GITHUB_ENV
 fi

examples/nop-preprocessor.rs

@@ -1,17 +1,18 @@
 use crate::nop_lib::Nop;
-use clap::{App, Arg, ArgMatches, SubCommand};
+use clap::{Arg, ArgMatches, Command};
 use mdbook::book::Book;
 use mdbook::errors::Error;
 use mdbook::preprocess::{CmdPreprocessor, Preprocessor, PreprocessorContext};
+use semver::{Version, VersionReq};
 use std::io;
 use std::process;
 
-pub fn make_app() -> App<'static, 'static> {
-    App::new("nop-preprocessor")
+pub fn make_app() -> Command {
+    Command::new("nop-preprocessor")
         .about("A mdbook preprocessor which does precisely nothing")
         .subcommand(
-            SubCommand::with_name("supports")
-                .arg(Arg::with_name("renderer").required(true))
+            Command::new("supports")
+                .arg(Arg::new("renderer").required(true))
                 .about("Check whether a renderer is supported by this preprocessor"),
         )
 }
@@ -33,9 +34,10 @@ fn main() {
 fn handle_preprocessing(pre: &dyn Preprocessor) -> Result<(), Error> {
     let (ctx, book) = CmdPreprocessor::parse_input(io::stdin())?;
 
-    if ctx.mdbook_version != mdbook::MDBOOK_VERSION {
-        // We should probably use the `semver` crate to check compatibility
-        // here...
+    let book_version = Version::parse(&ctx.mdbook_version)?;
+    let version_req = VersionReq::parse(mdbook::MDBOOK_VERSION)?;
+
+    if !version_req.matches(&book_version) {
         eprintln!(
             "Warning: The {} plugin was built against version {} of mdbook, \
              but we're being called from version {}",
@@ -52,8 +54,10 @@ fn handle_preprocessing(pre: &dyn Preprocessor) -> Result<(), Error> {
 }
 
 fn handle_supports(pre: &dyn Preprocessor, sub_args: &ArgMatches) -> ! {
-    let renderer = sub_args.value_of("renderer").expect("Required argument");
-    let supported = pre.supports_renderer(&renderer);
+    let renderer = sub_args
+        .get_one::<String>("renderer")
+        .expect("Required argument");
+    let supported = pre.supports_renderer(renderer);
 
     // Signal whether the renderer is supported by exiting with 1 or 0.
     if supported {
@@ -99,4 +103,58 @@ mod nop_lib {
             renderer != "not-supported"
         }
     }
+
+    #[cfg(test)]
+    mod test {
+        use super::*;
+
+        #[test]
+        fn nop_preprocessor_run() {
+            let input_json = r##"[
+                {
+                    "root": "/path/to/book",
+                    "config": {
+                        "book": {
+                            "authors": ["AUTHOR"],
+                            "language": "en",
+                            "multilingual": false,
+                            "src": "src",
+                            "title": "TITLE"
+                        },
+                        "preprocessor": {
+                            "nop": {}
+                        }
+                    },
+                    "renderer": "html",
+                    "mdbook_version": "0.4.21"
+                },
+                {
+                    "sections": [
+                        {
+                            "Chapter": {
+                                "name": "Chapter 1",
+                                "content": "# Chapter 1\n",
+                                "number": [1],
+                                "sub_items": [],
+                                "path": "chapter_1.md",
+                                "source_path": "chapter_1.md",
+                                "parent_names": []
+                            }
+                        }
+                    ],
+                    "__non_exhaustive": null
+                }
+            ]"##;
+            let input_json = input_json.as_bytes();
+
+            let (ctx, book) = mdbook::preprocess::CmdPreprocessor::parse_input(input_json).unwrap();
+            let expected_book = book.clone();
+            let result = Nop::new().run(&ctx, book);
+            assert!(result.is_ok());
+
+            // The nop-preprocessor should not have made any changes to the book content.
+            let actual_book = result.unwrap();
+            assert_eq!(actual_book, expected_book);
+        }
+    }
 }

guide/book.toml

@@ -10,11 +10,16 @@ edition = "2018"
 [output.html]
 mathjax-support = true
 site-url = "/mdBook/"
+git-repository-url = "https://github.com/rust-lang/mdBook/tree/master/guide"
+edit-url-template = "https://github.com/rust-lang/mdBook/edit/master/guide/{path}"
 
 [output.html.playground]
 editable = true
 line-numbers = true
 
+[output.html.code.hidelines]
+python = "~"
+
 [output.html.search]
 limit-results = 20
 use-boolean-and = true
@@ -23,3 +28,6 @@ boost-hierarchy = 2
 boost-paragraph = 1
 expand = true
 heading-split-level = 2
+
+[output.html.redirect]
+"/format/config.html" = "configuration/index.html"

guide/src/README.md

@@ -1,25 +1,41 @@
-# mdBook
+# Introduction
 
-**mdBook** is a command line tool and Rust crate to create books using Markdown
-(as by the [CommonMark](https://commonmark.org/) specification) files. It's very
-similar to Gitbook but written in [Rust](http://www.rust-lang.org).
+**mdBook** is a command line tool to create books with Markdown.
+It is ideal for creating product or API documentation, tutorials, course materials or anything that requires a clean,
+easily navigable and customizable presentation.
 
-What you are reading serves as an example of the output of mdBook and at the
-same time as a high-level documentation.
+* Lightweight [Markdown] syntax helps you focus more on your content
+* Integrated [search] support
+* Color [syntax highlighting] for code blocks for many different languages
+* [Theme] files allow customizing the formatting of the output
+* [Preprocessors] can provide extensions for custom syntax and modifying content
+* [Backends] can render the output to multiple formats
+* Written in [Rust] for speed, safety, and simplicity
+* Automated testing of [Rust code samples]
 
-mdBook is free and open source, you can find the source code on
-[GitHub](https://github.com/rust-lang/mdBook). Issues and feature
-requests can be posted on the [GitHub issue
-tracker](https://github.com/rust-lang/mdBook/issues).
+This guide is an example of what mdBook produces.
+mdBook is used by the Rust programming language project, and [The Rust Programming Language][trpl] book is another fine example of mdBook in action.
 
-## API docs
+[Markdown]: format/markdown.md
+[search]: guide/reading.md#search
+[syntax highlighting]: format/theme/syntax-highlighting.md
+[theme]: format/theme/index.html
+[preprocessors]: format/configuration/preprocessors.md
+[backends]: format/configuration/renderers.md
+[Rust]: https://www.rust-lang.org/
+[trpl]: https://doc.rust-lang.org/book/
+[Rust code samples]: cli/test.md
 
-Alongside this book you can also read the [API
-docs](https://docs.rs/mdbook/*/mdbook/) generated by Rustdoc if you would like
-to use mdBook as a crate or write a new renderer and need a more low-level
-overview.
+## Contributing
+
+mdBook is free and open source. You can find the source code on
+[GitHub](https://github.com/rust-lang/mdBook) and issues and feature requests can be posted on
+the [GitHub issue tracker](https://github.com/rust-lang/mdBook/issues). mdBook relies on the community to fix bugs and
+add features: if you'd like to contribute, please read
+the [CONTRIBUTING](https://github.com/rust-lang/mdBook/blob/master/CONTRIBUTING.md) guide and consider opening
+a [pull request](https://github.com/rust-lang/mdBook/pulls).
 
 ## License
 
-mdBook, all the source code, is released under the [Mozilla Public License
-v2.0](https://www.mozilla.org/MPL/2.0/).
+The mdBook source and documentation are released under
+the [Mozilla Public License v2.0](https://www.mozilla.org/MPL/2.0/).

guide/src/SUMMARY.md

@@ -1,6 +1,15 @@
 # Summary
 
-- [mdBook](README.md)
+[Introduction](README.md)
+
+# User Guide
+
+- [Installation](guide/installation.md)
+- [Reading Books](guide/reading.md)
+- [Creating a Book](guide/creating.md)
+
+# Reference Guide
+
 - [Command Line Tool](cli/README.md)
     - [init](cli/init.md)
     - [build](cli/build.md)
@@ -8,16 +17,22 @@
     - [serve](cli/serve.md)
     - [test](cli/test.md)
     - [clean](cli/clean.md)
+    - [completions](cli/completions.md)
 - [Format](format/README.md)
     - [SUMMARY.md](format/summary.md)
         - [Draft chapter]()
-    - [Configuration](format/config.md)
+    - [Configuration](format/configuration/README.md)
+        - [General](format/configuration/general.md)
+        - [Preprocessors](format/configuration/preprocessors.md)
+        - [Renderers](format/configuration/renderers.md)
+        - [Environment Variables](format/configuration/environment-variables.md)
     - [Theme](format/theme/README.md)
         - [index.hbs](format/theme/index-hbs.md)
         - [Syntax highlighting](format/theme/syntax-highlighting.md)
         - [Editor](format/theme/editor.md)
     - [MathJax Support](format/mathjax.md)
     - [mdBook-specific features](format/mdbook.md)
+    - [Markdown](format/markdown.md)
 - [Continuous Integration](continuous-integration.md)
 - [For Developers](for_developers/README.md)
     - [Preprocessors](for_developers/preprocessors.md)

guide/src/cli/README.md

@@ -1,55 +1,14 @@
 # Command Line Tool
 
-mdBook can be used either as a command line tool or a [Rust
-crate](https://crates.io/crates/mdbook). Let's focus on the command line tool
-capabilities first.
+The `mdbook` command-line tool is used to create and build books.
+After you have [installed](../guide/installation.md) `mdbook`, you can run the `mdbook help` command in your terminal to view the available commands.
 
-## Install From Binaries
+This following sections provide in-depth information on the different commands available.
 
-Precompiled binaries are provided for major platforms on a best-effort basis.
-Visit [the releases page](https://github.com/rust-lang/mdBook/releases)
-to download the appropriate version for your platform.
-
-## Install From Source
-
-mdBook can also be installed from source
-
-### Pre-requisite
-
-mdBook is written in **[Rust](https://www.rust-lang.org/)** and therefore needs
-to be compiled with **Cargo**. If you haven't already installed Rust, please go
-ahead and [install it](https://www.rust-lang.org/tools/install) now.
-
-### Install Crates.io version
-
-Installing mdBook is relatively easy if you already have Rust and Cargo
-installed. You just have to type this snippet in your terminal:
-
-```bash
-cargo install mdbook
-```
-
-This will fetch the source code for the latest release from
-[Crates.io](https://crates.io/) and compile it. You will have to add Cargo's
-`bin` directory to your `PATH`.
-
-Run `mdbook help` in your terminal to verify if it works. Congratulations, you
-have installed mdBook!
-
-
-### Install Git version
-
-The **[git version](https://github.com/rust-lang/mdBook)** contains all
-the latest bug-fixes and features, that will be released in the next version on
-**Crates.io**, if you can't wait until the next release. You can build the git
-version yourself. Open your terminal and navigate to the directory of you
-choice. We need to clone the git repository and then build it with Cargo.
-
-```bash
-git clone --depth=1 https://github.com/rust-lang/mdBook.git
-cd mdBook
-cargo build --release
-```
-
-The executable `mdbook` will be in the `./target/release` folder, this should be
-added to the path.
+* [`mdbook init <directory>`](init.md) — Creates a new book with minimal boilerplate to start with.
+* [`mdbook build`](build.md) — Renders the book.
+* [`mdbook watch`](watch.md) — Rebuilds the book any time a source file changes.
+* [`mdbook serve`](serve.md) — Runs a web server to view the book, and rebuilds on changes.
+* [`mdbook test`](test.md) — Tests Rust code samples.
+* [`mdbook clean`](clean.md) — Deletes the rendered output.
+* [`mdbook completions`](completions.md) — Support for shell auto-completion.

guide/src/cli/build.md

@@ -7,7 +7,8 @@ mdbook build
 ```
 
 It will try to parse your `SUMMARY.md` file to understand the structure of your
-book and fetch the corresponding files.
+book and fetch the corresponding files. Note that files mentioned in `SUMMARY.md`
+but not present will be created.
 
 The rendered output will maintain the same directory structure as the source for
 convenience. Large books will therefore remain structured when rendered.

guide/src/cli/completions.md

@@ -0,0 +1,20 @@
+# The completions command
+
+The completions command is used to generate auto-completions for some common shells.
+This means when you type `mdbook` in your shell, you can then press your shell's auto-complete key (usually the Tab key) and it may display what the valid options are, or finish partial input.
+
+The completions first need to be installed for your shell:
+
+```bash
+# bash
+mdbook completions bash > ~/.local/share/bash-completion/completions/mdbook
+# oh-my-zsh
+mdbook completions zsh > ~/.oh-my-zsh/completions/_mdbook
+autoload -U compinit && compinit
+```
+
+The command prints a completion script for the given shell.
+Run `mdbook completions --help` for a list of supported shells.
+
+Where to place the completions depend on which shell you are using and your operating system.
+Consult your shell's documentation for more information one where to place the script.

guide/src/cli/init.md

@@ -25,9 +25,9 @@ book-test/
 - The `book` directory is where your book is rendered. All the output is ready
   to be uploaded to a server to be seen by your audience.
 
-- The `SUMMARY.md` file is the most important file, it's the skeleton of your
-  book and is discussed in more detail [in another
-  chapter](../format/summary.md)
+- The `SUMMARY.md` is the skeleton of your
+  book, and is discussed in more detail [in another
+  chapter](../format/summary.md).
 
 #### Tip: Generate chapters from SUMMARY.md
 
@@ -52,3 +52,31 @@ directory called `theme` in your source directory so that you can modify it.
 
 The theme is selectively overwritten, this means that if you don't want to
 overwrite a specific file, just delete it and the default file will be used.
+
+#### --title
+
+Specify a title for the book. If not supplied, an interactive prompt will ask for 
+a title. 
+
+```bash
+mdbook init --title="my amazing book"
+```
+
+#### --ignore
+
+Create a `.gitignore` file configured to ignore the `book` directory created when [building] a book. 
+If not supplied, an interactive prompt will ask whether it should be created.
+
+```bash
+mdbook init --ignore=none
+```
+
+```bash
+mdbook init --ignore=git
+```
+
+[building]: build.md
+
+#### --force
+
+Skip the prompts to create a `.gitignore` and for the title for the book.

guide/src/cli/serve.md

@@ -1,8 +1,15 @@
 # The serve command
 
-The serve command is used to preview a book by serving it over HTTP at
-`localhost:3000` by default. Additionally it watches the book's directory for
-changes, rebuilding the book and refreshing clients for each change. A websocket
+The serve command is used to preview a book by serving it via HTTP at
+`localhost:3000` by default: 
+
+```bash
+mdbook serve
+```
+
+The `serve` command  watches the book's `src` directory for
+changes, rebuilding the book and refreshing clients for each change; this includes
+re-creating deleted files still mentioned in `SUMMARY.md`! A websocket
 connection is used to trigger the client-side refresh.
 
 ***Note:*** *The `serve` command is for testing a book's HTML output, and is not
@@ -17,24 +24,14 @@ root instead of the current working directory.
 mdbook serve path/to/book
 ```
 
-#### Server options
+### Server options
 
-`serve` has four options: the HTTP port, the WebSocket port, the HTTP hostname
-to listen on, and the hostname for the browser to connect to for WebSockets.
-
-For example: suppose you have an nginx server for SSL termination which has a
-public address of 192.168.1.100 on port 80 and proxied that to 127.0.0.1 on port
-8000\. To run use the nginx proxy do:
+The `serve` hostname defaults to `localhost`, and the port defaults to `3000`. Either option can be specified on the command line:
 
 ```bash
-mdbook serve path/to/book -p 8000 -n 127.0.0.1 --websocket-hostname 192.168.1.100
+mdbook serve path/to/book -p 8000 -n 127.0.0.1 
 ```
 
-If you were to want live reloading for this you would need to proxy the
-websocket calls through nginx as well from `192.168.1.100:<WS_PORT>` to
-`127.0.0.1:<WS_PORT>`. The `-w` flag allows for the websocket port to be
-configured.
-
 #### --open
 
 When you use the `--open` (`-o`) flag, mdbook will open the book in your
@@ -55,5 +52,5 @@ contain file patterns described in the [gitignore
 documentation](https://git-scm.com/docs/gitignore). This can be useful for
 ignoring temporary files created by some editors.
 
-_Note: Only `.gitignore` from book root directory is used. Global
-`$HOME/.gitignore` or `.gitignore` files in parent directories are not used._
+***Note:*** *Only the `.gitignore` from the book root directory is used. Global
+`$HOME/.gitignore` or `.gitignore` files in parent directories are not used.*

guide/src/cli/test.md

@@ -6,8 +6,7 @@ of code examples that could get outdated. Therefore it is very important for
 them to be able to automatically test these code examples.
 
 mdBook supports a `test` command that will run all available tests in a book. At
-the moment, only rustdoc tests are supported, but this may be expanded upon in
-the future.
+the moment, only Rust tests are supported.
 
 #### Disable tests on a code block
 
@@ -43,7 +42,17 @@ mdbook test path/to/book
 The `--library-path` (`-L`) option allows you to add directories to the library
 search path used by `rustdoc` when it builds and tests the examples. Multiple
 directories can be specified with multiple options (`-L foo -L bar`) or with a
-comma-delimited list (`-L foo,bar`).
+comma-delimited list (`-L foo,bar`). The path should point to the Cargo
+[build cache](https://doc.rust-lang.org/cargo/guide/build-cache.html) `deps` directory that
+contains the build output of your project. For example, if your Rust project's book is in a directory
+named `my-book`, the following command would include the crate's dependencies when running `test`:
+
+```shell
+mdbook test my-book -L target/debug/deps/
+```
+
+See the `rustdoc` command-line [documentation](https://doc.rust-lang.org/rustdoc/command-line-arguments.html#-l--library-path-where-to-look-for-dependencies)
+for more information.
 
 #### --dest-dir
 
@@ -51,3 +60,8 @@ The `--dest-dir` (`-d`) option allows you to change the output directory for the
 book. Relative paths are interpreted relative to the book's root directory. If
 not specified it will default to the value of the `build.build-dir` key in
 `book.toml`, or to `./book`.
+
+#### --chapter
+
+The `--chapter` (`-c`) option allows you to test a specific chapter of the
+book using the chapter name or the relative path to the chapter.

guide/src/cli/watch.md

@@ -3,7 +3,8 @@
 The `watch` command is useful when you want your book to be rendered on every
 file change. You could repeatedly issue `mdbook build` every time a file is
 changed. But using `mdbook watch` once will watch your files and will trigger a
-build automatically whenever you modify a file.
+build automatically whenever you modify a file; this includes re-creating
+deleted files still mentioned in `SUMMARY.md`!
 
 #### Specify a directory
 

guide/src/continuous-integration.md

@@ -1,89 +1,121 @@
 # Running `mdbook` in Continuous Integration
 
-While the following examples use Travis CI, their principles should
-straightforwardly transfer to other continuous integration providers as well.
+There are a variety of services such as [GitHub Actions] or [GitLab CI/CD] which can be used to test and deploy your book automatically.
 
-## Ensuring Your Book Builds and Tests Pass
+The following provides some general guidelines on how to configure your service to run mdBook.
+Specific recipes can be found at the [Automated Deployment] wiki page.
 
-Here is a sample Travis CI `.travis.yml` configuration that ensures `mdbook
-build` and `mdbook test` run successfully. The key to fast CI turnaround times
-is caching `mdbook` installs, so that you aren't compiling `mdbook` on every CI
-run.
+[GitHub Actions]: https://docs.github.com/en/actions
+[GitLab CI/CD]: https://docs.gitlab.com/ee/ci/
+[Automated Deployment]: https://github.com/rust-lang/mdBook/wiki/Automated-Deployment
 
-```yaml
-language: rust
-sudo: false
+## Installing mdBook
 
-cache:
-  - cargo
+There are several different strategies for installing mdBook.
+The particular method depends on your needs and preferences.
 
-rust:
-  - stable
+### Pre-compiled binaries
 
-before_script:
-  - (test -x $HOME/.cargo/bin/cargo-install-update || cargo install cargo-update)
-  - (test -x $HOME/.cargo/bin/mdbook || cargo install --vers "^0.3" mdbook)
-  - cargo install-update -a
+Perhaps the easiest method is to use the pre-compiled binaries found on the [GitHub Releases page][releases].
+A simple approach would be to use the popular `curl` CLI tool to download the executable:
 
-script:
-  - mdbook build path/to/mybook && mdbook test path/to/mybook
+```sh
+mkdir bin
+curl -sSL https://github.com/rust-lang/mdBook/releases/download/v0.4.35/mdbook-v0.4.35-x86_64-unknown-linux-gnu.tar.gz | tar -xz --directory=bin
+bin/mdbook build
 ```
 
-## Deploying Your Book to GitHub Pages
+Some considerations for this approach:
 
-Following these instructions will result in your book being published to GitHub
-pages after a successful CI run on your repository's `master` branch.
+* This is relatively fast, and does not necessarily require dealing with caching.
+* This does not require installing Rust.
+* Specifying a specific URL means you have to manually update your script to get a new version.
+  This may be a benefit if you want to lock to a specific version.
+  However, some users prefer to automatically get a newer version when they are published.
+* You are reliant on the GitHub CDN being available.
 
-First, create a new GitHub "Personal Access Token" with the "public_repo"
-permissions (or "repo" for private repositories). Go to your repository's Travis
-CI settings page and add an environment variable named `GITHUB_TOKEN` that is
-marked secure and *not* shown in the logs.
+[releases]: https://github.com/rust-lang/mdBook/releases
 
-Then, append this snippet to your `.travis.yml` and update the path to the
-`book` directory:
+### Building from source
 
-```yaml
-deploy:
-  provider: pages
-  skip-cleanup: true
-  github-token: $GITHUB_TOKEN
-  local-dir: path/to/mybook/book
-  keep-history: false
-  on:
-    branch: master
+Building from source will require having Rust installed.
+Some services have Rust pre-installed, but if your service does not, you will need to add a step to install it.
+
+After Rust is installed, `cargo install` can be used to build and install mdBook.
+We recommend using a SemVer version specifier so that you get the latest **non-breaking** version of mdBook.
+For example:
+
+```sh
+cargo install mdbook --no-default-features --features search --vers "^0.4" --locked
 ```
 
-That's it!
+This includes several recommended options:
 
-### Deploying to GitHub Pages manually
+* `--no-default-features` — Disables features like the HTTP server used by `mdbook serve` that is likely not needed on CI.
+  This will speed up the build time significantly.
+* `--features search` — Disabling default features means you should then manually enable features that you want, such as the built-in [search] capability.
+* `--vers "^0.4"` — This will install the most recent version of the `0.4` series.
+  However, versions after like `0.5.0` won't be installed, as they may break your build.
+  Cargo will automatically upgrade mdBook if you have an older version already installed.
+* `--locked` — This will use the dependencies that were used when mdBook was released.
+  Without `--locked`, it will use the latest version of all dependencies, which may include some fixes since the last release, but may also (rarely) cause build problems.
 
-If your CI doesn't support GitHub pages, or you're deploying somewhere else
-with integrations such as Github Pages:
- *note: you may want to use different tmp dirs*:
+You will likely want to investigate caching options, as building mdBook can be somewhat slow.
 
-```console
-$> git worktree add /tmp/book gh-pages
-$> mdbook build
-$> rm -rf /tmp/book/* # this won't delete the .git directory
-$> cp -rp book/* /tmp/book/
-$> cd /tmp/book
-$> git add -A
-$> git commit 'new book message'
-$> git push origin gh-pages
-$> cd -
+[search]: guide/reading.md#search
+
+## Running tests
+
+You may want to run tests using [`mdbook test`] every time you push a change or create a pull request.
+This can be used to validate Rust code examples in the book.
+
+This will require having Rust installed.
+Some services have Rust pre-installed, but if your service does not, you will need to add a step to install it.
+
+Other than making sure the appropriate version of Rust is installed, there's not much more than just running `mdbook test` from the book directory.
+
+You may also want to consider running other kinds of tests, like [mdbook-linkcheck] which will check for broken links.
+Or if you have your own style checks, spell checker, or any other tests it might be good to run them in CI.
+
+[`mdbook test`]: cli/test.md
+[mdbook-linkcheck]: https://github.com/Michael-F-Bryan/mdbook-linkcheck#continuous-integration
+
+## Deploying
+
+You may want to automatically deploy your book.
+Some may want to do this every time a change is pushed, and others may want to only deploy when a specific release is tagged.
+
+You'll also need to understand the specifics on how to push a change to your web service.
+For example, [GitHub Pages] just requires committing the output onto a specific git branch.
+Other services may require using something like SSH to connect to a remote server.
+
+The basic outline is that you need to run `mdbook build` to generate the output, and then transfer the files (which are in the `book` directory) to the correct location.
+
+You may then want to consider if you need to invalidate any caches on your web service.
+
+See the [Automated Deployment] wiki page for examples of various different services.
+
+[GitHub Pages]: https://docs.github.com/en/pages
+
+### 404 handling
+
+mdBook automatically generates a 404 page to be used for broken links.
+The default output is a file named `404.html` at the root of the book.
+Some services like [GitHub Pages] will automatically use this page for broken links.
+For other services, you may want to consider configuring the web server to use this page as it will provide the reader navigation to get back to the book.
+
+If your book is not deployed at the root of the domain, then you should set the [`output.html.site-url`] setting so that the 404 page works correctly.
+It needs to know where the book is deployed in order to load the static files (like CSS) correctly.
+For example, this guide is deployed at <https://rust-lang.github.io/mdBook/>, and the `site-url` setting is configured like this:
+
+```toml
+# book.toml
+[output.html]
+site-url = "/mdBook/"
 ```
 
-Or put this into a Makefile rule:
+You can customize the look of the 404 page by creating a file named `src/404.md` in your book.
+If you want to use a different filename, you can set [`output.html.input-404`] to a different filename.
 
-```makefile
-.PHONY: deploy
-deploy: book
-	@echo "====> deploying to github"
-	git worktree add /tmp/book gh-pages
-	rm -rf /tmp/book/*
-	cp -rp book/* /tmp/book/
-	cd /tmp/book && \
-		git add -A && \
-		git commit -m "deployed on $(shell date) by ${USER}" && \
-		git push origin gh-pages
-```
+[`output.html.site-url`]: format/configuration/renderers.md#html-renderer-options
+[`output.html.input-404`]: format/configuration/renderers.md#html-renderer-options

guide/src/for_developers/README.md

@@ -24,8 +24,9 @@ The process of rendering a book project goes through several steps.
        exist
     - Load the book chapters into memory
     - Discover which preprocessors/backends should be used
-2. Run the preprocessors
-3. Call each backend in turn
+2. For each backend:
+   1. Run all the preprocessors.
+   2. Call the backend to render the processed result.
 
 
 ## Using `mdbook` as a Library

guide/src/for_developers/backends.md

@@ -5,22 +5,17 @@ rendering process. This program is passed a JSON representation of the book and
 configuration information via `stdin`. Once the backend receives this
 information it is free to do whatever it wants.
 
-There are already several alternative backends on GitHub which can be used as a
-rough example of how this is accomplished in practice.
+See [Configuring Renderers](../format/configuration/renderers.md) for more information about using backends.
 
-- [mdbook-linkcheck] - a simple program for verifying the book doesn't contain
-  any broken links
-- [mdbook-epub] - an EPUB renderer
-- [mdbook-test] - a program to run the book's contents through [rust-skeptic] to
-  verify everything compiles and runs correctly (similar to `rustdoc --test`)
+The community has developed several backends.
+See the [Third Party Plugins] wiki page for a list of available backends.
+
+## Setting Up
 
 This page will step you through creating your own alternative backend in the form
 of a simple word counting program. Although it will be written in Rust, there's
 no reason why it couldn't be accomplished using something like Python or Ruby.
 
-
-## Setting Up
-
 First you'll want to create a new binary program and add `mdbook` as a
 dependency.
 
@@ -329,39 +324,6 @@ generation or a warning).
 All environment variables are passed through to the backend, allowing you to use
 the usual `RUST_LOG` to control logging verbosity.
 
-## Handling missing backends
-
-If you enable a backend that isn't installed, the default behavior is to throw an error:
-
-```text
-The command `mdbook-wordcount` wasn't found, is the "wordcount" backend installed?
-If you want to ignore this error when the "wordcount" backend is not installed,
-set `optional = true` in the `[output.wordcount]` section of the book.toml configuration file.
-```
-
-This behavior can be changed by marking the backend as optional.
-
-```diff
-  [book]
-  title = "mdBook Documentation"
-  description = "Create book from markdown files. Like Gitbook but implemented in Rust"
-  authors = ["Mathieu David", "Michael-F-Bryan"]
-
-  [output.html]
-
-  [output.wordcount]
-  command = "python /path/to/wordcount.py"
-+ optional = true
-```
-
-This demotes the error to a warning, and it will instead look like this:
-
-```text
-The command was not found, but was marked as optional.
-    Command: wordcount
-```
-
-
 ## Wrapping Up
 
 Although contrived, hopefully this example was enough to show how you'd create
@@ -374,10 +336,7 @@ as a good example of how it's done in real life, so feel free to skim through
 the source code or ask questions.
 
 
-[mdbook-linkcheck]: https://github.com/Michael-F-Bryan/mdbook-linkcheck
-[mdbook-epub]: https://github.com/Michael-F-Bryan/mdbook-epub
-[mdbook-test]: https://github.com/Michael-F-Bryan/mdbook-test
-[rust-skeptic]: https://github.com/budziq/rust-skeptic
+[Third Party Plugins]: https://github.com/rust-lang/mdBook/wiki/Third-party-plugins
 [`RenderContext`]: https://docs.rs/mdbook/*/mdbook/renderer/struct.RenderContext.html
 [`RenderContext::from_json()`]: https://docs.rs/mdbook/*/mdbook/renderer/struct.RenderContext.html#method.from_json
 [`semver`]: https://crates.io/crates/semver

guide/src/for_developers/preprocessors.md

@@ -5,37 +5,27 @@ book is loaded and before it gets rendered, allowing you to update and mutate
 the book. Possible use cases are:
 
 - Creating custom helpers like `\{{#include /path/to/file.md}}`
-- Updating links so `[some chapter](some_chapter.md)` is automatically changed
-  to `[some chapter](some_chapter.html)` for the HTML renderer
 - Substituting in latex-style expressions (`$$ \frac{1}{3} $$`) with their
   mathjax equivalents
 
+See [Configuring Preprocessors](../format/configuration/preprocessors.md) for more information about using preprocessors.
 
 ## Hooking Into MDBook
 
 MDBook uses a fairly simple mechanism for discovering third party plugins.
-A new table is added to `book.toml` (e.g. `preprocessor.foo` for the `foo`
+A new table is added to `book.toml` (e.g. `[preprocessor.foo]` for the `foo`
 preprocessor) and then `mdbook` will try to invoke the `mdbook-foo` program as
 part of the build process.
 
-While preprocessors can be hard-coded to specify which backend it should be run
-for (e.g. it doesn't make sense for MathJax to be used for non-HTML renderers)
-with the `preprocessor.foo.renderer` key.
+Once the preprocessor has been defined and the build process starts, mdBook executes the command defined in the `preprocessor.foo.command` key twice.
+The first time it runs the preprocessor to determine if it supports the given renderer.
+mdBook passes two arguments to the process: the first argument is the string `supports` and the second argument is the renderer name.
+The preprocessor should exit with a status code 0 if it supports the given renderer, or return a non-zero exit code if it does not.
 
-```toml
-[book]
-title = "My Book"
-authors = ["Michael-F-Bryan"]
+If the preprocessor supports the renderer, then mdbook runs it a second time, passing JSON data into stdin.
+The JSON consists of an array of `[context, book]` where `context` is the serialized object [`PreprocessorContext`] and `book` is a [`Book`] object containing the content of the book.
 
-[preprocessor.foo]
-# The command can also be specified manually
-command = "python3 /path/to/foo.py"
-# Only run the `foo` preprocessor for the HTML and EPUB renderer
-renderer = ["html", "epub"]
-```
-
-In typical unix style, all inputs to the plugin will be written to `stdin` as
-JSON and `mdbook` will read from `stdout` if it is expecting output.
+The preprocessor should return the JSON format of the [`Book`] object to stdout, with any modifications it wishes to perform.
 
 The easiest way to get started is by creating your own implementation of the
 `Preprocessor` trait (e.g. in `lib.rs`) and then creating a shell binary which
@@ -71,7 +61,7 @@ The `chapter.content` is just a string which happens to be markdown. While it's
 entirely possible to use regular expressions or do a manual find & replace,
 you'll probably want to process the input into something more computer-friendly.
 The [`pulldown-cmark`][pc] crate implements a production-quality event-based
-Markdown parser, with the [`pulldown-cmark-to-cmark`][pctc] allowing you to
+Markdown parser, with the [`pulldown-cmark-to-cmark`][pctc] crate allowing you to
 translate events back into markdown text.
 
 The following code block shows how to remove all emphasis from markdown,
@@ -106,6 +96,33 @@ fn remove_emphasis(
 
 For everything else, have a look [at the complete example][example].
 
+## Implementing a preprocessor with a different language
+
+The fact that mdBook utilizes stdin and stdout to communicate with the preprocessors makes it easy to implement them in a language other than Rust.
+The following code shows how to implement a simple preprocessor in Python, which will modify the content of the first chapter.
+The example below follows the configuration shown above with `preprocessor.foo.command` actually pointing to a Python script.
+
+```python
+import json
+import sys
+
+
+if __name__ == '__main__':
+    if len(sys.argv) > 1: # we check if we received any argument
+        if sys.argv[1] == "supports": 
+            # then we are good to return an exit status code of 0, since the other argument will just be the renderer's name
+            sys.exit(0)
+
+    # load both the context and the book representations from stdin
+    context, book = json.load(sys.stdin)
+    # and now, we can just modify the content of the first chapter
+    book['sections'][0]['Chapter']['content'] = '# Hello'
+    # we are done with the book's modification, we can just print it to stdout, 
+    print(json.dumps(book))
+```
+
+
+
 [preprocessor-docs]: https://docs.rs/mdbook/latest/mdbook/preprocess/trait.Preprocessor.html
 [pc]: https://crates.io/crates/pulldown-cmark
 [pctc]: https://crates.io/crates/pulldown-cmark-to-cmark
@@ -113,3 +130,5 @@ For everything else, have a look [at the complete example][example].
 [an example no-op preprocessor]: https://github.com/rust-lang/mdBook/blob/master/examples/nop-preprocessor.rs
 [`CmdPreprocessor::parse_input()`]: https://docs.rs/mdbook/latest/mdbook/preprocess/trait.Preprocessor.html#method.parse_input
 [`Book::for_each_mut()`]: https://docs.rs/mdbook/latest/mdbook/book/struct.Book.html#method.for_each_mut
+[`PreprocessorContext`]: https://docs.rs/mdbook/latest/mdbook/preprocess/struct.PreprocessorContext.html
+[`Book`]: https://docs.rs/mdbook/latest/mdbook/book/struct.Book.html

guide/src/format/config.md

@@ -1,396 +0,0 @@
-# Configuration
-
-You can configure the parameters for your book in the ***book.toml*** file.
-
-Here is an example of what a ***book.toml*** file might look like:
-
-```toml
-[book]
-title = "Example book"
-author = "John Doe"
-description = "The example book covers examples."
-
-[rust]
-edition = "2018"
-
-[build]
-build-dir = "my-example-book"
-create-missing = false
-
-[preprocessor.index]
-
-[preprocessor.links]
-
-[output.html]
-additional-css = ["custom.css"]
-
-[output.html.search]
-limit-results = 15
-```
-
-## Supported configuration options
-
-It is important to note that **any** relative path specified in the
-configuration will always be taken relative from the root of the book where the
-configuration file is located.
-
-### General metadata
-
-This is general information about your book.
-
-- **title:** The title of the book
-- **authors:** The author(s) of the book
-- **description:** A description for the book, which is added as meta
-  information in the html `<head>` of each page
-- **src:** By default, the source directory is found in the directory named
-  `src` directly under the root folder. But this is configurable with the `src`
-  key in the configuration file.
-- **language:** The main language of the book, which is used as a language attribute `<html lang="en">` for example.
-
-**book.toml**
-```toml
-[book]
-title = "Example book"
-authors = ["John Doe", "Jane Doe"]
-description = "The example book covers examples."
-src = "my-src"  # the source files will be found in `root/my-src` instead of `root/src`
-language = "en"
-```
-
-### Rust options
-
-Options for the Rust language, relevant to running tests and playground
-integration.
-
-- **edition**: Rust edition to use by default for the code snippets. Default
-  is "2015". Individual code blocks can be controlled with the `edition2015`
-  or `edition2018` annotations, such as:
-
-  ~~~text
-  ```rust,edition2015
-  // This only works in 2015.
-  let try = true;
-  ```
-  ~~~
-
-### Build options
-
-This controls the build process of your book.
-
-- **build-dir:** The directory to put the rendered book in. By default this is
-  `book/` in the book's root directory.
-- **create-missing:** By default, any missing files specified in `SUMMARY.md`
-  will be created when the book is built (i.e. `create-missing = true`). If this
-  is `false` then the build process will instead exit with an error if any files
-  do not exist.
-- **use-default-preprocessors:** Disable the default preprocessors of (`links` &
-  `index`) by setting this option to `false`.
-
-  If you have the same, and/or other preprocessors declared via their table
-  of configuration, they will run instead.
-
-  - For clarity, with no preprocessor configuration, the default `links` and
-    `index` will run.
-  - Setting `use-default-preprocessors = false` will disable these
-    default preprocessors from running.
-  - Adding `[preprocessor.links]`, for example, will ensure, regardless of
-    `use-default-preprocessors` that `links` it will run.
-
-## Configuring Preprocessors
-
-The following preprocessors are available and included by default:
-
-- `links`: Expand the `{{ #playground }}`, `{{ #include }}`, and `{{ #rustdoc_include }}` handlebars
-  helpers in a chapter to include the contents of a file.
-- `index`: Convert all chapter files named `README.md` into `index.md`. That is
-  to say, all `README.md` would be rendered to an index file `index.html` in the
-  rendered book.
-
-
-**book.toml**
-```toml
-[build]
-build-dir = "build"
-create-missing = false
-
-[preprocessor.links]
-
-[preprocessor.index]
-```
-
-### Custom Preprocessor Configuration
-
-Like renderers, preprocessor will need to be given its own table (e.g.
-`[preprocessor.mathjax]`). In the section, you may then pass extra
-configuration to the preprocessor by adding key-value pairs to the table.
-
-For example
-
-```toml
-[preprocessor.links]
-# set the renderers this preprocessor will run for
-renderers = ["html"]
-some_extra_feature = true
-```
-
-#### Locking a Preprocessor dependency to a renderer
-
-You can explicitly specify that a preprocessor should run for a renderer by
-binding the two together.
-
-```toml
-[preprocessor.mathjax]
-renderers = ["html"]  # mathjax only makes sense with the HTML renderer
-```
-
-### Provide Your Own Command
-
-By default when you add a `[preprocessor.foo]` table to your `book.toml` file,
-`mdbook` will try to invoke the `mdbook-foo` executable. If you want to use a
-different program name or pass in command-line arguments, this behaviour can
-be overridden by adding a `command` field.
-
-```toml
-[preprocessor.random]
-command = "python random.py"
-```
-
-## Configuring Renderers
-
-### HTML renderer options
-
-The HTML renderer has a couple of options as well. All the options for the
-renderer need to be specified under the TOML table `[output.html]`.
-
-The following configuration options are available:
-
-- **theme:** mdBook comes with a default theme and all the resource files needed
-  for it. But if this option is set, mdBook will selectively overwrite the theme
-  files with the ones found in the specified folder.
-- **default-theme:** The theme color scheme to select by default in the
-  'Change Theme' dropdown. Defaults to `light`.
-- **preferred-dark-theme:** The default dark theme. This theme will be used if
-  the browser requests the dark version of the site via the
-  ['prefers-color-scheme'](https://developer.mozilla.org/en-US/docs/Web/CSS/@media/prefers-color-scheme)
-  CSS media query. Defaults to `navy`.
-- **curly-quotes:** Convert straight quotes to curly quotes, except for those
-  that occur in code blocks and code spans. Defaults to `false`.
-- **mathjax-support:** Adds support for [MathJax](mathjax.md). Defaults to
-  `false`.
-- **copy-fonts:** Copies fonts.css and respective font files to the output directory and use them in the default theme. Defaults to `true`.
-- **google-analytics:** If you use Google Analytics, this option lets you enable
-  it by simply specifying your ID in the configuration file.
-- **additional-css:** If you need to slightly change the appearance of your book
-  without overwriting the whole style, you can specify a set of stylesheets that
-  will be loaded after the default ones where you can surgically change the
-  style.
-- **additional-js:** If you need to add some behaviour to your book without
-  removing the current behaviour, you can specify a set of JavaScript files that
-  will be loaded alongside the default one.
-- **print:** A subtable for configuration print settings. mdBook by default adds
-  support for printing out the book as a single page. This is accessed using the
-  print icon on the top right of the book.
-- **no-section-label:** mdBook by defaults adds section label in table of
-  contents column. For example, "1.", "2.1". Set this option to true to disable
-  those labels. Defaults to `false`.
-- **fold:** A subtable for configuring sidebar section-folding behavior.
-- **playground:** A subtable for configuring various playground settings.
-- **search:** A subtable for configuring the in-browser search functionality.
-  mdBook must be compiled with the `search` feature enabled (on by default).
-- **git-repository-url:**  A url to the git repository for the book. If provided
-  an icon link will be output in the menu bar of the book.
-- **git-repository-icon:** The FontAwesome icon class to use for the git
-  repository link. Defaults to `fa-github`.
-- **redirect:** A subtable used for generating redirects when a page is moved.
-  The table contains key-value pairs where the key is where the redirect file
-  needs to be created, as an absolute path from the build directory, (e.g.
-  `/appendices/bibliography.html`). The value can be any valid URI the
-  browser should navigate to (e.g. `https://rust-lang.org/`,
-  `/overview.html`, or `../bibliography.html`).
-- **input-404:** The name of the markdown file used for misssing files.
-  The corresponding output file will be the same, with the extension replaced with `html`.
-  Defaults to `404.md`.
-- **site-url:** The url where the book will be hosted. This is required to ensure
-  navigation links and script/css imports in the 404 file work correctly, even when accessing
-  urls in subdirectories. Defaults to `/`.
-- **cname:** The DNS subdomain or apex domain at which your book will be hosted.
-  This string will be written to a file named CNAME in the root of your site, as
-  required by GitHub Pages (see [*Managing a custom domain for your GitHub Pages
-  site*][custom domain]).
-
-[custom domain]: https://docs.github.com/en/github/working-with-github-pages/managing-a-custom-domain-for-your-github-pages-site
-
-Available configuration options for the `[output.html.print]` table:
-
-- **enable:** Enable print support. When `false`, all print support will not be
-  rendered. Defaults to `true`.
-
-Available configuration options for the `[output.html.fold]` table:
-
-- **enable:** Enable section-folding. When off, all folds are open.
-  Defaults to `false`.
-- **level:** The higher the more folded regions are open. When level is 0, all
-  folds are closed. Defaults to `0`.
-
-Available configuration options for the `[output.html.playground]` table:
-
-- **editable:** Allow editing the source code. Defaults to `false`.
-- **copyable:** Display the copy button on code snippets. Defaults to `true`.
-- **copy-js:** Copy JavaScript files for the editor to the output directory.
-  Defaults to `true`.
-- **line-numbers** Display line numbers on editable sections of code. Requires both `editable` and `copy-js` to be `true`. Defaults to `false`.
-
-[Ace]: https://ace.c9.io/
-
-Available configuration options for the `[output.html.search]` table:
-
-- **enable:** Enables the search feature. Defaults to `true`.
-- **limit-results:** The maximum number of search results. Defaults to `30`.
-- **teaser-word-count:** The number of words used for a search result teaser.
-  Defaults to `30`.
-- **use-boolean-and:** Define the logical link between multiple search words. If
-  true, all search words must appear in each result. Defaults to `false`.
-- **boost-title:** Boost factor for the search result score if a search word
-  appears in the header. Defaults to `2`.
-- **boost-hierarchy:** Boost factor for the search result score if a search word
-  appears in the hierarchy. The hierarchy contains all titles of the parent
-  documents and all parent headings. Defaults to `1`.
-- **boost-paragraph:** Boost factor for the search result score if a search word
-  appears in the text. Defaults to `1`.
-- **expand:** True if search should match longer results e.g. search `micro`
-  should match `microwave`. Defaults to `true`.
-- **heading-split-level:** Search results will link to a section of the document
-  which contains the result. Documents are split into sections by headings this
-  level or less. Defaults to `3`. (`### This is a level 3 heading`)
-- **copy-js:** Copy JavaScript files for the search implementation to the output
-  directory. Defaults to `true`.
-
-This shows all available HTML output options in the **book.toml**:
-
-```toml
-[book]
-title = "Example book"
-authors = ["John Doe", "Jane Doe"]
-description = "The example book covers examples."
-
-[output.html]
-theme = "my-theme"
-default-theme = "light"
-preferred-dark-theme = "navy"
-curly-quotes = true
-mathjax-support = false
-copy-fonts = true
-google-analytics = "UA-123456-7"
-additional-css = ["custom.css", "custom2.css"]
-additional-js = ["custom.js"]
-no-section-label = false
-git-repository-url = "https://github.com/rust-lang/mdBook"
-git-repository-icon = "fa-github"
-site-url = "/example-book/"
-cname = "myproject.rs"
-input-404 = "not-found.md"
-
-[output.html.print]
-enable = true
-
-[output.html.fold]
-enable = false
-level = 0
-
-[output.html.playground]
-editable = false
-copy-js = true
-line-numbers = false
-
-[output.html.search]
-enable = true
-limit-results = 30
-teaser-word-count = 30
-use-boolean-and = true
-boost-title = 2
-boost-hierarchy = 1
-boost-paragraph = 1
-expand = true
-heading-split-level = 3
-copy-js = true
-
-[output.html.redirect]
-"/appendices/bibliography.html" = "https://rustc-dev-guide.rust-lang.org/appendix/bibliography.html"
-"/other-installation-methods.html" = "../infra/other-installation-methods.html"
-```
-
-### Markdown Renderer
-
-The Markdown renderer will run preprocessors and then output the resulting
-Markdown. This is mostly useful for debugging preprocessors, especially in
-conjunction with `mdbook test` to see the Markdown that `mdbook` is passing
-to `rustdoc`.
-
-The Markdown renderer is included with `mdbook` but disabled by default.
-Enable it by adding an empty table to your `book.toml` as follows:
-
-```toml
-[output.markdown]
-```
-
-There are no configuration options for the Markdown renderer at this time;
-only whether it is enabled or disabled.
-
-See [the preprocessors documentation](#configuring-preprocessors) for how to
-specify which preprocessors should run before the Markdown renderer.
-
-### Custom Renderers
-
-A custom renderer can be enabled by adding a `[output.foo]` table to your
-`book.toml`. Similar to [preprocessors](#configuring-preprocessors) this will
-instruct `mdbook` to pass a representation of the book to `mdbook-foo` for
-rendering. See the [alternative backends] chapter for more detail.
-
-The custom renderer has access to all the fields within its table (i.e.
-anything under `[output.foo]`). mdBook checks for two common fields:
-
-- **command:** The command to execute for this custom renderer. Defaults to
-  the name of the renderer with the `mdbook-` prefix (such as `mdbook-foo`).
-- **optional:** If `true`, then the command will be ignored if it is not
-  installed, otherwise mdBook will fail with an error. Defaults to `false`.
-
-[alternative backends]: ../for_developers/backends.md
-
-## Environment Variables
-
-All configuration values can be overridden from the command line by setting the
-corresponding environment variable. Because many operating systems restrict
-environment variables to be alphanumeric characters or `_`, the configuration
-key needs to be formatted slightly differently to the normal `foo.bar.baz` form.
-
-Variables starting with `MDBOOK_` are used for configuration. The key is created
-by removing the `MDBOOK_` prefix and turning the resulting string into
-`kebab-case`. Double underscores (`__`) separate nested keys, while a single
-underscore (`_`) is replaced with a dash (`-`).
-
-For example:
-
-- `MDBOOK_foo` -> `foo`
-- `MDBOOK_FOO` -> `foo`
-- `MDBOOK_FOO__BAR` -> `foo.bar`
-- `MDBOOK_FOO_BAR` -> `foo-bar`
-- `MDBOOK_FOO_bar__baz` -> `foo-bar.baz`
-
-So by setting the `MDBOOK_BOOK__TITLE` environment variable you can override the
-book's title without needing to touch your `book.toml`.
-
-> **Note:** To facilitate setting more complex config items, the value of an
-> environment variable is first parsed as JSON, falling back to a string if the
-> parse fails.
->
-> This means, if you so desired, you could override all book metadata when
-> building the book with something like
->
-> ```shell
-> $ export MDBOOK_BOOK="{'title': 'My Awesome Book', authors: ['Michael-F-Bryan']}"
-> $ mdbook build
-> ```
-
-The latter case may be useful in situations where `mdbook` is invoked from a
-script or CI, where it sometimes isn't possible to update the `book.toml` before
-building.

guide/src/format/configuration/README.md

@@ -0,0 +1,12 @@
+# Configuration
+
+This section details the configuration options available in the ***book.toml***:
+- **[General]** configuration including the `book`, `rust`, `build` sections
+- **[Preprocessor]** configuration for default and custom book preprocessors
+- **[Renderer]** configuration for the HTML, Markdown and custom renderers
+- **[Environment Variable]** configuration for overriding configuration options in your environment
+
+[General]: general.md
+[Preprocessor]: preprocessors.md
+[Renderer]: renderers.md
+[Environment Variable]: environment-variables.md

guide/src/format/configuration/environment-variables.md

@@ -0,0 +1,38 @@
+# Environment Variables
+
+All configuration values can be overridden from the command line by setting the
+corresponding environment variable. Because many operating systems restrict
+environment variables to be alphanumeric characters or `_`, the configuration
+key needs to be formatted slightly differently to the normal `foo.bar.baz` form.
+
+Variables starting with `MDBOOK_` are used for configuration. The key is created
+by removing the `MDBOOK_` prefix and turning the resulting string into
+`kebab-case`. Double underscores (`__`) separate nested keys, while a single
+underscore (`_`) is replaced with a dash (`-`).
+
+For example:
+
+- `MDBOOK_foo` -> `foo`
+- `MDBOOK_FOO` -> `foo`
+- `MDBOOK_FOO__BAR` -> `foo.bar`
+- `MDBOOK_FOO_BAR` -> `foo-bar`
+- `MDBOOK_FOO_bar__baz` -> `foo-bar.baz`
+
+So by setting the `MDBOOK_BOOK__TITLE` environment variable you can override the
+book's title without needing to touch your `book.toml`.
+
+> **Note:** To facilitate setting more complex config items, the value of an
+> environment variable is first parsed as JSON, falling back to a string if the
+> parse fails.
+>
+> This means, if you so desired, you could override all book metadata when
+> building the book with something like
+>
+> ```shell
+> $ export MDBOOK_BOOK='{"title": "My Awesome Book", "authors": ["Michael-F-Bryan"]}'
+> $ mdbook build
+> ```
+
+The latter case may be useful in situations where `mdbook` is invoked from a
+script or CI, where it sometimes isn't possible to update the `book.toml` before
+building.

guide/src/format/configuration/general.md

@@ -0,0 +1,118 @@
+# General Configuration
+
+You can configure the parameters for your book in the ***book.toml*** file.
+
+Here is an example of what a ***book.toml*** file might look like:
+
+```toml
+[book]
+title = "Example book"
+authors = ["John Doe"]
+description = "The example book covers examples."
+
+[rust]
+edition = "2018"
+
+[build]
+build-dir = "my-example-book"
+create-missing = false
+
+[preprocessor.index]
+
+[preprocessor.links]
+
+[output.html]
+additional-css = ["custom.css"]
+
+[output.html.search]
+limit-results = 15
+```
+
+## Supported configuration options
+
+It is important to note that **any** relative path specified in the
+configuration will always be taken relative from the root of the book where the
+configuration file is located.
+
+### General metadata
+
+This is general information about your book.
+
+- **title:** The title of the book
+- **authors:** The author(s) of the book
+- **description:** A description for the book, which is added as meta
+  information in the html `<head>` of each page
+- **src:** By default, the source directory is found in the directory named
+  `src` directly under the root folder. But this is configurable with the `src`
+  key in the configuration file.
+- **language:** The main language of the book, which is used as a language attribute `<html lang="en">` for example.
+  This is also used to derive the direction of text (RTL, LTR) within the book.
+- **text-direction**: The direction of text in the book: Left-to-right (LTR) or Right-to-left (RTL). Possible values: `ltr`, `rtl`.
+  When not specified, the text direction is derived from the book's `language` attribute.
+
+**book.toml**
+```toml
+[book]
+title = "Example book"
+authors = ["John Doe", "Jane Doe"]
+description = "The example book covers examples."
+src = "my-src"  # the source files will be found in `root/my-src` instead of `root/src`
+language = "en"
+text-direction = "ltr"
+```
+
+### Rust options
+
+Options for the Rust language, relevant to running tests and playground
+integration.
+
+```toml
+[rust]
+edition = "2015"   # the default edition for code blocks
+```
+
+- **edition**: Rust edition to use by default for the code snippets. Default
+  is "2015". Individual code blocks can be controlled with the `edition2015`, 
+  `edition2018` or `edition2021` annotations, such as:
+
+  ~~~text
+  ```rust,edition2015
+  // This only works in 2015.
+  let try = true;
+  ```
+  ~~~
+
+### Build options
+
+This controls the build process of your book.
+
+```toml
+[build]
+build-dir = "book"                # the directory where the output is placed
+create-missing = true             # whether or not to create missing pages
+use-default-preprocessors = true  # use the default preprocessors
+extra-watch-dirs = []             # directories to watch for triggering builds
+```
+
+- **build-dir:** The directory to put the rendered book in. By default this is
+  `book/` in the book's root directory.
+  This can overridden with the `--dest-dir` CLI option.
+- **create-missing:** By default, any missing files specified in `SUMMARY.md`
+  will be created when the book is built (i.e. `create-missing = true`). If this
+  is `false` then the build process will instead exit with an error if any files
+  do not exist.
+- **use-default-preprocessors:** Disable the default preprocessors (of `links` &
+  `index`) by setting this option to `false`.
+
+  If you have the same, and/or other preprocessors declared via their table
+  of configuration, they will run instead.
+
+  - For clarity, with no preprocessor configuration, the default `links` and
+    `index` will run.
+  - Setting `use-default-preprocessors = false` will disable these
+    default preprocessors from running.
+  - Adding `[preprocessor.links]`, for example, will ensure, regardless of
+    `use-default-preprocessors` that `links` it will run.
+- **extra-watch-dirs**: A list of paths to directories that will be watched in
+  the `watch` and `serve` commands. Changes to files under these directories will
+  trigger rebuilds. Useful if your book depends on files outside its `src` directory.

guide/src/format/configuration/preprocessors.md

@@ -0,0 +1,87 @@
+# Configuring Preprocessors
+
+Preprocessors are extensions that can modify the raw Markdown source before it gets sent to the renderer.
+
+The following preprocessors are built-in and included by default:
+
+- `links`: Expands the `{{ #playground }}`, `{{ #include }}`, and `{{ #rustdoc_include }}` handlebars
+  helpers in a chapter to include the contents of a file.
+  See [Including files] for more.
+- `index`: Convert all chapter files named `README.md` into `index.md`. That is
+  to say, all `README.md` would be rendered to an index file `index.html` in the
+  rendered book.
+
+The built-in preprocessors can be disabled with the [`build.use-default-preprocessors`] config option.
+
+The community has developed several preprocessors.
+See the [Third Party Plugins] wiki page for a list of available preprocessors.
+
+For information on how to create a new preprocessor, see the [Preprocessors for Developers] chapter.
+
+[Including files]: ../mdbook.md#including-files
+[`build.use-default-preprocessors`]: general.md#build-options
+[Third Party Plugins]: https://github.com/rust-lang/mdBook/wiki/Third-party-plugins
+[Preprocessors for Developers]: ../../for_developers/preprocessors.md
+
+## Custom Preprocessor Configuration
+
+Preprocessors can be added by including a `preprocessor` table in `book.toml` with the name of the preprocessor.
+For example, if you have a preprocessor called `mdbook-example`, then you can include it with:
+
+```toml
+[preprocessor.example]
+```
+
+With this table, mdBook will execute the `mdbook-example` preprocessor.
+
+This table can include additional key-value pairs that are specific to the preprocessor.
+For example, if our example preprocessor needed some extra configuration options:
+
+```toml
+[preprocessor.example]
+some-extra-feature = true
+```
+
+## Locking a Preprocessor dependency to a renderer
+
+You can explicitly specify that a preprocessor should run for a renderer by
+binding the two together.
+
+```toml
+[preprocessor.example]
+renderers = ["html"]  # example preprocessor only runs with the HTML renderer
+```
+
+## Provide Your Own Command
+
+By default when you add a `[preprocessor.foo]` table to your `book.toml` file,
+`mdbook` will try to invoke the `mdbook-foo` executable. If you want to use a
+different program name or pass in command-line arguments, this behaviour can
+be overridden by adding a `command` field.
+
+```toml
+[preprocessor.random]
+command = "python random.py"
+```
+
+## Require A Certain Order
+
+The order in which preprocessors are run can be controlled with the `before` and `after` fields.
+For example, suppose you want your `linenos` preprocessor to process lines that may have been `{{#include}}`d; then you want it to run after the built-in `links` preprocessor, which you can require using either the `before` or `after` field:
+
+```toml
+[preprocessor.linenos]
+after = [ "links" ]
+```
+
+or
+
+```toml
+[preprocessor.links]
+before = [ "linenos" ]
+```
+
+It would also be possible, though redundant, to specify both of the above in the same config file.
+
+Preprocessors having the same priority specified through `before` and `after` are sorted by name.
+Any infinite loops will be detected and produce an error.

guide/src/format/configuration/renderers.md

@@ -0,0 +1,317 @@
+# Configuring Renderers
+
+Renderers (also called "backends") are responsible for creating the output of the book.
+
+The following backends are built-in:
+
+* [`html`](#html-renderer-options) — This renders the book to HTML.
+  This is enabled by default if no other `[output]` tables are defined in `book.toml`.
+* [`markdown`](#markdown-renderer) — This outputs the book as markdown after running the preprocessors.
+  This is useful for debugging preprocessors.
+
+The community has developed several backends.
+See the [Third Party Plugins] wiki page for a list of available backends.
+
+For information on how to create a new backend, see the [Backends for Developers] chapter.
+
+[Third Party Plugins]: https://github.com/rust-lang/mdBook/wiki/Third-party-plugins
+[Backends for Developers]: ../../for_developers/backends.md
+
+## Output tables
+
+Backends can be added by including a `output` table in `book.toml` with the name of the backend.
+For example, if you have a backend called `mdbook-wordcount`, then you can include it with:
+
+```toml
+[output.wordcount]
+```
+
+With this table, mdBook will execute the `mdbook-wordcount` backend.
+
+This table can include additional key-value pairs that are specific to the backend.
+For example, if our example backend needed some extra configuration options:
+
+```toml
+[output.wordcount]
+ignores = ["Example Chapter"]
+```
+
+If you define any `[output]` tables, then the `html` backend is not enabled by default.
+If you want to keep the `html` backend running, then just include it in the `book.toml` file.
+For example:
+
+```toml
+[book]
+title = "My Awesome Book"
+
+[output.wordcount]
+
+[output.html]
+```
+
+If more than one `output` table is included, this changes the behavior for the layout of the output directory.
+If there is only one backend, then it places its output directly in the `book` directory (see [`build.build-dir`] to override this location).
+If there is more than one backend, then each backend is placed in a separate directory underneath `book`.
+For example, the above would have directories `book/html` and `book/wordcount`.
+
+[`build.build-dir`]: general.md#build-options
+
+### Custom backend commands
+
+By default when you add an `[output.foo]` table to your `book.toml` file,
+`mdbook` will try to invoke the `mdbook-foo` executable.
+If you want to use a different program name or pass in command-line arguments,
+this behaviour can be overridden by adding a `command` field.
+
+```toml
+[output.random]
+command = "python random.py"
+```
+
+### Optional backends
+
+If you enable a backend that isn't installed, the default behavior is to throw an error.
+This behavior can be changed by marking the backend as optional:
+
+```toml
+[output.wordcount]
+optional = true
+```
+
+This demotes the error to a warning.
+
+
+## HTML renderer options
+
+The HTML renderer has a variety of options detailed below.
+They should be specified in the `[output.html]` table of the `book.toml` file.
+
+```toml
+# Example book.toml file with all output options.
+[book]
+title = "Example book"
+authors = ["John Doe", "Jane Doe"]
+description = "The example book covers examples."
+
+[output.html]
+theme = "my-theme"
+default-theme = "light"
+preferred-dark-theme = "navy"
+curly-quotes = true
+mathjax-support = false
+copy-fonts = true
+additional-css = ["custom.css", "custom2.css"]
+additional-js = ["custom.js"]
+no-section-label = false
+git-repository-url = "https://github.com/rust-lang/mdBook"
+git-repository-icon = "fa-github"
+edit-url-template = "https://github.com/rust-lang/mdBook/edit/master/guide/{path}"
+site-url = "/example-book/"
+cname = "myproject.rs"
+input-404 = "not-found.md"
+```
+
+The following configuration options are available:
+
+- **theme:** mdBook comes with a default theme and all the resource files needed
+  for it. But if this option is set, mdBook will selectively overwrite the theme
+  files with the ones found in the specified folder.
+- **default-theme:** The theme color scheme to select by default in the
+  'Change Theme' dropdown. Defaults to `light`.
+- **preferred-dark-theme:** The default dark theme. This theme will be used if
+  the browser requests the dark version of the site via the
+  ['prefers-color-scheme'](https://developer.mozilla.org/en-US/docs/Web/CSS/@media/prefers-color-scheme)
+  CSS media query. Defaults to `navy`.
+- **curly-quotes:** Convert straight quotes to curly quotes, except for those
+  that occur in code blocks and code spans. Defaults to `false`.
+- **mathjax-support:** Adds support for [MathJax](../mathjax.md). Defaults to
+  `false`.
+- **copy-fonts:** (**Deprecated**) If `true` (the default), mdBook uses its built-in fonts which are copied to the output directory.
+  If `false`, the built-in fonts will not be used.
+  This option is deprecated. If you want to define your own custom fonts,
+  create a `theme/fonts/fonts.css` file and store the fonts in the `theme/fonts/` directory.
+- **google-analytics:** This field has been deprecated and will be removed in a future release.
+  Use the `theme/head.hbs` file to add the appropriate Google Analytics code instead.
+- **additional-css:** If you need to slightly change the appearance of your book
+  without overwriting the whole style, you can specify a set of stylesheets that
+  will be loaded after the default ones where you can surgically change the
+  style.
+- **additional-js:** If you need to add some behaviour to your book without
+  removing the current behaviour, you can specify a set of JavaScript files that
+  will be loaded alongside the default one.
+- **no-section-label:** mdBook by defaults adds numeric section labels in the table of
+  contents column. For example, "1.", "2.1". Set this option to true to disable
+  those labels. Defaults to `false`.
+- **git-repository-url:**  A url to the git repository for the book. If provided
+  an icon link will be output in the menu bar of the book.
+- **git-repository-icon:** The FontAwesome icon class to use for the git
+  repository link. Defaults to `fa-github` which looks like <i class="fa fa-github"></i>.
+  If you are not using GitHub, another option to consider is `fa-code-fork` which looks like <i class="fa fa-code-fork"></i>.
+- **edit-url-template:** Edit url template, when provided shows a
+  "Suggest an edit" button (which looks like <i class="fa fa-edit"></i>) for directly jumping to editing the currently
+  viewed page. For e.g. GitHub projects set this to
+  `https://github.com/<owner>/<repo>/edit/<branch>/{path}` or for
+  Bitbucket projects set it to
+  `https://bitbucket.org/<owner>/<repo>/src/<branch>/{path}?mode=edit`
+  where {path} will be replaced with the full path of the file in the
+  repository.
+- **input-404:** The name of the markdown file used for missing files.
+  The corresponding output file will be the same, with the extension replaced with `html`.
+  Defaults to `404.md`.
+- **site-url:** The url where the book will be hosted. This is required to ensure
+  navigation links and script/css imports in the 404 file work correctly, even when accessing
+  urls in subdirectories. Defaults to `/`. If `site-url` is set,
+  make sure to use document relative links for your assets, meaning they should not start with `/`.
+- **cname:** The DNS subdomain or apex domain at which your book will be hosted.
+  This string will be written to a file named CNAME in the root of your site, as
+  required by GitHub Pages (see [*Managing a custom domain for your GitHub Pages
+  site*][custom domain]).
+
+[custom domain]: https://docs.github.com/en/github/working-with-github-pages/managing-a-custom-domain-for-your-github-pages-site
+
+### `[output.html.print]`
+
+The `[output.html.print]` table provides options for controlling the printable output.
+By default, mdBook will include an icon on the top right of the book (which looks like <i class="fa fa-print"></i>) that will print the book as a single page.
+
+```toml
+[output.html.print]
+enable = true    # include support for printable output
+page-break = true # insert page-break after each chapter
+```
+
+- **enable:** Enable print support. When `false`, all print support will not be
+  rendered. Defaults to `true`.
+- **page-break:** Insert page breaks between chapters. Defaults to `true`.
+
+### `[output.html.fold]`
+
+The `[output.html.fold]` table provides options for controlling folding of the chapter listing in the navigation sidebar.
+
+```toml
+[output.html.fold]
+enable = false    # whether or not to enable section folding
+level = 0         # the depth to start folding
+```
+
+- **enable:** Enable section-folding. When off, all folds are open.
+  Defaults to `false`.
+- **level:** The higher the more folded regions are open. When level is 0, all
+  folds are closed. Defaults to `0`.
+
+### `[output.html.playground]`
+
+The `[output.html.playground]` table provides options for controlling Rust sample code blocks, and their integration with the [Rust Playground].
+
+[Rust Playground]: https://play.rust-lang.org/
+
+```toml
+[output.html.playground]
+editable = false         # allows editing the source code
+copyable = true          # include the copy button for copying code snippets
+copy-js = true           # includes the JavaScript for the code editor
+line-numbers = false     # displays line numbers for editable code
+runnable = true          # displays a run button for rust code
+```
+
+- **editable:** Allow editing the source code. Defaults to `false`.
+- **copyable:** Display the copy button on code snippets. Defaults to `true`.
+- **copy-js:** Copy JavaScript files for the editor to the output directory.
+  Defaults to `true`.
+- **line-numbers:** Display line numbers on editable sections of code. Requires both `editable` and `copy-js` to be `true`. Defaults to `false`.
+- **runnable:** Displays a run button for rust code snippets. Changing this to `false` will disable the run in playground feature globally. Defaults to `true`.
+
+[Ace]: https://ace.c9.io/
+
+### `[output.html.code]`
+
+The `[output.html.code]` table provides options for controlling code blocks.
+
+```toml
+[output.html.code]
+# A prefix string per language (one or more chars).
+# Any line starting with whitespace+prefix is hidden.
+hidelines = { python = "~" }
+```
+
+- **hidelines:** A table that defines how [hidden code lines](../mdbook.md#hiding-code-lines) work for each language.
+  The key is the language and the value is a string that will cause code lines starting with that prefix to be hidden.
+
+### `[output.html.search]`
+
+The `[output.html.search]` table provides options for controlling the built-in text [search].
+mdBook must be compiled with the `search` feature enabled (on by default).
+
+[search]: ../../guide/reading.md#search
+
+```toml
+[output.html.search]
+enable = true            # enables the search feature
+limit-results = 30       # maximum number of search results
+teaser-word-count = 30   # number of words used for a search result teaser
+use-boolean-and = true   # multiple search terms must all match
+boost-title = 2          # ranking boost factor for matches in headers
+boost-hierarchy = 1      # ranking boost factor for matches in page names
+boost-paragraph = 1      # ranking boost factor for matches in text
+expand = true            # partial words will match longer terms
+heading-split-level = 3  # link results to heading levels
+copy-js = true           # include Javascript code for search
+```
+
+- **enable:** Enables the search feature. Defaults to `true`.
+- **limit-results:** The maximum number of search results. Defaults to `30`.
+- **teaser-word-count:** The number of words used for a search result teaser.
+  Defaults to `30`.
+- **use-boolean-and:** Define the logical link between multiple search words. If
+  true, all search words must appear in each result. Defaults to `false`.
+- **boost-title:** Boost factor for the search result score if a search word
+  appears in the header. Defaults to `2`.
+- **boost-hierarchy:** Boost factor for the search result score if a search word
+  appears in the hierarchy. The hierarchy contains all titles of the parent
+  documents and all parent headings. Defaults to `1`.
+- **boost-paragraph:** Boost factor for the search result score if a search word
+  appears in the text. Defaults to `1`.
+- **expand:** True if search should match longer results e.g. search `micro`
+  should match `microwave`. Defaults to `true`.
+- **heading-split-level:** Search results will link to a section of the document
+  which contains the result. Documents are split into sections by headings this
+  level or less. Defaults to `3`. (`### This is a level 3 heading`)
+- **copy-js:** Copy JavaScript files for the search implementation to the output
+  directory. Defaults to `true`.
+
+### `[output.html.redirect]`
+
+The `[output.html.redirect]` table provides a way to add redirects.
+This is useful when you move, rename, or remove a page to ensure that links to the old URL will go to the new location.
+
+```toml
+[output.html.redirect]
+"/appendices/bibliography.html" = "https://rustc-dev-guide.rust-lang.org/appendix/bibliography.html"
+"/other-installation-methods.html" = "../infra/other-installation-methods.html"
+```
+
+The table contains key-value pairs where the key is where the redirect file needs to be created, as an absolute path from the build directory, (e.g. `/appendices/bibliography.html`).
+The value can be any valid URI the browser should navigate to (e.g. `https://rust-lang.org/`, `/overview.html`, or `../bibliography.html`).
+
+This will generate an HTML page which will automatically redirect to the given location.
+Note that the source location does not support `#` anchor redirects.
+
+## Markdown Renderer
+
+The Markdown renderer will run preprocessors and then output the resulting
+Markdown. This is mostly useful for debugging preprocessors, especially in
+conjunction with `mdbook test` to see the Markdown that `mdbook` is passing
+to `rustdoc`.
+
+The Markdown renderer is included with `mdbook` but disabled by default.
+Enable it by adding an empty table to your `book.toml` as follows:
+
+```toml
+[output.markdown]
+```
+
+There are no configuration options for the Markdown renderer at this time;
+only whether it is enabled or disabled.
+
+See [the preprocessors documentation](preprocessors.md) for how to
+specify which preprocessors should run before the Markdown renderer.

guide/src/format/example.rs

@@ -1,6 +1,6 @@
 fn main() {
     println!("Hello World!");
 #
-#    // You can even hide lines! :D
-#   println!("I am hidden! Expand the code snippet to see me");
+#     // You can even hide lines! :D
+#     println!("I am hidden! Expand the code snippet to see me");
 }

guide/src/format/images/rust-logo-blk.svg

@@ -0,0 +1 @@
+<svg height="144" width="144" xmlns="http://www.w3.org/2000/svg"><path d="m71.05 23.68c-26.06 0-47.27 21.22-47.27 47.27s21.22 47.27 47.27 47.27 47.27-21.22 47.27-47.27-21.22-47.27-47.27-47.27zm-.07 4.2a3.1 3.11 0 0 1 3.02 3.11 3.11 3.11 0 0 1 -6.22 0 3.11 3.11 0 0 1 3.2-3.11zm7.12 5.12a38.27 38.27 0 0 1 26.2 18.66l-3.67 8.28c-.63 1.43.02 3.11 1.44 3.75l7.06 3.13a38.27 38.27 0 0 1 .08 6.64h-3.93c-.39 0-.55.26-.55.64v1.8c0 4.24-2.39 5.17-4.49 5.4-2 .23-4.21-.84-4.49-2.06-1.18-6.63-3.14-8.04-6.24-10.49 3.85-2.44 7.85-6.05 7.85-10.87 0-5.21-3.57-8.49-6-10.1-3.42-2.25-7.2-2.7-8.22-2.7h-40.6a38.27 38.27 0 0 1 21.41-12.08l4.79 5.02c1.08 1.13 2.87 1.18 4 .09zm-44.2 23.02a3.11 3.11 0 0 1 3.02 3.11 3.11 3.11 0 0 1 -6.22 0 3.11 3.11 0 0 1 3.2-3.11zm74.15.14a3.11 3.11 0 0 1 3.02 3.11 3.11 3.11 0 0 1 -6.22 0 3.11 3.11 0 0 1 3.2-3.11zm-68.29.5h5.42v24.44h-10.94a38.27 38.27 0 0 1 -1.24-14.61l6.7-2.98c1.43-.64 2.08-2.31 1.44-3.74zm22.62.26h12.91c.67 0 4.71.77 4.71 3.8 0 2.51-3.1 3.41-5.65 3.41h-11.98zm0 17.56h9.89c.9 0 4.83.26 6.08 5.28.39 1.54 1.26 6.56 1.85 8.17.59 1.8 2.98 5.4 5.53 5.4h16.14a38.27 38.27 0 0 1 -3.54 4.1l-6.57-1.41c-1.53-.33-3.04.65-3.37 2.18l-1.56 7.28a38.27 38.27 0 0 1 -31.91-.15l-1.56-7.28c-.33-1.53-1.83-2.51-3.36-2.18l-6.43 1.38a38.27 38.27 0 0 1 -3.32-3.92h31.27c.35 0 .59-.06.59-.39v-11.06c0-.32-.24-.39-.59-.39h-9.15zm-14.43 25.33a3.11 3.11 0 0 1 3.02 3.11 3.11 3.11 0 0 1 -6.22 0 3.11 3.11 0 0 1 3.2-3.11zm46.05.14a3.11 3.11 0 0 1 3.02 3.11 3.11 3.11 0 0 1 -6.22 0 3.11 3.11 0 0 1 3.2-3.11z"/><path d="m115.68 70.95a44.63 44.63 0 0 1 -44.63 44.63 44.63 44.63 0 0 1 -44.63-44.63 44.63 44.63 0 0 1 44.63-44.63 44.63 44.63 0 0 1 44.63 44.63zm-.84-4.31 6.96 4.31-6.96 4.31 5.98 5.59-7.66 2.87 4.78 6.65-8.09 1.32 3.4 7.46-8.19-.29 1.88 7.98-7.98-1.88.29 8.19-7.46-3.4-1.32 8.09-6.65-4.78-2.87 7.66-5.59-5.98-4.31 6.96-4.31-6.96-5.59 5.98-2.87-7.66-6.65 4.78-1.32-8.09-7.46 3.4.29-8.19-7.98 1.88 1.88-7.98-8.19.29 3.4-7.46-8.09-1.32 4.78-6.65-7.66-2.87 5.98-5.59-6.96-4.31 6.96-4.31-5.98-5.59 7.66-2.87-4.78-6.65 8.09-1.32-3.4-7.46 8.19.29-1.88-7.98 7.98 1.88-.29-8.19 7.46 3.4 1.32-8.09 6.65 4.78 2.87-7.66 5.59 5.98 4.31-6.96 4.31 6.96 5.59-5.98 2.87 7.66 6.65-4.78 1.32 8.09 7.46-3.4-.29 8.19 7.98-1.88-1.88 7.98 8.19-.29-3.4 7.46 8.09 1.32-4.78 6.65 7.66 2.87z" fill-rule="evenodd" stroke="#000" stroke-linecap="round" stroke-linejoin="round" stroke-width="3"/></svg>

guide/src/format/markdown.md

@@ -0,0 +1,235 @@
+# Markdown
+
+mdBook's [parser](https://github.com/raphlinus/pulldown-cmark) adheres to the [CommonMark](https://commonmark.org/) specification with some extensions described below.
+You can take a quick [tutorial](https://commonmark.org/help/tutorial/),
+or [try out](https://spec.commonmark.org/dingus/) CommonMark in real time. A complete Markdown overview is out of scope for 
+this documentation, but below is a high level overview of some of the basics. For a more in-depth experience, check out the
+[Markdown Guide](https://www.markdownguide.org).
+
+## Text and Paragraphs
+
+Text is rendered relatively predictably: 
+
+```markdown
+Here is a line of text.
+
+This is a new line.
+```
+
+Will look like you might expect:
+
+Here is a line of text.
+
+This is a new line.
+
+## Headings
+
+Headings use the `#` marker and should be on a line by themselves. More `#` mean smaller headings:
+
+```markdown
+### A heading 
+
+Some text.
+
+#### A smaller heading 
+
+More text.
+```
+
+### A heading 
+
+Some text.
+
+#### A smaller heading 
+
+More text.
+
+## Lists
+
+Lists can be unordered or ordered. Ordered lists will order automatically:
+
+```markdown
+* milk
+* eggs
+* butter
+
+1. carrots
+1. celery
+1. radishes
+```
+
+* milk
+* eggs
+* butter
+
+1. carrots
+1. celery
+1. radishes
+
+## Links
+
+Linking to a URL or local file is easy:
+
+```markdown
+Use [mdBook](https://github.com/rust-lang/mdBook). 
+
+Read about [mdBook](mdbook.md).
+
+A bare url: <https://www.rust-lang.org>.
+```
+
+Use [mdBook](https://github.com/rust-lang/mdBook). 
+
+Read about [mdBook](mdbook.md).
+
+A bare url: <https://www.rust-lang.org>.
+
+----
+
+Relative links that end with `.md` will be converted to the `.html` extension.
+It is recommended to use `.md` links when possible.
+This is useful when viewing the Markdown file outside of mdBook, for example on GitHub or GitLab which render Markdown automatically.
+
+Links to `README.md` will be converted to `index.html`.
+This is done since some services like GitHub render README files automatically, but web servers typically expect the root file to be called `index.html`.
+
+You can link to individual headings with `#` fragments.
+For example, `mdbook.md#text-and-paragraphs` would link to the [Text and Paragraphs](#text-and-paragraphs) section above.
+The ID is created by transforming the heading such as converting to lowercase and replacing spaces with dashes.
+You can click on any heading and look at the URL in your browser to see what the fragment looks like.
+
+## Images
+
+Including images is simply a matter of including a link to them, much like in the _Links_ section above. The following markdown
+includes the Rust logo SVG image found in the `images` directory at the same level as this file:
+
+```markdown
+![The Rust Logo](images/rust-logo-blk.svg)
+```
+
+Produces the following HTML when built with mdBook:
+
+```html
+<p><img src="images/rust-logo-blk.svg" alt="The Rust Logo" /></p>
+```
+
+Which, of course displays the image like so:
+
+![The Rust Logo](images/rust-logo-blk.svg)
+
+## Extensions
+
+mdBook has several extensions beyond the standard CommonMark specification.
+
+### Strikethrough
+
+Text may be rendered with a horizontal line through the center by wrapping the
+text with one or two tilde characters on each side:
+
+```text
+An example of ~~strikethrough text~~.
+```
+
+This example will render as:
+
+> An example of ~~strikethrough text~~.
+
+This follows the [GitHub Strikethrough extension][strikethrough].
+
+### Footnotes
+
+A footnote generates a small numbered link in the text which when clicked
+takes the reader to the footnote text at the bottom of the item. The footnote
+label is written similarly to a link reference with a caret at the front. The
+footnote text is written like a link reference definition, with the text
+following the label. Example:
+
+```text
+This is an example of a footnote[^note].
+
+[^note]: This text is the contents of the footnote, which will be rendered
+    towards the bottom.
+```
+
+This example will render as:
+
+> This is an example of a footnote[^note].
+>
+> [^note]: This text is the contents of the footnote, which will be rendered
+>     towards the bottom.
+
+The footnotes are automatically numbered based on the order the footnotes are
+written.
+
+### Tables
+
+Tables can be written using pipes and dashes to draw the rows and columns of
+the table. These will be translated to HTML table matching the shape. Example:
+
+```text
+| Header1 | Header2 |
+|---------|---------|
+| abc     | def     |
+```
+
+This example will render similarly to this:
+
+| Header1 | Header2 |
+|---------|---------|
+| abc     | def     |
+
+See the specification for the [GitHub Tables extension][tables] for more
+details on the exact syntax supported.
+
+### Task lists
+
+Task lists can be used as a checklist of items that have been completed.
+Example:
+
+```md
+- [x] Complete task
+- [ ] Incomplete task
+```
+
+This will render as:
+
+> - [x] Complete task
+> - [ ] Incomplete task
+
+See the specification for the [task list extension] for more details.
+
+### Smart punctuation
+
+Some ASCII punctuation sequences will be automatically turned into fancy Unicode
+characters:
+
+| ASCII sequence | Unicode |
+|----------------|---------|
+| `--`           | –       |
+| `---`          | —       |
+| `...`          | …       |
+| `"`            | “ or ”, depending on context |
+| `'`            | ‘ or ’, depending on context |
+
+So, no need to manually enter those Unicode characters!
+
+This feature is disabled by default.
+To enable it, see the [`output.html.curly-quotes`] config option.
+
+[strikethrough]: https://github.github.com/gfm/#strikethrough-extension-
+[tables]: https://github.github.com/gfm/#tables-extension-
+[task list extension]: https://github.github.com/gfm/#task-list-items-extension-
+[`output.html.curly-quotes`]: configuration/renderers.md#html-renderer-options
+
+### Heading attributes
+
+Headings can have a custom HTML ID and classes. This lets you maintain the same ID even if you change the heading's text, it also lets you add multiple classes in the heading.
+
+Example:
+```md
+# Example heading { #first .class1 .class2 }
+```
+
+This makes the level 1 heading with the content `Example heading`, ID `first`, and classes `class1` and `class2`. Note that the attributes should be space-separated.
+
+More information can be found in the [heading attrs spec page](https://github.com/raphlinus/pulldown-cmark/blob/master/specs/heading_attrs.txt).

guide/src/format/mdbook.md

@@ -2,10 +2,11 @@
 
 ## Hiding code lines
 
-There is a feature in mdBook that lets you hide code lines by prepending them
-with a `#` [like you would with Rustdoc][rustdoc-hide].
+There is a feature in mdBook that lets you hide code lines by prepending them with a specific prefix.
 
-[rustdoc-hide]: https://doc.rust-lang.org/stable/rustdoc/documentation-tests.html#hiding-portions-of-the-example
+For the Rust language, you can use the `#` character as a prefix which will hide lines [like you would with Rustdoc][rustdoc-hide].
+
+[rustdoc-hide]: https://doc.rust-lang.org/stable/rustdoc/write-documentation/documentation-tests.html#hiding-portions-of-the-example
 
 ```bash
 # fn main() {
@@ -21,12 +22,113 @@ Will render as
 ```rust
 # fn main() {
     let x = 5;
-    let y = 7;
+    let y = 6;
 
     println!("{}", x + y);
 # }
 ```
 
+When you tap or hover the mouse over the code block, there will be an eyeball icon (<i class="fa fa-eye"></i>) which will toggle the visibility of the hidden lines.
+
+By default, this only works for code examples that are annotated with `rust`.
+However, you can define custom prefixes for other languages by adding a new line-hiding prefix in your `book.toml` with the language name and prefix character(s):
+
+```toml
+[output.html.code.hidelines]
+python = "~"
+```
+
+The prefix will hide any lines that begin with the given prefix. With the python prefix shown above, this:
+
+```bash
+~hidden()
+nothidden():
+~    hidden()
+    ~hidden()
+    nothidden()
+```
+
+will render as
+
+```python
+~hidden()
+nothidden():
+~    hidden()
+    ~hidden()
+    nothidden()
+```
+
+This behavior can be overridden locally with a different prefix. This has the same effect as above:
+
+~~~markdown
+```python,hidelines=!!!
+!!!hidden()
+nothidden():
+!!!    hidden()
+    !!!hidden()
+    nothidden()
+```
+~~~
+
+## Rust Playground
+
+Rust language code blocks will automatically get a play button (<i class="fa fa-play"></i>) which will execute the code and display the output just below the code block.
+This works by sending the code to the [Rust Playground].
+
+```rust
+println!("Hello, World!");
+```
+
+If there is no `main` function, then the code is automatically wrapped inside one.
+
+If you wish to disable the play button for a code block, you can include the `noplayground` option on the code block like this:
+
+~~~markdown
+```rust,noplayground
+let mut name = String::new();
+std::io::stdin().read_line(&mut name).expect("failed to read line");
+println!("Hello {}!", name);
+```
+~~~
+
+Or, if you wish to disable the play button for all code blocks in your book, you can write the config to the `book.toml` like this.
+
+```toml
+[output.html.playground]
+runnable = false
+```
+
+## Rust code block attributes
+
+Additional attributes can be included in Rust code blocks with comma, space, or tab-separated terms just after the language term. For example:
+
+~~~markdown
+```rust,ignore
+# This example won't be tested.
+panic!("oops!");
+```
+~~~
+
+These are particularly important when using [`mdbook test`] to test Rust examples.
+These use the same attributes as [rustdoc attributes], with a few additions:
+
+* `editable` — Enables the [editor].
+* `noplayground` — Removes the play button, but will still be tested.
+* `mdbook-runnable` — Forces the play button to be displayed.
+  This is intended to be combined with the `ignore` attribute for examples that should not be tested, but you want to allow the reader to run.
+* `ignore` — Will not be tested and no play button is shown, but it is still highlighted as Rust syntax.
+* `should_panic` — When executed, it should produce a panic.
+* `no_run` — The code is compiled when tested, but it is not run.
+  The play button is also not shown.
+* `compile_fail` — The code should fail to compile.
+* `edition2015`, `edition2018`, `edition2021` — Forces the use of a specific Rust edition.
+  See [`rust.edition`] to set this globally.
+
+[`mdbook test`]: ../cli/test.md
+[rustdoc attributes]: https://doc.rust-lang.org/rustdoc/documentation-tests.html#attributes
+[editor]: theme/editor.md
+[`rust.edition`]: configuration/general.md#rust-options
+
 ## Including files
 
 With the following syntax, you can include files into your book:
@@ -40,7 +142,7 @@ The path to the file has to be relative from the current source file.
 mdBook will interpret included files as Markdown. Since the include command
 is usually used for inserting code snippets and examples, you will often
 wrap the command with ```` ``` ```` to display the file contents without
-interpretting them.
+interpreting them.
 
 ````hbs
 ```
@@ -49,7 +151,7 @@ interpretting them.
 ````
 
 ## Including portions of a file
-Often you only need a specific part of the file e.g. relevant lines for an
+Often you only need a specific part of the file, e.g. relevant lines for an
 example. We support four different modes of partial includes:
 
 ```hbs
@@ -68,8 +170,8 @@ consisting of lines 2 to 10.
 To avoid breaking your book when modifying included files, you can also
 include a specific section using anchors instead of line numbers.
 An anchor is a pair of matching lines. The line beginning an anchor must
-match the regex "ANCHOR:\s*[\w_-]+" and similarly the ending line must match
-the regex "ANCHOR_END:\s*[\w_-]+". This allows you to put anchors in
+match the regex `ANCHOR:\s*[\w_-]+` and similarly the ending line must match
+the regex `ANCHOR_END:\s*[\w_-]+`. This allows you to put anchors in
 any kind of commented line.
 
 Consider the following file to include:
@@ -156,7 +258,7 @@ To call the `add_one` function, we pass it an `i32` and bind the returned value
 #
 # fn add_one(num: i32) -> i32 {
 #     num + 1
-#}
+# }
 ```
 ````
 
@@ -170,7 +272,7 @@ That is, it looks like this (click the "expand" icon to see the rest of the file
 #
 # fn add_one(num: i32) -> i32 {
 #     num + 1
-#}
+# }
 ```
 
 ## Inserting runnable Rust files
@@ -191,4 +293,72 @@ Here is what a rendered code snippet looks like:
 
 {{#playground example.rs}}
 
+Any additional values passed after the filename will be included as attributes of the code block.
+For example `\{{#playground example.rs editable}}` will create the code block like the following:
+
+~~~markdown
+```rust,editable
+# Contents of example.rs here.
+```
+~~~
+
+And the `editable` attribute will enable the [editor] as described at [Rust code block attributes](#rust-code-block-attributes).
+
 [Rust Playground]: https://play.rust-lang.org/
+
+## Controlling page \<title\>
+
+A chapter can set a \<title\> that is different from its entry in the table of
+contents (sidebar) by including a `\{{#title ...}}` near the top of the page.
+
+```hbs
+\{{#title My Title}}
+```
+
+## HTML classes provided by mdBook
+
+<img class="right" src="images/rust-logo-blk.svg" alt="The Rust logo">
+
+### `class="left"` and `"right"`
+
+These classes are provided by default, for inline HTML to float images.
+
+```html
+<img class="right" src="images/rust-logo-blk.svg" alt="The Rust logo">
+```
+
+### `class="hidden"`
+
+HTML tags with class `hidden` will not be shown.
+
+```html
+<div class="hidden">This will not be seen.</div>
+```
+
+<div class="hidden">This will not be seen.</div>
+
+### `class="warning"`
+
+To make a warning or similar note stand out, wrap it in a warning div.
+
+```html
+<div class="warning">
+
+This is a bad thing that you should pay attention to.
+
+Warning blocks should be used sparingly in documentation, to avoid "warning
+fatique," where people are trained to ignore them because they usually don't
+matter for what they're doing.
+
+</div>
+```
+
+<div class="warning">
+
+This is a bad thing that you should pay attention to.
+
+Warning blocks should be used sparingly in documentation, to avoid "warning
+fatique," where people are trained to ignore them because they usually don't
+matter for what they're doing.
+
+</div>

guide/src/format/summary.md

@@ -4,63 +4,96 @@ The summary file is used by mdBook to know what chapters to include, in what
 order they should appear, what their hierarchy is and where the source files
 are. Without this file, there is no book.
 
-Even though `SUMMARY.md` is a markdown file, the formatting is very strict to
-allow for easy parsing. Let's see how you should format your `SUMMARY.md` file.
+This markdown file must be named `SUMMARY.md`. Its formatting
+is very strict and must follow the structure outlined below to allow for easy
+parsing. Any element not specified below, be it formatting or textual, is likely
+to be ignored at best, or may cause an error when attempting to build the book.
 
-#### Structure
+### Structure
 
-1. ***Title*** It's common practice to begin with a title, generally <code
-   class="language-markdown"># Summary</code>. But it is not mandatory, the
-   parser just ignores it. So you can too if you feel like it.
-
-2. ***Prefix Chapter*** Before the main numbered chapters you can add a couple
-   of elements that will not be numbered. This is useful for forewords,
-   introductions, etc. There are however some constraints. You can not nest
-   prefix chapters, they should all be on the root level. And you can not add
-   prefix chapters once you have added numbered chapters.
+1. ***Title*** - While optional, it's common practice to begin with a title, generally <code
+   class="language-markdown"># Summary</code>. This is ignored by the parser however, and
+   can be omitted.
    ```markdown
-   [Title of prefix element](relative/path/to/markdown.md)
+   # Summary
    ```
 
-3. ***Part Title:*** Headers can be used as a title for the following numbered
+1. ***Prefix Chapter*** - Before the main numbered chapters, prefix chapters can be added
+   that will not be numbered. This is useful for forewords,
+   introductions, etc. There are, however, some constraints. Prefix chapters cannot be
+   nested; they should all be on the root level. And you cannot add
+   prefix chapters once you have added numbered chapters.
+   ```markdown
+   [A Prefix Chapter](relative/path/to/markdown.md)
+
+   - [First Chapter](relative/path/to/markdown2.md)
+   ```
+
+1. ***Part Title*** - Headers can be used as a title for the following numbered
    chapters. This can be used to logically separate different sections
-   of book. The title is rendered as unclickable text.
+   of the book. The title is rendered as unclickable text.
    Titles are optional, and the numbered chapters can be broken into as many
    parts as desired.
+   ```markdown
+   # My Part Title
 
-4. ***Numbered Chapter*** Numbered chapters are the main content of the book,
-   they will be numbered and can be nested, resulting in a nice hierarchy
-   (chapters, sub-chapters, etc.)
+   - [First Chapter](relative/path/to/markdown.md)
+   ```
+
+1. ***Numbered Chapter*** - Numbered chapters outline the main content of the book
+   and can be nested, resulting in a nice hierarchy
+   (chapters, sub-chapters, etc.).
    ```markdown
    # Title of Part
 
-   - [Title of the Chapter](relative/path/to/markdown.md)
+   - [First Chapter](relative/path/to/markdown.md)
+   - [Second Chapter](relative/path/to/markdown2.md)
+      - [Sub Chapter](relative/path/to/markdown3.md)
 
    # Title of Another Part
 
-   - [More Chapters](relative/path/to/markdown2.md)
+   - [Another Chapter](relative/path/to/markdown4.md)
    ```
-   You can either use `-` or `*` to indicate a numbered chapter.
+   Numbered chapters can be denoted with either `-` or `*` (do not mix delimiters). 
+   
+1. ***Suffix Chapter*** - Like prefix chapters, suffix chapters are unnumbered, but they come after 
+   numbered chapters.
+   ```markdown
+   - [Last Chapter](relative/path/to/markdown.md)
 
-5. ***Suffix Chapter*** After the numbered chapters you can add a couple of
-   non-numbered chapters. They are the same as prefix chapters but come after
-   the numbered chapters instead of before.
+   [Title of Suffix Chapter](relative/path/to/markdown2.md)
+   ```
 
-All other elements are unsupported and will be ignored at best or result in an
-error.
+1. ***Draft chapters*** - Draft chapters are chapters without a file and thus content.
+   The purpose of a draft chapter is to signal future chapters still to be written.
+   Or when still laying out the structure of the book to avoid creating the files
+   while you are still changing the structure of the book a lot.
+   Draft chapters will be rendered in the HTML renderer as disabled links in the table
+   of contents, as you can see for the next chapter in the table of contents on the left.
+   Draft chapters are written like normal chapters but without writing the path to the file.
+   ```markdown
+   - [Draft Chapter]()
+   ```
 
-#### Other elements
+1. ***Separators*** - Separators can be added before, in between, and after any other element. They result
+   in an HTML rendered line in the built table of contents.  A separator is
+   a line containing exclusively dashes and at least three of them: `---`.
+   ```markdown
+   # My Part Title
+   
+   [A Prefix Chapter](relative/path/to/markdown.md)
 
-- ***Separators*** In between chapters you can add a separator. In the HTML renderer
-  this will result in a line being rendered in the table of contents. A separator is
-  a line containing exclusively dashes and at least three of them: `---`.
-- ***Draft chapters*** Draft chapters are chapters without a file and thus content.
-  The purpose of a draft chapter is to signal future chapters still to be written.
-  Or when still laying out the structure of the book to avoid creating the files
-  while you are still changing the structure of the book a lot.
-  Draft chapters will be rendered in the HTML renderer as disabled links in the table
-  of contents, as you can see for the next chapter in the table of contents on the left.
-  Draft chapters are written like normal chapters but without writing the path to the file
-  ```markdown
-  - [Draft chapter]()
-  ```
+   ---
+
+   - [First Chapter](relative/path/to/markdown2.md)
+   ```
+  
+
+### Example
+
+Below is the markdown source for the `SUMMARY.md` for this guide, with the resulting table
+of contents as rendered to the left.
+
+```markdown
+{{#include ../SUMMARY.md}}
+```

guide/src/format/theme/README.md

@@ -1,6 +1,6 @@
 # Theme
 
-The default renderer uses a [handlebars](http://handlebarsjs.com/) template to
+The default renderer uses a [handlebars](https://handlebarsjs.com) template to
 render your markdown files and comes with a default theme included in the mdBook
 binary.
 
@@ -14,9 +14,11 @@ Here are the files you can override:
 - **_index.hbs_** is the handlebars template.
 - **_head.hbs_** is appended to the HTML `<head>` section.
 - **_header.hbs_** content is appended on top of every book page.
-- **_book.css_** is the style used in the output. If you want to change the
-  design of your book, this is probably the file you want to modify. Sometimes
-  in conjunction with `index.hbs` when you want to radically change the layout.
+- **_css/_** contains the CSS files for styling the book.
+    - **_css/chrome.css_** is for UI elements.
+    - **_css/general.css_** is the base styles.
+    - **_css/print.css_** is the style for printer output.
+    - **_css/variables.css_** contains variables used in other CSS files.
 - **_book.js_** is mostly used to add client side functionality, like hiding /
   un-hiding the sidebar, changing the theme, ...
 - **_highlight.js_** is the JavaScript that is used to highlight code snippets,
@@ -24,6 +26,8 @@ Here are the files you can override:
 - **_highlight.css_** is the theme used for the code highlighting.
 - **_favicon.svg_** and **_favicon.png_** the favicon that will be used. The SVG
   version is used by [newer browsers].
+- **fonts/fonts.css** contains the definition of which fonts to load.
+  Custom fonts can be included in the `fonts` directory.
 
 Generally, when you want to tweak the theme, you don't need to override all the
 files. If you only need changes in the stylesheet, there is no point in
@@ -33,12 +37,16 @@ built-in ones, they will not get updated with new fixes / features.
 **Note:** When you override a file, it is possible that you break some
 functionality. Therefore I recommend to use the file from the default theme as
 template and only add / modify what you need. You can copy the default theme
-into your source directory automatically by using `mdbook init --theme` just
+into your source directory automatically by using `mdbook init --theme` and just
 remove the files you don't want to override.
 
+`mdbook init --theme` will not create every file listed above.
+Some files, such as `head.hbs`, do not have built-in equivalents.
+Just create the file if you need it.
+
 If you completely replace all built-in themes, be sure to also set
 [`output.html.preferred-dark-theme`] in the config, which defaults to the
 built-in `navy` theme.
 
-[`output.html.preferred-dark-theme`]: ../config.md#html-renderer-options
+[`output.html.preferred-dark-theme`]: ../configuration/renderers.md#html-renderer-options
 [newer browsers]: https://caniuse.com/#feat=link-icon-svg

guide/src/format/theme/editor.md

@@ -12,12 +12,14 @@ editable = true
 To make a specific block available for editing, the attribute `editable` needs
 to be added to it:
 
-<pre><code class="language-markdown">```rust,editable
+~~~markdown
+```rust,editable
 fn main() {
     let number = 5;
     print!("{}", number);
 }
-```</code></pre>
+```
+~~~
 
 The above will result in this editable playground:
 
@@ -33,7 +35,7 @@ Note the new `Undo Changes` button in the editable playgrounds.
 ## Customizing the Editor
 
 By default, the editor is the [Ace](https://ace.c9.io/) editor, but, if desired,
-the functionality may be overriden by providing a different folder:
+the functionality may be overridden by providing a different folder:
 
 ```toml
 [output.html.playground]
@@ -42,5 +44,5 @@ editor = "/path/to/editor"
 ```
 
 Note that for the editor changes to function correctly, the `book.js` inside of
-the `theme` folder will need to be overriden as it has some couplings with the
+the `theme` folder will need to be overridden as it has some couplings with the
 default Ace editor.

guide/src/format/theme/index-hbs.md

@@ -19,7 +19,7 @@ Here is a list of the properties that are exposed:
 
 - ***language*** Language of the book in the form `en`, as specified in `book.toml` (if not specified, defaults to `en`). To use in <code
   class="language-html">\<html lang="{{ language }}"></code> for example.
-- ***title*** Title used for the current page. This is identical to `{{ book_title }} - {{ chapter_title }}` unless `book_title` is not set in which case it just defaults to the `chapter_title`.
+- ***title*** Title used for the current page. This is identical to `{{ chapter_title }} - {{ book_title }}` unless `book_title` is not set in which case it just defaults to the `chapter_title`.
 - ***book_title*** Title of the book, as specified in `book.toml`
 - ***chapter_title*** Title of the current chapter, as listed in `SUMMARY.md`
 

guide/src/format/theme/syntax-highlighting.md

@@ -77,45 +77,13 @@ the `theme` folder of your book.
 
 Now your theme will be used instead of the default theme.
 
-## Hiding code lines
-
-There is a feature in mdBook that lets you hide code lines by prepending them
-with a `#`.
-
-
-```bash
-# fn main() {
-    let x = 5;
-    let y = 6;
-
-    println!("{}", x + y);
-# }
-```
-
-Will render as
-
-```rust
-# fn main() {
-    let x = 5;
-    let y = 7;
-
-    println!("{}", x + y);
-# }
-```
-
-**At the moment, this only works for code examples that are annotated with
-`rust`. Because it would collide with semantics of some programming languages.
-In the future, we want to make this configurable through the `book.toml` so that
-everyone can benefit from it.**
-
-
 ## Improve default theme
 
 If you think the default theme doesn't look quite right for a specific language,
-or could be improved. Feel free to [submit a new
+or could be improved, feel free to [submit a new
 issue](https://github.com/rust-lang/mdBook/issues) explaining what you
 have in mind and I will take a look at it.
 
 You could also create a pull-request with the proposed improvements.
 
-Overall the theme should be light and sober, without to many flashy colors.
+Overall the theme should be light and sober, without too many flashy colors.

guide/src/guide/README.md

@@ -0,0 +1,7 @@
+# User Guide
+
+This user guide provides an introduction to basic concepts of using mdBook.
+
+- [Installation](installation.md)
+- [Reading Books](reading.md)
+- [Creating a Book](creating.md)

guide/src/guide/creating.md

@@ -0,0 +1,109 @@
+# Creating a Book
+
+Once you have the `mdbook` CLI tool installed, you can use it to create and render a book.
+
+## Initializing a book
+
+The `mdbook init` command will create a new directory containing an empty book for you to get started.
+Give it the name of the directory that you want to create:
+
+```sh
+mdbook init my-first-book
+```
+
+It will ask a few questions before generating the book.
+After answering the questions, you can change the current directory into the new book:
+
+```sh
+cd my-first-book
+```
+
+There are several ways to render a book, but one of the easiest methods is to use the `serve` command, which will build your book and start a local webserver:
+
+```sh
+mdbook serve --open
+```
+
+The `--open` option will open your default web browser to view your new book.
+You can leave the server running even while you edit the content of the book, and `mdbook` will automatically rebuild the output *and* automatically refresh your web browser.
+
+Check out the [CLI Guide](../cli/index.html) for more information about other `mdbook` commands and CLI options.
+
+## Anatomy of a book
+
+A book is built from several files which define the settings and layout of the book.
+
+### `book.toml`
+
+In the root of your book, there is a `book.toml` file which contains settings for describing how to build your book.
+This is written in the [TOML markup language](https://toml.io/).
+The default settings are usually good enough to get you started.
+When you are interested in exploring more features and options that mdBook provides, check out the [Configuration chapter](../format/configuration/index.html) for more details.
+
+A very basic `book.toml` can be as simple as this:
+
+```toml
+[book]
+title = "My First Book"
+```
+
+### `SUMMARY.md`
+
+The next major part of a book is the summary file located at `src/SUMMARY.md`.
+This file contains a list of all the chapters in the book.
+Before a chapter can be viewed, it must be added to this list.
+
+Here's a basic summary file with a few chapters:
+
+```md
+# Summary
+
+[Introduction](README.md)
+
+- [My First Chapter](my-first-chapter.md)
+- [Nested example](nested/README.md)
+    - [Sub-chapter](nested/sub-chapter.md)
+```
+
+Try opening up `src/SUMMARY.md` in your editor and adding a few chapters.
+If any of the chapter files do not exist, `mdbook` will automatically create them for you.
+
+For more details on other formatting options for the summary file, check out the [Summary chapter](../format/summary.md).
+
+### Source files
+
+The content of your book is all contained in the `src` directory.
+Each chapter is a separate Markdown file.
+Typically, each chapter starts with a level 1 heading with the title of the chapter.
+
+```md
+# My First Chapter
+
+Fill out your content here.
+```
+
+The precise layout of the files is up to you.
+The organization of the files will correspond to the HTML files generated, so keep in mind that the file layout is part of the URL of each chapter.
+
+While the `mdbook serve` command is running, you can open any of the chapter files and start editing them.
+Each time you save the file, `mdbook` will rebuild the book and refresh your web browser.
+
+Check out the [Markdown chapter](../format/markdown.md) for more information on formatting the content of your chapters.
+
+All other files in the `src` directory will be included in the output.
+So if you have images or other static files, just include them somewhere in the `src` directory.
+
+## Publishing a book
+
+Once you've written your book, you may want to host it somewhere for others to view.
+The first step is to build the output of the book.
+This can be done with the `mdbook build` command in the same directory where the `book.toml` file is located:
+
+```sh
+mdbook build
+```
+
+This will generate a directory named `book` which contains the HTML content of your book.
+You can then place this directory on any web server to host it.
+
+For more information about publishing and deploying, check out the [Continuous Integration chapter](../continuous-integration.md) for more.

guide/src/guide/installation.md

@@ -0,0 +1,52 @@
+# Installation
+
+There are multiple ways to install the mdBook CLI tool.
+Choose any one of the methods below that best suit your needs.
+If you are installing mdBook for automatic deployment, check out the [continuous integration] chapter for more examples on how to install.
+
+[continuous integration]: ../continuous-integration.md
+
+## Pre-compiled binaries
+
+Executable binaries are available for download on the [GitHub Releases page][releases].
+Download the binary for your platform (Windows, macOS, or Linux) and extract the archive.
+The archive contains an `mdbook` executable which you can run to build your books.
+
+To make it easier to run, put the path to the binary into your `PATH`.
+
+[releases]: https://github.com/rust-lang/mdBook/releases
+
+## Build from source using Rust
+
+To build the `mdbook` executable from source, you will first need to install Rust and Cargo.
+Follow the instructions on the [Rust installation page].
+mdBook currently requires at least Rust version 1.66.
+
+Once you have installed Rust, the following command can be used to build and install mdBook:
+
+```sh
+cargo install mdbook
+```
+
+This will automatically download mdBook from [crates.io], build it, and install it in Cargo's global binary directory (`~/.cargo/bin/` by default).
+
+To uninstall, run the command `cargo uninstall mdbook`.
+
+[Rust installation page]: https://www.rust-lang.org/tools/install
+[crates.io]: https://crates.io/
+
+### Installing the latest master version
+
+The version published to crates.io will ever so slightly be behind the version hosted on GitHub.
+If you need the latest version you can build the git version of mdBook yourself.
+Cargo makes this ***super easy***!
+
+```sh
+cargo install --git https://github.com/rust-lang/mdBook.git mdbook
+```
+
+Again, make sure to add the Cargo bin directory to your `PATH`.
+
+If you are interested in making modifications to mdBook itself, check out the [Contributing Guide] for more information.
+
+[Contributing Guide]: https://github.com/rust-lang/mdBook/blob/master/CONTRIBUTING.md

guide/src/guide/reading.md

@@ -0,0 +1,74 @@
+# Reading Books
+
+This chapter gives an introduction on how to interact with a book produced by mdBook.
+This assumes you are reading an HTML book.
+The options and formatting will be different for other output formats such as PDF.
+
+A book is organized into *chapters*.
+Each chapter is a separate page.
+Chapters can be nested into a hierarchy of sub-chapters.
+Typically, each chapter will be organized into a series of *headings* to subdivide a chapter.
+
+## Navigation
+
+There are several methods for navigating through the chapters of a book.
+
+The **sidebar** on the left provides a list of all chapters.
+Clicking on any of the chapter titles will load that page.
+
+The sidebar may not automatically appear if the window is too narrow, particularly on mobile displays.
+In that situation, the menu icon (three horizontal bars) at the top-left of the page can be pressed to open and close the sidebar.
+
+The **arrow buttons** at the bottom of the page can be used to navigate to the previous or the next chapter.
+
+The **left and right arrow keys** on the keyboard can be used to navigate to the previous or the next chapter.
+
+## Top menu bar
+
+The menu bar at the top of the page provides some icons for interacting with the book.
+The icons displayed will depend on the settings of how the book was generated.
+
+| Icon | Description |
+|------|-------------|
+| <i class="fa fa-bars"></i> | Opens and closes the chapter listing sidebar. |
+| <i class="fa fa-paint-brush"></i> | Opens a picker to choose a different color theme. |
+| <i class="fa fa-search"></i> | Opens a search bar for searching within the book. |
+| <i class="fa fa-print"></i> | Instructs the web browser to print the entire book. |
+| <i class="fa fa-github"></i> | Opens a link to the website that hosts the source code of the book. |
+| <i class="fa fa-edit"></i> | Opens a page to directly edit the source of the page you are currently reading. |
+
+Tapping the menu bar will scroll the page to the top.
+
+## Search
+
+Each book has a built-in search system.
+Pressing the search icon (<i class="fa fa-search"></i>) in the menu bar, or pressing the `S` key on the keyboard will open an input box for entering search terms.
+Typing some terms will show matching chapters and sections in real time.
+
+Clicking any of the results will jump to that section.
+The up and down arrow keys can be used to navigate the results, and enter will open the highlighted section.
+
+After loading a search result, the matching search terms will be highlighted in the text.
+Clicking a highlighted word or pressing the `Esc` key will remove the highlighting.
+
+## Code blocks
+
+mdBook books are often used for programming projects, and thus support highlighting code blocks and samples.
+Code blocks may contain several different icons for interacting with them:
+
+| Icon | Description |
+|------|-------------|
+| <i class="fa fa-copy"></i> | Copies the code block into your local clipboard, to allow pasting into another application. |
+| <i class="fa fa-play"></i> | For Rust code examples, this will execute the sample code and display the compiler output just below the example (see [playground]). |
+| <i class="fa fa-eye"></i> | For Rust code examples, this will toggle visibility of "hidden" lines. Sometimes, larger examples will hide lines which are not particularly relevant to what is being illustrated (see [hiding code lines]). |
+| <i class="fa fa-history"></i> | For [editable code examples][editor], this will undo any changes you have made. |
+
+Here's an example:
+
+```rust
+println!("Hello, World!");
+```
+
+[editor]: ../format/theme/editor.md
+[playground]: ../format/mdbook.md#rust-playground
+[hiding code lines]: ../format/mdbook.md#hiding-code-lines

guide/src/misc/contributors.md

@@ -15,6 +15,10 @@ shout-out to them!
 - [projektir](https://github.com/projektir)
 - [Phaiax](https://github.com/Phaiax)
 - Matt Ickstadt ([mattico](https://github.com/mattico))
-- Weihang Lo ([@weihanglo](https://github.com/weihanglo))
+- Weihang Lo ([weihanglo](https://github.com/weihanglo))
+- Avision Ho ([avisionh](https://github.com/avisionh))
+- Vivek Akupatni ([apatniv](https://github.com/apatniv))
+- Eric Huss ([ehuss](https://github.com/ehuss))
+- Josh Rotenberg ([joshrotenberg](https://github.com/joshrotenberg))
 
-If you feel you're missing from this list, feel free to add yourself in a PR.
+If you feel you're missing from this list, feel free to add yourself in a PR.

guide/src/misc/introduction.md

@@ -1,3 +0,0 @@
-# Introduction
-
-A frontmatter chapter.

src/book/book.rs

@@ -7,6 +7,9 @@ use std::path::{Path, PathBuf};
 use super::summary::{parse_summary, Link, SectionNumber, Summary, SummaryItem};
 use crate::config::BuildConfig;
 use crate::errors::*;
+use crate::utils::bracket_escape;
+use log::debug;
+use serde::{Deserialize, Serialize};
 
 /// Load a book into memory from its `src/` directory.
 pub fn load_book<P: AsRef<Path>>(src_dir: P, cfg: &BuildConfig) -> Result<Book> {
@@ -14,14 +17,15 @@ pub fn load_book<P: AsRef<Path>>(src_dir: P, cfg: &BuildConfig) -> Result<Book>
     let summary_md = src_dir.join("SUMMARY.md");
 
     let mut summary_content = String::new();
-    File::open(summary_md)
-        .with_context(|| "Couldn't open SUMMARY.md")?
+    File::open(&summary_md)
+        .with_context(|| format!("Couldn't open SUMMARY.md in {:?} directory", src_dir))?
         .read_to_string(&mut summary_content)?;
 
-    let summary = parse_summary(&summary_content).with_context(|| "Summary parsing failed")?;
+    let summary = parse_summary(&summary_content)
+        .with_context(|| format!("Summary parsing failed for file={:?}", summary_md))?;
 
     if cfg.create_missing {
-        create_missing(&src_dir, &summary).with_context(|| "Unable to create missing chapters")?;
+        create_missing(src_dir, &summary).with_context(|| "Unable to create missing chapters")?;
     }
 
     load_book_from_disk(&summary, src_dir)
@@ -35,9 +39,7 @@ fn create_missing(src_dir: &Path, summary: &Summary) -> Result<()> {
         .chain(summary.suffix_chapters.iter())
         .collect();
 
-    while !items.is_empty() {
-        let next = items.pop().expect("already checked");
-
+    while let Some(next) = items.pop() {
         if let SummaryItem::Link(ref link) = *next {
             if let Some(ref location) = link.location {
                 let filename = src_dir.join(location);
@@ -49,8 +51,10 @@ fn create_missing(src_dir: &Path, summary: &Summary) -> Result<()> {
                     }
                     debug!("Creating missing file {}", filename.display());
 
-                    let mut f = File::create(&filename)?;
-                    writeln!(f, "# {}", link.name)?;
+                    let mut f = File::create(&filename).with_context(|| {
+                        format!("Unable to create missing file: {}", filename.display())
+                    })?;
+                    writeln!(f, "# {}", bracket_escape(&link.name))?;
                 }
             }
 
@@ -63,7 +67,7 @@ fn create_missing(src_dir: &Path, summary: &Summary) -> Result<()> {
 
 /// A dumb tree structure representing a book.
 ///
-/// For the moment a book is just a collection of `BookItems` which are
+/// For the moment a book is just a collection of [`BookItems`] which are
 /// accessible by either iterating (immutably) over the book with [`iter()`], or
 /// recursively applying a closure to each section to mutate the chapters, using
 /// [`for_each_mut()`].
@@ -157,7 +161,9 @@ pub struct Chapter {
     pub sub_items: Vec<BookItem>,
     /// The chapter's location, relative to the `SUMMARY.md` file.
     pub path: Option<PathBuf>,
-    /// An ordered list of the names of each chapter above this one, in the hierarchy.
+    /// The chapter's source file, relative to the `SUMMARY.md` file.
+    pub source_path: Option<PathBuf>,
+    /// An ordered list of the names of each chapter above this one in the hierarchy.
     pub parent_names: Vec<String>,
 }
 
@@ -166,36 +172,36 @@ impl Chapter {
     pub fn new<P: Into<PathBuf>>(
         name: &str,
         content: String,
-        path: P,
+        p: P,
         parent_names: Vec<String>,
     ) -> Chapter {
+        let path: PathBuf = p.into();
         Chapter {
             name: name.to_string(),
             content,
-            path: Some(path.into()),
+            path: Some(path.clone()),
+            source_path: Some(path),
             parent_names,
             ..Default::default()
         }
     }
 
-    /// Create a new draft chapter that is not attached to a source markdown file and has
-    /// thus no content.
+    /// Create a new draft chapter that is not attached to a source markdown file (and thus
+    /// has no content).
     pub fn new_draft(name: &str, parent_names: Vec<String>) -> Self {
         Chapter {
             name: name.to_string(),
             content: String::new(),
             path: None,
+            source_path: None,
             parent_names,
             ..Default::default()
         }
     }
 
-    /// Check if the chapter is a draft chapter, meaning it has no path to a source markdown file
+    /// Check if the chapter is a draft chapter, meaning it has no path to a source markdown file.
     pub fn is_draft_chapter(&self) -> bool {
-        match self.path {
-            Some(_) => false,
-            None => true,
-        }
+        self.path.is_none()
     }
 }
 
@@ -264,8 +270,12 @@ fn load_chapter<P: AsRef<Path>>(
             format!("Unable to read \"{}\" ({})", link.name, location.display())
         })?;
 
+        if content.as_bytes().starts_with(b"\xef\xbb\xbf") {
+            content.replace_range(..3, "");
+        }
+
         let stripped = location
-            .strip_prefix(&src_dir)
+            .strip_prefix(src_dir)
             .expect("Chapters are always inside a book");
 
         Chapter::new(&link.name, content, stripped, parent_names.clone())
@@ -273,7 +283,7 @@ fn load_chapter<P: AsRef<Path>>(
         Chapter::new_draft(&link.name, parent_names.clone())
     };
 
-    let mut sub_item_parents = parent_names.clone();
+    let mut sub_item_parents = parent_names;
 
     ch.number = link.number.clone();
 
@@ -295,8 +305,6 @@ fn load_chapter<P: AsRef<Path>>(
 ///
 /// This struct shouldn't be created directly, instead prefer the
 /// [`Book::iter()`] method.
-///
-/// [`Book::iter()`]: struct.Book.html#method.iter
 pub struct BookItems<'a> {
     items: VecDeque<&'a BookItem>,
 }
@@ -307,7 +315,7 @@ impl<'a> Iterator for BookItems<'a> {
     fn next(&mut self) -> Option<Self::Item> {
         let item = self.items.pop_front();
 
-        if let Some(&BookItem::Chapter(ref ch)) = item {
+        if let Some(BookItem::Chapter(ch)) = item {
             // if we wanted a breadth-first iterator we'd `extend()` here
             for sub_item in ch.sub_items.iter().rev() {
                 self.items.push_front(sub_item);
@@ -374,7 +382,7 @@ And here is some \
 
         root.nested_items.push(second.clone().into());
         root.nested_items.push(SummaryItem::Separator);
-        root.nested_items.push(second.clone().into());
+        root.nested_items.push(second.into());
 
         (root, temp_dir)
     }
@@ -393,6 +401,29 @@ And here is some \
         assert_eq!(got, should_be);
     }
 
+    #[test]
+    fn load_a_single_chapter_with_utf8_bom_from_disk() {
+        let temp_dir = TempFileBuilder::new().prefix("book").tempdir().unwrap();
+
+        let chapter_path = temp_dir.path().join("chapter_1.md");
+        File::create(&chapter_path)
+            .unwrap()
+            .write_all(("\u{feff}".to_owned() + DUMMY_SRC).as_bytes())
+            .unwrap();
+
+        let link = Link::new("Chapter 1", chapter_path);
+
+        let should_be = Chapter::new(
+            "Chapter 1",
+            DUMMY_SRC.to_string(),
+            "chapter_1.md",
+            Vec::new(),
+        );
+
+        let got = load_chapter(&link, temp_dir.path(), Vec::new()).unwrap();
+        assert_eq!(got, should_be);
+    }
+
     #[test]
     fn cant_load_a_nonexistent_chapter() {
         let link = Link::new("Chapter 1", "/foo/bar/baz.md");
@@ -410,6 +441,7 @@ And here is some \
             content: String::from("Hello World!"),
             number: Some(SectionNumber(vec![1, 2])),
             path: Some(PathBuf::from("second.md")),
+            source_path: Some(PathBuf::from("second.md")),
             parent_names: vec![String::from("Chapter 1")],
             sub_items: Vec::new(),
         };
@@ -418,11 +450,12 @@ And here is some \
             content: String::from(DUMMY_SRC),
             number: None,
             path: Some(PathBuf::from("chapter_1.md")),
+            source_path: Some(PathBuf::from("chapter_1.md")),
             parent_names: Vec::new(),
             sub_items: vec![
                 BookItem::Chapter(nested.clone()),
                 BookItem::Separator,
-                BookItem::Chapter(nested.clone()),
+                BookItem::Chapter(nested),
             ],
         });
 
@@ -442,6 +475,7 @@ And here is some \
                 name: String::from("Chapter 1"),
                 content: String::from(DUMMY_SRC),
                 path: Some(PathBuf::from("chapter_1.md")),
+                source_path: Some(PathBuf::from("chapter_1.md")),
                 ..Default::default()
             })],
             ..Default::default()
@@ -482,6 +516,7 @@ And here is some \
                     content: String::from(DUMMY_SRC),
                     number: None,
                     path: Some(PathBuf::from("Chapter_1/index.md")),
+                    source_path: Some(PathBuf::from("Chapter_1/index.md")),
                     parent_names: Vec::new(),
                     sub_items: vec![
                         BookItem::Chapter(Chapter::new(
@@ -534,6 +569,7 @@ And here is some \
                     content: String::from(DUMMY_SRC),
                     number: None,
                     path: Some(PathBuf::from("Chapter_1/index.md")),
+                    source_path: Some(PathBuf::from("Chapter_1/index.md")),
                     parent_names: Vec::new(),
                     sub_items: vec![
                         BookItem::Chapter(Chapter::new(

src/book/init.rs

@@ -6,6 +6,8 @@ use super::MDBook;
 use crate::config::Config;
 use crate::errors::*;
 use crate::theme;
+use crate::utils::fs::write_file;
+use log::{debug, error, info, trace};
 
 /// A helper for setting up a new book and its directory structure.
 #[derive(Debug, Clone, PartialEq)]
@@ -28,7 +30,7 @@ impl BookBuilder {
         }
     }
 
-    /// Set the `Config` to be used.
+    /// Set the [`Config`] to be used.
     pub fn with_config(&mut self, cfg: Config) -> &mut BookBuilder {
         self.config = cfg;
         self
@@ -110,10 +112,7 @@ impl BookBuilder {
         debug!("Copying theme");
 
         let html_config = self.config.html_config().unwrap_or_default();
-        let themedir = html_config
-            .theme
-            .unwrap_or_else(|| self.config.book.src.join("theme"));
-        let themedir = self.root.join(themedir);
+        let themedir = html_config.theme_dir(&self.root);
 
         if !themedir.exists() {
             debug!(
@@ -127,7 +126,9 @@ impl BookBuilder {
         index.write_all(theme::INDEX)?;
 
         let cssdir = themedir.join("css");
-        fs::create_dir(&cssdir)?;
+        if !cssdir.exists() {
+            fs::create_dir(&cssdir)?;
+        }
 
         let mut general_css = File::create(cssdir.join("general.css"))?;
         general_css.write_all(theme::GENERAL_CSS)?;
@@ -158,6 +159,19 @@ impl BookBuilder {
         let mut highlight_js = File::create(themedir.join("highlight.js"))?;
         highlight_js.write_all(theme::HIGHLIGHT_JS)?;
 
+        write_file(&themedir.join("fonts"), "fonts.css", theme::fonts::CSS)?;
+        for (file_name, contents) in theme::fonts::LICENSES {
+            write_file(&themedir, file_name, contents)?;
+        }
+        for (file_name, contents) in theme::fonts::OPEN_SANS.iter() {
+            write_file(&themedir, file_name, contents)?;
+        }
+        write_file(
+            &themedir,
+            theme::fonts::SOURCE_CODE_PRO.0,
+            theme::fonts::SOURCE_CODE_PRO.1,
+        )?;
+
         Ok(())
     }
 
@@ -184,8 +198,7 @@ impl BookBuilder {
             writeln!(f, "- [Chapter 1](./chapter_1.md)")?;
 
             let chapter_1 = src_dir.join("chapter_1.md");
-            let mut f =
-                File::create(&chapter_1).with_context(|| "Unable to create chapter_1.md")?;
+            let mut f = File::create(chapter_1).with_context(|| "Unable to create chapter_1.md")?;
             writeln!(f, "# Chapter 1")?;
         } else {
             trace!("Existing summary found, no need to create stub files.");
@@ -198,10 +211,10 @@ impl BookBuilder {
         fs::create_dir_all(&self.root)?;
 
         let src = self.root.join(&self.config.book.src);
-        fs::create_dir_all(&src)?;
+        fs::create_dir_all(src)?;
 
         let build = self.root.join(&self.config.build.build_dir);
-        fs::create_dir_all(&build)?;
+        fs::create_dir_all(build)?;
 
         Ok(())
     }

src/book/mod.rs

@@ -14,12 +14,14 @@ pub use self::book::{load_book, Book, BookItem, BookItems, Chapter};
 pub use self::init::BookBuilder;
 pub use self::summary::{parse_summary, Link, SectionNumber, Summary, SummaryItem};
 
+use log::{debug, error, info, log_enabled, trace, warn};
 use std::io::Write;
 use std::path::PathBuf;
 use std::process::Command;
 use std::string::ToString;
 use tempfile::Builder as TempFileBuilder;
 use toml::Value;
+use topological_sort::TopologicalSort;
 
 use crate::errors::*;
 use crate::preprocess::{
@@ -40,7 +42,7 @@ pub struct MDBook {
     pub book: Book,
     renderers: Vec<Box<dyn Renderer>>,
 
-    /// List of pre-processors to be run on the book
+    /// List of pre-processors to be run on the book.
     preprocessors: Vec<Box<dyn Preprocessor>>,
 }
 
@@ -69,6 +71,20 @@ impl MDBook {
 
         config.update_from_env();
 
+        if config
+            .html_config()
+            .map_or(false, |html| html.google_analytics.is_some())
+        {
+            warn!(
+                "The output.html.google-analytics field has been deprecated; \
+                 it will be removed in a future release.\n\
+                 Consider placing the appropriate site tag code into the \
+                 theme/head.hbs file instead.\n\
+                 The tracking code may be found in the Google Analytics Admin page.\n\
+               "
+            );
+        }
+
         if log_enabled!(log::Level::Trace) {
             for line in format!("Config: {:#?}", config).lines() {
                 trace!("{}", line);
@@ -78,12 +94,12 @@ impl MDBook {
         MDBook::load_with_config(book_root, config)
     }
 
-    /// Load a book from its root directory using a custom config.
+    /// Load a book from its root directory using a custom `Config`.
     pub fn load_with_config<P: Into<PathBuf>>(book_root: P, config: Config) -> Result<MDBook> {
         let root = book_root.into();
 
         let src_dir = root.join(&config.book.src);
-        let book = book::load_book(&src_dir, &config.build)?;
+        let book = book::load_book(src_dir, &config.build)?;
 
         let renderers = determine_renderers(&config);
         let preprocessors = determine_preprocessors(&config)?;
@@ -97,7 +113,7 @@ impl MDBook {
         })
     }
 
-    /// Load a book from its root directory using a custom config and a custom summary.
+    /// Load a book from its root directory using a custom `Config` and a custom summary.
     pub fn load_with_config_and_summary<P: Into<PathBuf>>(
         book_root: P,
         config: Config,
@@ -106,7 +122,7 @@ impl MDBook {
         let root = book_root.into();
 
         let src_dir = root.join(&config.book.src);
-        let book = book::load_book_from_disk(&summary, &src_dir)?;
+        let book = book::load_book_from_disk(&summary, src_dir)?;
 
         let renderers = determine_renderers(&config);
         let preprocessors = determine_preprocessors(&config)?;
@@ -121,7 +137,7 @@ impl MDBook {
     }
 
     /// Returns a flat depth-first iterator over the elements of the book,
-    /// it returns an [BookItem enum](bookitem.html):
+    /// it returns a [`BookItem`] enum:
     /// `(section: String, bookitem: &BookItem)`
     ///
     /// ```no_run
@@ -180,53 +196,55 @@ impl MDBook {
         Ok(())
     }
 
-    /// Run the entire build process for a particular `Renderer`.
-    pub fn execute_build_process(&self, renderer: &dyn Renderer) -> Result<()> {
-        let mut preprocessed_book = self.book.clone();
+    /// Run preprocessors and return the final book.
+    pub fn preprocess_book(&self, renderer: &dyn Renderer) -> Result<(Book, PreprocessorContext)> {
         let preprocess_ctx = PreprocessorContext::new(
             self.root.clone(),
             self.config.clone(),
             renderer.name().to_string(),
         );
-
+        let mut preprocessed_book = self.book.clone();
         for preprocessor in &self.preprocessors {
             if preprocessor_should_run(&**preprocessor, renderer, &self.config) {
                 debug!("Running the {} preprocessor.", preprocessor.name());
                 preprocessed_book = preprocessor.run(&preprocess_ctx, preprocessed_book)?;
             }
         }
-
-        info!("Running the {} backend", renderer.name());
-        self.render(&preprocessed_book, renderer)?;
-
-        Ok(())
+        Ok((preprocessed_book, preprocess_ctx))
     }
 
-    fn render(&self, preprocessed_book: &Book, renderer: &dyn Renderer) -> Result<()> {
+    /// Run the entire build process for a particular [`Renderer`].
+    pub fn execute_build_process(&self, renderer: &dyn Renderer) -> Result<()> {
+        let (preprocessed_book, preprocess_ctx) = self.preprocess_book(renderer)?;
+
         let name = renderer.name();
         let build_dir = self.build_dir_for(name);
 
-        let render_context = RenderContext::new(
+        let mut render_context = RenderContext::new(
             self.root.clone(),
-            preprocessed_book.clone(),
+            preprocessed_book,
             self.config.clone(),
             build_dir,
         );
+        render_context
+            .chapter_titles
+            .extend(preprocess_ctx.chapter_titles.borrow_mut().drain());
 
+        info!("Running the {} backend", renderer.name());
         renderer
             .render(&render_context)
             .with_context(|| "Rendering failed")
     }
 
     /// You can change the default renderer to another one by using this method.
-    /// The only requirement is for your renderer to implement the [`Renderer`
-    /// trait](../renderer/trait.Renderer.html)
+    /// The only requirement is that your renderer implement the [`Renderer`]
+    /// trait.
     pub fn with_renderer<R: Renderer + 'static>(&mut self, renderer: R) -> &mut Self {
         self.renderers.push(Box::new(renderer));
         self
     }
 
-    /// Register a [`Preprocessor`](../preprocess/trait.Preprocessor.html) to be used when rendering the book.
+    /// Register a [`Preprocessor`] to be used when rendering the book.
     pub fn with_preprocessor<P: Preprocessor + 'static>(&mut self, preprocessor: P) -> &mut Self {
         self.preprocessors.push(Box::new(preprocessor));
         self
@@ -234,6 +252,13 @@ impl MDBook {
 
     /// Run `rustdoc` tests on the book, linking against the provided libraries.
     pub fn test(&mut self, library_paths: Vec<&str>) -> Result<()> {
+        // test_chapter with chapter:None will run all tests.
+        self.test_chapter(library_paths, None)
+    }
+
+    /// Run `rustdoc` tests on a specific chapter of the book, linking against the provided libraries.
+    /// If `chapter` is `None`, all tests will be run.
+    pub fn test_chapter(&mut self, library_paths: Vec<&str>, chapter: Option<&str>) -> Result<()> {
         let library_args: Vec<&str> = (0..library_paths.len())
             .map(|_| "-L")
             .zip(library_paths.into_iter())
@@ -242,13 +267,27 @@ impl MDBook {
 
         let temp_dir = TempFileBuilder::new().prefix("mdbook-").tempdir()?;
 
-        // FIXME: Is "test" the proper renderer name to use here?
-        let preprocess_context =
-            PreprocessorContext::new(self.root.clone(), self.config.clone(), "test".to_string());
+        let mut chapter_found = false;
 
-        let book = LinkPreprocessor::new().run(&preprocess_context, self.book.clone())?;
-        // Index Preprocessor is disabled so that chapter paths continue to point to the
-        // actual markdown files.
+        struct TestRenderer;
+        impl Renderer for TestRenderer {
+            // FIXME: Is "test" the proper renderer name to use here?
+            fn name(&self) -> &str {
+                "test"
+            }
+
+            fn render(&self, _: &RenderContext) -> Result<()> {
+                Ok(())
+            }
+        }
+
+        // Index Preprocessor is disabled so that chapter paths
+        // continue to point to the actual markdown files.
+        self.preprocessors = determine_preprocessors(&self.config)?
+            .into_iter()
+            .filter(|pre| pre.name() != IndexPreprocessor::NAME)
+            .collect();
+        let (book, _) = self.preprocess_book(&TestRenderer)?;
 
         let mut failed = false;
         for item in book.iter() {
@@ -258,11 +297,19 @@ impl MDBook {
                     _ => continue,
                 };
 
-                let path = self.source_dir().join(&chapter_path);
-                info!("Testing file: {:?}", path);
+                if let Some(chapter) = chapter {
+                    if ch.name != chapter && chapter_path.to_str() != Some(chapter) {
+                        if chapter == "?" {
+                            info!("Skipping chapter '{}'...", ch.name);
+                        }
+                        continue;
+                    }
+                }
+                chapter_found = true;
+                info!("Testing chapter '{}': {:?}", ch.name, chapter_path);
 
                 // write preprocessed file to tempdir
-                let path = temp_dir.path().join(&chapter_path);
+                let path = temp_dir.path().join(chapter_path);
                 let mut tmpf = utils::fs::create_file(&path)?;
                 tmpf.write_all(ch.content.as_bytes())?;
 
@@ -272,14 +319,18 @@ impl MDBook {
                 if let Some(edition) = self.config.rust.edition {
                     match edition {
                         RustEdition::E2015 => {
-                            cmd.args(&["--edition", "2015"]);
+                            cmd.args(["--edition", "2015"]);
                         }
                         RustEdition::E2018 => {
-                            cmd.args(&["--edition", "2018"]);
+                            cmd.args(["--edition", "2018"]);
+                        }
+                        RustEdition::E2021 => {
+                            cmd.args(["--edition", "2021"]);
                         }
                     }
                 }
 
+                debug!("running {:?}", cmd);
                 let output = cmd.output()?;
 
                 if !output.status.success() {
@@ -296,6 +347,11 @@ impl MDBook {
         if failed {
             bail!("One or more tests failed");
         }
+        if let Some(chapter) = chapter {
+            if !chapter_found {
+                bail!("Chapter not found: {}", chapter);
+            }
+        }
         Ok(())
     }
 
@@ -303,7 +359,7 @@ impl MDBook {
     /// artefacts.
     ///
     /// If there is only 1 renderer, put it in the directory pointed to by the
-    /// `build.build_dir` key in `Config`. If there is more than one then the
+    /// `build.build_dir` key in [`Config`]. If there is more than one then the
     /// renderer gets its own directory within the main build dir.
     ///
     /// i.e. If there were only one renderer (in this case, the HTML renderer):
@@ -371,12 +427,7 @@ fn determine_renderers(config: &Config) -> Vec<Box<dyn Renderer>> {
     renderers
 }
 
-fn default_preprocessors() -> Vec<Box<dyn Preprocessor>> {
-    vec![
-        Box::new(LinkPreprocessor::new()),
-        Box::new(IndexPreprocessor::new()),
-    ]
-}
+const DEFAULT_PREPROCESSORS: &[&str] = &["links", "index"];
 
 fn is_default_preprocessor(pre: &dyn Preprocessor) -> bool {
     let name = pre.name();
@@ -385,36 +436,127 @@ fn is_default_preprocessor(pre: &dyn Preprocessor) -> bool {
 
 /// Look at the `MDBook` and try to figure out what preprocessors to run.
 fn determine_preprocessors(config: &Config) -> Result<Vec<Box<dyn Preprocessor>>> {
-    let mut preprocessors = Vec::new();
+    // Collect the names of all preprocessors intended to be run, and the order
+    // in which they should be run.
+    let mut preprocessor_names = TopologicalSort::<String>::new();
 
     if config.build.use_default_preprocessors {
-        preprocessors.extend(default_preprocessors());
+        for name in DEFAULT_PREPROCESSORS {
+            preprocessor_names.insert(name.to_string());
+        }
     }
 
     if let Some(preprocessor_table) = config.get("preprocessor").and_then(Value::as_table) {
-        for key in preprocessor_table.keys() {
-            match key.as_ref() {
-                "links" => preprocessors.push(Box::new(LinkPreprocessor::new())),
-                "index" => preprocessors.push(Box::new(IndexPreprocessor::new())),
-                name => preprocessors.push(interpret_custom_preprocessor(
-                    name,
-                    &preprocessor_table[name],
-                )),
+        for (name, table) in preprocessor_table.iter() {
+            preprocessor_names.insert(name.to_string());
+
+            let exists = |name| {
+                (config.build.use_default_preprocessors && DEFAULT_PREPROCESSORS.contains(&name))
+                    || preprocessor_table.contains_key(name)
+            };
+
+            if let Some(before) = table.get("before") {
+                let before = before.as_array().ok_or_else(|| {
+                    Error::msg(format!(
+                        "Expected preprocessor.{}.before to be an array",
+                        name
+                    ))
+                })?;
+                for after in before {
+                    let after = after.as_str().ok_or_else(|| {
+                        Error::msg(format!(
+                            "Expected preprocessor.{}.before to contain strings",
+                            name
+                        ))
+                    })?;
+
+                    if !exists(after) {
+                        // Only warn so that preprocessors can be toggled on and off (e.g. for
+                        // troubleshooting) without having to worry about order too much.
+                        warn!(
+                            "preprocessor.{}.after contains \"{}\", which was not found",
+                            name, after
+                        );
+                    } else {
+                        preprocessor_names.add_dependency(name, after);
+                    }
+                }
+            }
+
+            if let Some(after) = table.get("after") {
+                let after = after.as_array().ok_or_else(|| {
+                    Error::msg(format!(
+                        "Expected preprocessor.{}.after to be an array",
+                        name
+                    ))
+                })?;
+                for before in after {
+                    let before = before.as_str().ok_or_else(|| {
+                        Error::msg(format!(
+                            "Expected preprocessor.{}.after to contain strings",
+                            name
+                        ))
+                    })?;
+
+                    if !exists(before) {
+                        // See equivalent warning above for rationale
+                        warn!(
+                            "preprocessor.{}.before contains \"{}\", which was not found",
+                            name, before
+                        );
+                    } else {
+                        preprocessor_names.add_dependency(before, name);
+                    }
+                }
             }
         }
     }
 
-    Ok(preprocessors)
+    // Now that all links have been established, queue preprocessors in a suitable order
+    let mut preprocessors = Vec::with_capacity(preprocessor_names.len());
+    // `pop_all()` returns an empty vector when no more items are not being depended upon
+    for mut names in std::iter::repeat_with(|| preprocessor_names.pop_all())
+        .take_while(|names| !names.is_empty())
+    {
+        // The `topological_sort` crate does not guarantee a stable order for ties, even across
+        // runs of the same program. Thus, we break ties manually by sorting.
+        // Careful: `str`'s default sorting, which we are implicitly invoking here, uses code point
+        // values ([1]), which may not be an alphabetical sort.
+        // As mentioned in [1], doing so depends on locale, which is not desirable for deciding
+        // preprocessor execution order.
+        // [1]: https://doc.rust-lang.org/stable/std/cmp/trait.Ord.html#impl-Ord-14
+        names.sort();
+        for name in names {
+            let preprocessor: Box<dyn Preprocessor> = match name.as_str() {
+                "links" => Box::new(LinkPreprocessor::new()),
+                "index" => Box::new(IndexPreprocessor::new()),
+                _ => {
+                    // The only way to request a custom preprocessor is through the `preprocessor`
+                    // table, so it must exist, be a table, and contain the key.
+                    let table = &config.get("preprocessor").unwrap().as_table().unwrap()[&name];
+                    let command = get_custom_preprocessor_cmd(&name, table);
+                    Box::new(CmdPreprocessor::new(name, command))
+                }
+            };
+            preprocessors.push(preprocessor);
+        }
+    }
+
+    // "If `pop_all` returns an empty vector and `len` is not 0, there are cyclic dependencies."
+    // Normally, `len() == 0` is equivalent to `is_empty()`, so we'll use that.
+    if preprocessor_names.is_empty() {
+        Ok(preprocessors)
+    } else {
+        Err(Error::msg("Cyclic dependency detected in preprocessors"))
+    }
 }
 
-fn interpret_custom_preprocessor(key: &str, table: &Value) -> Box<CmdPreprocessor> {
-    let command = table
+fn get_custom_preprocessor_cmd(key: &str, table: &Value) -> String {
+    table
         .get("command")
         .and_then(Value::as_str)
         .map(ToString::to_string)
-        .unwrap_or_else(|| format!("mdbook-{}", key));
-
-    Box::new(CmdPreprocessor::new(key.to_string(), command))
+        .unwrap_or_else(|| format!("mdbook-{}", key))
 }
 
 fn interpret_custom_renderer(key: &str, table: &Value) -> Box<CmdRenderer> {
@@ -514,8 +656,8 @@ mod tests {
 
         assert!(got.is_ok());
         assert_eq!(got.as_ref().unwrap().len(), 2);
-        assert_eq!(got.as_ref().unwrap()[0].name(), "links");
-        assert_eq!(got.as_ref().unwrap()[1].name(), "index");
+        assert_eq!(got.as_ref().unwrap()[0].name(), "index");
+        assert_eq!(got.as_ref().unwrap()[1].name(), "links");
     }
 
     #[test]
@@ -562,9 +704,121 @@ mod tests {
 
         // make sure the `preprocessor.random` table exists
         let random = cfg.get_preprocessor("random").unwrap();
-        let random = interpret_custom_preprocessor("random", &Value::Table(random.clone()));
+        let random = get_custom_preprocessor_cmd("random", &Value::Table(random.clone()));
 
-        assert_eq!(random.cmd(), "python random.py");
+        assert_eq!(random, "python random.py");
+    }
+
+    #[test]
+    fn preprocessor_before_must_be_array() {
+        let cfg_str = r#"
+        [preprocessor.random]
+        before = 0
+        "#;
+
+        let cfg = Config::from_str(cfg_str).unwrap();
+
+        assert!(determine_preprocessors(&cfg).is_err());
+    }
+
+    #[test]
+    fn preprocessor_after_must_be_array() {
+        let cfg_str = r#"
+        [preprocessor.random]
+        after = 0
+        "#;
+
+        let cfg = Config::from_str(cfg_str).unwrap();
+
+        assert!(determine_preprocessors(&cfg).is_err());
+    }
+
+    #[test]
+    fn preprocessor_order_is_honored() {
+        let cfg_str = r#"
+        [preprocessor.random]
+        before = [ "last" ]
+        after = [ "index" ]
+
+        [preprocessor.last]
+        after = [ "links", "index" ]
+        "#;
+
+        let cfg = Config::from_str(cfg_str).unwrap();
+
+        let preprocessors = determine_preprocessors(&cfg).unwrap();
+        let index = |name| {
+            preprocessors
+                .iter()
+                .enumerate()
+                .find(|(_, preprocessor)| preprocessor.name() == name)
+                .unwrap()
+                .0
+        };
+        let assert_before = |before, after| {
+            if index(before) >= index(after) {
+                eprintln!("Preprocessor order:");
+                for preprocessor in &preprocessors {
+                    eprintln!("  {}", preprocessor.name());
+                }
+                panic!("{} should come before {}", before, after);
+            }
+        };
+
+        assert_before("index", "random");
+        assert_before("index", "last");
+        assert_before("random", "last");
+        assert_before("links", "last");
+    }
+
+    #[test]
+    fn cyclic_dependencies_are_detected() {
+        let cfg_str = r#"
+        [preprocessor.links]
+        before = [ "index" ]
+
+        [preprocessor.index]
+        before = [ "links" ]
+        "#;
+
+        let cfg = Config::from_str(cfg_str).unwrap();
+
+        assert!(determine_preprocessors(&cfg).is_err());
+    }
+
+    #[test]
+    fn dependencies_dont_register_undefined_preprocessors() {
+        let cfg_str = r#"
+        [preprocessor.links]
+        before = [ "random" ]
+        "#;
+
+        let cfg = Config::from_str(cfg_str).unwrap();
+
+        let preprocessors = determine_preprocessors(&cfg).unwrap();
+
+        assert!(!preprocessors
+            .iter()
+            .any(|preprocessor| preprocessor.name() == "random"));
+    }
+
+    #[test]
+    fn dependencies_dont_register_builtin_preprocessors_if_disabled() {
+        let cfg_str = r#"
+        [preprocessor.random]
+        before = [ "links" ]
+
+        [build]
+        use-default-preprocessors = false
+        "#;
+
+        let cfg = Config::from_str(cfg_str).unwrap();
+
+        let preprocessors = determine_preprocessors(&cfg).unwrap();
+
+        assert!(!preprocessors
+            .iter()
+            .any(|preprocessor| preprocessor.name() == "links"));
     }
 
     #[test]

src/book/summary.rs

@@ -1,6 +1,8 @@
 use crate::errors::*;
+use log::{debug, trace, warn};
 use memchr::{self, Memchr};
-use pulldown_cmark::{self, Event, Tag};
+use pulldown_cmark::{self, Event, HeadingLevel, Tag};
+use serde::{Deserialize, Serialize};
 use std::fmt::{self, Display, Formatter};
 use std::iter::FromIterator;
 use std::ops::{Deref, DerefMut};
@@ -161,7 +163,7 @@ impl From<Link> for SummaryItem {
 /// > match the following regex: "[^<>\n[]]+".
 struct SummaryParser<'a> {
     src: &'a str,
-    stream: pulldown_cmark::OffsetIter<'a>,
+    stream: pulldown_cmark::OffsetIter<'a, 'a>,
     offset: usize,
 
     /// We can't actually put an event back into the `OffsetIter` stream, so instead we store it
@@ -173,7 +175,7 @@ struct SummaryParser<'a> {
 /// `Event::End` is encountered which matches the `$delimiter` pattern.
 ///
 /// This is the equivalent of doing
-/// `$stream.take_while(|e| e != $delimeter).collect()` but it allows you to
+/// `$stream.take_while(|e| e != $delimiter).collect()` but it allows you to
 /// use pattern matching and you won't get errors because `take_while()`
 /// moves `$stream` out of self.
 macro_rules! collect_events {
@@ -263,7 +265,7 @@ impl<'a> SummaryParser<'a> {
         loop {
             match self.next_event() {
                 Some(ev @ Event::Start(Tag::List(..)))
-                | Some(ev @ Event::Start(Tag::Heading(1))) => {
+                | Some(ev @ Event::Start(Tag::Heading(HeadingLevel::H1, ..))) => {
                     if is_prefix {
                         // we've finished prefix chapters and are at the start
                         // of the numbered section.
@@ -302,10 +304,10 @@ impl<'a> SummaryParser<'a> {
                     break;
                 }
 
-                Some(Event::Start(Tag::Heading(1))) => {
+                Some(Event::Start(Tag::Heading(HeadingLevel::H1, ..))) => {
                     debug!("Found a h1 in the SUMMARY");
 
-                    let tags = collect_events!(self.stream, end Tag::Heading(1));
+                    let tags = collect_events!(self.stream, end Tag::Heading(HeadingLevel::H1, ..));
                     Some(stringify_events(tags))
                 }
 
@@ -375,14 +377,14 @@ impl<'a> SummaryParser<'a> {
                 }
                 // The expectation is that pulldown cmark will terminate a paragraph before a new
                 // heading, so we can always count on this to return without skipping headings.
-                Some(ev @ Event::Start(Tag::Heading(1))) => {
+                Some(ev @ Event::Start(Tag::Heading(HeadingLevel::H1, ..))) => {
                     // we're starting a new part
                     self.back(ev);
                     break;
                 }
                 Some(ev @ Event::Start(Tag::List(..))) => {
                     self.back(ev);
-                    let mut bunch_of_items = self.parse_nested_numbered(&root_number)?;
+                    let mut bunch_of_items = self.parse_nested_numbered(root_number)?;
 
                     // if we've resumed after something like a rule the root sections
                     // will be numbered from 1. We need to manually go back and update
@@ -452,7 +454,7 @@ impl<'a> SummaryParser<'a> {
                     items.push(item);
                 }
                 Some(Event::Start(Tag::List(..))) => {
-                    // Skip this tag after comment bacause it is not nested.
+                    // Skip this tag after comment because it is not nested.
                     if items.is_empty() {
                         continue;
                     }
@@ -525,14 +527,23 @@ impl<'a> SummaryParser<'a> {
 
     /// Try to parse the title line.
     fn parse_title(&mut self) -> Option<String> {
-        match self.next_event() {
-            Some(Event::Start(Tag::Heading(1))) => {
-                debug!("Found a h1 in the SUMMARY");
+        loop {
+            match self.next_event() {
+                Some(Event::Start(Tag::Heading(HeadingLevel::H1, ..))) => {
+                    debug!("Found a h1 in the SUMMARY");
 
-                let tags = collect_events!(self.stream, end Tag::Heading(1));
-                Some(stringify_events(tags))
+                    let tags = collect_events!(self.stream, end Tag::Heading(HeadingLevel::H1, ..));
+                    return Some(stringify_events(tags));
+                }
+                // Skip a HTML element such as a comment line.
+                Some(Event::Html(_)) => {}
+                // Otherwise, no title.
+                Some(ev) => {
+                    self.back(ev);
+                    return None;
+                }
+                _ => return None,
             }
-            _ => None,
         }
     }
 }
@@ -642,6 +653,18 @@ mod tests {
         assert_eq!(got, should_be);
     }
 
+    #[test]
+    fn no_initial_title() {
+        let src = "[Link]()";
+        let mut parser = SummaryParser::new(src);
+
+        assert!(parser.parse_title().is_none());
+        assert!(matches!(
+            parser.next_event(),
+            Some(Event::Start(Tag::Paragraph))
+        ));
+    }
+
     #[test]
     fn parse_title_with_styling() {
         let src = "# My **Awesome** Summary";
@@ -973,4 +996,103 @@ mod tests {
 
         assert_eq!(got, should_be);
     }
+
+    #[test]
+    fn skip_html_comments() {
+        let src = r#"<!--
+# Title - En
+-->
+# Title - Local
+
+<!--
+[Prefix 00-01 - En](ch00-01.md)
+[Prefix 00-02 - En](ch00-02.md)
+-->
+[Prefix 00-01 - Local](ch00-01.md)
+[Prefix 00-02 - Local](ch00-02.md)
+
+<!--
+## Section Title - En
+-->
+## Section Title - Localized
+
+<!--
+- [Ch 01-00 - En](ch01-00.md)
+    - [Ch 01-01 - En](ch01-01.md)
+    - [Ch 01-02 - En](ch01-02.md)
+-->
+- [Ch 01-00 - Local](ch01-00.md)
+    - [Ch 01-01 - Local](ch01-01.md)
+    - [Ch 01-02 - Local](ch01-02.md)
+
+<!--
+- [Ch 02-00 - En](ch02-00.md)
+-->
+- [Ch 02-00 - Local](ch02-00.md)
+
+<!--
+[Appendix A - En](appendix-01.md)
+[Appendix B - En](appendix-02.md)
+-->`
+[Appendix A - Local](appendix-01.md)
+[Appendix B - Local](appendix-02.md)
+"#;
+
+        let mut parser = SummaryParser::new(src);
+
+        // ---- Title ----
+        let title = parser.parse_title();
+        assert_eq!(title, Some(String::from("Title - Local")));
+
+        // ---- Prefix Chapters ----
+
+        let new_affix_item = |name, location| {
+            SummaryItem::Link(Link {
+                name: String::from(name),
+                location: Some(PathBuf::from(location)),
+                ..Default::default()
+            })
+        };
+
+        let should_be = vec![
+            new_affix_item("Prefix 00-01 - Local", "ch00-01.md"),
+            new_affix_item("Prefix 00-02 - Local", "ch00-02.md"),
+        ];
+
+        let got = parser.parse_affix(true).unwrap();
+        assert_eq!(got, should_be);
+
+        // ---- Numbered Chapters ----
+
+        let new_numbered_item = |name, location, numbers: &[u32], nested_items| {
+            SummaryItem::Link(Link {
+                name: String::from(name),
+                location: Some(PathBuf::from(location)),
+                number: Some(SectionNumber(numbers.to_vec())),
+                nested_items,
+            })
+        };
+
+        let ch01_nested = vec![
+            new_numbered_item("Ch 01-01 - Local", "ch01-01.md", &[1, 1], vec![]),
+            new_numbered_item("Ch 01-02 - Local", "ch01-02.md", &[1, 2], vec![]),
+        ];
+
+        let should_be = vec![
+            new_numbered_item("Ch 01-00 - Local", "ch01-00.md", &[1], ch01_nested),
+            new_numbered_item("Ch 02-00 - Local", "ch02-00.md", &[2], vec![]),
+        ];
+        let got = parser.parse_parts().unwrap();
+        assert_eq!(got, should_be);
+
+        // ---- Suffix Chapters ----
+
+        let should_be = vec![
+            new_affix_item("Appendix A - Local", "appendix-01.md"),
+            new_affix_item("Appendix B - Local", "appendix-02.md"),
+        ];
+
+        let got = parser.parse_affix(false).unwrap();
+        assert_eq!(got, should_be);
+    }
 }

src/cmd/build.rs

@@ -1,38 +1,37 @@
+use super::command_prelude::*;
 use crate::{get_book_dir, open};
-use clap::{App, ArgMatches, SubCommand};
 use mdbook::errors::Result;
 use mdbook::MDBook;
+use std::path::PathBuf;
 
 // Create clap subcommand arguments
-pub fn make_subcommand<'a, 'b>() -> App<'a, 'b> {
-    SubCommand::with_name("build")
+pub fn make_subcommand() -> Command {
+    Command::new("build")
         .about("Builds a book from its markdown files")
-        .arg_from_usage(
-            "-d, --dest-dir=[dest-dir] 'Output directory for the book{n}\
-             Relative paths are interpreted relative to the book's root directory.{n}\
-             If omitted, mdBook uses build.build-dir from book.toml or defaults to `./book`.'",
-        )
-        .arg_from_usage(
-            "[dir] 'Root directory for the book{n}\
-             (Defaults to the Current Directory when omitted)'",
-        )
-        .arg_from_usage("-o, --open 'Opens the compiled book in a web browser'")
+        .arg_dest_dir()
+        .arg_root_dir()
+        .arg_open()
 }
 
 // Build command implementation
 pub fn execute(args: &ArgMatches) -> Result<()> {
     let book_dir = get_book_dir(args);
-    let mut book = MDBook::load(&book_dir)?;
+    let mut book = MDBook::load(book_dir)?;
 
-    if let Some(dest_dir) = args.value_of("dest-dir") {
+    if let Some(dest_dir) = args.get_one::<PathBuf>("dest-dir") {
         book.config.build.build_dir = dest_dir.into();
     }
 
     book.build()?;
 
-    if args.is_present("open") {
+    if args.get_flag("open") {
         // FIXME: What's the right behaviour if we don't use the HTML renderer?
-        open(book.build_dir_for("html").join("index.html"));
+        let path = book.build_dir_for("html").join("index.html");
+        if !path.exists() {
+            error!("No chapter available to open");
+            std::process::exit(1)
+        }
+        open(path);
     }
 
     Ok(())

src/cmd/clean.rs

@@ -1,31 +1,24 @@
+use super::command_prelude::*;
 use crate::get_book_dir;
 use anyhow::Context;
-use clap::{App, ArgMatches, SubCommand};
 use mdbook::MDBook;
 use std::fs;
+use std::path::PathBuf;
 
 // Create clap subcommand arguments
-pub fn make_subcommand<'a, 'b>() -> App<'a, 'b> {
-    SubCommand::with_name("clean")
+pub fn make_subcommand() -> Command {
+    Command::new("clean")
         .about("Deletes a built book")
-        .arg_from_usage(
-            "-d, --dest-dir=[dest-dir] 'Output directory for the book{n}\
-             Relative paths are interpreted relative to the book's root directory.{n}\
-             Running this command deletes this directory.{n}\
-             If omitted, mdBook uses build.build-dir from book.toml or defaults to `./book`.'",
-        )
-        .arg_from_usage(
-            "[dir] 'Root directory for the book{n}\
-             (Defaults to the Current Directory when omitted)'",
-        )
+        .arg_dest_dir()
+        .arg_root_dir()
 }
 
 // Clean command implementation
 pub fn execute(args: &ArgMatches) -> mdbook::errors::Result<()> {
     let book_dir = get_book_dir(args);
-    let book = MDBook::load(&book_dir)?;
+    let book = MDBook::load(book_dir)?;
 
-    let dir_to_remove = match args.value_of("dest-dir") {
+    let dir_to_remove = match args.get_one::<PathBuf>("dest-dir") {
         Some(dest_dir) => dest_dir.into(),
         None => book.root.join(&book.config.build.build_dir),
     };

src/cmd/command_prelude.rs

@@ -0,0 +1,45 @@
+//! Helpers for building the command-line arguments for commands.
+
+pub use clap::{arg, Arg, ArgMatches, Command};
+use std::path::PathBuf;
+
+pub trait CommandExt: Sized {
+    fn _arg(self, arg: Arg) -> Self;
+
+    fn arg_dest_dir(self) -> Self {
+        self._arg(
+            Arg::new("dest-dir")
+                .short('d')
+                .long("dest-dir")
+                .value_name("dest-dir")
+                .value_parser(clap::value_parser!(PathBuf))
+                .help(
+                    "Output directory for the book\n\
+                    Relative paths are interpreted relative to the book's root directory.\n\
+                    If omitted, mdBook uses build.build-dir from book.toml \
+                    or defaults to `./book`.",
+                ),
+        )
+    }
+
+    fn arg_root_dir(self) -> Self {
+        self._arg(
+            Arg::new("dir")
+                .help(
+                    "Root directory for the book\n\
+                    (Defaults to the current directory when omitted)",
+                )
+                .value_parser(clap::value_parser!(PathBuf)),
+        )
+    }
+
+    fn arg_open(self) -> Self {
+        self._arg(arg!(-o --open "Opens the compiled book in a web browser"))
+    }
+}
+
+impl CommandExt for Command {
+    fn _arg(self, arg: Arg) -> Self {
+        self.arg(arg)
+    }
+}

src/cmd/init.rs

@@ -1,5 +1,5 @@
 use crate::get_book_dir;
-use clap::{App, ArgMatches, SubCommand};
+use clap::{arg, ArgMatches, Command as ClapCommand};
 use mdbook::config;
 use mdbook::errors::Result;
 use mdbook::MDBook;
@@ -8,16 +8,23 @@ use std::io::Write;
 use std::process::Command;
 
 // Create clap subcommand arguments
-pub fn make_subcommand<'a, 'b>() -> App<'a, 'b> {
-    SubCommand::with_name("init")
+pub fn make_subcommand() -> ClapCommand {
+    ClapCommand::new("init")
         .about("Creates the boilerplate structure and files for a new book")
-        // the {n} denotes a newline which will properly aligned in all help messages
-        .arg_from_usage(
-            "[dir] 'Directory to create the book in{n}\
-             (Defaults to the Current Directory when omitted)'",
+        .arg(
+            arg!([dir]
+                "Directory to create the book in\n\
+                (Defaults to the current directory when omitted)"
+            )
+            .value_parser(clap::value_parser!(std::path::PathBuf)),
+        )
+        .arg(arg!(--theme "Copies the default theme into your source folder"))
+        .arg(arg!(--force "Skips confirmation prompts"))
+        .arg(arg!(--title <title> "Sets the book title"))
+        .arg(
+            arg!(--ignore <ignore> "Creates a VCS ignore file (i.e. .gitignore)")
+                .value_parser(["none", "git"]),
         )
-        .arg_from_usage("--theme 'Copies the default theme into your source folder'")
-        .arg_from_usage("--force 'Skips confirmation prompts'")
 }
 
 // Init command implementation
@@ -25,18 +32,13 @@ pub fn execute(args: &ArgMatches) -> Result<()> {
     let book_dir = get_book_dir(args);
     let mut builder = MDBook::init(&book_dir);
     let mut config = config::Config::default();
-
     // If flag `--theme` is present, copy theme to src
-    if args.is_present("theme") {
-        config.set("output.html.theme", "src/theme")?;
+    if args.get_flag("theme") {
+        let theme_dir = book_dir.join("theme");
+        println!();
+        println!("Copying the default theme to {}", theme_dir.display());
         // Skip this if `--force` is present
-        if !args.is_present("force") {
-            // Print warning
-            println!();
-            println!(
-                "Copying the default theme to {}",
-                builder.config().book.src.display()
-            );
+        if !args.get_flag("force") && theme_dir.exists() {
             println!("This could potentially overwrite files already present in that directory.");
             print!("\nAre you sure you want to continue? (y/n) ");
 
@@ -49,13 +51,25 @@ pub fn execute(args: &ArgMatches) -> Result<()> {
         }
     }
 
-    println!("\nDo you want a .gitignore to be created? (y/n)");
-
-    if confirm() {
-        builder.create_gitignore(true);
+    if let Some(ignore) = args.get_one::<String>("ignore").map(|s| s.as_str()) {
+        match ignore {
+            "git" => builder.create_gitignore(true),
+            _ => builder.create_gitignore(false),
+        };
+    } else if !args.get_flag("force") {
+        println!("\nDo you want a .gitignore to be created? (y/n)");
+        if confirm() {
+            builder.create_gitignore(true);
+        }
     }
 
-    config.book.title = request_book_title();
+    config.book.title = if args.contains_id("title") {
+        args.get_one::<String>("title").map(String::from)
+    } else if args.get_flag("force") {
+        None
+    } else {
+        request_book_title()
+    };
 
     if let Some(author) = get_author_name() {
         debug!("Obtained user name from gitconfig: {:?}", author);
@@ -72,7 +86,7 @@ pub fn execute(args: &ArgMatches) -> Result<()> {
 /// Obtains author name from git config file by running the `git config` command.
 fn get_author_name() -> Option<String> {
     let output = Command::new("git")
-        .args(&["config", "--get", "user.name"])
+        .args(["config", "--get", "user.name"])
         .output()
         .ok()?;
 
@@ -102,8 +116,5 @@ fn confirm() -> bool {
     io::stdout().flush().unwrap();
     let mut s = String::new();
     io::stdin().read_line(&mut s).ok();
-    match &*s.trim() {
-        "Y" | "y" | "yes" | "Yes" => true,
-        _ => false,
-    }
+    matches!(s.trim(), "Y" | "y" | "yes" | "Yes")
 }

src/cmd/mod.rs

@@ -2,6 +2,7 @@
 
 pub mod build;
 pub mod clean;
+pub mod command_prelude;
 pub mod init;
 #[cfg(feature = "serve")]
 pub mod serve;

src/cmd/serve.rs

@@ -1,7 +1,8 @@
+use super::command_prelude::*;
 #[cfg(feature = "watch")]
 use super::watch;
 use crate::{get_book_dir, open};
-use clap::{App, Arg, ArgMatches, SubCommand};
+use clap::builder::NonEmptyStringValueParser;
 use futures_util::sink::SinkExt;
 use futures_util::StreamExt;
 use mdbook::errors::*;
@@ -18,56 +19,48 @@ use warp::Filter;
 const LIVE_RELOAD_ENDPOINT: &str = "__livereload";
 
 // Create clap subcommand arguments
-pub fn make_subcommand<'a, 'b>() -> App<'a, 'b> {
-    SubCommand::with_name("serve")
+pub fn make_subcommand() -> Command {
+    Command::new("serve")
         .about("Serves a book at http://localhost:3000, and rebuilds it on changes")
-        .arg_from_usage(
-            "-d, --dest-dir=[dest-dir] 'Output directory for the book{n}\
-             Relative paths are interpreted relative to the book's root directory.{n}\
-             If omitted, mdBook uses build.build-dir from book.toml or defaults to `./book`.'",
-        )
-        .arg_from_usage(
-            "[dir] 'Root directory for the book{n}\
-             (Defaults to the Current Directory when omitted)'",
-        )
+        .arg_dest_dir()
+        .arg_root_dir()
         .arg(
-            Arg::with_name("hostname")
-                .short("n")
+            Arg::new("hostname")
+                .short('n')
                 .long("hostname")
-                .takes_value(true)
+                .num_args(1)
                 .default_value("localhost")
-                .empty_values(false)
+                .value_parser(NonEmptyStringValueParser::new())
                 .help("Hostname to listen on for HTTP connections"),
         )
         .arg(
-            Arg::with_name("port")
-                .short("p")
+            Arg::new("port")
+                .short('p')
                 .long("port")
-                .takes_value(true)
+                .num_args(1)
                 .default_value("3000")
-                .empty_values(false)
+                .value_parser(NonEmptyStringValueParser::new())
                 .help("Port to use for HTTP connections"),
         )
-        .arg_from_usage("-o, --open 'Opens the book server in a web browser'")
+        .arg_open()
 }
 
 // Serve command implementation
 pub fn execute(args: &ArgMatches) -> Result<()> {
     let book_dir = get_book_dir(args);
-    let mut book = MDBook::load(&book_dir)?;
+    let mut book = MDBook::load(book_dir)?;
 
-    let port = args.value_of("port").unwrap();
-    let hostname = args.value_of("hostname").unwrap();
-    let open_browser = args.is_present("open");
+    let port = args.get_one::<String>("port").unwrap();
+    let hostname = args.get_one::<String>("hostname").unwrap();
+    let open_browser = args.get_flag("open");
 
     let address = format!("{}:{}", hostname, port);
 
-    let livereload_url = format!("ws://{}/{}", address, LIVE_RELOAD_ENDPOINT);
     let update_config = |book: &mut MDBook| {
         book.config
-            .set("output.html.livereload-url", &livereload_url)
-            .expect("livereload-url update failed");
-        if let Some(dest_dir) = args.value_of("dest-dir") {
+            .set("output.html.live-reload-endpoint", LIVE_RELOAD_ENDPOINT)
+            .expect("live-reload-endpoint update failed");
+        if let Some(dest_dir) = args.get_one::<PathBuf>("dest-dir") {
             book.config.build.build_dir = dest_dir.into();
         }
         // Override site-url for local serving of the 404 file
@@ -84,8 +77,7 @@ pub fn execute(args: &ArgMatches) -> Result<()> {
     let input_404 = book
         .config
         .get("output.html.input-404")
-        .map(toml::Value::as_str)
-        .and_then(std::convert::identity) // flatten
+        .and_then(toml::Value::as_str)
         .map(ToString::to_string);
     let file_404 = get_404_output_file(&input_404);
 
@@ -110,7 +102,7 @@ pub fn execute(args: &ArgMatches) -> Result<()> {
         info!("Building book...");
 
         // FIXME: This area is really ugly because we need to re-set livereload :(
-        let result = MDBook::load(&book_dir).and_then(|mut b| {
+        let result = MDBook::load(book_dir).and_then(|mut b| {
             update_config(&mut b);
             b.build()
         });
@@ -161,5 +153,12 @@ async fn serve(
     let fallback_route = warp::fs::file(build_dir.join(file_404))
         .map(|reply| warp::reply::with_status(reply, warp::http::StatusCode::NOT_FOUND));
     let routes = livereload.or(book_route).or(fallback_route);
+
+    std::panic::set_hook(Box::new(move |panic_info| {
+        // exit if serve panics
+        error!("Unable to serve: {}", panic_info);
+        std::process::exit(1);
+    }));
+
     warp::serve(routes).run(address).await;
 }

src/cmd/test.rs

@@ -1,46 +1,58 @@
+use super::command_prelude::*;
 use crate::get_book_dir;
-use clap::{App, Arg, ArgMatches, SubCommand};
+use clap::builder::NonEmptyStringValueParser;
+use clap::{Arg, ArgAction, ArgMatches, Command};
 use mdbook::errors::Result;
 use mdbook::MDBook;
+use std::path::PathBuf;
 
 // Create clap subcommand arguments
-pub fn make_subcommand<'a, 'b>() -> App<'a, 'b> {
-    SubCommand::with_name("test")
+pub fn make_subcommand() -> Command {
+    Command::new("test")
         .about("Tests that a book's Rust code samples compile")
-        .arg_from_usage(
-            "-d, --dest-dir=[dest-dir] 'Output directory for the book{n}\
-             Relative paths are interpreted relative to the book's root directory.{n}\
-             If omitted, mdBook uses build.build-dir from book.toml or defaults to `./book`.'",
+        // FIXME: --dest-dir is unused by the test command, it should be removed
+        .arg_dest_dir()
+        .arg_root_dir()
+        .arg(
+            Arg::new("chapter")
+                .short('c')
+                .long("chapter")
+                .value_name("chapter"),
         )
-        .arg_from_usage(
-            "[dir] 'Root directory for the book{n}\
-             (Defaults to the Current Directory when omitted)'",
+        .arg(
+            Arg::new("library-path")
+                .short('L')
+                .long("library-path")
+                .value_name("dir")
+                .value_delimiter(',')
+                .value_parser(NonEmptyStringValueParser::new())
+                .action(ArgAction::Append)
+                .help(
+                    "A comma-separated list of directories to add to the crate \
+                    search path when building tests",
+                ),
         )
-        .arg(Arg::with_name("library-path")
-            .short("L")
-            .long("library-path")
-            .value_name("dir")
-            .takes_value(true)
-            .require_delimiter(true)
-            .multiple(true)
-            .empty_values(false)
-            .help("A comma-separated list of directories to add to {n}the crate search path when building tests"))
 }
 
 // test command implementation
 pub fn execute(args: &ArgMatches) -> Result<()> {
     let library_paths: Vec<&str> = args
-        .values_of("library-path")
-        .map(std::iter::Iterator::collect)
+        .get_many("library-path")
+        .map(|it| it.map(String::as_str).collect())
         .unwrap_or_default();
+
+    let chapter: Option<&str> = args.get_one::<String>("chapter").map(|s| s.as_str());
+
     let book_dir = get_book_dir(args);
-    let mut book = MDBook::load(&book_dir)?;
+    let mut book = MDBook::load(book_dir)?;
 
-    if let Some(dest_dir) = args.value_of("dest-dir") {
-        book.config.build.build_dir = dest_dir.into();
+    if let Some(dest_dir) = args.get_one::<PathBuf>("dest-dir") {
+        book.config.build.build_dir = dest_dir.to_path_buf();
     }
-
-    book.test(library_paths)?;
+    match chapter {
+        Some(_) => book.test_chapter(library_paths, chapter),
+        None => book.test(library_paths),
+    }?;
 
     Ok(())
 }

src/cmd/watch.rs

@@ -1,50 +1,48 @@
+use super::command_prelude::*;
 use crate::{get_book_dir, open};
-use clap::{App, ArgMatches, SubCommand};
+use ignore::gitignore::Gitignore;
 use mdbook::errors::Result;
 use mdbook::utils;
 use mdbook::MDBook;
-use notify::Watcher;
 use std::path::{Path, PathBuf};
 use std::sync::mpsc::channel;
 use std::thread::sleep;
 use std::time::Duration;
 
 // Create clap subcommand arguments
-pub fn make_subcommand<'a, 'b>() -> App<'a, 'b> {
-    SubCommand::with_name("watch")
+pub fn make_subcommand() -> Command {
+    Command::new("watch")
         .about("Watches a book's files and rebuilds it on changes")
-        .arg_from_usage(
-            "-d, --dest-dir=[dest-dir] 'Output directory for the book{n}\
-             Relative paths are interpreted relative to the book's root directory.{n}\
-             If omitted, mdBook uses build.build-dir from book.toml or defaults to `./book`.'",
-        )
-        .arg_from_usage(
-            "[dir] 'Root directory for the book{n}\
-             (Defaults to the Current Directory when omitted)'",
-        )
-        .arg_from_usage("-o, --open 'Open the compiled book in a web browser'")
+        .arg_dest_dir()
+        .arg_root_dir()
+        .arg_open()
 }
 
 // Watch command implementation
 pub fn execute(args: &ArgMatches) -> Result<()> {
     let book_dir = get_book_dir(args);
-    let mut book = MDBook::load(&book_dir)?;
+    let mut book = MDBook::load(book_dir)?;
 
     let update_config = |book: &mut MDBook| {
-        if let Some(dest_dir) = args.value_of("dest-dir") {
+        if let Some(dest_dir) = args.get_one::<PathBuf>("dest-dir") {
             book.config.build.build_dir = dest_dir.into();
         }
     };
     update_config(&mut book);
 
-    if args.is_present("open") {
+    if args.get_flag("open") {
         book.build()?;
-        open(book.build_dir_for("html").join("index.html"));
+        let path = book.build_dir_for("html").join("index.html");
+        if !path.exists() {
+            error!("No chapter available to open");
+            std::process::exit(1)
+        }
+        open(path);
     }
 
     trigger_on_change(&book, |paths, book_dir| {
         info!("Files changed: {:?}\nBuilding book...\n", paths);
-        let result = MDBook::load(&book_dir).and_then(|mut b| {
+        let result = MDBook::load(book_dir).and_then(|mut b| {
             update_config(&mut b);
             b.build()
         });
@@ -58,21 +56,21 @@ pub fn execute(args: &ArgMatches) -> Result<()> {
     Ok(())
 }
 
-fn remove_ignored_files(book_root: &PathBuf, paths: &[PathBuf]) -> Vec<PathBuf> {
+fn remove_ignored_files(book_root: &Path, paths: &[PathBuf]) -> Vec<PathBuf> {
     if paths.is_empty() {
         return vec![];
     }
 
     match find_gitignore(book_root) {
         Some(gitignore_path) => {
-            match gitignore::File::new(gitignore_path.as_path()) {
-                Ok(exclusion_checker) => filter_ignored_files(exclusion_checker, paths),
-                Err(_) => {
-                    // We're unable to read the .gitignore file, so we'll silently allow everything.
-                    // Please see discussion: https://github.com/rust-lang/mdBook/pull/1051
-                    paths.iter().map(|path| path.to_path_buf()).collect()
-                }
+            let (ignore, err) = Gitignore::new(&gitignore_path);
+            if let Some(err) = err {
+                warn!(
+                    "error reading gitignore `{}`: {err}",
+                    gitignore_path.display()
+                );
             }
+            filter_ignored_files(ignore, paths)
         }
         None => {
             // There is no .gitignore file.
@@ -81,25 +79,20 @@ fn remove_ignored_files(book_root: &PathBuf, paths: &[PathBuf]) -> Vec<PathBuf>
     }
 }
 
-fn find_gitignore(book_root: &PathBuf) -> Option<PathBuf> {
+fn find_gitignore(book_root: &Path) -> Option<PathBuf> {
     book_root
         .ancestors()
         .map(|p| p.join(".gitignore"))
         .find(|p| p.exists())
 }
 
-fn filter_ignored_files(exclusion_checker: gitignore::File, paths: &[PathBuf]) -> Vec<PathBuf> {
+fn filter_ignored_files(ignore: Gitignore, paths: &[PathBuf]) -> Vec<PathBuf> {
     paths
         .iter()
-        .filter(|path| match exclusion_checker.is_excluded(path) {
-            Ok(exclude) => !exclude,
-            Err(error) => {
-                warn!(
-                    "Unable to determine if {:?} is excluded: {:?}. Including it.",
-                    &path, error
-                );
-                true
-            }
+        .filter(|path| {
+            !ignore
+                .matched_path_or_any_parents(path, path.is_dir())
+                .is_ignore()
         })
         .map(|path| path.to_path_buf())
         .collect()
@@ -110,30 +103,47 @@ pub fn trigger_on_change<F>(book: &MDBook, closure: F)
 where
     F: Fn(Vec<PathBuf>, &Path),
 {
-    use notify::DebouncedEvent::*;
     use notify::RecursiveMode::*;
 
     // Create a channel to receive the events.
     let (tx, rx) = channel();
 
-    let mut watcher = match notify::watcher(tx, Duration::from_secs(1)) {
-        Ok(w) => w,
+    let mut debouncer = match notify_debouncer_mini::new_debouncer(Duration::from_secs(1), None, tx)
+    {
+        Ok(d) => d,
         Err(e) => {
             error!("Error while trying to watch the files:\n\n\t{:?}", e);
             std::process::exit(1)
         }
     };
+    let watcher = debouncer.watcher();
 
     // Add the source directory to the watcher
-    if let Err(e) = watcher.watch(book.source_dir(), Recursive) {
+    if let Err(e) = watcher.watch(&book.source_dir(), Recursive) {
         error!("Error while watching {:?}:\n    {:?}", book.source_dir(), e);
         std::process::exit(1);
     };
 
-    let _ = watcher.watch(book.theme_dir(), Recursive);
+    let _ = watcher.watch(&book.theme_dir(), Recursive);
 
     // Add the book.toml file to the watcher if it exists
-    let _ = watcher.watch(book.root.join("book.toml"), NonRecursive);
+    let _ = watcher.watch(&book.root.join("book.toml"), NonRecursive);
+
+    for dir in &book.config.build.extra_watch_dirs {
+        let path = book.root.join(dir);
+        let canonical_path = path.canonicalize().unwrap_or_else(|e| {
+            error!("Error while watching extra directory {path:?}:\n    {e}");
+            std::process::exit(1);
+        });
+
+        if let Err(e) = watcher.watch(&canonical_path, Recursive) {
+            error!(
+                "Error while watching extra directory {:?}:\n    {:?}",
+                canonical_path, e
+            );
+            std::process::exit(1);
+        }
+    }
 
     info!("Listening for changes...");
 
@@ -144,18 +154,25 @@ where
 
         let all_events = std::iter::once(first_event).chain(other_events);
 
-        let paths = all_events
-            .filter_map(|event| {
-                debug!("Received filesystem event: {:?}", event);
-
-                match event {
-                    Create(path) | Write(path) | Remove(path) | Rename(_, path) => Some(path),
-                    _ => None,
+        let paths: Vec<_> = all_events
+            .filter_map(|event| match event {
+                Ok(events) => Some(events),
+                Err(errors) => {
+                    for error in errors {
+                        log::warn!("error while watching for changes: {error}");
+                    }
+                    None
                 }
             })
-            .collect::<Vec<_>>();
+            .flatten()
+            .map(|event| event.path)
+            .collect();
 
-        let paths = remove_ignored_files(&book.root, &paths[..]);
+        // If we are watching files outside the current repository (via extra-watch-dirs), then they are definitionally
+        // ignored by gitignore. So we handle this case by including such files into the watched paths list.
+        let any_external_paths = paths.iter().filter(|p| !p.starts_with(&book.root)).cloned();
+        let mut paths = remove_ignored_files(&book.root, &paths[..]);
+        paths.extend(any_external_paths);
 
         if !paths.is_empty() {
             closure(paths, &book.root);

src/config.rs

@@ -2,7 +2,7 @@
 //!
 //! The main entrypoint of the `config` module is the `Config` struct. This acts
 //! essentially as a bag of configuration information, with a couple
-//! pre-determined tables (`BookConfig` and `BuildConfig`) as well as support
+//! pre-determined tables ([`BookConfig`] and [`BuildConfig`]) as well as support
 //! for arbitrary data which is exposed to plugins and alternative backends.
 //!
 //!
@@ -49,6 +49,7 @@
 
 #![deny(missing_docs)]
 
+use log::{debug, trace, warn};
 use serde::{Deserialize, Deserializer, Serialize, Serializer};
 use std::collections::HashMap;
 use std::env;
@@ -227,10 +228,10 @@ impl Config {
         let value = Value::try_from(value)
             .with_context(|| "Unable to represent the item as a JSON Value")?;
 
-        if index.starts_with("book.") {
-            self.book.update_value(&index[5..], value);
-        } else if index.starts_with("build.") {
-            self.build.update_value(&index[6..], value);
+        if let Some(key) = index.strip_prefix("book.") {
+            self.book.update_value(key, value);
+        } else if let Some(key) = index.strip_prefix("build.") {
+            self.build.update_value(key, value);
         } else {
             self.rest.insert(index, value);
         }
@@ -294,7 +295,8 @@ impl Default for Config {
         }
     }
 }
-impl<'de> Deserialize<'de> for Config {
+
+impl<'de> serde::Deserialize<'de> for Config {
     fn deserialize<D: Deserializer<'de>>(de: D) -> std::result::Result<Self, D::Error> {
         let raw = Value::deserialize(de)?;
 
@@ -306,14 +308,14 @@ impl<'de> Deserialize<'de> for Config {
             warn!("`description` under a table called `[book]`, move the `destination` entry");
             warn!("from `[output.html]`, renamed to `build-dir`, under a table called");
             warn!("`[build]`, and it should all work.");
-            warn!("Documentation: http://rust-lang.github.io/mdBook/format/config.html");
+            warn!("Documentation: https://rust-lang.github.io/mdBook/format/config.html");
             return Ok(Config::from_legacy(raw));
         }
 
+        use serde::de::Error;
         let mut table = match raw {
             Value::Table(t) => t,
             _ => {
-                use serde::de::Error;
                 return Err(D::Error::custom(
                     "A config file should always be a toml table",
                 ));
@@ -322,17 +324,20 @@ impl<'de> Deserialize<'de> for Config {
 
         let book: BookConfig = table
             .remove("book")
-            .and_then(|value| value.try_into().ok())
+            .map(|book| book.try_into().map_err(D::Error::custom))
+            .transpose()?
             .unwrap_or_default();
 
         let build: BuildConfig = table
             .remove("build")
-            .and_then(|value| value.try_into().ok())
+            .map(|build| build.try_into().map_err(D::Error::custom))
+            .transpose()?
             .unwrap_or_default();
 
         let rust: RustConfig = table
             .remove("rust")
-            .and_then(|value| value.try_into().ok())
+            .map(|rust| rust.try_into().map_err(D::Error::custom))
+            .transpose()?
             .unwrap_or_default();
 
         Ok(Config {
@@ -352,6 +357,11 @@ impl Serialize for Config {
         let book_config = Value::try_from(&self.book).expect("should always be serializable");
         table.insert("book", book_config);
 
+        if self.build != BuildConfig::default() {
+            let build_config = Value::try_from(&self.build).expect("should always be serializable");
+            table.insert("build", build_config);
+        }
+
         if self.rust != RustConfig::default() {
             let rust_config = Value::try_from(&self.rust).expect("should always be serializable");
             table.insert("rust", rust_config);
@@ -362,15 +372,8 @@ impl Serialize for Config {
 }
 
 fn parse_env(key: &str) -> Option<String> {
-    const PREFIX: &str = "MDBOOK_";
-
-    if key.starts_with(PREFIX) {
-        let key = &key[PREFIX.len()..];
-
-        Some(key.to_lowercase().replace("__", ".").replace("_", "-"))
-    } else {
-        None
-    }
+    key.strip_prefix("MDBOOK_")
+        .map(|key| key.to_lowercase().replace("__", ".").replace('_', "-"))
 }
 
 fn is_legacy_format(table: &Value) -> bool {
@@ -408,6 +411,9 @@ pub struct BookConfig {
     pub multilingual: bool,
     /// The main language of the book.
     pub language: Option<String>,
+    /// The direction of text in the book: Left-to-right (LTR) or Right-to-left (RTL).
+    /// When not specified, the text direction is derived from [`BookConfig::language`].
+    pub text_direction: Option<TextDirection>,
 }
 
 impl Default for BookConfig {
@@ -419,6 +425,43 @@ impl Default for BookConfig {
             src: PathBuf::from("src"),
             multilingual: false,
             language: Some(String::from("en")),
+            text_direction: None,
+        }
+    }
+}
+
+impl BookConfig {
+    /// Gets the realized text direction, either from [`BookConfig::text_direction`]
+    /// or derived from [`BookConfig::language`], to be used by templating engines.
+    pub fn realized_text_direction(&self) -> TextDirection {
+        if let Some(direction) = self.text_direction {
+            direction
+        } else {
+            TextDirection::from_lang_code(self.language.as_deref().unwrap_or_default())
+        }
+    }
+}
+
+/// Text direction to use for HTML output
+#[derive(Debug, Copy, Clone, PartialEq, Serialize, Deserialize)]
+pub enum TextDirection {
+    /// Left to right.
+    #[serde(rename = "ltr")]
+    LeftToRight,
+    /// Right to left
+    #[serde(rename = "rtl")]
+    RightToLeft,
+}
+
+impl TextDirection {
+    /// Gets the text direction from language code
+    pub fn from_lang_code(code: &str) -> Self {
+        match code {
+            // list sourced from here: https://github.com/abarrak/rtl/blob/master/lib/rtl/core.rb#L16
+            "ar" | "ara" | "arc" | "ae" | "ave" | "egy" | "he" | "heb" | "nqo" | "pal" | "phn"
+            | "sam" | "syc" | "syr" | "fa" | "per" | "fas" | "ku" | "kur" | "ur" | "urd"
+            | "pus" | "ps" | "yi" | "yid" => TextDirection::RightToLeft,
+            _ => TextDirection::LeftToRight,
         }
     }
 }
@@ -435,6 +478,8 @@ pub struct BuildConfig {
     /// Should the default preprocessors always be used when they are
     /// compatible with the renderer?
     pub use_default_preprocessors: bool,
+    /// Extra directories to trigger rebuild when watching/serving
+    pub extra_watch_dirs: Vec<PathBuf>,
 }
 
 impl Default for BuildConfig {
@@ -443,6 +488,7 @@ impl Default for BuildConfig {
             build_dir: PathBuf::from("book"),
             create_missing: true,
             use_default_preprocessors: true,
+            extra_watch_dirs: Vec::new(),
         }
     }
 }
@@ -458,6 +504,9 @@ pub struct RustConfig {
 #[derive(Debug, Copy, Clone, PartialEq, Serialize, Deserialize)]
 /// Rust edition to use for the code.
 pub enum RustEdition {
+    /// The 2021 edition of Rust
+    #[serde(rename = "2021")]
+    E2021,
     /// The 2018 edition of Rust
     #[serde(rename = "2018")]
     E2018,
@@ -495,6 +544,8 @@ pub struct HtmlConfig {
     /// Playground settings.
     #[serde(alias = "playpen")]
     pub playground: Playground,
+    /// Code settings.
+    pub code: Code,
     /// Print settings.
     pub print: Print,
     /// Don't render section labels.
@@ -517,14 +568,17 @@ pub struct HtmlConfig {
     ///
     /// [custom domain]: https://docs.github.com/en/github/working-with-github-pages/managing-a-custom-domain-for-your-github-pages-site
     pub cname: Option<String>,
-    /// This is used as a bit of a workaround for the `mdbook serve` command.
-    /// Basically, because you set the websocket port from the command line, the
-    /// `mdbook serve` command needs a way to let the HTML renderer know where
-    /// to point livereloading at, if it has been enabled.
+    /// Edit url template, when set shows a "Suggest an edit" button for
+    /// directly jumping to editing the currently viewed page.
+    /// Contains {path} that is replaced with chapter source file path
+    pub edit_url_template: Option<String>,
+    /// Endpoint of websocket, for livereload usage. Value loaded from .toml
+    /// file is ignored, because our code overrides this field with an
+    /// internal value (`LIVE_RELOAD_ENDPOINT)
     ///
     /// This config item *should not be edited* by the end user.
     #[doc(hidden)]
-    pub livereload_url: Option<String>,
+    pub live_reload_endpoint: Option<String>,
     /// The mapping from old pages to new pages/URLs to use when generating
     /// redirects.
     pub redirect: HashMap<String, String>,
@@ -544,15 +598,17 @@ impl Default for HtmlConfig {
             additional_js: Vec::new(),
             fold: Fold::default(),
             playground: Playground::default(),
+            code: Code::default(),
             print: Print::default(),
             no_section_label: false,
             search: None,
             git_repository_url: None,
             git_repository_icon: None,
+            edit_url_template: None,
             input_404: None,
             site_url: None,
             cname: None,
-            livereload_url: None,
+            live_reload_endpoint: None,
             redirect: HashMap::new(),
         }
     }
@@ -561,7 +617,7 @@ impl Default for HtmlConfig {
 impl HtmlConfig {
     /// Returns the directory of theme from the provided root directory. If the
     /// directory is not present it will append the default directory of "theme"
-    pub fn theme_dir(&self, root: &PathBuf) -> PathBuf {
+    pub fn theme_dir(&self, root: &Path) -> PathBuf {
         match self.theme {
             Some(ref d) => root.join(d),
             None => root.join("theme"),
@@ -571,15 +627,20 @@ impl HtmlConfig {
 
 /// Configuration for how to render the print icon, print.html, and print.css.
 #[derive(Debug, Clone, PartialEq, Serialize, Deserialize)]
-#[serde(rename_all = "kebab-case")]
+#[serde(default, rename_all = "kebab-case")]
 pub struct Print {
     /// Whether print support is enabled.
     pub enable: bool,
+    /// Insert page breaks between chapters. Default: `true`.
+    pub page_break: bool,
 }
 
 impl Default for Print {
     fn default() -> Self {
-        Self { enable: true }
+        Self {
+            enable: true,
+            page_break: true,
+        }
     }
 }
 
@@ -608,6 +669,8 @@ pub struct Playground {
     pub copy_js: bool,
     /// Display line numbers on playground snippets. Default: `false`.
     pub line_numbers: bool,
+    /// Display the run button. Default: `true`
+    pub runnable: bool,
 }
 
 impl Default for Playground {
@@ -617,6 +680,23 @@ impl Default for Playground {
             copyable: true,
             copy_js: true,
             line_numbers: false,
+            runnable: true,
+        }
+    }
+}
+
+/// Configuration for tweaking how the the HTML renderer handles code blocks.
+#[derive(Debug, Clone, PartialEq, Serialize, Deserialize)]
+#[serde(default, rename_all = "kebab-case")]
+pub struct Code {
+    /// A prefix string to hide lines per language (one or more chars).
+    pub hidelines: HashMap<String, String>,
+}
+
+impl Default for Code {
+    fn default() -> Code {
+        Code {
+            hidelines: HashMap::new(),
         }
     }
 }
@@ -646,7 +726,7 @@ pub struct Search {
     pub boost_paragraph: u8,
     /// True if the searchword `micro` should match `microwave`. Default: `true`.
     pub expand: bool,
-    /// Documents are split into smaller parts, seperated by headings. This defines, until which
+    /// Documents are split into smaller parts, separated by headings. This defines, until which
     /// level of heading documents should be split. Default: `3`. (`### This is a level 3 heading`)
     pub heading_split_level: u8,
     /// Copy JavaScript files for the search functionality to the output directory?
@@ -682,7 +762,7 @@ trait Updateable<'de>: Serialize + Deserialize<'de> {
         let mut raw = Value::try_from(&self).expect("unreachable");
 
         if let Ok(value) = Value::try_from(value) {
-            let _ = raw.insert(key, value);
+            raw.insert(key, value);
         } else {
             return;
         }
@@ -699,6 +779,7 @@ impl<'de, T> Updateable<'de> for T where T: Serialize + Deserialize<'de> {}
 mod tests {
     use super::*;
     use crate::utils::fs::get_404_output_file;
+    use serde_json::json;
 
     const COMPLEX_CONFIG: &str = r#"
         [book]
@@ -747,11 +828,13 @@ mod tests {
             multilingual: true,
             src: PathBuf::from("source"),
             language: Some(String::from("ja")),
+            text_direction: None,
         };
         let build_should_be = BuildConfig {
             build_dir: PathBuf::from("outputs"),
             create_missing: false,
             use_default_preprocessors: true,
+            extra_watch_dirs: Vec::new(),
         };
         let rust_should_be = RustConfig { edition: None };
         let playground_should_be = Playground {
@@ -759,6 +842,7 @@ mod tests {
             copyable: true,
             copy_js: true,
             line_numbers: false,
+            runnable: true,
         };
         let html_should_be = HtmlConfig {
             curly_quotes: true,
@@ -789,6 +873,22 @@ mod tests {
         assert_eq!(got.html_config().unwrap(), html_should_be);
     }
 
+    #[test]
+    fn disable_runnable() {
+        let src = r#"
+        [book]
+        title = "Some Book"
+        description = "book book book"
+        authors = ["Shogo Takata"]
+
+        [output.html.playground]
+        runnable = false
+        "#;
+
+        let got = Config::from_str(src).unwrap();
+        assert!(!got.html_config().unwrap().playground.runnable);
+    }
+
     #[test]
     fn edition_2015() {
         let src = r#"
@@ -841,6 +941,26 @@ mod tests {
         assert_eq!(got.rust, rust_should_be);
     }
 
+    #[test]
+    fn edition_2021() {
+        let src = r#"
+        [book]
+        title = "mdBook Documentation"
+        description = "Create book from markdown files. Like Gitbook but implemented in Rust"
+        authors = ["Mathieu David"]
+        src = "./source"
+        [rust]
+        edition = "2021"
+        "#;
+
+        let rust_should_be = RustConfig {
+            edition: Some(RustEdition::E2021),
+        };
+
+        let got = Config::from_str(src).unwrap();
+        assert_eq!(got.rust, rust_should_be);
+    }
+
     #[test]
     fn load_arbitrary_output_type() {
         #[derive(Debug, Deserialize, PartialEq)]
@@ -925,6 +1045,7 @@ mod tests {
             build_dir: PathBuf::from("my-book"),
             create_missing: true,
             use_default_preprocessors: true,
+            extra_watch_dirs: Vec::new(),
         };
 
         let html_should_be = HtmlConfig {
@@ -975,7 +1096,7 @@ mod tests {
     fn encode_env_var(key: &str) -> String {
         format!(
             "MDBOOK_{}",
-            key.to_uppercase().replace('.', "__").replace("-", "_")
+            key.to_uppercase().replace('.', "__").replace('-', "_")
         )
     }
 
@@ -999,11 +1120,10 @@ mod tests {
     }
 
     #[test]
-    #[allow(clippy::approx_constant)]
     fn update_config_using_env_var_and_complex_value() {
         let mut cfg = Config::default();
         let key = "foo-bar.baz";
-        let value = json!({"array": [1, 2, 3], "number": 3.14});
+        let value = json!({"array": [1, 2, 3], "number": 13.37});
         let value_str = serde_json::to_string(&value).unwrap();
 
         assert!(cfg.get(key).is_none());
@@ -1060,4 +1180,144 @@ mod tests {
         assert_eq!(html_config.input_404, Some("missing.md".to_string()));
         assert_eq!(&get_404_output_file(&html_config.input_404), "missing.html");
     }
+
+    #[test]
+    fn text_direction_ltr() {
+        let src = r#"
+        [book]
+        text-direction = "ltr"
+        "#;
+
+        let got = Config::from_str(src).unwrap();
+        assert_eq!(got.book.text_direction, Some(TextDirection::LeftToRight));
+    }
+
+    #[test]
+    fn text_direction_rtl() {
+        let src = r#"
+        [book]
+        text-direction = "rtl"
+        "#;
+
+        let got = Config::from_str(src).unwrap();
+        assert_eq!(got.book.text_direction, Some(TextDirection::RightToLeft));
+    }
+
+    #[test]
+    fn text_direction_none() {
+        let src = r#"
+        [book]
+        "#;
+
+        let got = Config::from_str(src).unwrap();
+        assert_eq!(got.book.text_direction, None);
+    }
+
+    #[test]
+    fn test_text_direction() {
+        let mut cfg = BookConfig::default();
+
+        // test deriving the text direction from language codes
+        cfg.language = Some("ar".into());
+        assert_eq!(cfg.realized_text_direction(), TextDirection::RightToLeft);
+
+        cfg.language = Some("he".into());
+        assert_eq!(cfg.realized_text_direction(), TextDirection::RightToLeft);
+
+        cfg.language = Some("en".into());
+        assert_eq!(cfg.realized_text_direction(), TextDirection::LeftToRight);
+
+        cfg.language = Some("ja".into());
+        assert_eq!(cfg.realized_text_direction(), TextDirection::LeftToRight);
+
+        // test forced direction
+        cfg.language = Some("ar".into());
+        cfg.text_direction = Some(TextDirection::LeftToRight);
+        assert_eq!(cfg.realized_text_direction(), TextDirection::LeftToRight);
+
+        cfg.language = Some("ar".into());
+        cfg.text_direction = Some(TextDirection::RightToLeft);
+        assert_eq!(cfg.realized_text_direction(), TextDirection::RightToLeft);
+
+        cfg.language = Some("en".into());
+        cfg.text_direction = Some(TextDirection::LeftToRight);
+        assert_eq!(cfg.realized_text_direction(), TextDirection::LeftToRight);
+
+        cfg.language = Some("en".into());
+        cfg.text_direction = Some(TextDirection::RightToLeft);
+        assert_eq!(cfg.realized_text_direction(), TextDirection::RightToLeft);
+    }
+
+    #[test]
+    #[should_panic(expected = "Invalid configuration file")]
+    fn invalid_language_type_error() {
+        let src = r#"
+        [book]
+        title = "mdBook Documentation"
+        language = ["en", "pt-br"]
+        description = "Create book from markdown files. Like Gitbook but implemented in Rust"
+        authors = ["Mathieu David"]
+        src = "./source"
+        "#;
+
+        Config::from_str(src).unwrap();
+    }
+
+    #[test]
+    #[should_panic(expected = "Invalid configuration file")]
+    fn invalid_title_type() {
+        let src = r#"
+        [book]
+        title = 20
+        language = "en"
+        description = "Create book from markdown files. Like Gitbook but implemented in Rust"
+        authors = ["Mathieu David"]
+        src = "./source"
+        "#;
+
+        Config::from_str(src).unwrap();
+    }
+
+    #[test]
+    #[should_panic(expected = "Invalid configuration file")]
+    fn invalid_build_dir_type() {
+        let src = r#"
+        [build]
+        build-dir = 99
+        create-missing = false
+        "#;
+
+        Config::from_str(src).unwrap();
+    }
+
+    #[test]
+    #[should_panic(expected = "Invalid configuration file")]
+    fn invalid_rust_edition() {
+        let src = r#"
+        [rust]
+        edition = "1999"
+        "#;
+
+        Config::from_str(src).unwrap();
+    }
+
+    #[test]
+    fn print_config() {
+        let src = r#"
+        [output.html.print]
+        enable = false
+        "#;
+        let got = Config::from_str(src).unwrap();
+        let html_config = got.html_config().unwrap();
+        assert!(!html_config.print.enable);
+        assert!(html_config.print.page_break);
+        let src = r#"
+        [output.html.print]
+        page-break = false
+        "#;
+        let got = Config::from_str(src).unwrap();
+        let html_config = got.html_config().unwrap();
+        assert!(html_config.print.enable);
+        assert!(!html_config.print.page_break);
+    }
 }

src/lib.rs

@@ -76,26 +76,12 @@
 //! access to the various methods for working with the [`Config`].
 //!
 //! [user guide]: https://rust-lang.github.io/mdBook/
-//! [`RenderContext`]: renderer/struct.RenderContext.html
+//! [`RenderContext`]: renderer::RenderContext
 //! [relevant chapter]: https://rust-lang.github.io/mdBook/for_developers/backends.html
-//! [`Config`]: config/struct.Config.html
+//! [`Config`]: config::Config
 
 #![deny(missing_docs)]
 #![deny(rust_2018_idioms)]
-#![allow(clippy::comparison_chain)]
-
-#[macro_use]
-extern crate lazy_static;
-#[macro_use]
-extern crate log;
-#[macro_use]
-extern crate serde_derive;
-#[macro_use]
-extern crate serde_json;
-
-#[cfg(test)]
-#[macro_use]
-extern crate pretty_assertions;
 
 pub mod book;
 pub mod config;

src/main.rs

@@ -3,15 +3,17 @@ extern crate clap;
 #[macro_use]
 extern crate log;
 
+use anyhow::anyhow;
 use chrono::Local;
-use clap::{App, AppSettings, ArgMatches};
+use clap::{Arg, ArgMatches, Command};
+use clap_complete::Shell;
 use env_logger::Builder;
 use log::LevelFilter;
 use mdbook::utils;
 use std::env;
 use std::ffi::OsStr;
 use std::io::Write;
-use std::path::{Path, PathBuf};
+use std::path::PathBuf;
 
 mod cmd;
 
@@ -20,39 +22,33 @@ const VERSION: &str = concat!("v", crate_version!());
 fn main() {
     init_logger();
 
-    // Create a list of valid arguments and sub-commands
-    let app = App::new(crate_name!())
-        .about(crate_description!())
-        .author("Mathieu David <mathieudavid@mathieudavid.org>")
-        .version(VERSION)
-        .setting(AppSettings::GlobalVersion)
-        .setting(AppSettings::ArgRequiredElseHelp)
-        .setting(AppSettings::ColoredHelp)
-        .after_help(
-            "For more information about a specific command, try `mdbook <command> --help`\n\
-             The source code for mdBook is available at: https://github.com/rust-lang/mdBook",
-        )
-        .subcommand(cmd::init::make_subcommand())
-        .subcommand(cmd::build::make_subcommand())
-        .subcommand(cmd::test::make_subcommand())
-        .subcommand(cmd::clean::make_subcommand());
+    let command = create_clap_command();
 
-    #[cfg(feature = "watch")]
-    let app = app.subcommand(cmd::watch::make_subcommand());
-    #[cfg(feature = "serve")]
-    let app = app.subcommand(cmd::serve::make_subcommand());
-
-    // Check which subcomamnd the user ran...
-    let res = match app.get_matches().subcommand() {
-        ("init", Some(sub_matches)) => cmd::init::execute(sub_matches),
-        ("build", Some(sub_matches)) => cmd::build::execute(sub_matches),
-        ("clean", Some(sub_matches)) => cmd::clean::execute(sub_matches),
+    // Check which subcommand the user ran...
+    let res = match command.get_matches().subcommand() {
+        Some(("init", sub_matches)) => cmd::init::execute(sub_matches),
+        Some(("build", sub_matches)) => cmd::build::execute(sub_matches),
+        Some(("clean", sub_matches)) => cmd::clean::execute(sub_matches),
         #[cfg(feature = "watch")]
-        ("watch", Some(sub_matches)) => cmd::watch::execute(sub_matches),
+        Some(("watch", sub_matches)) => cmd::watch::execute(sub_matches),
         #[cfg(feature = "serve")]
-        ("serve", Some(sub_matches)) => cmd::serve::execute(sub_matches),
-        ("test", Some(sub_matches)) => cmd::test::execute(sub_matches),
-        (_, _) => unreachable!(),
+        Some(("serve", sub_matches)) => cmd::serve::execute(sub_matches),
+        Some(("test", sub_matches)) => cmd::test::execute(sub_matches),
+        Some(("completions", sub_matches)) => (|| {
+            let shell = sub_matches
+                .get_one::<Shell>("shell")
+                .ok_or_else(|| anyhow!("Shell name missing."))?;
+
+            let mut complete_app = create_clap_command();
+            clap_complete::generate(
+                *shell,
+                &mut complete_app,
+                "mdbook",
+                &mut std::io::stdout().lock(),
+            );
+            Ok(())
+        })(),
+        _ => unreachable!(),
     };
 
     if let Err(e) = res {
@@ -62,6 +58,42 @@ fn main() {
     }
 }
 
+/// Create a list of valid arguments and sub-commands
+fn create_clap_command() -> Command {
+    let app = Command::new(crate_name!())
+        .about(crate_description!())
+        .author("Mathieu David <mathieudavid@mathieudavid.org>")
+        .version(VERSION)
+        .propagate_version(true)
+        .arg_required_else_help(true)
+        .after_help(
+            "For more information about a specific command, try `mdbook <command> --help`\n\
+             The source code for mdBook is available at: https://github.com/rust-lang/mdBook",
+        )
+        .subcommand(cmd::init::make_subcommand())
+        .subcommand(cmd::build::make_subcommand())
+        .subcommand(cmd::test::make_subcommand())
+        .subcommand(cmd::clean::make_subcommand())
+        .subcommand(
+            Command::new("completions")
+                .about("Generate shell completions for your shell to stdout")
+                .arg(
+                    Arg::new("shell")
+                        .value_parser(clap::value_parser!(Shell))
+                        .help("the shell to generate completions for")
+                        .value_name("SHELL")
+                        .required(true),
+                ),
+        );
+
+    #[cfg(feature = "watch")]
+    let app = app.subcommand(cmd::watch::make_subcommand());
+    #[cfg(feature = "serve")]
+    let app = app.subcommand(cmd::serve::make_subcommand());
+
+    app
+}
+
 fn init_logger() {
     let mut builder = Builder::new();
 
@@ -89,11 +121,10 @@ fn init_logger() {
 }
 
 fn get_book_dir(args: &ArgMatches) -> PathBuf {
-    if let Some(dir) = args.value_of("dir") {
+    if let Some(p) = args.get_one::<PathBuf>("dir") {
         // Check if path is relative from current dir, or absolute...
-        let p = Path::new(dir);
         if p.is_relative() {
-            env::current_dir().unwrap().join(dir)
+            env::current_dir().unwrap().join(p)
         } else {
             p.to_path_buf()
         }
@@ -103,7 +134,13 @@ fn get_book_dir(args: &ArgMatches) -> PathBuf {
 }
 
 fn open<P: AsRef<OsStr>>(path: P) {
-    if let Err(e) = open::that(path) {
+    info!("Opening web browser");
+    if let Err(e) = opener::open(path) {
         error!("Error opening web browser: {}", e);
     }
 }
+
+#[test]
+fn verify_app() {
+    create_clap_command().debug_assert();
+}

src/preprocess/cmd.rs

@@ -1,6 +1,7 @@
 use super::{Preprocessor, PreprocessorContext};
 use crate::book::Book;
 use crate::errors::*;
+use log::{debug, trace, warn};
 use shlex::Shlex;
 use std::io::{self, Read, Write};
 use std::process::{Child, Command, Stdio};
@@ -49,7 +50,7 @@ impl CmdPreprocessor {
     fn write_input_to_child(&self, child: &mut Child, book: &Book, ctx: &PreprocessorContext) {
         let stdin = child.stdin.take().expect("Child has stdin");
 
-        if let Err(e) = self.write_input(stdin, &book, &ctx) {
+        if let Err(e) = self.write_input(stdin, book, ctx) {
             // Looks like the backend hung up before we could finish
             // sending it the render context. Log the error and keep going
             warn!("Error writing the RenderContext to the backend, {}", e);
@@ -109,18 +110,28 @@ impl Preprocessor for CmdPreprocessor {
 
         self.write_input_to_child(&mut child, &book, ctx);
 
-        let output = child
-            .wait_with_output()
-            .with_context(|| "Error waiting for the preprocessor to complete")?;
+        let output = child.wait_with_output().with_context(|| {
+            format!(
+                "Error waiting for the \"{}\" preprocessor to complete",
+                self.name
+            )
+        })?;
 
         trace!("{} exited with output: {:?}", self.cmd, output);
         ensure!(
             output.status.success(),
-            "The preprocessor exited unsuccessfully"
+            format!(
+                "The \"{}\" preprocessor exited unsuccessfully with {} status",
+                self.name, output.status
+            )
         );
 
-        serde_json::from_slice(&output.stdout)
-            .with_context(|| "Unable to parse the preprocessed book")
+        serde_json::from_slice(&output.stdout).with_context(|| {
+            format!(
+                "Unable to parse the preprocessed book from \"{}\" processor",
+                self.name
+            )
+        })
     }
 
     fn supports_renderer(&self, renderer: &str) -> bool {

src/preprocess/index.rs

@@ -1,10 +1,11 @@
 use regex::Regex;
 use std::path::Path;
 
-use crate::errors::*;
-
 use super::{Preprocessor, PreprocessorContext};
 use crate::book::{Book, BookItem};
+use crate::errors::*;
+use log::warn;
+use once_cell::sync::Lazy;
 
 /// A preprocessor for converting file name `README.md` to `index.md` since
 /// `README.md` is the de facto index file in markdown-based documentation.
@@ -67,9 +68,8 @@ fn warn_readme_name_conflict<P: AsRef<Path>>(readme_path: P, index_path: P) {
 }
 
 fn is_readme_file<P: AsRef<Path>>(path: P) -> bool {
-    lazy_static! {
-        static ref RE: Regex = Regex::new(r"(?i)^readme$").unwrap();
-    }
+    static RE: Lazy<Regex> = Lazy::new(|| Regex::new(r"(?i)^readme$").unwrap());
+
     RE.is_match(
         path.as_ref()
             .file_stem()

src/preprocess/links.rs

@@ -10,6 +10,8 @@ use std::path::{Path, PathBuf};
 
 use super::{Preprocessor, PreprocessorContext};
 use crate::book::{Book, BookItem};
+use log::{error, warn};
+use once_cell::sync::Lazy;
 
 const ESCAPE_CHAR: char = '\\';
 const MAX_LINK_NESTED_DEPTH: usize = 10;
@@ -23,6 +25,7 @@ const MAX_LINK_NESTED_DEPTH: usize = 10;
 ///   This hides the lines from initial display but shows them when the reader expands the code
 ///   block and provides them to Rustdoc for testing.
 /// - `{{# playground}}` - Insert runnable Rust files
+/// - `{{# title}}` - Override \<title\> of a webpage.
 #[derive(Default)]
 pub struct LinkPreprocessor;
 
@@ -51,8 +54,15 @@ impl Preprocessor for LinkPreprocessor {
                         .map(|dir| src_dir.join(dir))
                         .expect("All book items have a parent");
 
-                    let content = replace_all(&ch.content, base, chapter_path, 0);
+                    let mut chapter_title = ch.name.clone();
+                    let content =
+                        replace_all(&ch.content, base, chapter_path, 0, &mut chapter_title);
                     ch.content = content;
+                    if chapter_title != ch.name {
+                        ctx.chapter_titles
+                            .borrow_mut()
+                            .insert(chapter_path.clone(), chapter_title);
+                    }
                 }
             }
         });
@@ -61,7 +71,13 @@ impl Preprocessor for LinkPreprocessor {
     }
 }
 
-fn replace_all<P1, P2>(s: &str, path: P1, source: P2, depth: usize) -> String
+fn replace_all<P1, P2>(
+    s: &str,
+    path: P1,
+    source: P2,
+    depth: usize,
+    chapter_title: &mut String,
+) -> String
 where
     P1: AsRef<Path>,
     P2: AsRef<Path>,
@@ -77,11 +93,17 @@ where
     for link in find_links(s) {
         replaced.push_str(&s[previous_end_index..link.start_index]);
 
-        match link.render_with_path(&path) {
+        match link.render_with_path(path, chapter_title) {
             Ok(new_content) => {
                 if depth < MAX_LINK_NESTED_DEPTH {
                     if let Some(rel_path) = link.link_type.relative_path(path) {
-                        replaced.push_str(&replace_all(&new_content, rel_path, source, depth + 1));
+                        replaced.push_str(&replace_all(
+                            &new_content,
+                            rel_path,
+                            source,
+                            depth + 1,
+                            chapter_title,
+                        ));
                     } else {
                         replaced.push_str(&new_content);
                     }
@@ -116,6 +138,7 @@ enum LinkType<'a> {
     Include(PathBuf, RangeOrAnchor),
     Playground(PathBuf, Vec<&'a str>),
     RustdocInclude(PathBuf, RangeOrAnchor),
+    Title(&'a str),
 }
 
 #[derive(PartialEq, Debug, Clone)]
@@ -125,6 +148,7 @@ enum RangeOrAnchor {
 }
 
 // A range of lines specified with some include directive.
+#[allow(clippy::enum_variant_names)] // The prefix can't be removed, and is meant to mirror the contained type
 #[derive(PartialEq, Debug, Clone)]
 enum LineRange {
     Range(Range<usize>),
@@ -185,6 +209,7 @@ impl<'a> LinkType<'a> {
             LinkType::Include(p, _) => Some(return_relative_path(base, &p)),
             LinkType::Playground(p, _) => Some(return_relative_path(base, &p)),
             LinkType::RustdocInclude(p, _) => Some(return_relative_path(base, &p)),
+            LinkType::Title(_) => None,
         }
     }
 }
@@ -255,6 +280,9 @@ struct Link<'a> {
 impl<'a> Link<'a> {
     fn from_capture(cap: Captures<'a>) -> Option<Link<'a>> {
         let link_type = match (cap.get(0), cap.get(1), cap.get(2)) {
+            (_, Some(typ), Some(title)) if typ.as_str() == "title" => {
+                Some(LinkType::Title(title.as_str()))
+            }
             (_, Some(typ), Some(rest)) => {
                 let mut path_props = rest.as_str().split_whitespace();
                 let file_arg = path_props.next();
@@ -291,11 +319,15 @@ impl<'a> Link<'a> {
         })
     }
 
-    fn render_with_path<P: AsRef<Path>>(&self, base: P) -> Result<String> {
+    fn render_with_path<P: AsRef<Path>>(
+        &self,
+        base: P,
+        chapter_title: &mut String,
+    ) -> Result<String> {
         let base = base.as_ref();
         match self.link_type {
             // omit the escape char
-            LinkType::Escaped => Ok((&self.link_text[1..]).to_owned()),
+            LinkType::Escaped => Ok(self.link_text[1..].to_owned()),
             LinkType::Include(ref pat, ref range_or_anchor) => {
                 let target = base.join(pat);
 
@@ -335,7 +367,7 @@ impl<'a> Link<'a> {
             LinkType::Playground(ref pat, ref attrs) => {
                 let target = base.join(pat);
 
-                let contents = fs::read_to_string(&target).with_context(|| {
+                let mut contents = fs::read_to_string(&target).with_context(|| {
                     format!(
                         "Could not read file for link {} ({})",
                         self.link_text,
@@ -343,13 +375,20 @@ impl<'a> Link<'a> {
                     )
                 })?;
                 let ftype = if !attrs.is_empty() { "rust," } else { "rust" };
+                if !contents.ends_with('\n') {
+                    contents.push('\n');
+                }
                 Ok(format!(
-                    "```{}{}\n{}\n```\n",
+                    "```{}{}\n{}```\n",
                     ftype,
                     attrs.join(","),
                     contents
                 ))
             }
+            LinkType::Title(title) => {
+                *chapter_title = title.to_owned();
+                Ok(String::new())
+            }
         }
     }
 }
@@ -370,20 +409,21 @@ impl<'a> Iterator for LinkIter<'a> {
 
 fn find_links(contents: &str) -> LinkIter<'_> {
     // lazily compute following regex
-    // r"\\\{\{#.*\}\}|\{\{#([a-zA-Z0-9]+)\s*([a-zA-Z0-9_.\-:/\\\s]+)\}\}")?;
-    lazy_static! {
-        static ref RE: Regex = Regex::new(
-            r"(?x)                       # insignificant whitespace mode
-            \\\{\{\#.*\}\}               # match escaped link
-            |                            # or
-            \{\{\s*                      # link opening parens and whitespace
-            \#([a-zA-Z0-9_]+)            # link type
-            \s+                          # separating whitespace
-            ([a-zA-Z0-9\s_.\-:/\\\+]+)   # link target path and space separated properties
-            \s*\}\}                      # whitespace and link closing parens"
+    // r"\\\{\{#.*\}\}|\{\{#([a-zA-Z0-9]+)\s*([^}]+)\}\}")?;
+    static RE: Lazy<Regex> = Lazy::new(|| {
+        Regex::new(
+            r"(?x)              # insignificant whitespace mode
+        \\\{\{\#.*\}\}      # match escaped link
+        |                   # or
+        \{\{\s*             # link opening parens and whitespace
+        \#([a-zA-Z0-9_]+)   # link type
+        \s+                 # separating whitespace
+        ([^}]+)             # link target path and space separated properties
+        \}\}                # link closing parens",
         )
-        .unwrap();
-    }
+        .unwrap()
+    });
+
     LinkIter(RE.captures_iter(contents))
 }
 
@@ -403,7 +443,21 @@ mod tests {
         ```hbs
         {{#include file.rs}} << an escaped link!
         ```";
-        assert_eq!(replace_all(start, "", "", 0), end);
+        let mut chapter_title = "test_replace_all_escaped".to_owned();
+        assert_eq!(replace_all(start, "", "", 0, &mut chapter_title), end);
+    }
+
+    #[test]
+    fn test_set_chapter_title() {
+        let start = r"{{#title My Title}}
+        # My Chapter
+        ";
+        let end = r"
+        # My Chapter
+        ";
+        let mut chapter_title = "test_set_chapter_title".to_owned();
+        assert_eq!(replace_all(start, "", "", 0, &mut chapter_title), end);
+        assert_eq!(chapter_title, "My Title");
     }
 
     #[test]

src/preprocess/mod.rs

@@ -12,6 +12,9 @@ use crate::book::Book;
 use crate::config::Config;
 use crate::errors::*;
 
+use serde::{Deserialize, Serialize};
+use std::cell::RefCell;
+use std::collections::HashMap;
 use std::path::PathBuf;
 
 /// Extra information for a `Preprocessor` to give them more context when
@@ -27,6 +30,8 @@ pub struct PreprocessorContext {
     /// The calling `mdbook` version.
     pub mdbook_version: String,
     #[serde(skip)]
+    pub(crate) chapter_titles: RefCell<HashMap<PathBuf, String>>,
+    #[serde(skip)]
     __non_exhaustive: (),
 }
 
@@ -38,6 +43,7 @@ impl PreprocessorContext {
             config,
             renderer,
             mdbook_version: crate::MDBOOK_VERSION.to_string(),
+            chapter_titles: RefCell::new(HashMap::new()),
             __non_exhaustive: (),
         }
     }

src/renderer/html_handlebars/hbs_renderer.rs

@@ -1,5 +1,5 @@
 use crate::book::{Book, BookItem};
-use crate::config::{Config, HtmlConfig, Playground, RustEdition};
+use crate::config::{BookConfig, Code, Config, HtmlConfig, Playground, RustEdition};
 use crate::errors::*;
 use crate::renderer::html_handlebars::helpers;
 use crate::renderer::{RenderContext, Renderer};
@@ -14,7 +14,10 @@ use std::path::{Path, PathBuf};
 
 use crate::utils::fs::get_404_output_file;
 use handlebars::Handlebars;
+use log::{debug, trace, warn};
+use once_cell::sync::Lazy;
 use regex::{Captures, Regex};
+use serde_json::json;
 
 #[derive(Default)]
 pub struct HtmlHandlebars;
@@ -37,14 +40,32 @@ impl HtmlHandlebars {
             _ => return Ok(()),
         };
 
+        if let Some(ref edit_url_template) = ctx.html_config.edit_url_template {
+            let full_path = ctx.book_config.src.to_str().unwrap_or_default().to_owned()
+                + "/"
+                + ch.source_path
+                    .clone()
+                    .unwrap_or_default()
+                    .to_str()
+                    .unwrap_or_default();
+
+            let edit_url = edit_url_template.replace("{path}", &full_path);
+            ctx.data
+                .insert("git_repository_edit_url".to_owned(), json!(edit_url));
+        }
+
         let content = ch.content.clone();
         let content = utils::render_markdown(&content, ctx.html_config.curly_quotes);
 
-        let fixed_content = utils::render_markdown_with_path(
-            &ch.content,
-            ctx.html_config.curly_quotes,
-            Some(&path),
-        );
+        let fixed_content =
+            utils::render_markdown_with_path(&ch.content, ctx.html_config.curly_quotes, Some(path));
+        if !ctx.is_index && ctx.html_config.print.page_break {
+            // Add page break between chapters
+            // See https://developer.mozilla.org/en-US/docs/Web/CSS/break-before and https://developer.mozilla.org/en-US/docs/Web/CSS/page-break-before
+            // Add both two CSS properties because of the compatibility issue
+            print_content
+                .push_str(r#"<div style="break-before: page; page-break-before: always;"></div>"#);
+        }
         print_content.push_str(&fixed_content);
 
         // Update the context with data for this file
@@ -64,9 +85,12 @@ impl HtmlHandlebars {
             .and_then(serde_json::Value::as_str)
             .unwrap_or("");
 
-        let title = match book_title {
-            "" => ch.name.clone(),
-            _ => ch.name.clone() + " - " + book_title,
+        let title = if let Some(title) = ctx.chapter_titles.get(path) {
+            title.clone()
+        } else if book_title.is_empty() {
+            ch.name.clone()
+        } else {
+            ch.name.clone() + " - " + book_title
         };
 
         ctx.data.insert("path".to_owned(), json!(path));
@@ -75,7 +99,7 @@ impl HtmlHandlebars {
         ctx.data.insert("title".to_owned(), json!(title));
         ctx.data.insert(
             "path_to_root".to_owned(),
-            json!(utils::fs::path_to_root(&path)),
+            json!(utils::fs::path_to_root(path)),
         );
         if let Some(ref section) = ch.number {
             ctx.data
@@ -86,7 +110,12 @@ impl HtmlHandlebars {
         debug!("Render template");
         let rendered = ctx.handlebars.render("index", &ctx.data)?;
 
-        let rendered = self.post_process(rendered, &ctx.html_config.playground, ctx.edition);
+        let rendered = self.post_process(
+            rendered,
+            &ctx.html_config.playground,
+            &ctx.html_config.code,
+            ctx.edition,
+        );
 
         // Write to file
         debug!("Creating {}", filepath.display());
@@ -95,10 +124,14 @@ impl HtmlHandlebars {
         if ctx.is_index {
             ctx.data.insert("path".to_owned(), json!("index.md"));
             ctx.data.insert("path_to_root".to_owned(), json!(""));
-            ctx.data.insert("is_index".to_owned(), json!("true"));
+            ctx.data.insert("is_index".to_owned(), json!(true));
             let rendered_index = ctx.handlebars.render("index", &ctx.data)?;
-            let rendered_index =
-                self.post_process(rendered_index, &ctx.html_config.playground, ctx.edition);
+            let rendered_index = self.post_process(
+                rendered_index,
+                &ctx.html_config.playground,
+                &ctx.html_config.code,
+                ctx.edition,
+            );
             debug!("Creating index.html from {}", ctx_path);
             utils::fs::write_file(&ctx.destination, "index.html", rendered_index.as_bytes())?;
         }
@@ -110,7 +143,7 @@ impl HtmlHandlebars {
         &self,
         ctx: &RenderContext,
         html_config: &HtmlConfig,
-        src_dir: &PathBuf,
+        src_dir: &Path,
         handlebars: &mut Handlebars<'_>,
         data: &mut serde_json::Map<String, serde_json::Value>,
     ) -> Result<()> {
@@ -149,12 +182,23 @@ impl HtmlHandlebars {
         // Set a dummy path to ensure other paths (e.g. in the TOC) are generated correctly
         data_404.insert("path".to_owned(), json!("404.md"));
         data_404.insert("content".to_owned(), json!(html_content_404));
+
+        let mut title = String::from("Page not found");
+        if let Some(book_title) = &ctx.config.book.title {
+            title.push_str(" - ");
+            title.push_str(book_title);
+        }
+        data_404.insert("title".to_owned(), json!(title));
         let rendered = handlebars.render("index", &data_404)?;
 
-        let rendered =
-            self.post_process(rendered, &html_config.playground, ctx.config.rust.edition);
+        let rendered = self.post_process(
+            rendered,
+            &html_config.playground,
+            &html_config.code,
+            ctx.config.rust.edition,
+        );
         let output_file = get_404_output_file(&html_config.input_404);
-        utils::fs::write_file(&destination, output_file, rendered.as_bytes())?;
+        utils::fs::write_file(destination, output_file, rendered.as_bytes())?;
         debug!("Creating 404.html ✓");
         Ok(())
     }
@@ -164,11 +208,13 @@ impl HtmlHandlebars {
         &self,
         rendered: String,
         playground_config: &Playground,
+        code_config: &Code,
         edition: Option<RustEdition>,
     ) -> String {
         let rendered = build_header_links(&rendered);
         let rendered = fix_code_blocks(&rendered);
         let rendered = add_playground_pre(&rendered, playground_config, edition);
+        let rendered = hide_lines(&rendered, code_config);
 
         rendered
     }
@@ -199,10 +245,10 @@ impl HtmlHandlebars {
         }
         write_file(destination, "css/variables.css", &theme.variables_css)?;
         if let Some(contents) = &theme.favicon_png {
-            write_file(destination, "favicon.png", &contents)?;
+            write_file(destination, "favicon.png", contents)?;
         }
         if let Some(contents) = &theme.favicon_svg {
-            write_file(destination, "favicon.svg", &contents)?;
+            write_file(destination, "favicon.svg", contents)?;
         }
         write_file(destination, "highlight.css", &theme.highlight_css)?;
         write_file(destination, "tomorrow-night.css", &theme.tomorrow_night_css)?;
@@ -244,7 +290,8 @@ impl HtmlHandlebars {
             "FontAwesome/fonts/FontAwesome.ttf",
             theme::FONT_AWESOME_TTF,
         )?;
-        if html_config.copy_fonts {
+        // Don't copy the stock fonts if the user has specified their own fonts to use.
+        if html_config.copy_fonts && theme.fonts_css.is_none() {
             write_file(destination, "fonts/fonts.css", theme::fonts::CSS)?;
             for (file_name, contents) in theme::fonts::LICENSES.iter() {
                 write_file(destination, file_name, contents)?;
@@ -258,6 +305,24 @@ impl HtmlHandlebars {
                 theme::fonts::SOURCE_CODE_PRO.1,
             )?;
         }
+        if let Some(fonts_css) = &theme.fonts_css {
+            if !fonts_css.is_empty() {
+                write_file(destination, "fonts/fonts.css", fonts_css)?;
+            }
+        }
+        if !html_config.copy_fonts && theme.fonts_css.is_none() {
+            warn!(
+                "output.html.copy-fonts is deprecated.\n\
+                This book appears to have copy-fonts=false in book.toml without a fonts.css file.\n\
+                Add an empty `theme/fonts/fonts.css` file to squelch this warning."
+            );
+        }
+        for font_file in &theme.font_files {
+            let contents = fs::read(font_file)?;
+            let filename = font_file.file_name().unwrap();
+            let filename = Path::new("fonts").join(filename);
+            write_file(destination, filename, &contents)?;
+        }
 
         let playground_config = &html_config.playground;
 
@@ -309,6 +374,7 @@ impl HtmlHandlebars {
         );
         handlebars.register_helper("previous", Box::new(helpers::navigation::previous));
         handlebars.register_helper("next", Box::new(helpers::navigation::next));
+        // TODO: remove theme_option in 0.5, it is not needed.
         handlebars.register_helper("theme_option", Box::new(helpers::theme::theme_option));
     }
 
@@ -366,7 +432,7 @@ impl HtmlHandlebars {
             // Note: all paths are relative to the build directory, so the
             // leading slash in an absolute path means nothing (and would mess
             // up `root.join(original)`).
-            let original = original.trim_start_matches("/");
+            let original = original.trim_start_matches('/');
             let filename = root.join(original);
             self.emit_redirect(handlebars, &filename, new)?;
         }
@@ -437,6 +503,7 @@ impl Renderer for HtmlHandlebars {
     }
 
     fn render(&self, ctx: &RenderContext) -> Result<()> {
+        let book_config = &ctx.config.book;
         let html_config = ctx.config.html_config().unwrap_or_default();
         let src_dir = ctx.root.join(&ctx.config.book.src);
         let destination = &ctx.destination;
@@ -452,7 +519,13 @@ impl Renderer for HtmlHandlebars {
         let mut handlebars = Handlebars::new();
 
         let theme_dir = match html_config.theme {
-            Some(ref theme) => theme.to_path_buf(),
+            Some(ref theme) => {
+                let dir = ctx.root.join(theme);
+                if !dir.is_dir() {
+                    bail!("theme dir {} does not exist", dir.display());
+                }
+                dir
+            }
             None => ctx.root.join("theme"),
         };
 
@@ -484,12 +557,12 @@ impl Renderer for HtmlHandlebars {
         debug!("Register handlebars helpers");
         self.register_hbs_helpers(&mut handlebars, &html_config);
 
-        let mut data = make_data(&ctx.root, &book, &ctx.config, &html_config, &theme)?;
+        let mut data = make_data(&ctx.root, book, &ctx.config, &html_config, &theme)?;
 
         // Print version
         let mut print_content = String::new();
 
-        fs::create_dir_all(&destination)
+        fs::create_dir_all(destination)
             .with_context(|| "Unexpected error when constructing destination path")?;
 
         let mut is_index = true;
@@ -499,11 +572,14 @@ impl Renderer for HtmlHandlebars {
                 destination: destination.to_path_buf(),
                 data: data.clone(),
                 is_index,
+                book_config: book_config.clone(),
                 html_config: html_config.clone(),
                 edition: ctx.config.rust.edition,
+                chapter_titles: &ctx.chapter_titles,
             };
             self.render_item(item, ctx, &mut print_content)?;
-            is_index = false;
+            // Only the first non-draft chapter item should be treated as the "index"
+            is_index &= !matches!(item, BookItem::Chapter(ch) if !ch.is_draft_chapter());
         }
 
         // Render 404 page
@@ -522,17 +598,21 @@ impl Renderer for HtmlHandlebars {
             debug!("Render template");
             let rendered = handlebars.render("index", &data)?;
 
-            let rendered =
-                self.post_process(rendered, &html_config.playground, ctx.config.rust.edition);
+            let rendered = self.post_process(
+                rendered,
+                &html_config.playground,
+                &html_config.code,
+                ctx.config.rust.edition,
+            );
 
-            utils::fs::write_file(&destination, "print.html", rendered.as_bytes())?;
+            utils::fs::write_file(destination, "print.html", rendered.as_bytes())?;
             debug!("Creating print.html ✓");
         }
 
         debug!("Copy static files");
-        self.copy_static_files(&destination, &theme, &html_config)
+        self.copy_static_files(destination, &theme, &html_config)
             .with_context(|| "Unable to copy across static files")?;
-        self.copy_additional_css_and_js(&html_config, &ctx.root, &destination)
+        self.copy_additional_css_and_js(&html_config, &ctx.root, destination)
             .with_context(|| "Unable to copy across additional CSS and JS")?;
 
         // Render search index
@@ -540,7 +620,7 @@ impl Renderer for HtmlHandlebars {
         {
             let search = html_config.search.unwrap_or_default();
             if search.enable {
-                super::search::create_files(&search, &destination, &book)?;
+                super::search::create_files(&search, destination, book)?;
             }
         }
 
@@ -548,7 +628,7 @@ impl Renderer for HtmlHandlebars {
             .context("Unable to emit redirects")?;
 
         // Copy all remaining files, avoid a recursive copy from/to the book build dir
-        utils::fs::copy_files_except_ext(&src_dir, &destination, true, Some(&build_dir), &["md"])?;
+        utils::fs::copy_files_except_ext(&src_dir, destination, true, Some(&build_dir), &["md"])?;
 
         Ok(())
     }
@@ -568,6 +648,10 @@ fn make_data(
         "language".to_owned(),
         json!(config.book.language.clone().unwrap_or_default()),
     );
+    data.insert(
+        "text_direction".to_owned(),
+        json!(config.book.realized_text_direction()),
+    );
     data.insert(
         "book_title".to_owned(),
         json!(config.book.title.clone().unwrap_or_default()),
@@ -582,10 +666,14 @@ fn make_data(
     if theme.favicon_svg.is_some() {
         data.insert("favicon_svg".to_owned(), json!("favicon.svg"));
     }
-    if let Some(ref livereload) = html_config.livereload_url {
-        data.insert("livereload".to_owned(), json!(livereload));
+    if let Some(ref live_reload_endpoint) = html_config.live_reload_endpoint {
+        data.insert(
+            "live_reload_endpoint".to_owned(),
+            json!(live_reload_endpoint),
+        );
     }
 
+    // TODO: remove default_theme in 0.5, it is not needed.
     let default_theme = match html_config.default_theme {
         Some(ref theme) => theme.to_lowercase(),
         None => "light".to_string(),
@@ -610,7 +698,8 @@ fn make_data(
         data.insert("mathjax_support".to_owned(), json!(true));
     }
 
-    if html_config.copy_fonts {
+    // This `matches!` checks for a non-empty file.
+    if html_config.copy_fonts || matches!(theme.fonts_css.as_deref(), Some([_, ..])) {
         data.insert("copy_fonts".to_owned(), json!(true));
     }
 
@@ -723,16 +812,35 @@ fn make_data(
 /// Goes through the rendered HTML, making sure all header tags have
 /// an anchor respectively so people can link to sections directly.
 fn build_header_links(html: &str) -> String {
-    let regex = Regex::new(r"<h(\d)>(.*?)</h\d>").unwrap();
+    static BUILD_HEADER_LINKS: Lazy<Regex> = Lazy::new(|| {
+        Regex::new(r#"<h(\d)(?: id="([^"]+)")?(?: class="([^"]+)")?>(.*?)</h\d>"#).unwrap()
+    });
+    static IGNORE_CLASS: &[&str] = &["menu-title"];
+
     let mut id_counter = HashMap::new();
 
-    regex
+    BUILD_HEADER_LINKS
         .replace_all(html, |caps: &Captures<'_>| {
             let level = caps[1]
                 .parse()
                 .expect("Regex should ensure we only ever get numbers here");
 
-            insert_link_into_header(level, &caps[2], &mut id_counter)
+            // Ignore .menu-title because now it's getting detected by the regex.
+            if let Some(classes) = caps.get(3) {
+                for class in classes.as_str().split(" ") {
+                    if IGNORE_CLASS.contains(&class) {
+                        return caps[0].to_string();
+                    }
+                }
+            }
+
+            insert_link_into_header(
+                level,
+                &caps[4],
+                caps.get(2).map(|x| x.as_str().to_string()),
+                caps.get(3).map(|x| x.as_str().to_string()),
+                &mut id_counter,
+            )
         })
         .into_owned()
 }
@@ -742,24 +850,21 @@ fn build_header_links(html: &str) -> String {
 fn insert_link_into_header(
     level: usize,
     content: &str,
+    id: Option<String>,
+    classes: Option<String>,
     id_counter: &mut HashMap<String, usize>,
 ) -> String {
-    let raw_id = utils::id_from_content(content);
-
-    let id_count = id_counter.entry(raw_id.clone()).or_insert(0);
-
-    let id = match *id_count {
-        0 => raw_id,
-        other => format!("{}-{}", raw_id, other),
-    };
-
-    *id_count += 1;
+    let id = id.unwrap_or_else(|| utils::unique_id_from_content(content, id_counter));
+    let classes = classes
+        .map(|s| format!(" class=\"{s}\""))
+        .unwrap_or_default();
 
     format!(
-        r##"<h{level}><a class="header" href="#{id}" id="{id}">{text}</a></h{level}>"##,
+        r##"<h{level} id="{id}"{classes}><a class="header" href="#{id}">{text}</a></h{level}>"##,
         level = level,
         id = id,
-        text = content
+        text = content,
+        classes = classes
     )
 }
 
@@ -772,11 +877,13 @@ fn insert_link_into_header(
 // ```
 // This function replaces all commas by spaces in the code block classes
 fn fix_code_blocks(html: &str) -> String {
-    let regex = Regex::new(r##"<code([^>]+)class="([^"]+)"([^>]*)>"##).unwrap();
-    regex
+    static FIX_CODE_BLOCKS: Lazy<Regex> =
+        Lazy::new(|| Regex::new(r##"<code([^>]+)class="([^"]+)"([^>]*)>"##).unwrap());
+
+    FIX_CODE_BLOCKS
         .replace_all(html, |caps: &Captures<'_>| {
             let before = &caps[1];
-            let classes = &caps[2].replace(",", " ");
+            let classes = &caps[2].replace(',', " ");
             let after = &caps[3];
 
             format!(
@@ -789,65 +896,64 @@ fn fix_code_blocks(html: &str) -> String {
         .into_owned()
 }
 
+static CODE_BLOCK_RE: Lazy<Regex> =
+    Lazy::new(|| Regex::new(r##"((?s)<code[^>]?class="([^"]+)".*?>(.*?)</code>)"##).unwrap());
+
 fn add_playground_pre(
     html: &str,
     playground_config: &Playground,
     edition: Option<RustEdition>,
 ) -> String {
-    let regex = Regex::new(r##"((?s)<code[^>]?class="([^"]+)".*?>(.*?)</code>)"##).unwrap();
-    regex
+    CODE_BLOCK_RE
         .replace_all(html, |caps: &Captures<'_>| {
             let text = &caps[1];
             let classes = &caps[2];
             let code = &caps[3];
 
-            if classes.contains("language-rust") {
-                if (!classes.contains("ignore")
+            if classes.contains("language-rust")
+                && ((!classes.contains("ignore")
                     && !classes.contains("noplayground")
-                    && !classes.contains("noplaypen"))
-                    || classes.contains("mdbook-runnable")
-                {
-                    let contains_e2015 = classes.contains("edition2015");
-                    let contains_e2018 = classes.contains("edition2018");
-                    let edition_class = if contains_e2015 || contains_e2018 {
-                        // the user forced edition, we should not overwrite it
-                        ""
-                    } else {
-                        match edition {
-                            Some(RustEdition::E2015) => " edition2015",
-                            Some(RustEdition::E2018) => " edition2018",
-                            None => "",
-                        }
-                    };
-
-                    // wrap the contents in an external pre block
-                    format!(
-                        "<pre class=\"playground\"><code class=\"{}{}\">{}</code></pre>",
-                        classes,
-                        edition_class,
-                        {
-                            let content: Cow<'_, str> = if playground_config.editable
-                                && classes.contains("editable")
-                                || text.contains("fn main")
-                                || text.contains("quick_main!")
-                            {
-                                code.into()
-                            } else {
-                                // we need to inject our own main
-                                let (attrs, code) = partition_source(code);
-
-                                format!(
-                                    "\n# #![allow(unused)]\n{}#fn main() {{\n{}#}}",
-                                    attrs, code
-                                )
-                                .into()
-                            };
-                            hide_lines(&content)
-                        }
-                    )
+                    && !classes.contains("noplaypen")
+                    && playground_config.runnable)
+                    || classes.contains("mdbook-runnable"))
+            {
+                let contains_e2015 = classes.contains("edition2015");
+                let contains_e2018 = classes.contains("edition2018");
+                let contains_e2021 = classes.contains("edition2021");
+                let edition_class = if contains_e2015 || contains_e2018 || contains_e2021 {
+                    // the user forced edition, we should not overwrite it
+                    ""
                 } else {
-                    format!("<code class=\"{}\">{}</code>", classes, hide_lines(code))
-                }
+                    match edition {
+                        Some(RustEdition::E2015) => " edition2015",
+                        Some(RustEdition::E2018) => " edition2018",
+                        Some(RustEdition::E2021) => " edition2021",
+                        None => "",
+                    }
+                };
+
+                // wrap the contents in an external pre block
+                format!(
+                    "<pre class=\"playground\"><code class=\"{}{}\">{}</code></pre>",
+                    classes,
+                    edition_class,
+                    {
+                        let content: Cow<'_, str> = if playground_config.editable
+                            && classes.contains("editable")
+                            || text.contains("fn main")
+                            || text.contains("quick_main!")
+                        {
+                            code.into()
+                        } else {
+                            // we need to inject our own main
+                            let (attrs, code) = partition_source(code);
+
+                            format!("# #![allow(unused)]\n{}#fn main() {{\n{}#}}", attrs, code)
+                                .into()
+                        };
+                        content
+                    }
+                )
             } else {
                 // not language-rust, so no-op
                 text.to_owned()
@@ -856,19 +962,63 @@ fn add_playground_pre(
         .into_owned()
 }
 
-lazy_static! {
-    static ref BORING_LINES_REGEX: Regex = Regex::new(r"^(\s*)#(.?)(.*)$").unwrap();
+/// Modifies all `<code>` blocks to convert "hidden" lines and to wrap them in
+/// a `<span class="boring">`.
+fn hide_lines(html: &str, code_config: &Code) -> String {
+    let language_regex = Regex::new(r"\blanguage-(\w+)\b").unwrap();
+    let hidelines_regex = Regex::new(r"\bhidelines=(\S+)").unwrap();
+    CODE_BLOCK_RE
+        .replace_all(html, |caps: &Captures<'_>| {
+            let text = &caps[1];
+            let classes = &caps[2];
+            let code = &caps[3];
+
+            if classes.contains("language-rust") {
+                format!(
+                    "<code class=\"{}\">{}</code>",
+                    classes,
+                    hide_lines_rust(code)
+                )
+            } else {
+                // First try to get the prefix from the code block
+                let hidelines_capture = hidelines_regex.captures(classes);
+                let hidelines_prefix = match &hidelines_capture {
+                    Some(capture) => Some(&capture[1]),
+                    None => {
+                        // Then look up the prefix by language
+                        language_regex.captures(classes).and_then(|capture| {
+                            code_config.hidelines.get(&capture[1]).map(|p| p.as_str())
+                        })
+                    }
+                };
+
+                match hidelines_prefix {
+                    Some(prefix) => format!(
+                        "<code class=\"{}\">{}</code>",
+                        classes,
+                        hide_lines_with_prefix(code, prefix)
+                    ),
+                    None => text.to_owned(),
+                }
+            }
+        })
+        .into_owned()
 }
 
-fn hide_lines(content: &str) -> String {
+fn hide_lines_rust(content: &str) -> String {
+    static BORING_LINES_REGEX: Lazy<Regex> = Lazy::new(|| Regex::new(r"^(\s*)#(.?)(.*)$").unwrap());
+
     let mut result = String::with_capacity(content.len());
-    for line in content.lines() {
+    let mut lines = content.lines().peekable();
+    while let Some(line) = lines.next() {
+        // Don't include newline on the last line.
+        let newline = if lines.peek().is_none() { "" } else { "\n" };
         if let Some(caps) = BORING_LINES_REGEX.captures(line) {
             if &caps[2] == "#" {
                 result += &caps[1];
                 result += &caps[2];
                 result += &caps[3];
-                result += "\n";
+                result += newline;
                 continue;
             } else if &caps[2] != "!" && &caps[2] != "[" {
                 result += "<span class=\"boring\">";
@@ -877,12 +1027,32 @@ fn hide_lines(content: &str) -> String {
                     result += &caps[2];
                 }
                 result += &caps[3];
-                result += "\n";
+                result += newline;
                 result += "</span>";
                 continue;
             }
         }
         result += line;
+        result += newline;
+    }
+    result
+}
+
+fn hide_lines_with_prefix(content: &str, prefix: &str) -> String {
+    let mut result = String::with_capacity(content.len());
+    for line in content.lines() {
+        if line.trim_start().starts_with(prefix) {
+            let pos = line.find(prefix).unwrap();
+            let (ws, rest) = (&line[..pos], &line[pos + prefix.len()..]);
+
+            result += "<span class=\"boring\">";
+            result += ws;
+            result += rest;
+            result += "\n";
+            result += "</span>";
+            continue;
+        }
+        result += line;
         result += "\n";
     }
     result
@@ -899,10 +1069,10 @@ fn partition_source(s: &str) -> (String, String) {
         if !header || after_header {
             after_header = true;
             after.push_str(line);
-            after.push_str("\n");
+            after.push('\n');
         } else {
             before.push_str(line);
-            before.push_str("\n");
+            before.push('\n');
         }
     }
 
@@ -914,45 +1084,65 @@ struct RenderItemContext<'a> {
     destination: PathBuf,
     data: serde_json::Map<String, serde_json::Value>,
     is_index: bool,
+    book_config: BookConfig,
     html_config: HtmlConfig,
     edition: Option<RustEdition>,
+    chapter_titles: &'a HashMap<PathBuf, String>,
 }
 
 #[cfg(test)]
 mod tests {
+    use crate::config::TextDirection;
+
     use super::*;
+    use pretty_assertions::assert_eq;
 
     #[test]
     fn original_build_header_links() {
         let inputs = vec![
             (
                 "blah blah <h1>Foo</h1>",
-                r##"blah blah <h1><a class="header" href="#foo" id="foo">Foo</a></h1>"##,
+                r##"blah blah <h1 id="foo"><a class="header" href="#foo">Foo</a></h1>"##,
             ),
             (
                 "<h1>Foo</h1>",
-                r##"<h1><a class="header" href="#foo" id="foo">Foo</a></h1>"##,
+                r##"<h1 id="foo"><a class="header" href="#foo">Foo</a></h1>"##,
             ),
             (
                 "<h3>Foo^bar</h3>",
-                r##"<h3><a class="header" href="#foobar" id="foobar">Foo^bar</a></h3>"##,
+                r##"<h3 id="foobar"><a class="header" href="#foobar">Foo^bar</a></h3>"##,
             ),
             (
                 "<h4></h4>",
-                r##"<h4><a class="header" href="#" id=""></a></h4>"##,
+                r##"<h4 id=""><a class="header" href="#"></a></h4>"##,
             ),
             (
                 "<h4><em>Hï</em></h4>",
-                r##"<h4><a class="header" href="#hï" id="hï"><em>Hï</em></a></h4>"##,
+                r##"<h4 id="hï"><a class="header" href="#hï"><em>Hï</em></a></h4>"##,
             ),
             (
                 "<h1>Foo</h1><h3>Foo</h3>",
-                r##"<h1><a class="header" href="#foo" id="foo">Foo</a></h1><h3><a class="header" href="#foo-1" id="foo-1">Foo</a></h3>"##,
+                r##"<h1 id="foo"><a class="header" href="#foo">Foo</a></h1><h3 id="foo-1"><a class="header" href="#foo-1">Foo</a></h3>"##,
+            ),
+            // id only
+            (
+                r##"<h1 id="foobar">Foo</h1>"##,
+                r##"<h1 id="foobar"><a class="header" href="#foobar">Foo</a></h1>"##,
+            ),
+            // class only
+            (
+                r##"<h1 class="class1 class2">Foo</h1>"##,
+                r##"<h1 id="foo" class="class1 class2"><a class="header" href="#foo">Foo</a></h1>"##,
+            ),
+            // both id and class
+            (
+                r##"<h1 id="foobar" class="class1 class2">Foo</h1>"##,
+                r##"<h1 id="foobar" class="class1 class2"><a class="header" href="#foobar">Foo</a></h1>"##,
             ),
         ];
 
         for (src, should_be) in inputs {
-            let got = build_header_links(&src);
+            let got = build_header_links(src);
             assert_eq!(got, should_be);
         }
     }
@@ -961,19 +1151,19 @@ mod tests {
     fn add_playground() {
         let inputs = [
           ("<code class=\"language-rust\">x()</code>",
-           "<pre class=\"playground\"><code class=\"language-rust\">\n<span class=\"boring\">#![allow(unused)]\n</span><span class=\"boring\">fn main() {\n</span>x()\n<span class=\"boring\">}\n</span></code></pre>"),
+           "<pre class=\"playground\"><code class=\"language-rust\"># #![allow(unused)]\n#fn main() {\nx()\n#}</code></pre>"),
           ("<code class=\"language-rust\">fn main() {}</code>",
-           "<pre class=\"playground\"><code class=\"language-rust\">fn main() {}\n</code></pre>"),
+           "<pre class=\"playground\"><code class=\"language-rust\">fn main() {}</code></pre>"),
           ("<code class=\"language-rust editable\">let s = \"foo\n # bar\n\";</code>",
-           "<pre class=\"playground\"><code class=\"language-rust editable\">let s = \"foo\n<span class=\"boring\"> bar\n</span>\";\n</code></pre>"),
+           "<pre class=\"playground\"><code class=\"language-rust editable\">let s = \"foo\n # bar\n\";</code></pre>"),
           ("<code class=\"language-rust editable\">let s = \"foo\n ## bar\n\";</code>",
-           "<pre class=\"playground\"><code class=\"language-rust editable\">let s = \"foo\n # bar\n\";\n</code></pre>"),
+           "<pre class=\"playground\"><code class=\"language-rust editable\">let s = \"foo\n ## bar\n\";</code></pre>"),
           ("<code class=\"language-rust editable\">let s = \"foo\n # bar\n#\n\";</code>",
-           "<pre class=\"playground\"><code class=\"language-rust editable\">let s = \"foo\n<span class=\"boring\"> bar\n</span><span class=\"boring\">\n</span>\";\n</code></pre>"),
+           "<pre class=\"playground\"><code class=\"language-rust editable\">let s = \"foo\n # bar\n#\n\";</code></pre>"),
           ("<code class=\"language-rust ignore\">let s = \"foo\n # bar\n\";</code>",
-           "<code class=\"language-rust ignore\">let s = \"foo\n<span class=\"boring\"> bar\n</span>\";\n</code>"),
+           "<code class=\"language-rust ignore\">let s = \"foo\n # bar\n\";</code>"),
           ("<code class=\"language-rust editable\">#![no_std]\nlet s = \"foo\";\n #[some_attr]</code>",
-           "<pre class=\"playground\"><code class=\"language-rust editable\">#![no_std]\nlet s = \"foo\";\n #[some_attr]\n</code></pre>"),
+           "<pre class=\"playground\"><code class=\"language-rust editable\">#![no_std]\nlet s = \"foo\";\n #[some_attr]</code></pre>"),
         ];
         for (src, should_be) in &inputs {
             let got = add_playground_pre(
@@ -991,13 +1181,13 @@ mod tests {
     fn add_playground_edition2015() {
         let inputs = [
           ("<code class=\"language-rust\">x()</code>",
-           "<pre class=\"playground\"><code class=\"language-rust edition2015\">\n<span class=\"boring\">#![allow(unused)]\n</span><span class=\"boring\">fn main() {\n</span>x()\n<span class=\"boring\">}\n</span></code></pre>"),
+           "<pre class=\"playground\"><code class=\"language-rust edition2015\"># #![allow(unused)]\n#fn main() {\nx()\n#}</code></pre>"),
           ("<code class=\"language-rust\">fn main() {}</code>",
-           "<pre class=\"playground\"><code class=\"language-rust edition2015\">fn main() {}\n</code></pre>"),
+           "<pre class=\"playground\"><code class=\"language-rust edition2015\">fn main() {}</code></pre>"),
           ("<code class=\"language-rust edition2015\">fn main() {}</code>",
-           "<pre class=\"playground\"><code class=\"language-rust edition2015\">fn main() {}\n</code></pre>"),
+           "<pre class=\"playground\"><code class=\"language-rust edition2015\">fn main() {}</code></pre>"),
           ("<code class=\"language-rust edition2018\">fn main() {}</code>",
-           "<pre class=\"playground\"><code class=\"language-rust edition2018\">fn main() {}\n</code></pre>"),
+           "<pre class=\"playground\"><code class=\"language-rust edition2018\">fn main() {}</code></pre>"),
         ];
         for (src, should_be) in &inputs {
             let got = add_playground_pre(
@@ -1015,13 +1205,13 @@ mod tests {
     fn add_playground_edition2018() {
         let inputs = [
           ("<code class=\"language-rust\">x()</code>",
-           "<pre class=\"playground\"><code class=\"language-rust edition2018\">\n<span class=\"boring\">#![allow(unused)]\n</span><span class=\"boring\">fn main() {\n</span>x()\n<span class=\"boring\">}\n</span></code></pre>"),
+           "<pre class=\"playground\"><code class=\"language-rust edition2018\"># #![allow(unused)]\n#fn main() {\nx()\n#}</code></pre>"),
           ("<code class=\"language-rust\">fn main() {}</code>",
-           "<pre class=\"playground\"><code class=\"language-rust edition2018\">fn main() {}\n</code></pre>"),
+           "<pre class=\"playground\"><code class=\"language-rust edition2018\">fn main() {}</code></pre>"),
           ("<code class=\"language-rust edition2015\">fn main() {}</code>",
-           "<pre class=\"playground\"><code class=\"language-rust edition2015\">fn main() {}\n</code></pre>"),
+           "<pre class=\"playground\"><code class=\"language-rust edition2015\">fn main() {}</code></pre>"),
           ("<code class=\"language-rust edition2018\">fn main() {}</code>",
-           "<pre class=\"playground\"><code class=\"language-rust edition2018\">fn main() {}\n</code></pre>"),
+           "<pre class=\"playground\"><code class=\"language-rust edition2018\">fn main() {}</code></pre>"),
         ];
         for (src, should_be) in &inputs {
             let got = add_playground_pre(
@@ -1035,4 +1225,90 @@ mod tests {
             assert_eq!(&*got, *should_be);
         }
     }
+    #[test]
+    fn add_playground_edition2021() {
+        let inputs = [
+            ("<code class=\"language-rust\">x()</code>",
+             "<pre class=\"playground\"><code class=\"language-rust edition2021\"># #![allow(unused)]\n#fn main() {\nx()\n#}</code></pre>"),
+            ("<code class=\"language-rust\">fn main() {}</code>",
+             "<pre class=\"playground\"><code class=\"language-rust edition2021\">fn main() {}</code></pre>"),
+            ("<code class=\"language-rust edition2015\">fn main() {}</code>",
+             "<pre class=\"playground\"><code class=\"language-rust edition2015\">fn main() {}</code></pre>"),
+            ("<code class=\"language-rust edition2018\">fn main() {}</code>",
+             "<pre class=\"playground\"><code class=\"language-rust edition2018\">fn main() {}</code></pre>"),
+        ];
+        for (src, should_be) in &inputs {
+            let got = add_playground_pre(
+                src,
+                &Playground {
+                    editable: true,
+                    ..Playground::default()
+                },
+                Some(RustEdition::E2021),
+            );
+            assert_eq!(&*got, *should_be);
+        }
+    }
+
+    #[test]
+    fn hide_lines_language_rust() {
+        let inputs = [
+          (
+           "<pre class=\"playground\"><code class=\"language-rust\">\n# #![allow(unused)]\n#fn main() {\nx()\n#}</code></pre>",
+           "<pre class=\"playground\"><code class=\"language-rust\">\n<span class=\"boring\">#![allow(unused)]\n</span><span class=\"boring\">fn main() {\n</span>x()\n<span class=\"boring\">}</span></code></pre>",),
+          (
+           "<pre class=\"playground\"><code class=\"language-rust\">fn main() {}</code></pre>",
+           "<pre class=\"playground\"><code class=\"language-rust\">fn main() {}</code></pre>",),
+          (
+           "<pre class=\"playground\"><code class=\"language-rust editable\">let s = \"foo\n # bar\n\";</code></pre>",
+           "<pre class=\"playground\"><code class=\"language-rust editable\">let s = \"foo\n<span class=\"boring\"> bar\n</span>\";</code></pre>",),
+          (
+           "<pre class=\"playground\"><code class=\"language-rust editable\">let s = \"foo\n ## bar\n\";</code></pre>",
+           "<pre class=\"playground\"><code class=\"language-rust editable\">let s = \"foo\n # bar\n\";</code></pre>",),
+          (
+           "<pre class=\"playground\"><code class=\"language-rust editable\">let s = \"foo\n # bar\n#\n\";</code></pre>",
+           "<pre class=\"playground\"><code class=\"language-rust editable\">let s = \"foo\n<span class=\"boring\"> bar\n</span><span class=\"boring\">\n</span>\";</code></pre>",),
+          (
+           "<code class=\"language-rust ignore\">let s = \"foo\n # bar\n\";</code>",
+           "<code class=\"language-rust ignore\">let s = \"foo\n<span class=\"boring\"> bar\n</span>\";</code>",),
+          (
+           "<pre class=\"playground\"><code class=\"language-rust editable\">#![no_std]\nlet s = \"foo\";\n #[some_attr]</code></pre>",
+           "<pre class=\"playground\"><code class=\"language-rust editable\">#![no_std]\nlet s = \"foo\";\n #[some_attr]</code></pre>",),
+        ];
+        for (src, should_be) in &inputs {
+            let got = hide_lines(src, &Code::default());
+            assert_eq!(&*got, *should_be);
+        }
+    }
+
+    #[test]
+    fn hide_lines_language_other() {
+        let inputs = [
+          (
+           "<code class=\"language-python\">~hidden()\nnothidden():\n~    hidden()\n    ~hidden()\n    nothidden()</code>",
+           "<code class=\"language-python\"><span class=\"boring\">hidden()\n</span>nothidden():\n<span class=\"boring\">    hidden()\n</span><span class=\"boring\">    hidden()\n</span>    nothidden()\n</code>",),
+           (
+            "<code class=\"language-python hidelines=!!!\">!!!hidden()\nnothidden():\n!!!    hidden()\n    !!!hidden()\n    nothidden()</code>",
+            "<code class=\"language-python hidelines=!!!\"><span class=\"boring\">hidden()\n</span>nothidden():\n<span class=\"boring\">    hidden()\n</span><span class=\"boring\">    hidden()\n</span>    nothidden()\n</code>",),
+        ];
+        for (src, should_be) in &inputs {
+            let got = hide_lines(
+                src,
+                &Code {
+                    hidelines: {
+                        let mut map = HashMap::new();
+                        map.insert("python".to_string(), "~".to_string());
+                        map
+                    },
+                },
+            );
+            assert_eq!(&*got, *should_be);
+        }
+    }
+
+    #[test]
+    fn test_json_direction() {
+        assert_eq!(json!(TextDirection::RightToLeft), json!("rtl"));
+        assert_eq!(json!(TextDirection::LeftToRight), json!("ltr"));
+    }
 }

src/renderer/html_handlebars/helpers/navigation.rs

@@ -4,6 +4,8 @@ use std::path::Path;
 use handlebars::{Context, Handlebars, Helper, Output, RenderContext, RenderError, Renderable};
 
 use crate::utils;
+use log::{debug, trace};
+use serde_json::json;
 
 type StringMap = BTreeMap<String, String>;
 
@@ -61,7 +63,7 @@ fn find_chapter(
         .as_json()
         .as_str()
         .ok_or_else(|| RenderError::new("Type error for `path`, string expected"))?
-        .replace("\"", "");
+        .replace('\"', "");
 
     if !rc.evaluate(ctx, "@root/is_index")?.is_missing() {
         // Special case for index.md which may be a synthetic page.
@@ -91,7 +93,7 @@ fn find_chapter(
         match item.get("path") {
             Some(path) if !path.is_empty() => {
                 if let Some(previous) = previous {
-                    if let Some(item) = target.find(&base_path, &path, &item, &previous)? {
+                    if let Some(item) = target.find(&base_path, path, &item, &previous)? {
                         return Ok(Some(item));
                     }
                 }
@@ -121,11 +123,11 @@ fn render(
         .as_json()
         .as_str()
         .ok_or_else(|| RenderError::new("Type error for `path`, string expected"))?
-        .replace("\"", "");
+        .replace('\"', "");
 
     context.insert(
         "path_to_root".to_owned(),
-        json!(utils::fs::path_to_root(&base_path)),
+        json!(utils::fs::path_to_root(base_path)),
     );
 
     chapter
@@ -141,20 +143,17 @@ fn render(
                 .with_extension("html")
                 .to_str()
                 .ok_or_else(|| RenderError::new("Link could not be converted to str"))
-                .map(|p| context.insert("link".to_owned(), json!(p.replace("\\", "/"))))
+                .map(|p| context.insert("link".to_owned(), json!(p.replace('\\', "/"))))
         })?;
 
     trace!("Render template");
 
-    _h.template()
-        .ok_or_else(|| RenderError::new("Error with the handlebars template"))
-        .and_then(|t| {
-            let mut local_rc = rc.clone();
-            let local_ctx = Context::wraps(&context)?;
-            t.render(r, &local_ctx, &mut local_rc, out)
-        })?;
-
-    Ok(())
+    let t = _h
+        .template()
+        .ok_or_else(|| RenderError::new("Error with the handlebars template"))?;
+    let local_ctx = Context::wraps(&context)?;
+    let mut local_rc = rc.clone();
+    t.render(r, &local_ctx, &mut local_rc, out)
 }
 
 pub fn previous(

src/renderer/html_handlebars/helpers/theme.rs

@@ -1,4 +1,5 @@
 use handlebars::{Context, Handlebars, Helper, Output, RenderContext, RenderError};
+use log::trace;
 
 pub fn theme_option(
     h: &Helper<'_, '_>,

src/renderer/html_handlebars/helpers/toc.rs

@@ -1,10 +1,10 @@
-use std::collections::BTreeMap;
 use std::path::Path;
+use std::{cmp::Ordering, collections::BTreeMap};
 
 use crate::utils;
+use crate::utils::bracket_escape;
 
 use handlebars::{Context, Handlebars, Helper, HelperDef, Output, RenderContext, RenderError};
-use pulldown_cmark::{html, Event, Parser};
 
 // Handlebars helper to construct TOC
 #[derive(Clone, Copy)]
@@ -33,7 +33,7 @@ impl HelperDef for RenderToc {
             .as_json()
             .as_str()
             .ok_or_else(|| RenderError::new("Type error for `path`, string expected"))?
-            .replace("\"", "");
+            .replace('\"', "");
 
         let current_section = rc
             .evaluate(ctx, "@root/section")?
@@ -57,6 +57,11 @@ impl HelperDef for RenderToc {
         out.write("<ol class=\"chapter\">")?;
 
         let mut current_level = 1;
+        // The "index" page, which has this attribute set, is supposed to alias the first chapter in
+        // the book, i.e. the first link. There seems to be no easy way to determine which chapter
+        // the "index" is aliasing from within the renderer, so this is used instead to force the
+        // first link to be active. See further below.
+        let mut is_first_chapter = ctx.data().get("is_index").is_some();
 
         for item in chapters {
             // Spacer
@@ -81,86 +86,78 @@ impl HelperDef for RenderToc {
                     level - 1 < fold_level as usize
                 };
 
-            if level > current_level {
-                while level > current_level {
-                    out.write("<li>")?;
-                    out.write("<ol class=\"section\">")?;
-                    current_level += 1;
+            match level.cmp(&current_level) {
+                Ordering::Greater => {
+                    while level > current_level {
+                        out.write("<li>")?;
+                        out.write("<ol class=\"section\">")?;
+                        current_level += 1;
+                    }
+                    write_li_open_tag(out, is_expanded, false)?;
                 }
-                write_li_open_tag(out, is_expanded, false)?;
-            } else if level < current_level {
-                while level < current_level {
-                    out.write("</ol>")?;
-                    out.write("</li>")?;
-                    current_level -= 1;
+                Ordering::Less => {
+                    while level < current_level {
+                        out.write("</ol>")?;
+                        out.write("</li>")?;
+                        current_level -= 1;
+                    }
+                    write_li_open_tag(out, is_expanded, false)?;
+                }
+                Ordering::Equal => {
+                    write_li_open_tag(out, is_expanded, item.get("section").is_none())?;
                 }
-                write_li_open_tag(out, is_expanded, false)?;
-            } else {
-                write_li_open_tag(out, is_expanded, item.get("section").is_none())?;
             }
 
             // Part title
             if let Some(title) = item.get("part") {
                 out.write("<li class=\"part-title\">")?;
-                out.write(title)?;
+                out.write(&bracket_escape(title))?;
                 out.write("</li>")?;
                 continue;
             }
 
             // Link
-            let path_exists = if let Some(path) =
-                item.get("path")
-                    .and_then(|p| if p.is_empty() { None } else { Some(p) })
-            {
-                out.write("<a href=\"")?;
+            let path_exists: bool;
+            match item.get("path") {
+                Some(path) if !path.is_empty() => {
+                    out.write("<a href=\"")?;
+                    let tmp = Path::new(path)
+                        .with_extension("html")
+                        .to_str()
+                        .unwrap()
+                        // Hack for windows who tends to use `\` as separator instead of `/`
+                        .replace('\\', "/");
 
-                let tmp = Path::new(item.get("path").expect("Error: path should be Some(_)"))
-                    .with_extension("html")
-                    .to_str()
-                    .unwrap()
-                    // Hack for windows who tends to use `\` as separator instead of `/`
-                    .replace("\\", "/");
+                    // Add link
+                    out.write(&utils::fs::path_to_root(&current_path))?;
+                    out.write(&tmp)?;
+                    out.write("\"")?;
 
-                // Add link
-                out.write(&utils::fs::path_to_root(&current_path))?;
-                out.write(&tmp)?;
-                out.write("\"")?;
+                    if path == &current_path || is_first_chapter {
+                        is_first_chapter = false;
+                        out.write(" class=\"active\"")?;
+                    }
 
-                if path == &current_path {
-                    out.write(" class=\"active\"")?;
+                    out.write(">")?;
+                    path_exists = true;
                 }
-
-                out.write(">")?;
-                true
-            } else {
-                out.write("<div>")?;
-                false
-            };
+                _ => {
+                    out.write("<div>")?;
+                    path_exists = false;
+                }
+            }
 
             if !self.no_section_label {
                 // Section does not necessarily exist
                 if let Some(section) = item.get("section") {
                     out.write("<strong aria-hidden=\"true\">")?;
-                    out.write(&section)?;
+                    out.write(section)?;
                     out.write("</strong> ")?;
                 }
             }
 
             if let Some(name) = item.get("name") {
-                // Render only inline code blocks
-
-                // filter all events that are not inline code blocks
-                let parser = Parser::new(name).filter(|event| match *event {
-                    Event::Code(_) | Event::Html(_) | Event::Text(_) => true,
-                    _ => false,
-                });
-
-                // render markdown to html
-                let mut markdown_parsed_name = String::with_capacity(name.len() * 3 / 2);
-                html::push_html(&mut markdown_parsed_name, parser);
-
-                // write to the handlebars template
-                out.write(&markdown_parsed_name)?;
+                out.write(&bracket_escape(name))?
             }
 
             if path_exists {

src/renderer/html_handlebars/search.rs

@@ -2,7 +2,8 @@ use std::borrow::Cow;
 use std::collections::{HashMap, HashSet};
 use std::path::Path;
 
-use elasticlunr::Index;
+use elasticlunr::{Index, IndexBuilder};
+use once_cell::sync::Lazy;
 use pulldown_cmark::*;
 
 use crate::book::{Book, BookItem};
@@ -10,17 +11,35 @@ use crate::config::Search;
 use crate::errors::*;
 use crate::theme::searcher;
 use crate::utils;
+use log::{debug, warn};
+use serde::Serialize;
+
+const MAX_WORD_LENGTH_TO_INDEX: usize = 80;
+
+/// Tokenizes in the same way as elasticlunr-rs (for English), but also drops long tokens.
+fn tokenize(text: &str) -> Vec<String> {
+    text.split(|c: char| c.is_whitespace() || c == '-')
+        .filter(|s| !s.is_empty())
+        .map(|s| s.trim().to_lowercase())
+        .filter(|s| s.len() <= MAX_WORD_LENGTH_TO_INDEX)
+        .collect()
+}
 
 /// Creates all files required for search.
 pub fn create_files(search_config: &Search, destination: &Path, book: &Book) -> Result<()> {
-    let mut index = Index::new(&["title", "body", "breadcrumbs"]);
+    let mut index = IndexBuilder::new()
+        .add_field_with_tokenizer("title", Box::new(&tokenize))
+        .add_field_with_tokenizer("body", Box::new(&tokenize))
+        .add_field_with_tokenizer("breadcrumbs", Box::new(&tokenize))
+        .build();
+
     let mut doc_urls = Vec::with_capacity(book.sections.len());
 
     for item in book.iter() {
-        render_item(&mut index, &search_config, &mut doc_urls, item)?;
+        render_item(&mut index, search_config, &mut doc_urls, item)?;
     }
 
-    let index = write_to_json(index, &search_config, doc_urls)?;
+    let index = write_to_json(index, search_config, doc_urls)?;
     debug!("Writing search index ✓");
     if index.len() > 10_000_000 {
         warn!("searchindex.json is very large ({} bytes)", index.len());
@@ -85,7 +104,7 @@ fn render_item(
         .with_context(|| "Could not convert HTML path to str")?;
     let anchor_base = utils::fs::normalize_path(filepath);
 
-    let mut p = utils::new_cmark_parser(&chapter.content).peekable();
+    let mut p = utils::new_cmark_parser(&chapter.content, false).peekable();
 
     let mut in_heading = false;
     let max_section_depth = u32::from(search_config.heading_split_level);
@@ -95,9 +114,12 @@ fn render_item(
     let mut breadcrumbs = chapter.parent_names.clone();
     let mut footnote_numbers = HashMap::new();
 
+    breadcrumbs.push(chapter.name.clone());
+
+    let mut id_counter = HashMap::new();
     while let Some(event) = p.next() {
         match event {
-            Event::Start(Tag::Heading(i)) if i <= max_section_depth => {
+            Event::Start(Tag::Heading(i, ..)) if i as u32 <= max_section_depth => {
                 if !heading.is_empty() {
                     // Section finished, the next heading is following now
                     // Write the data to the index, and clear it for the next section
@@ -116,9 +138,11 @@ fn render_item(
 
                 in_heading = true;
             }
-            Event::End(Tag::Heading(i)) if i <= max_section_depth => {
+            Event::End(Tag::Heading(i, id, _classes)) if i as u32 <= max_section_depth => {
                 in_heading = false;
-                section_id = Some(utils::id_from_content(&heading));
+                section_id = id
+                    .map(|id| id.to_string())
+                    .or_else(|| Some(utils::unique_id_from_content(&heading, &mut id_counter)));
                 breadcrumbs.push(heading.clone());
             }
             Event::Start(Tag::FootnoteDefinition(name)) => {
@@ -132,14 +156,14 @@ fn render_item(
                 // in an HtmlBlock tag. We must collect consecutive Html events
                 // into a block ourselves.
                 while let Some(Event::Html(html)) = p.peek() {
-                    html_block.push_str(&html);
+                    html_block.push_str(html);
                     p.next();
                 }
 
                 body.push_str(&clean_html(&html_block));
             }
             Event::Start(_) | Event::End(_) | Event::Rule | Event::SoftBreak | Event::HardBreak => {
-                // Insert spaces where HTML output would usually seperate text
+                // Insert spaces where HTML output would usually separate text
                 // to ensure words don't get merged together
                 if in_heading {
                     heading.push(' ');
@@ -163,7 +187,12 @@ fn render_item(
         }
     }
 
-    if !heading.is_empty() {
+    if !body.is_empty() || !heading.is_empty() {
+        if heading.is_empty() {
+            if let Some(chapter) = breadcrumbs.first() {
+                heading = chapter.clone();
+            }
+        }
         // Make sure the last section is added to the index
         add_doc(
             index,
@@ -201,12 +230,13 @@ fn write_to_json(index: Index, search_config: &Search, doc_urls: Vec<String>) ->
 
     let mut fields = BTreeMap::new();
     let mut opt = SearchOptionsField::default();
-    opt.boost = Some(search_config.boost_title);
-    fields.insert("title".into(), opt);
-    opt.boost = Some(search_config.boost_paragraph);
-    fields.insert("body".into(), opt);
-    opt.boost = Some(search_config.boost_hierarchy);
-    fields.insert("breadcrumbs".into(), opt);
+    let mut insert_boost = |key: &str, boost| {
+        opt.boost = Some(boost);
+        fields.insert(key.into(), opt);
+    };
+    insert_boost("title", search_config.boost_title);
+    insert_boost("body", search_config.boost_paragraph);
+    insert_boost("breadcrumbs", search_config.boost_hierarchy);
 
     let search_options = SearchOptions {
         bool: if search_config.use_boolean_and {
@@ -239,21 +269,19 @@ fn write_to_json(index: Index, search_config: &Search, doc_urls: Vec<String>) ->
 }
 
 fn clean_html(html: &str) -> String {
-    lazy_static! {
-        static ref AMMONIA: ammonia::Builder<'static> = {
-            let mut clean_content = HashSet::new();
-            clean_content.insert("script");
-            clean_content.insert("style");
-            let mut builder = ammonia::Builder::new();
-            builder
-                .tags(HashSet::new())
-                .tag_attributes(HashMap::new())
-                .generic_attributes(HashSet::new())
-                .link_rel(None)
-                .allowed_classes(HashMap::new())
-                .clean_content_tags(clean_content);
-            builder
-        };
-    }
+    static AMMONIA: Lazy<ammonia::Builder<'static>> = Lazy::new(|| {
+        let mut clean_content = HashSet::new();
+        clean_content.insert("script");
+        clean_content.insert("style");
+        let mut builder = ammonia::Builder::new();
+        builder
+            .tags(HashSet::new())
+            .tag_attributes(HashMap::new())
+            .generic_attributes(HashSet::new())
+            .link_rel(None)
+            .allowed_classes(HashMap::new())
+            .clean_content_tags(clean_content);
+        builder
+    });
     AMMONIA.clean(html).to_string()
 }

src/renderer/markdown_renderer.rs

@@ -2,7 +2,7 @@ use crate::book::BookItem;
 use crate::errors::*;
 use crate::renderer::{RenderContext, Renderer};
 use crate::utils;
-
+use log::trace;
 use std::fs;
 
 #[derive(Default)]
@@ -37,14 +37,14 @@ impl Renderer for MarkdownRenderer {
                 if !ch.is_draft_chapter() {
                     utils::fs::write_file(
                         &ctx.destination,
-                        &ch.path.as_ref().expect("Checked path exists before"),
+                        ch.path.as_ref().expect("Checked path exists before"),
                         ch.content.as_bytes(),
                     )?;
                 }
             }
         }
 
-        fs::create_dir_all(&destination)
+        fs::create_dir_all(destination)
             .with_context(|| "Unexpected error when constructing destination path")?;
 
         Ok(())

src/renderer/mod.rs

@@ -18,28 +18,29 @@ mod html_handlebars;
 mod markdown_renderer;
 
 use shlex::Shlex;
+use std::collections::HashMap;
 use std::fs;
 use std::io::{self, ErrorKind, Read};
-use std::path::PathBuf;
+use std::path::{Path, PathBuf};
 use std::process::{Command, Stdio};
 
 use crate::book::Book;
 use crate::config::Config;
 use crate::errors::*;
+use log::{error, info, trace, warn};
 use toml::Value;
 
+use serde::{Deserialize, Serialize};
+
 /// An arbitrary `mdbook` backend.
 ///
 /// Although it's quite possible for you to import `mdbook` as a library and
 /// provide your own renderer, there are two main renderer implementations that
 /// 99% of users will ever use:
 ///
-/// - [HtmlHandlebars] - the built-in HTML renderer
-/// - [CmdRenderer] - a generic renderer which shells out to a program to do the
+/// - [`HtmlHandlebars`] - the built-in HTML renderer
+/// - [`CmdRenderer`] - a generic renderer which shells out to a program to do the
 ///   actual rendering
-///
-/// [HtmlHandlebars]: struct.HtmlHandlebars.html
-/// [CmdRenderer]: struct.CmdRenderer.html
 pub trait Renderer {
     /// The `Renderer`'s name.
     fn name(&self) -> &str;
@@ -67,6 +68,8 @@ pub struct RenderContext {
     /// guaranteed to be empty or even exist.
     pub destination: PathBuf,
     #[serde(skip)]
+    pub(crate) chapter_titles: HashMap<PathBuf, String>,
+    #[serde(skip)]
     __non_exhaustive: (),
 }
 
@@ -83,6 +86,7 @@ impl RenderContext {
             version: crate::MDBOOK_VERSION.to_string(),
             root: root.into(),
             destination: destination.into(),
+            chapter_titles: HashMap::new(),
             __non_exhaustive: (),
         }
     }
@@ -133,14 +137,44 @@ impl CmdRenderer {
         CmdRenderer { name, cmd }
     }
 
-    fn compose_command(&self) -> Result<Command> {
+    fn compose_command(&self, root: &Path, destination: &Path) -> Result<Command> {
         let mut words = Shlex::new(&self.cmd);
-        let executable = match words.next() {
-            Some(e) => e,
+        let exe = match words.next() {
+            Some(e) => PathBuf::from(e),
             None => bail!("Command string was empty"),
         };
 
-        let mut cmd = Command::new(executable);
+        let exe = if exe.components().count() == 1 {
+            // Search PATH for the executable.
+            exe
+        } else {
+            // Relative paths are preferred to be relative to the book root.
+            let abs_exe = root.join(&exe);
+            if abs_exe.exists() {
+                abs_exe
+            } else {
+                // Historically paths were relative to the destination, but
+                // this is not the preferred way.
+                let legacy_path = destination.join(&exe);
+                if legacy_path.exists() {
+                    warn!(
+                        "Renderer command `{}` uses a path relative to the \
+                        renderer output directory `{}`. This was previously \
+                        accepted, but has been deprecated. Relative executable \
+                        paths should be relative to the book root.",
+                        exe.display(),
+                        destination.display()
+                    );
+                    legacy_path
+                } else {
+                    // Let this bubble through to later be handled by
+                    // handle_render_command_error.
+                    abs_exe
+                }
+            }
+        };
+
+        let mut cmd = Command::new(exe);
 
         for arg in words {
             cmd.arg(arg);
@@ -195,7 +229,7 @@ impl Renderer for CmdRenderer {
         let _ = fs::create_dir_all(&ctx.destination);
 
         let mut child = match self
-            .compose_command()?
+            .compose_command(&ctx.root, &ctx.destination)?
             .stdin(Stdio::piped())
             .stdout(Stdio::inherit())
             .stderr(Stdio::inherit())

src/theme/ayu-highlight.css

@@ -8,7 +8,6 @@ Original by Dempfi (https://github.com/dempfi/ayu)
   overflow-x: auto;
   background: #191f26;
   color: #e6e1cf;
-  padding: 0.5em;
 }
 
 .hljs-comment,

src/theme/book.js

@@ -4,14 +4,16 @@
 window.onunload = function () { };
 
 // Global variable, shared between modules
-function playground_text(playground) {
+function playground_text(playground, hidden = true) {
     let code_block = playground.querySelector("code");
 
     if (window.ace && code_block.classList.contains("editable")) {
         let editor = window.ace.edit(code_block);
         return editor.getValue();
-    } else {
+    } else if (hidden) {
         return code_block.textContent;
+    } else {
+        return code_block.innerText;
     }
 }
 
@@ -66,7 +68,7 @@ function playground_text(playground) {
     }
 
     // updates the visibility of play button based on `no_run` class and
-    // used crates vs ones available on http://play.rust-lang.org
+    // used crates vs ones available on https://play.rust-lang.org
     function update_play_button(pre_block, playground_crates) {
         var play_button = pre_block.querySelector(".play-button");
 
@@ -108,9 +110,12 @@ function playground_text(playground) {
 
         let text = playground_text(code_block);
         let classes = code_block.querySelector('code').classList;
-        let has_2018 = classes.contains("edition2018");
-        let edition = has_2018 ? "2018" : "2015";
-
+        let edition = "2015";
+        if(classes.contains("edition2018")) {
+            edition = "2018";
+        } else if(classes.contains("edition2021")) {
+            edition = "2021";
+        }
         var params = {
             version: "stable",
             optimize: "0",
@@ -133,7 +138,15 @@ function playground_text(playground) {
             body: JSON.stringify(params)
         })
         .then(response => response.json())
-        .then(response => result_block.innerText = response.result)
+        .then(response => {
+            if (response.result.trim() === '') {
+                result_block.innerText = "No output";
+                result_block.classList.add("result-no-output");
+            } else {
+                result_block.innerText = response.result;
+                result_block.classList.remove("result-no-output");
+            }
+        })
         .catch(error => result_block.innerText = "Playground Communication: " + error.message);
     }
 
@@ -151,12 +164,12 @@ function playground_text(playground) {
     if (window.ace) {
         // language-rust class needs to be removed for editable
         // blocks or highlightjs will capture events
-        Array
-            .from(document.querySelectorAll('code.editable'))
+        code_nodes
+            .filter(function (node) {return node.classList.contains("editable"); })
             .forEach(function (block) { block.classList.remove('language-rust'); });
 
-        Array
-            .from(document.querySelectorAll('code:not(.editable)'))
+        code_nodes
+            .filter(function (node) {return !node.classList.contains("editable"); })
             .forEach(function (block) { hljs.highlightBlock(block); });
     } else {
         code_nodes.forEach(function (block) { hljs.highlightBlock(block); });
@@ -166,7 +179,7 @@ function playground_text(playground) {
     // even if highlighting doesn't apply
     code_nodes.forEach(function (block) { block.classList.add('hljs'); });
 
-    Array.from(document.querySelectorAll("code.language-rust")).forEach(function (block) {
+    Array.from(document.querySelectorAll("code.hljs")).forEach(function (block) {
 
         var lines = Array.from(block.querySelectorAll('.boring'));
         // If no lines were hidden, return
@@ -288,6 +301,13 @@ function playground_text(playground) {
         themePopup.querySelector("button#" + get_theme()).focus();
     }
 
+    function updateThemeSelected() {
+        themePopup.querySelectorAll('.theme-selected').forEach(function (el) {
+            el.classList.remove('theme-selected');
+        });
+        themePopup.querySelector("button#" + get_theme()).classList.add('theme-selected');
+    }
+
     function hideThemes() {
         themePopup.style.display = 'none';
         themeToggleButton.setAttribute('aria-expanded', false);
@@ -326,7 +346,7 @@ function playground_text(playground) {
         }
 
         setTimeout(function () {
-            themeColorMetaTag.content = getComputedStyle(document.body).backgroundColor;
+            themeColorMetaTag.content = getComputedStyle(document.documentElement).backgroundColor;
         }, 1);
 
         if (window.ace && window.editors) {
@@ -343,6 +363,7 @@ function playground_text(playground) {
 
         html.classList.remove(previousTheme);
         html.classList.add(theme);
+        updateThemeSelected();
     }
 
     // Set theme
@@ -359,7 +380,14 @@ function playground_text(playground) {
     });
 
     themePopup.addEventListener('click', function (e) {
-        var theme = e.target.id || e.target.parentElement.id;
+        var theme;
+        if (e.target.className === "theme") {
+            theme = e.target.id;
+        } else if (e.target.parentElement.className === "theme") {
+            theme = e.target.parentElement.id;
+        } else {
+            return;
+        }
         set_theme(theme);
     });
 
@@ -413,7 +441,7 @@ function playground_text(playground) {
 })();
 
 (function sidebar() {
-    var html = document.querySelector("html");
+    var body = document.querySelector("body");
     var sidebar = document.getElementById("sidebar");
     var sidebarLinks = document.querySelectorAll('#sidebar a');
     var sidebarToggleButton = document.getElementById("sidebar-toggle");
@@ -421,8 +449,8 @@ function playground_text(playground) {
     var firstContact = null;
 
     function showSidebar() {
-        html.classList.remove('sidebar-hidden')
-        html.classList.add('sidebar-visible');
+        body.classList.remove('sidebar-hidden')
+        body.classList.add('sidebar-visible');
         Array.from(sidebarLinks).forEach(function (link) {
             link.setAttribute('tabIndex', 0);
         });
@@ -443,8 +471,8 @@ function playground_text(playground) {
     });
 
     function hideSidebar() {
-        html.classList.remove('sidebar-visible')
-        html.classList.add('sidebar-hidden');
+        body.classList.remove('sidebar-visible')
+        body.classList.add('sidebar-hidden');
         Array.from(sidebarLinks).forEach(function (link) {
             link.setAttribute('tabIndex', -1);
         });
@@ -455,14 +483,14 @@ function playground_text(playground) {
 
     // Toggle sidebar
     sidebarToggleButton.addEventListener('click', function sidebarToggle() {
-        if (html.classList.contains("sidebar-hidden")) {
+        if (body.classList.contains("sidebar-hidden")) {
             var current_width = parseInt(
                 document.documentElement.style.getPropertyValue('--sidebar-width'), 10);
             if (current_width < 150) {
                 document.documentElement.style.setProperty('--sidebar-width', '150px');
             }
             showSidebar();
-        } else if (html.classList.contains("sidebar-visible")) {
+        } else if (body.classList.contains("sidebar-visible")) {
             hideSidebar();
         } else {
             if (getComputedStyle(sidebar)['transform'] === 'none') {
@@ -478,14 +506,14 @@ function playground_text(playground) {
     function initResize(e) {
         window.addEventListener('mousemove', resize, false);
         window.addEventListener('mouseup', stopResize, false);
-        html.classList.add('sidebar-resizing');
+        body.classList.add('sidebar-resizing');
     }
     function resize(e) {
         var pos = (e.clientX - sidebar.offsetLeft);
         if (pos < 20) {
             hideSidebar();
         } else {
-            if (html.classList.contains("sidebar-hidden")) {
+            if (body.classList.contains("sidebar-hidden")) {
                 showSidebar();
             }
             pos = Math.min(pos, window.innerWidth - 100);
@@ -494,7 +522,7 @@ function playground_text(playground) {
     }
     //on mouseup remove windows functions mousemove & mouseup
     function stopResize(e) {
-        html.classList.remove('sidebar-resizing');
+        body.classList.remove('sidebar-resizing');
         window.removeEventListener('mousemove', resize, false);
         window.removeEventListener('mouseup', stopResize, false);
     }
@@ -523,33 +551,41 @@ function playground_text(playground) {
             firstContact = null;
         }
     }, { passive: true });
-
-    // Scroll sidebar to current active section
-    var activeSection = document.getElementById("sidebar").querySelector(".active");
-    if (activeSection) {
-        // https://developer.mozilla.org/en-US/docs/Web/API/Element/scrollIntoView
-        activeSection.scrollIntoView({ block: 'center' });
-    }
 })();
 
 (function chapterNavigation() {
     document.addEventListener('keydown', function (e) {
         if (e.altKey || e.ctrlKey || e.metaKey || e.shiftKey) { return; }
         if (window.search && window.search.hasFocus()) { return; }
+        var html = document.querySelector('html');
 
+        function next() {
+            var nextButton = document.querySelector('.nav-chapters.next');
+            if (nextButton) {
+                window.location.href = nextButton.href;
+            }
+        }
+        function prev() {
+            var previousButton = document.querySelector('.nav-chapters.previous');
+            if (previousButton) {
+                window.location.href = previousButton.href;
+            }
+        }
         switch (e.key) {
             case 'ArrowRight':
                 e.preventDefault();
-                var nextButton = document.querySelector('.nav-chapters.next');
-                if (nextButton) {
-                    window.location.href = nextButton.href;
+                if (html.dir == 'rtl') {
+                    prev();
+                } else {
+                    next();
                 }
                 break;
             case 'ArrowLeft':
                 e.preventDefault();
-                var previousButton = document.querySelector('.nav-chapters.previous');
-                if (previousButton) {
-                    window.location.href = previousButton.href;
+                if (html.dir == 'rtl') {
+                    next();
+                } else {
+                    prev();
                 }
                 break;
         }
@@ -573,7 +609,7 @@ function playground_text(playground) {
         text: function (trigger) {
             hideTooltip(trigger);
             let playground = trigger.closest("pre");
-            return playground_text(playground);
+            return playground_text(playground, false);
         }
     });
 
@@ -648,13 +684,14 @@ function playground_text(playground) {
         }, { passive: true });
     })();
     (function controllBorder() {
-        menu.classList.remove('bordered');
-        document.addEventListener('scroll', function () {
+        function updateBorder() {
             if (menu.offsetTop === 0) {
                 menu.classList.remove('bordered');
             } else {
                 menu.classList.add('bordered');
             }
-        }, { passive: true });
+        }
+        updateBorder();
+        document.addEventListener('scroll', updateBorder, { passive: true });
     })();
 })();

src/theme/css/chrome.css

@@ -2,12 +2,6 @@
 
 @import 'variables.css';
 
-::-webkit-scrollbar {
-    background: var(--bg);
-}
-::-webkit-scrollbar-thumb {
-    background: var(--scrollbar);
-}
 html {
     scrollbar-color: var(--scrollbar) var(--bg);
 }
@@ -18,6 +12,19 @@ a > .hljs {
     color: var(--links);
 }
 
+/*
+    body-container is necessary because mobile browsers don't seem to like
+    overflow-x on the body tag when there is a <meta name="viewport"> tag.
+*/
+#body-container {
+    /*
+        This is used when the sidebar pushes the body content off the side of
+        the screen on small screens. Without it, dragging on mobile Safari
+        will want to reposition the viewport in a weird way.
+    */
+    overflow-x: clip;
+}
+
 /* Menu Bar */
 
 #menu-bar,
@@ -30,9 +37,9 @@ a > .hljs {
     display: flex;
     flex-wrap: wrap;
     background-color: var(--bg);
-    border-bottom-color: var(--bg);
-    border-bottom-width: 1px;
-    border-bottom-style: solid;
+    border-block-end-color: var(--bg);
+    border-block-end-width: 1px;
+    border-block-end-style: solid;
 }
 #menu-bar.sticky,
 .js #menu-bar-hover-placeholder:hover + #menu-bar,
@@ -49,7 +56,7 @@ a > .hljs {
     height: var(--menu-bar-height);
 }
 #menu-bar.bordered {
-    border-bottom-color: var(--table-border-color);
+    border-block-end-color: var(--table-border-color);
 }
 #menu-bar i, #menu-bar .icon-button {
     position: relative;
@@ -86,14 +93,14 @@ a > .hljs {
     display: flex;
     margin: 0 5px;
 }
-.no-js .left-buttons {
+.no-js .left-buttons button {
     display: none;
 }
 
 .menu-title {
     display: inline-block;
     font-weight: 200;
-    font-size: 2rem;
+    font-size: 2.4rem;
     line-height: var(--menu-bar-height);
     text-align: center;
     margin: 0;
@@ -153,7 +160,7 @@ a > .hljs {
 }
 
 .nav-wrapper {
-    margin-top: 50px;
+    margin-block-start: 50px;
     display: none;
 }
 
@@ -166,23 +173,34 @@ a > .hljs {
     background-color: var(--sidebar-bg);
 }
 
-.previous {
-    float: left;
-}
+/* Only Firefox supports flow-relative values */
+.previous { float: left; }
+[dir=rtl] .previous { float: right; }
 
+/* Only Firefox supports flow-relative values */
 .next {
     float: right;
     right: var(--page-padding);
 }
+[dir=rtl] .next {
+    float: left;
+    right: unset;
+    left: var(--page-padding);
+}
+
+/* Use the correct buttons for RTL layouts*/
+[dir=rtl] .previous i.fa-angle-left:before {content:"\f105";}
+[dir=rtl] .next i.fa-angle-right:before { content:"\f104"; }
 
 @media only screen and (max-width: 1080px) {
     .nav-wide-wrapper { display: none; }
     .nav-wrapper { display: block; }
 }
 
+/* sidebar-visible */
 @media only screen and (max-width: 1380px) {
-    .sidebar-visible .nav-wide-wrapper { display: none; }
-    .sidebar-visible .nav-wrapper { display: block; }
+    #sidebar-toggle-anchor:checked ~ .page-wrapper .nav-wide-wrapper { display: none; }
+    #sidebar-toggle-anchor:checked ~ .page-wrapper .nav-wrapper { display: block; }
 }
 
 /* Inline code */
@@ -208,26 +226,65 @@ pre {
 pre > .buttons {
     position: absolute;
     z-index: 100;
-    right: 5px;
-    top: 5px;
+    right: 0px;
+    top: 2px;
+    margin: 0px;
+    padding: 2px 0px;
 
     color: var(--sidebar-fg);
     cursor: pointer;
+    visibility: hidden;
+    opacity: 0;
+    transition: visibility 0.1s linear, opacity 0.1s linear;
+}
+pre:hover > .buttons {
+    visibility: visible;
+    opacity: 1
 }
 pre > .buttons :hover {
     color: var(--sidebar-active);
+    border-color: var(--icons-hover);
+    background-color: var(--theme-hover);
 }
 pre > .buttons i {
-    margin-left: 8px;
+    margin-inline-start: 8px;
 }
 pre > .buttons button {
-    color: inherit;
-    background: transparent;
-    border: none;
     cursor: inherit;
+    margin: 0px 5px;
+    padding: 3px 5px;
+    font-size: 14px;
+
+    border-style: solid;
+    border-width: 1px;
+    border-radius: 4px;
+    border-color: var(--icons);
+    background-color: var(--theme-popup-bg);
+    transition: 100ms;
+    transition-property: color,border-color,background-color;
+    color: var(--icons);
 }
+@media (pointer: coarse) {
+    pre > .buttons button {
+        /* On mobile, make it easier to tap buttons. */
+        padding: 0.3rem 1rem;
+    }
+}
+pre > code {
+    padding: 1rem;
+}
+
+/* FIXME: ACE editors overlap their buttons because ACE does absolute
+   positioning within the code block which breaks padding. The only solution I
+   can think of is to move the padding to the outer pre tag (or insert a div
+   wrapper), but that would require fixing a whole bunch of CSS rules.
+*/
+.hljs.ace_editor {
+  padding: 0rem 0rem;
+}
+
 pre > .result {
-    margin-top: 10px;
+    margin-block-start: 10px;
 }
 
 /* Search */
@@ -238,8 +295,14 @@ pre > .result {
 
 mark {
     border-radius: 2px;
-    padding: 0 3px 1px 3px;
-    margin: 0 -3px -1px -3px;
+    padding-block-start: 0;
+    padding-block-end: 1px;
+    padding-inline-start: 3px;
+    padding-inline-end: 3px;
+    margin-block-start: 0;
+    margin-block-end: -1px;
+    margin-inline-start: -3px;
+    margin-inline-end: -3px;
     background-color: var(--search-mark-bg);
     transition: background-color 300ms linear;
     cursor: pointer;
@@ -251,14 +314,17 @@ mark.fade-out {
 }
 
 .searchbar-outer {
-    margin-left: auto;
-    margin-right: auto;
+    margin-inline-start: auto;
+    margin-inline-end: auto;
     max-width: var(--content-max-width);
 }
 
 #searchbar {
     width: 100%;
-    margin: 5px auto 0px auto;
+    margin-block-start: 5px;
+    margin-block-end: 0;
+    margin-inline-start: auto;
+    margin-inline-end: auto;
     padding: 10px 16px;
     transition: box-shadow 300ms ease-in-out;
     border: 1px solid var(--searchbar-border-color);
@@ -274,20 +340,23 @@ mark.fade-out {
 .searchresults-header {
     font-weight: bold;
     font-size: 1em;
-    padding: 18px 0 0 5px;
+    padding-block-start: 18px;
+    padding-block-end: 0;
+    padding-inline-start: 5px;
+    padding-inline-end: 0;
     color: var(--searchresults-header-fg);
 }
 
 .searchresults-outer {
-    margin-left: auto;
-    margin-right: auto;
+    margin-inline-start: auto;
+    margin-inline-end: auto;
     max-width: var(--content-max-width);
-    border-bottom: 1px dashed var(--searchresults-border-color);
+    border-block-end: 1px dashed var(--searchresults-border-color);
 }
 
 ul#searchresults {
     list-style: none;
-    padding-left: 20px;
+    padding-inline-start: 20px;
 }
 ul#searchresults li {
     margin: 10px 0px;
@@ -300,7 +369,10 @@ ul#searchresults li.focus {
 ul#searchresults span.teaser {
     display: block;
     clear: both;
-    margin: 5px 0 0 20px;
+    margin-block-start: 5px;
+    margin-block-end: 0;
+    margin-inline-start: 20px;
+    margin-inline-end: 0;
     font-size: 0.8em;
 }
 ul#searchresults span.teaser em {
@@ -323,12 +395,14 @@ ul#searchresults span.teaser em {
     background-color: var(--sidebar-bg);
     color: var(--sidebar-fg);
 }
+[dir=rtl] .sidebar { left: unset; right: 0; }
 .sidebar-resizing {
     -moz-user-select: none;
     -webkit-user-select: none;
     -ms-user-select: none;
     user-select: none;
 }
+.no-js .sidebar,
 .js:not(.sidebar-resizing) .sidebar {
     transition: transform 0.3s; /* Animation: slide away */
 }
@@ -352,12 +426,18 @@ ul#searchresults span.teaser em {
     top: 0;
     bottom: 0;
 }
+[dir=rtl] .sidebar .sidebar-resize-handle { right:  unset; left: 0; }
 .js .sidebar .sidebar-resize-handle {
     cursor: col-resize;
     width: 5px;
 }
-.sidebar-hidden .sidebar {
+/* sidebar-hidden */
+#sidebar-toggle-anchor:not(:checked) ~ .sidebar {
     transform: translateX(calc(0px - var(--sidebar-width)));
+    z-index: -1;
+}
+[dir=rtl] #sidebar-toggle-anchor:not(:checked) ~ .sidebar {
+    transform: translateX(var(--sidebar-width));
 }
 .sidebar::-webkit-scrollbar {
     background: var(--sidebar-bg);
@@ -366,19 +446,26 @@ ul#searchresults span.teaser em {
     background: var(--scrollbar);
 }
 
-.sidebar-visible .page-wrapper {
+/* sidebar-visible */
+#sidebar-toggle-anchor:checked ~ .page-wrapper {
     transform: translateX(var(--sidebar-width));
 }
+[dir=rtl] #sidebar-toggle-anchor:checked ~ .page-wrapper {
+    transform: translateX(calc(0px - var(--sidebar-width)));
+}
 @media only screen and (min-width: 620px) {
-    .sidebar-visible .page-wrapper {
+    #sidebar-toggle-anchor:checked ~ .page-wrapper {
+        transform: none;
+        margin-inline-start: var(--sidebar-width);
+    }
+    [dir=rtl] #sidebar-toggle-anchor:checked ~ .page-wrapper {
         transform: none;
-        margin-left: var(--sidebar-width);
     }
 }
 
 .chapter {
     list-style: none outside none;
-    padding-left: 0;
+    padding-inline-start: 0;
     line-height: 2.2em;
 }
 
@@ -408,7 +495,7 @@ ul#searchresults span.teaser em {
 .chapter li > a.toggle {
     cursor: pointer;
     display: block;
-    margin-left: auto;
+    margin-inline-start: auto;
     padding: 0 10px;
     user-select: none;
     opacity: 0.68;
@@ -425,7 +512,7 @@ ul#searchresults span.teaser em {
 
 .chapter li.chapter-item {
     line-height: 1.5em;
-    margin-top: 0.6em;
+    margin-block-start: 0.6em;
 }
 
 .chapter li.expanded > a.toggle div {
@@ -448,7 +535,7 @@ ul#searchresults span.teaser em {
 
 .section {
     list-style: none outside none;
-    padding-left: 20px;
+    padding-inline-start: 20px;
     line-height: 1.9em;
 }
 
@@ -468,7 +555,10 @@ ul#searchresults span.teaser em {
     padding: 0;
     list-style: none;
     display: none;
+    /* Don't let the children's background extend past the rounded corners. */
+    overflow: hidden;
 }
+[dir=rtl] .theme-popup { left: unset;  right: 10px; }
 .theme-popup .default {
     color: var(--icons);
 }
@@ -476,10 +566,10 @@ ul#searchresults span.teaser em {
     width: 100%;
     border: 0;
     margin: 0;
-    padding: 2px 10px;
+    padding: 2px 20px;
     line-height: 25px;
     white-space: nowrap;
-    text-align: left;
+    text-align: start;
     cursor: pointer;
     color: inherit;
     background: inherit;
@@ -488,8 +578,10 @@ ul#searchresults span.teaser em {
 .theme-popup .theme:hover {
     background-color: var(--theme-hover);
 }
-.theme-popup .theme:hover:first-child,
-.theme-popup .theme:hover:last-child {
-    border-top-left-radius: inherit;
-    border-top-right-radius: inherit;
+
+.theme-selected::before {
+    display: inline-block;
+    content: "✓";
+    margin-inline-start: -14px;
+    width: 14px;
 }

src/theme/css/general.css

@@ -5,6 +5,7 @@
 :root {
     /* Browser default font-size is 16px, this way 1 rem = 10px */
     font-size: 62.5%;
+    color-scheme: var(--color-scheme);
 }
 
 html {
@@ -12,6 +13,7 @@ html {
     color: var(--fg);
     background-color: var(--bg);
     text-size-adjust: none;
+    -webkit-text-size-adjust: none;
 }
 
 body {
@@ -21,8 +23,19 @@ body {
 }
 
 code {
-    font-family: "Source Code Pro", Consolas, "Ubuntu Mono", Menlo, "DejaVu Sans Mono", monospace, monospace !important;
-    font-size: 0.875em; /* please adjust the ace font size accordingly in editor.js */
+    font-family: var(--mono-font) !important;
+    font-size: var(--code-font-size);
+    direction: ltr !important;
+}
+
+/* make long words/inline code not x overflow */
+main {
+    overflow-wrap: break-word;
+}
+
+/* make wide tables scroll if they overflow */
+.table-wrapper {
+    overflow-x: auto;
 }
 
 /* Don't change font size in headers. */
@@ -36,52 +49,60 @@ h1 code, h2 code, h3 code, h4 code, h5 code, h6 code {
 .hide-boring .boring { display: none; }
 .hidden { display: none !important; }
 
-h2, h3 { margin-top: 2.5em; }
-h4, h5 { margin-top: 2em; }
+h2, h3 { margin-block-start: 2.5em; }
+h4, h5 { margin-block-start: 2em; }
 
 .header + .header h3,
 .header + .header h4,
 .header + .header h5 {
-    margin-top: 1em;
+    margin-block-start: 1em;
 }
 
-h1 a.header:target::before,
-h2 a.header:target::before,
-h3 a.header:target::before,
-h4 a.header:target::before {
+h1:target::before,
+h2:target::before,
+h3:target::before,
+h4:target::before,
+h5:target::before,
+h6:target::before {
     display: inline-block;
     content: "»";
-    margin-left: -30px;
+    margin-inline-start: -30px;
     width: 30px;
 }
 
-h1 a.header:target,
-h2 a.header:target,
-h3 a.header:target,
-h4 a.header:target {
+/* This is broken on Safari as of version 14, but is fixed
+   in Safari Technology Preview 117 which I think will be Safari 14.2.
+   https://bugs.webkit.org/show_bug.cgi?id=218076
+*/
+:target {
+    /* Safari does not support logical properties */
     scroll-margin-top: calc(var(--menu-bar-height) + 0.5em);
 }
 
 .page {
     outline: 0;
     padding: 0 var(--page-padding);
-    margin-top: calc(0px - var(--menu-bar-height)); /* Compensate for the #menu-bar-hover-placeholder */
+    margin-block-start: calc(0px - var(--menu-bar-height)); /* Compensate for the #menu-bar-hover-placeholder */
 }
 .page-wrapper {
     box-sizing: border-box;
+    background-color: var(--bg);
 }
+.no-js .page-wrapper,
 .js:not(.sidebar-resizing) .page-wrapper {
     transition: margin-left 0.3s ease, transform 0.3s ease; /* Animation: slide away */
 }
+[dir=rtl] .js:not(.sidebar-resizing) .page-wrapper {
+    transition: margin-right 0.3s ease, transform 0.3s ease; /* Animation: slide away */
+}
 
 .content {
     overflow-y: auto;
-    padding: 0 15px;
-    padding-bottom: 50px;
+    padding: 0 5px 50px 5px;
 }
 .content main {
-    margin-left: auto;
-    margin-right: auto;
+    margin-inline-start: auto;
+    margin-inline-end: auto;
     max-width: var(--content-max-width);
 }
 .content p { line-height: 1.45em; }
@@ -89,7 +110,7 @@ h4 a.header:target {
 .content ul { line-height: 1.45em; }
 .content a { text-decoration: none; }
 .content a:hover { text-decoration: underline; }
-.content img { max-width: 100%; }
+.content img, .content video { max-width: 100%; }
 .content .header:link,
 .content .header:visited {
     color: var(--fg);
@@ -131,14 +152,49 @@ blockquote {
     padding: 0 20px;
     color: var(--fg);
     background-color: var(--quote-bg);
-    border-top: .1em solid var(--quote-border);
-    border-bottom: .1em solid var(--quote-border);
+    border-block-start: .1em solid var(--quote-border);
+    border-block-end: .1em solid var(--quote-border);
 }
 
+.warning {
+    margin: 20px;
+    padding: 0 20px;
+    border-inline-start: 2px solid var(--warning-border);
+}
+
+.warning:before {
+    position: absolute;
+    width: 3rem;
+    height: 3rem;
+    margin-inline-start: calc(-1.5rem - 21px);
+    content: "ⓘ";
+    text-align: center;
+    background-color: var(--bg);
+    color: var(--warning-border);
+    font-weight: bold;
+    font-size: 2rem;
+}
+
+blockquote .warning:before {
+    background-color: var(--quote-bg);
+}
+
+kbd {
+    background-color: var(--table-border-color);
+    border-radius: 4px;
+    border: solid 1px var(--theme-popup-border);
+    box-shadow: inset 0 -1px 0 var(--theme-hover);
+    display: inline-block;
+    font-size: var(--code-font-size);
+    font-family: var(--mono-font);
+    line-height: 10px;
+    padding: 4px 5px;
+    vertical-align: middle;
+}
 
 :not(.footnote-definition) + .footnote-definition,
 .footnote-definition + :not(.footnote-definition) {
-    margin-top: 2em;
+    margin-block-start: 2em;
 }
 .footnote-definition {
     font-size: 0.9em;
@@ -172,3 +228,7 @@ blockquote {
     margin: 5px 0px;
     font-weight: bold;
 }
+
+.result-no-output {
+    font-style: italic;
+}

src/theme/css/print.css

@@ -8,7 +8,7 @@
 
 #page-wrapper.page-wrapper {
     transform: none;
-    margin-left: 0px;
+    margin-inline-start: 0px;
     overflow-y: initial;
 }
 
@@ -23,11 +23,7 @@
 }
 
 code {
-    background-color: #666666;
-    border-radius: 5px;
-
-    /* Force background to be printed in Chrome */
-    -webkit-print-color-adjust: exact;
+    direction: ltr !important;
 }
 
 pre > .buttons {

src/theme/css/variables.css

@@ -6,6 +6,8 @@
     --page-padding: 15px;
     --content-max-width: 750px;
     --menu-bar-height: 50px;
+    --mono-font: "Source Code Pro", Consolas, "Ubuntu Mono", Menlo, "DejaVu Sans Mono", monospace, monospace;
+    --code-font-size: 0.875em /* please adjust the ace font size accordingly in editor.js */
 }
 
 /* Themes */
@@ -36,6 +38,8 @@
     --quote-bg: hsl(226, 15%, 17%);
     --quote-border: hsl(226, 15%, 22%);
 
+    --warning-border: #ff8e00;
+
     --table-border-color: hsl(210, 25%, 13%);
     --table-header-bg: hsl(210, 25%, 28%);
     --table-alternate-bg: hsl(210, 25%, 11%);
@@ -48,6 +52,8 @@
     --searchresults-border-color: #888;
     --searchresults-li-bg: #252932;
     --search-mark-bg: #e3b171;
+
+    --color-scheme: dark;
 }
 
 .coal {
@@ -67,7 +73,7 @@
 
     --links: #2b79a2;
 
-    --inline-code-color: #c5c8c6;;
+    --inline-code-color: #c5c8c6;
 
     --theme-popup-bg: #141617;
     --theme-popup-border: #43484d;
@@ -76,6 +82,8 @@
     --quote-bg: hsl(234, 21%, 18%);
     --quote-border: hsl(234, 21%, 23%);
 
+    --warning-border: #ff8e00;
+
     --table-border-color: hsl(200, 7%, 13%);
     --table-header-bg: hsl(200, 7%, 28%);
     --table-alternate-bg: hsl(200, 7%, 11%);
@@ -88,26 +96,28 @@
     --searchresults-border-color: #98a3ad;
     --searchresults-li-bg: #2b2b2f;
     --search-mark-bg: #355c7d;
+
+    --color-scheme: dark;
 }
 
 .light {
     --bg: hsl(0, 0%, 100%);
-    --fg: #333333;
+    --fg: hsl(0, 0%, 0%);
 
     --sidebar-bg: #fafafa;
-    --sidebar-fg: #364149;
+    --sidebar-fg: hsl(0, 0%, 0%);
     --sidebar-non-existant: #aaaaaa;
-    --sidebar-active: #008cff;
+    --sidebar-active: #1f1fff;
     --sidebar-spacer: #f4f4f4;
 
-    --scrollbar: #cccccc;
+    --scrollbar: #8F8F8F;
 
-    --icons: #cccccc;
-    --icons-hover: #333333;
+    --icons: #747474;
+    --icons-hover: #000000;
 
-    --links: #4183c4;
+    --links: #20609f;
 
-    --inline-code-color: #6e6b5e;
+    --inline-code-color: #301900;
 
     --theme-popup-bg: #fafafa;
     --theme-popup-border: #cccccc;
@@ -116,6 +126,8 @@
     --quote-bg: hsl(197, 37%, 96%);
     --quote-border: hsl(197, 37%, 91%);
 
+    --warning-border: #ff8e00;
+
     --table-border-color: hsl(0, 0%, 95%);
     --table-header-bg: hsl(0, 0%, 80%);
     --table-alternate-bg: hsl(0, 0%, 97%);
@@ -128,6 +140,8 @@
     --searchresults-border-color: #888;
     --searchresults-li-bg: #e4f2fe;
     --search-mark-bg: #a2cff5;
+
+    --color-scheme: light;
 }
 
 .navy {
@@ -147,7 +161,7 @@
 
     --links: #2b79a2;
 
-    --inline-code-color: #c5c8c6;;
+    --inline-code-color: #c5c8c6;
 
     --theme-popup-bg: #161923;
     --theme-popup-border: #737480;
@@ -156,6 +170,8 @@
     --quote-bg: hsl(226, 15%, 17%);
     --quote-border: hsl(226, 15%, 22%);
 
+    --warning-border: #ff8e00;
+
     --table-border-color: hsl(226, 23%, 16%);
     --table-header-bg: hsl(226, 23%, 31%);
     --table-alternate-bg: hsl(226, 23%, 14%);
@@ -168,6 +184,8 @@
     --searchresults-border-color: #5c5c68;
     --searchresults-li-bg: #242430;
     --search-mark-bg: #a2cff5;
+
+    --color-scheme: dark;
 }
 
 .rust {
@@ -196,6 +214,8 @@
     --quote-bg: hsl(60, 5%, 75%);
     --quote-border: hsl(60, 5%, 70%);
 
+    --warning-border: #ff8e00;
+
     --table-border-color: hsl(60, 9%, 82%);
     --table-header-bg: #b3a497;
     --table-alternate-bg: hsl(60, 9%, 84%);
@@ -208,6 +228,8 @@
     --searchresults-border-color: #888;
     --searchresults-li-bg: #dec2a2;
     --search-mark-bg: #e69f67;
+
+    --color-scheme: light;
 }
 
 @media (prefers-color-scheme: dark) {
@@ -228,7 +250,7 @@
 
         --links: #2b79a2;
 
-        --inline-code-color: #c5c8c6;;
+        --inline-code-color: #c5c8c6;
 
         --theme-popup-bg: #141617;
         --theme-popup-border: #43484d;
@@ -237,6 +259,8 @@
         --quote-bg: hsl(234, 21%, 18%);
         --quote-border: hsl(234, 21%, 23%);
 
+        --warning-border: #ff8e00;
+
         --table-border-color: hsl(200, 7%, 13%);
         --table-header-bg: hsl(200, 7%, 28%);
         --table-alternate-bg: hsl(200, 7%, 11%);

src/theme/highlight.css

@@ -1,14 +1,18 @@
-/* Base16 Atelier Dune Light - Theme */
-/* by Bram de Haan (http://atelierbram.github.io/syntax-highlighting/atelier-schemes/dune) */
-/* Original Base16 color scheme by Chris Kempson (https://github.com/chriskempson/base16) */
+/*
+ * An increased contrast highlighting scheme loosely based on the
+ * "Base16 Atelier Dune Light" theme by Bram de Haan
+ * (http://atelierbram.github.io/syntax-highlighting/atelier-schemes/dune)
+ * Original Base16 color scheme by Chris Kempson
+ * (https://github.com/chriskempson/base16)
+ */
 
-/* Atelier-Dune Comment */
+/* Comment */
 .hljs-comment,
 .hljs-quote {
-  color: #AAA;
+  color: #575757;
 }
 
-/* Atelier-Dune Red */
+/* Red */
 .hljs-variable,
 .hljs-template-variable,
 .hljs-attribute,
@@ -19,10 +23,10 @@
 .hljs-name,
 .hljs-selector-id,
 .hljs-selector-class {
-  color: #d73737;
+  color: #d70025;
 }
 
-/* Atelier-Dune Orange */
+/* Orange */
 .hljs-number,
 .hljs-meta,
 .hljs-built_in,
@@ -30,34 +34,33 @@
 .hljs-literal,
 .hljs-type,
 .hljs-params {
-  color: #b65611;
+  color: #b21e00;
 }
 
-/* Atelier-Dune Green */
+/* Green */
 .hljs-string,
 .hljs-symbol,
 .hljs-bullet {
-  color: #60ac39;
+  color: #008200;
 }
 
-/* Atelier-Dune Blue */
+/* Blue */
 .hljs-title,
 .hljs-section {
-  color: #6684e1;
+  color: #0030f2;
 }
 
-/* Atelier-Dune Purple */
+/* Purple */
 .hljs-keyword,
 .hljs-selector-tag {
-  color: #b854d4;
+  color: #9d00ec;
 }
 
 .hljs {
   display: block;
   overflow-x: auto;
-  background: #f1f1f1;
-  color: #6e6b5e;
-  padding: 0.5em;
+  background: #f6f7f6;
+  color: #000;
 }
 
 .hljs-emphasis {

src/theme/index.hbs

@@ -1,11 +1,11 @@
 <!DOCTYPE HTML>
-<html lang="{{ language }}" class="sidebar-visible no-js {{ default_theme }}">
+<html lang="{{ language }}" class="{{ default_theme }}" dir="{{ text_direction }}">
     <head>
         <!-- Book generated using mdBook -->
         <meta charset="UTF-8">
         <title>{{ title }}</title>
         {{#if is_print }}
-        <meta name="robots" content="noindex" />
+        <meta name="robots" content="noindex">
         {{/if}}
         {{#if base_url}}
         <base href="{{ base_url }}">
@@ -15,10 +15,9 @@
         <!-- Custom HTML head -->
         {{> head}}
 
-        <meta content="text/html; charset=utf-8" http-equiv="Content-Type">
         <meta name="description" content="{{ description }}">
         <meta name="viewport" content="width=device-width, initial-scale=1">
-        <meta name="theme-color" content="#ffffff" />
+        <meta name="theme-color" content="#ffffff">
 
         {{#if favicon_svg}}
         <link rel="icon" href="{{ path_to_root }}favicon.svg">
@@ -51,18 +50,19 @@
 
         {{#if mathjax_support}}
         <!-- MathJax -->
-        <script async type="text/javascript" src="https://cdnjs.cloudflare.com/ajax/libs/mathjax/2.7.1/MathJax.js?config=TeX-AMS-MML_HTMLorMML"></script>
+        <script async src="https://cdnjs.cloudflare.com/ajax/libs/mathjax/2.7.1/MathJax.js?config=TeX-AMS-MML_HTMLorMML"></script>
         {{/if}}
     </head>
-    <body>
+    <body class="sidebar-visible no-js">
+    <div id="body-container">
         <!-- Provide site root to javascript -->
-        <script type="text/javascript">
+        <script>
             var path_to_root = "{{ path_to_root }}";
             var default_theme = window.matchMedia("(prefers-color-scheme: dark)").matches ? "{{ preferred_dark_theme }}" : "{{ default_theme }}";
         </script>
 
         <!-- Work around some values being stored in localStorage wrapped in quotes -->
-        <script type="text/javascript">
+        <script>
             try {
                 var theme = localStorage.getItem('mdbook-theme');
                 var sidebar = localStorage.getItem('mdbook-sidebar');
@@ -78,27 +78,34 @@
         </script>
 
         <!-- Set the theme before any content is loaded, prevents flash -->
-        <script type="text/javascript">
+        <script>
             var theme;
             try { theme = localStorage.getItem('mdbook-theme'); } catch(e) { }
             if (theme === null || theme === undefined) { theme = default_theme; }
             var html = document.querySelector('html');
-            html.classList.remove('no-js')
             html.classList.remove('{{ default_theme }}')
             html.classList.add(theme);
-            html.classList.add('js');
+            var body = document.querySelector('body');
+            body.classList.remove('no-js')
+            body.classList.add('js');
         </script>
 
+        <input type="checkbox" id="sidebar-toggle-anchor" class="hidden">
+
         <!-- Hide / unhide sidebar before it is displayed -->
-        <script type="text/javascript">
-            var html = document.querySelector('html');
-            var sidebar = 'hidden';
+        <script>
+            var body = document.querySelector('body');
+            var sidebar = null;
+            var sidebar_toggle = document.getElementById("sidebar-toggle-anchor");
             if (document.body.clientWidth >= 1080) {
                 try { sidebar = localStorage.getItem('mdbook-sidebar'); } catch(e) { }
                 sidebar = sidebar || 'visible';
+            } else {
+                sidebar = 'hidden';
             }
-            html.classList.remove('sidebar-visible');
-            html.classList.add("sidebar-" + sidebar);
+            sidebar_toggle.checked = sidebar === 'visible';
+            body.classList.remove('sidebar-visible');
+            body.classList.add("sidebar-" + sidebar);
         </script>
 
         <nav id="sidebar" class="sidebar" aria-label="Table of contents">
@@ -108,25 +115,47 @@
             <div id="sidebar-resize-handle" class="sidebar-resize-handle"></div>
         </nav>
 
+        <!-- Track and set sidebar scroll position -->
+        <script>
+            var sidebarScrollbox = document.querySelector('#sidebar .sidebar-scrollbox');
+            sidebarScrollbox.addEventListener('click', function(e) {
+                if (e.target.tagName === 'A') {
+                    sessionStorage.setItem('sidebar-scroll', sidebarScrollbox.scrollTop);
+                }
+            }, { passive: true });
+            var sidebarScrollTop = sessionStorage.getItem('sidebar-scroll');
+            sessionStorage.removeItem('sidebar-scroll');
+            if (sidebarScrollTop) {
+                // preserve sidebar scroll position when navigating via links within sidebar
+                sidebarScrollbox.scrollTop = sidebarScrollTop;
+            } else {
+                // scroll sidebar to current active section when navigating via "next/previous chapter" buttons
+                var activeSection = document.querySelector('#sidebar .active');
+                if (activeSection) {
+                    activeSection.scrollIntoView({ block: 'center' });
+                }
+            }
+        </script>
+
         <div id="page-wrapper" class="page-wrapper">
 
             <div class="page">
                 {{> header}}
                 <div id="menu-bar-hover-placeholder"></div>
-                <div id="menu-bar" class="menu-bar sticky bordered">
+                <div id="menu-bar" class="menu-bar sticky">
                     <div class="left-buttons">
-                        <button id="sidebar-toggle" class="icon-button" type="button" title="Toggle Table of Contents" aria-label="Toggle Table of Contents" aria-controls="sidebar">
+                        <label id="sidebar-toggle" class="icon-button" for="sidebar-toggle-anchor" title="Toggle Table of Contents" aria-label="Toggle Table of Contents" aria-controls="sidebar">
                             <i class="fa fa-bars"></i>
-                        </button>
+                        </label>
                         <button id="theme-toggle" class="icon-button" type="button" title="Change theme" aria-label="Change theme" aria-haspopup="true" aria-expanded="false" aria-controls="theme-list">
                             <i class="fa fa-paint-brush"></i>
                         </button>
                         <ul id="theme-list" class="theme-popup" aria-label="Themes" role="menu">
-                            <li role="none"><button role="menuitem" class="theme" id="light">{{ theme_option "Light" }}</button></li>
-                            <li role="none"><button role="menuitem" class="theme" id="rust">{{ theme_option "Rust" }}</button></li>
-                            <li role="none"><button role="menuitem" class="theme" id="coal">{{ theme_option "Coal" }}</button></li>
-                            <li role="none"><button role="menuitem" class="theme" id="navy">{{ theme_option "Navy" }}</button></li>
-                            <li role="none"><button role="menuitem" class="theme" id="ayu">{{ theme_option "Ayu" }}</button></li>
+                            <li role="none"><button role="menuitem" class="theme" id="light">Light</button></li>
+                            <li role="none"><button role="menuitem" class="theme" id="rust">Rust</button></li>
+                            <li role="none"><button role="menuitem" class="theme" id="coal">Coal</button></li>
+                            <li role="none"><button role="menuitem" class="theme" id="navy">Navy</button></li>
+                            <li role="none"><button role="menuitem" class="theme" id="ayu">Ayu</button></li>
                         </ul>
                         {{#if search_enabled}}
                         <button id="search-toggle" class="icon-button" type="button" title="Search. (Shortkey: s)" aria-label="Toggle Searchbar" aria-expanded="false" aria-keyshortcuts="S" aria-controls="searchbar">
@@ -148,13 +177,19 @@
                             <i id="git-repository-button" class="fa {{git_repository_icon}}"></i>
                         </a>
                         {{/if}}
+                        {{#if git_repository_edit_url}}
+                        <a href="{{git_repository_edit_url}}" title="Suggest an edit" aria-label="Suggest an edit">
+                            <i id="git-edit-button" class="fa fa-edit"></i>
+                        </a>
+                        {{/if}}
+
                     </div>
                 </div>
 
                 {{#if search_enabled}}
                 <div id="search-wrapper" class="hidden">
                     <form id="searchbar-outer" class="searchbar-outer">
-                        <input type="search" name="search" id="searchbar" name="searchbar" placeholder="Search this book ..." aria-controls="searchresults-outer" aria-describedby="searchresults-header">
+                        <input type="search" id="searchbar" name="searchbar" placeholder="Search this book ..." aria-controls="searchresults-outer" aria-describedby="searchresults-header">
                     </form>
                     <div id="searchresults-outer" class="searchresults-outer hidden">
                         <div id="searchresults-header" class="searchresults-header"></div>
@@ -165,7 +200,7 @@
                 {{/if}}
 
                 <!-- Apply ARIA attributes after the sidebar and the sidebar toggle button are added to the DOM -->
-                <script type="text/javascript">
+                <script>
                     document.getElementById('sidebar-toggle').setAttribute('aria-expanded', sidebar === 'visible');
                     document.getElementById('sidebar').setAttribute('aria-hidden', sidebar !== 'visible');
                     Array.from(document.querySelectorAll('#sidebar a')).forEach(function(link) {
@@ -187,7 +222,7 @@
                         {{/previous}}
 
                         {{#next}}
-                            <a rel="next" href="{{ path_to_root }}{{link}}" class="mobile-nav-chapters next" title="Next chapter" aria-label="Next chapter" aria-keyshortcuts="Right">
+                            <a rel="next prefetch" href="{{ path_to_root }}{{link}}" class="mobile-nav-chapters next" title="Next chapter" aria-label="Next chapter" aria-keyshortcuts="Right">
                                 <i class="fa fa-angle-right"></i>
                             </a>
                         {{/next}}
@@ -205,7 +240,7 @@
                 {{/previous}}
 
                 {{#next}}
-                    <a rel="next" href="{{ path_to_root }}{{link}}" class="nav-chapters next" title="Next chapter" aria-label="Next chapter" aria-keyshortcuts="Right">
+                    <a rel="next prefetch" href="{{ path_to_root }}{{link}}" class="nav-chapters next" title="Next chapter" aria-label="Next chapter" aria-keyshortcuts="Right">
                         <i class="fa fa-angle-right"></i>
                     </a>
                 {{/next}}
@@ -213,10 +248,12 @@
 
         </div>
 
-        {{#if livereload}}
+        {{#if live_reload_endpoint}}
         <!-- Livereload script (if served using the cli tool) -->
-        <script type="text/javascript">
-            var socket = new WebSocket("{{{livereload}}}");
+        <script>
+            const wsProtocol = location.protocol === 'https:' ? 'wss:' : 'ws:';
+            const wsAddress = wsProtocol + "//" + location.host + "/" + "{{{live_reload_endpoint}}}";
+            const socket = new WebSocket(wsAddress);
             socket.onmessage = function (event) {
                 if (event.data === "reload") {
                     socket.close();
@@ -232,7 +269,7 @@
 
         {{#if google_analytics}}
         <!-- Google Analytics Tag -->
-        <script type="text/javascript">
+        <script>
             var localAddrs = ["localhost", "127.0.0.1", ""];
 
             // make sure we don't activate google analytics if the developer is
@@ -250,43 +287,43 @@
         {{/if}}
 
         {{#if playground_line_numbers}}
-        <script type="text/javascript">
+        <script>
             window.playground_line_numbers = true;
         </script>
         {{/if}}
 
         {{#if playground_copyable}}
-        <script type="text/javascript">
+        <script>
             window.playground_copyable = true;
         </script>
         {{/if}}
 
         {{#if playground_js}}
-        <script src="{{ path_to_root }}ace.js" type="text/javascript" charset="utf-8"></script>
-        <script src="{{ path_to_root }}editor.js" type="text/javascript" charset="utf-8"></script>
-        <script src="{{ path_to_root }}mode-rust.js" type="text/javascript" charset="utf-8"></script>
-        <script src="{{ path_to_root }}theme-dawn.js" type="text/javascript" charset="utf-8"></script>
-        <script src="{{ path_to_root }}theme-tomorrow_night.js" type="text/javascript" charset="utf-8"></script>
+        <script src="{{ path_to_root }}ace.js"></script>
+        <script src="{{ path_to_root }}editor.js"></script>
+        <script src="{{ path_to_root }}mode-rust.js"></script>
+        <script src="{{ path_to_root }}theme-dawn.js"></script>
+        <script src="{{ path_to_root }}theme-tomorrow_night.js"></script>
         {{/if}}
 
         {{#if search_js}}
-        <script src="{{ path_to_root }}elasticlunr.min.js" type="text/javascript" charset="utf-8"></script>
-        <script src="{{ path_to_root }}mark.min.js" type="text/javascript" charset="utf-8"></script>
-        <script src="{{ path_to_root }}searcher.js" type="text/javascript" charset="utf-8"></script>
+        <script src="{{ path_to_root }}elasticlunr.min.js"></script>
+        <script src="{{ path_to_root }}mark.min.js"></script>
+        <script src="{{ path_to_root }}searcher.js"></script>
         {{/if}}
 
-        <script src="{{ path_to_root }}clipboard.min.js" type="text/javascript" charset="utf-8"></script>
-        <script src="{{ path_to_root }}highlight.js" type="text/javascript" charset="utf-8"></script>
-        <script src="{{ path_to_root }}book.js" type="text/javascript" charset="utf-8"></script>
+        <script src="{{ path_to_root }}clipboard.min.js"></script>
+        <script src="{{ path_to_root }}highlight.js"></script>
+        <script src="{{ path_to_root }}book.js"></script>
 
         <!-- Custom JS scripts -->
         {{#each additional_js}}
-        <script type="text/javascript" src="{{ ../path_to_root }}{{this}}"></script>
+        <script src="{{ ../path_to_root }}{{this}}"></script>
         {{/each}}
 
         {{#if is_print}}
         {{#if mathjax_support}}
-        <script type="text/javascript">
+        <script>
         window.addEventListener('load', function() {
             MathJax.Hub.Register.StartupHook('End', function() {
                 window.setTimeout(window.print, 100);
@@ -294,7 +331,7 @@
         });
         </script>
         {{else}}
-        <script type="text/javascript">
+        <script>
         window.addEventListener('load', function() {
             window.setTimeout(window.print, 100);
         });
@@ -302,5 +339,6 @@
         {{/if}}
         {{/if}}
 
+    </div>
     </body>
 </html>

src/theme/mod.rs

@@ -9,10 +9,10 @@ pub mod searcher;
 
 use std::fs::File;
 use std::io::Read;
-use std::path::Path;
+use std::path::{Path, PathBuf};
 
 use crate::errors::*;
-
+use log::warn;
 pub static INDEX: &[u8] = include_bytes!("index.hbs");
 pub static HEAD: &[u8] = include_bytes!("head.hbs");
 pub static REDIRECT: &[u8] = include_bytes!("redirect.hbs");
@@ -54,6 +54,8 @@ pub struct Theme {
     pub general_css: Vec<u8>,
     pub print_css: Vec<u8>,
     pub variables_css: Vec<u8>,
+    pub fonts_css: Option<Vec<u8>>,
+    pub font_files: Vec<PathBuf>,
     pub favicon_png: Option<Vec<u8>>,
     pub favicon_svg: Option<Vec<u8>>,
     pub js: Vec<u8>,
@@ -104,7 +106,7 @@ impl Theme {
                 ),
             ];
 
-            let load_with_warn = |filename: &Path, dest| {
+            let load_with_warn = |filename: &Path, dest: &mut Vec<u8>| {
                 if !filename.exists() {
                     // Don't warn if the file doesn't exist.
                     return false;
@@ -121,6 +123,29 @@ impl Theme {
                 load_with_warn(&filename, dest);
             }
 
+            let fonts_dir = theme_dir.join("fonts");
+            if fonts_dir.exists() {
+                let mut fonts_css = Vec::new();
+                if load_with_warn(&fonts_dir.join("fonts.css"), &mut fonts_css) {
+                    theme.fonts_css.replace(fonts_css);
+                }
+                if let Ok(entries) = fonts_dir.read_dir() {
+                    theme.font_files = entries
+                        .filter_map(|entry| {
+                            let entry = entry.ok()?;
+                            if entry.file_name() == "fonts.css" {
+                                None
+                            } else if entry.file_type().ok()?.is_dir() {
+                                log::info!("skipping font directory {:?}", entry.path());
+                                None
+                            } else {
+                                Some(entry.path())
+                            }
+                        })
+                        .collect();
+                }
+            }
+
             // If the user overrides one favicon, but not the other, do not
             // copy the default for the other.
             let favicon_png = &mut theme.favicon_png.as_mut().unwrap();
@@ -153,6 +178,8 @@ impl Default for Theme {
             general_css: GENERAL_CSS.to_owned(),
             print_css: PRINT_CSS.to_owned(),
             variables_css: VARIABLES_CSS.to_owned(),
+            fonts_css: None,
+            font_files: Vec::new(),
             favicon_png: Some(FAVICON_PNG.to_owned()),
             favicon_svg: Some(FAVICON_SVG.to_owned()),
             js: JS.to_owned(),
@@ -209,10 +236,10 @@ mod tests {
             "favicon.png",
             "favicon.svg",
             "css/chrome.css",
-            "css/fonts.css",
             "css/general.css",
             "css/print.css",
             "css/variables.css",
+            "fonts/fonts.css",
             "book.js",
             "highlight.js",
             "tomorrow-night.css",
@@ -223,6 +250,7 @@ mod tests {
 
         let temp = TempFileBuilder::new().prefix("mdbook-").tempdir().unwrap();
         fs::create_dir(temp.path().join("css")).unwrap();
+        fs::create_dir(temp.path().join("fonts")).unwrap();
 
         // "touch" all of the special files so we have empty copies
         for file in &files {
@@ -240,6 +268,8 @@ mod tests {
             general_css: Vec::new(),
             print_css: Vec::new(),
             variables_css: Vec::new(),
+            fonts_css: Some(Vec::new()),
+            font_files: Vec::new(),
             favicon_png: Some(Vec::new()),
             favicon_svg: Some(Vec::new()),
             js: Vec::new(),

src/theme/redirect.hbs

@@ -3,8 +3,8 @@
   <head>
     <meta charset="utf-8">
     <title>Redirecting...</title>
-    <meta http-equiv="refresh" content="0;URL='{{url}}'">
-    <meta rel="canonical" href="{{url}}">
+    <meta http-equiv="refresh" content="0; URL={{url}}">
+    <link rel="canonical" href="{{url}}">
   </head>
   <body>
       <p>Redirecting to... <a href="{{url}}">{{url}}</a>.</p>

src/theme/searcher/searcher.js

@@ -145,6 +145,11 @@ window.search = window.search || {};
             url.push("");
         }
 
+        // encodeURIComponent escapes all chars that could allow an XSS except
+        // for '. Due to that we also manually replace ' with its url-encoded
+        // representation (%27).
+        var searchterms = encodeURIComponent(searchterms.join(" ")).replace(/\'/g, "%27");
+
         return '<a href="' + path_to_root + url[0] + '?' + URL_MARK_PARAM + '=' + searchterms + '#' + url[1]
             + '" aria-details="teaser_' + teaser_count + '">' + result.doc.breadcrumbs + '</a>'
             + '<span class="teaser" id="teaser_' + teaser_count + '" aria-label="Search Result Teaser">' 
@@ -291,7 +296,7 @@ window.search = window.search || {};
         }
 
         if (url.params.hasOwnProperty(URL_MARK_PARAM)) {
-            var words = url.params[URL_MARK_PARAM].split(' ');
+            var words = decodeURIComponent(url.params[URL_MARK_PARAM]).split(' ');
             marker.mark(words, {
                 exclude: mark_exclude
             });
@@ -422,6 +427,7 @@ window.search = window.search || {};
             delete url.params[URL_MARK_PARAM];
             url.hash = "";
         } else {
+            delete url.params[URL_MARK_PARAM];
             delete url.params[URL_SEARCH_PARAM];
         }
         // A new search will also add a new history item, so the user can go back

src/theme/tomorrow-night.css

@@ -1,7 +1,7 @@
 /* Tomorrow Night Theme */
-/* http://jmblog.github.com/color-themes-for-google-code-highlightjs */
+/* https://github.com/jmblog/color-themes-for-highlightjs */
 /* Original theme - https://github.com/chriskempson/tomorrow-theme */
-/* http://jmblog.github.com/color-themes-for-google-code-highlightjs */
+/* https://github.com/jmblog/color-themes-for-highlightjs */
 
 /* Tomorrow Comment */
 .hljs-comment {
@@ -81,8 +81,6 @@
   overflow-x: auto;
   background: #1d1f21;
   color: #c5c8c6;
-  padding: 0.5em;
-  -webkit-text-size-adjust: none;
 }
 
 .coffeescript .javascript,

src/utils/fs.rs

@@ -1,10 +1,11 @@
 use crate::errors::*;
+use log::{debug, trace};
 use std::convert::Into;
 use std::fs::{self, File};
 use std::io::Write;
 use std::path::{Component, Path, PathBuf};
 
-/// Naively replaces any path seperator with a forward-slash '/'
+/// Naively replaces any path separator with a forward-slash '/'
 pub fn normalize_path(path: &str) -> String {
     use std::path::is_separator;
     path.chars()
@@ -37,7 +38,6 @@ pub fn write_file<P: AsRef<Path>>(build_dir: &Path, filename: P, content: &[u8])
 /// Consider [submitting a new issue](https://github.com/rust-lang/mdBook/issues)
 /// or a [pull-request](https://github.com/rust-lang/mdBook/pulls) to improve it.
 pub fn path_to_root<P: Into<PathBuf>>(path: P) -> String {
-    debug!("path_to_root");
     // Remove filename and add "../" for every directory
 
     path.into()
@@ -110,7 +110,10 @@ pub fn copy_files_except_ext(
 
     for entry in fs::read_dir(from)? {
         let entry = entry?;
-        let metadata = entry.path().metadata()?;
+        let metadata = entry
+            .path()
+            .metadata()
+            .with_context(|| format!("Failed to read {:?}", entry.path()))?;
 
         // If the entry is a dir and the recursive option is enabled, call itself
         if metadata.is_dir() && recursive {
@@ -163,7 +166,7 @@ pub fn copy_files_except_ext(
                         .expect("a file should have a file name...")
                 )
             );
-            fs::copy(
+            copy(
                 entry.path(),
                 &to.join(
                     entry
@@ -177,6 +180,62 @@ pub fn copy_files_except_ext(
     Ok(())
 }
 
+/// Copies a file.
+fn copy<P: AsRef<Path>, Q: AsRef<Path>>(from: P, to: Q) -> Result<()> {
+    let from = from.as_ref();
+    let to = to.as_ref();
+    return copy_inner(from, to)
+        .with_context(|| format!("failed to copy `{}` to `{}`", from.display(), to.display()));
+
+    // This is a workaround for an issue with the macOS file watcher.
+    // Rust's `std::fs::copy` function uses `fclonefileat`, which creates
+    // clones on APFS. Unfortunately fs events seem to trigger on both
+    // sides of the clone, and there doesn't seem to be a way to differentiate
+    // which side it is.
+    // https://github.com/notify-rs/notify/issues/465#issuecomment-1657261035
+    // contains more information.
+    //
+    // This is essentially a copy of the simple copy code path in Rust's
+    // standard library.
+    #[cfg(target_os = "macos")]
+    fn copy_inner(from: &Path, to: &Path) -> Result<()> {
+        use std::fs::OpenOptions;
+        use std::os::unix::fs::{OpenOptionsExt, PermissionsExt};
+
+        let mut reader = File::open(from)?;
+        let metadata = reader.metadata()?;
+        if !metadata.is_file() {
+            anyhow::bail!(
+                "expected a file, `{}` appears to be {:?}",
+                from.display(),
+                metadata.file_type()
+            );
+        }
+        let perm = metadata.permissions();
+        let mut writer = OpenOptions::new()
+            .mode(perm.mode())
+            .write(true)
+            .create(true)
+            .truncate(true)
+            .open(to)?;
+        let writer_metadata = writer.metadata()?;
+        if writer_metadata.is_file() {
+            // Set the correct file permissions, in case the file already existed.
+            // Don't set the permissions on already existing non-files like
+            // pipes/FIFOs or device nodes.
+            writer.set_permissions(perm)?;
+        }
+        std::io::copy(&mut reader, &mut writer)?;
+        Ok(())
+    }
+
+    #[cfg(not(target_os = "macos"))]
+    fn copy_inner(from: &Path, to: &Path) -> Result<()> {
+        fs::copy(from, to)?;
+        Ok(())
+    }
+}
+
 pub fn get_404_output_file(input_404: &Option<String>) -> String {
     input_404
         .as_ref()
@@ -207,65 +266,62 @@ mod tests {
         };
 
         // Create a couple of files
-        if let Err(err) = fs::File::create(&tmp.path().join("file.txt")) {
+        if let Err(err) = fs::File::create(tmp.path().join("file.txt")) {
             panic!("Could not create file.txt: {}", err);
         }
-        if let Err(err) = fs::File::create(&tmp.path().join("file.md")) {
+        if let Err(err) = fs::File::create(tmp.path().join("file.md")) {
             panic!("Could not create file.md: {}", err);
         }
-        if let Err(err) = fs::File::create(&tmp.path().join("file.png")) {
+        if let Err(err) = fs::File::create(tmp.path().join("file.png")) {
             panic!("Could not create file.png: {}", err);
         }
-        if let Err(err) = fs::create_dir(&tmp.path().join("sub_dir")) {
+        if let Err(err) = fs::create_dir(tmp.path().join("sub_dir")) {
             panic!("Could not create sub_dir: {}", err);
         }
-        if let Err(err) = fs::File::create(&tmp.path().join("sub_dir/file.png")) {
+        if let Err(err) = fs::File::create(tmp.path().join("sub_dir/file.png")) {
             panic!("Could not create sub_dir/file.png: {}", err);
         }
-        if let Err(err) = fs::create_dir(&tmp.path().join("sub_dir_exists")) {
+        if let Err(err) = fs::create_dir(tmp.path().join("sub_dir_exists")) {
             panic!("Could not create sub_dir_exists: {}", err);
         }
-        if let Err(err) = fs::File::create(&tmp.path().join("sub_dir_exists/file.txt")) {
+        if let Err(err) = fs::File::create(tmp.path().join("sub_dir_exists/file.txt")) {
             panic!("Could not create sub_dir_exists/file.txt: {}", err);
         }
-        if let Err(err) = symlink(
-            &tmp.path().join("file.png"),
-            &tmp.path().join("symlink.png"),
-        ) {
+        if let Err(err) = symlink(tmp.path().join("file.png"), tmp.path().join("symlink.png")) {
             panic!("Could not symlink file.png: {}", err);
         }
 
         // Create output dir
-        if let Err(err) = fs::create_dir(&tmp.path().join("output")) {
+        if let Err(err) = fs::create_dir(tmp.path().join("output")) {
             panic!("Could not create output: {}", err);
         }
-        if let Err(err) = fs::create_dir(&tmp.path().join("output/sub_dir_exists")) {
+        if let Err(err) = fs::create_dir(tmp.path().join("output/sub_dir_exists")) {
             panic!("Could not create output/sub_dir_exists: {}", err);
         }
 
         if let Err(e) =
-            copy_files_except_ext(&tmp.path(), &tmp.path().join("output"), true, None, &["md"])
+            copy_files_except_ext(tmp.path(), &tmp.path().join("output"), true, None, &["md"])
         {
             panic!("Error while executing the function:\n{:?}", e);
         }
 
         // Check if the correct files where created
-        if !(&tmp.path().join("output/file.txt")).exists() {
+        if !tmp.path().join("output/file.txt").exists() {
             panic!("output/file.txt should exist")
         }
-        if (&tmp.path().join("output/file.md")).exists() {
+        if tmp.path().join("output/file.md").exists() {
             panic!("output/file.md should not exist")
         }
-        if !(&tmp.path().join("output/file.png")).exists() {
+        if !tmp.path().join("output/file.png").exists() {
             panic!("output/file.png should exist")
         }
-        if !(&tmp.path().join("output/sub_dir/file.png")).exists() {
+        if !tmp.path().join("output/sub_dir/file.png").exists() {
             panic!("output/sub_dir/file.png should exist")
         }
-        if !(&tmp.path().join("output/sub_dir_exists/file.txt")).exists() {
+        if !tmp.path().join("output/sub_dir_exists/file.txt").exists() {
             panic!("output/sub_dir/file.png should exist")
         }
-        if !(&tmp.path().join("output/symlink.png")).exists() {
+        if !tmp.path().join("output/symlink.png").exists() {
             panic!("output/symlink.png should exist")
         }
     }

src/utils/mod.rs

@@ -4,11 +4,13 @@ pub mod fs;
 mod string;
 pub(crate) mod toml_ext;
 use crate::errors::Error;
+use log::error;
+use once_cell::sync::Lazy;
+use pulldown_cmark::{html, CodeBlockKind, CowStr, Event, Options, Parser, Tag};
 use regex::Regex;
 
-use pulldown_cmark::{html, CodeBlockKind, CowStr, Event, Options, Parser, Tag};
-
 use std::borrow::Cow;
+use std::collections::HashMap;
 use std::fmt::Write;
 use std::path::Path;
 
@@ -19,9 +21,7 @@ pub use self::string::{
 
 /// Replaces multiple consecutive whitespace characters with a single space character.
 pub fn collapse_whitespace(text: &str) -> Cow<'_, str> {
-    lazy_static! {
-        static ref RE: Regex = Regex::new(r"\s\s+").unwrap();
-    }
+    static RE: Lazy<Regex> = Lazy::new(|| Regex::new(r"\s\s+").unwrap());
     RE.replace_all(text, " ")
 }
 
@@ -44,33 +44,45 @@ pub fn normalize_id(content: &str) -> String {
 
 /// Generate an ID for use with anchors which is derived from a "normalised"
 /// string.
+// This function should be made private when the deprecation expires.
+#[deprecated(since = "0.4.16", note = "use unique_id_from_content instead")]
 pub fn id_from_content(content: &str) -> String {
     let mut content = content.to_string();
 
     // Skip any tags or html-encoded stuff
-    const REPL_SUB: &[&str] = &[
-        "<em>",
-        "</em>",
-        "<code>",
-        "</code>",
-        "<strong>",
-        "</strong>",
-        "&lt;",
-        "&gt;",
-        "&amp;",
-        "&#39;",
-        "&quot;",
-    ];
+    static HTML: Lazy<Regex> = Lazy::new(|| Regex::new(r"(<.*?>)").unwrap());
+    content = HTML.replace_all(&content, "").into();
+    const REPL_SUB: &[&str] = &["&lt;", "&gt;", "&amp;", "&#39;", "&quot;"];
     for sub in REPL_SUB {
         content = content.replace(sub, "");
     }
 
     // Remove spaces and hashes indicating a header
     let trimmed = content.trim().trim_start_matches('#').trim();
-
     normalize_id(trimmed)
 }
 
+/// Generate an ID for use with anchors which is derived from a "normalised"
+/// string.
+///
+/// Each ID returned will be unique, if the same `id_counter` is provided on
+/// each call.
+pub fn unique_id_from_content(content: &str, id_counter: &mut HashMap<String, usize>) -> String {
+    let id = {
+        #[allow(deprecated)]
+        id_from_content(content)
+    };
+
+    // If we have headers with the same normalized id, append an incrementing counter
+    let id_count = id_counter.entry(id.clone()).or_insert(0);
+    let unique_id = match *id_count {
+        0 => id,
+        id_count => format!("{}-{}", id, id_count),
+    };
+    *id_count += 1;
+    unique_id
+}
+
 /// Fix links to the correct location.
 ///
 /// This adjusts links, such as turning `.md` extensions to `.html`.
@@ -81,10 +93,9 @@ pub fn id_from_content(content: &str) -> String {
 /// None. Ideally, print page links would link to anchors on the print page,
 /// but that is very difficult.
 fn adjust_links<'a>(event: Event<'a>, path: Option<&Path>) -> Event<'a> {
-    lazy_static! {
-        static ref SCHEME_LINK: Regex = Regex::new(r"^[a-z][a-z0-9+.-]*:").unwrap();
-        static ref MD_LINK: Regex = Regex::new(r"(?P<link>.*)\.md(?P<anchor>#.*)?").unwrap();
-    }
+    static SCHEME_LINK: Lazy<Regex> = Lazy::new(|| Regex::new(r"^[a-z][a-z0-9+.-]*:").unwrap());
+    static MD_LINK: Lazy<Regex> =
+        Lazy::new(|| Regex::new(r"(?P<link>.*)\.md(?P<anchor>#.*)?").unwrap());
 
     fn fix<'a>(dest: CowStr<'a>, path: Option<&Path>) -> CowStr<'a> {
         if dest.starts_with('#') {
@@ -137,10 +148,8 @@ fn adjust_links<'a>(event: Event<'a>, path: Option<&Path>) -> Event<'a> {
         // There are dozens of HTML tags/attributes that contain paths, so
         // feel free to add more tags if desired; these are the only ones I
         // care about right now.
-        lazy_static! {
-            static ref HTML_LINK: Regex =
-                Regex::new(r#"(<(?:a|img) [^>]*?(?:src|href)=")([^"]+?)""#).unwrap();
-        }
+        static HTML_LINK: Lazy<Regex> =
+            Lazy::new(|| Regex::new(r#"(<(?:a|img) [^>]*?(?:src|href)=")([^"]+?)""#).unwrap());
 
         HTML_LINK
             .replace_all(&html, |caps: &regex::Captures<'_>| {
@@ -168,67 +177,57 @@ pub fn render_markdown(text: &str, curly_quotes: bool) -> String {
     render_markdown_with_path(text, curly_quotes, None)
 }
 
-pub fn new_cmark_parser(text: &str) -> Parser<'_> {
+pub fn new_cmark_parser(text: &str, curly_quotes: bool) -> Parser<'_, '_> {
     let mut opts = Options::empty();
     opts.insert(Options::ENABLE_TABLES);
     opts.insert(Options::ENABLE_FOOTNOTES);
     opts.insert(Options::ENABLE_STRIKETHROUGH);
     opts.insert(Options::ENABLE_TASKLISTS);
+    opts.insert(Options::ENABLE_HEADING_ATTRIBUTES);
+    if curly_quotes {
+        opts.insert(Options::ENABLE_SMART_PUNCTUATION);
+    }
     Parser::new_ext(text, opts)
 }
 
 pub fn render_markdown_with_path(text: &str, curly_quotes: bool, path: Option<&Path>) -> String {
     let mut s = String::with_capacity(text.len() * 3 / 2);
-    let p = new_cmark_parser(text);
-    let mut converter = EventQuoteConverter::new(curly_quotes);
+    let p = new_cmark_parser(text, curly_quotes);
     let events = p
         .map(clean_codeblock_headers)
         .map(|event| adjust_links(event, path))
-        .map(|event| converter.convert(event));
+        .flat_map(|event| {
+            let (a, b) = wrap_tables(event);
+            a.into_iter().chain(b)
+        });
 
     html::push_html(&mut s, events);
     s
 }
 
-struct EventQuoteConverter {
-    enabled: bool,
-    convert_text: bool,
-}
-
-impl EventQuoteConverter {
-    fn new(enabled: bool) -> Self {
-        EventQuoteConverter {
-            enabled,
-            convert_text: true,
-        }
-    }
-
-    fn convert<'a>(&mut self, event: Event<'a>) -> Event<'a> {
-        if !self.enabled {
-            return event;
-        }
-
-        match event {
-            Event::Start(Tag::CodeBlock(_)) => {
-                self.convert_text = false;
-                event
-            }
-            Event::End(Tag::CodeBlock(_)) => {
-                self.convert_text = true;
-                event
-            }
-            Event::Text(ref text) if self.convert_text => {
-                Event::Text(CowStr::from(convert_quotes_to_curly(text)))
-            }
-            _ => event,
-        }
+/// Wraps tables in a `.table-wrapper` class to apply overflow-x rules to.
+fn wrap_tables(event: Event<'_>) -> (Option<Event<'_>>, Option<Event<'_>>) {
+    match event {
+        Event::Start(Tag::Table(_)) => (
+            Some(Event::Html(r#"<div class="table-wrapper">"#.into())),
+            Some(event),
+        ),
+        Event::End(Tag::Table(_)) => (Some(event), Some(Event::Html(r#"</div>"#.into()))),
+        _ => (Some(event), None),
     }
 }
 
 fn clean_codeblock_headers(event: Event<'_>) -> Event<'_> {
     match event {
         Event::Start(Tag::CodeBlock(CodeBlockKind::Fenced(ref info))) => {
-            let info: String = info.chars().filter(|ch| !ch.is_whitespace()).collect();
+            let info: String = info
+                .chars()
+                .map(|x| match x {
+                    ' ' | '\t' => ',',
+                    _ => x,
+                })
+                .filter(|ch| !ch.is_whitespace())
+                .collect();
 
             Event::Start(Tag::CodeBlock(CodeBlockKind::Fenced(CowStr::from(info))))
         }
@@ -236,38 +235,6 @@ fn clean_codeblock_headers(event: Event<'_>) -> Event<'_> {
     }
 }
 
-fn convert_quotes_to_curly(original_text: &str) -> String {
-    // We'll consider the start to be "whitespace".
-    let mut preceded_by_whitespace = true;
-
-    original_text
-        .chars()
-        .map(|original_char| {
-            let converted_char = match original_char {
-                '\'' => {
-                    if preceded_by_whitespace {
-                        '‘'
-                    } else {
-                        '’'
-                    }
-                }
-                '"' => {
-                    if preceded_by_whitespace {
-                        '“'
-                    } else {
-                        '”'
-                    }
-                }
-                _ => original_char,
-            };
-
-            preceded_by_whitespace = original_char.is_whitespace();
-
-            converted_char
-        })
-        .collect()
-}
-
 /// Prints a "backtrace" of some `Error`.
 pub fn log_backtrace(e: &Error) {
     error!("Error: {}", e);
@@ -277,8 +244,26 @@ pub fn log_backtrace(e: &Error) {
     }
 }
 
+pub(crate) fn bracket_escape(mut s: &str) -> String {
+    let mut escaped = String::with_capacity(s.len());
+    let needs_escape: &[char] = &['<', '>'];
+    while let Some(next) = s.find(needs_escape) {
+        escaped.push_str(&s[..next]);
+        match s.as_bytes()[next] {
+            b'<' => escaped.push_str("&lt;"),
+            b'>' => escaped.push_str("&gt;"),
+            _ => unreachable!(),
+        }
+        s = &s[next + 1..];
+    }
+    escaped.push_str(s);
+    escaped
+}
+
 #[cfg(test)]
 mod tests {
+    use super::bracket_escape;
+
     mod render_markdown {
         use super::super::render_markdown;
 
@@ -308,6 +293,22 @@ mod tests {
             );
         }
 
+        #[test]
+        fn it_can_wrap_tables() {
+            let src = r#"
+| Original        | Punycode        | Punycode + Encoding |
+|-----------------|-----------------|---------------------|
+| føø             | f-5gaa          | f_5gaa              |
+"#;
+            let out = r#"
+<div class="table-wrapper"><table><thead><tr><th>Original</th><th>Punycode</th><th>Punycode + Encoding</th></tr></thead><tbody>
+<tr><td>føø</td><td>f-5gaa</td><td>f_5gaa</td></tr>
+</tbody></table>
+</div>
+"#.trim();
+            assert_eq!(render_markdown(src, false), out);
+        }
+
         #[test]
         fn it_can_keep_quotes_straight() {
             assert_eq!(render_markdown("'one'", false), "<p>'one'</p>\n");
@@ -372,7 +373,7 @@ more text with spaces
 ```
 "#;
 
-            let expected = r#"<pre><code class="language-rust,no_run,,,should_panic,,property_3"></code></pre>
+            let expected = r#"<pre><code class="language-rust,,,,,no_run,,,should_panic,,,,property_3"></code></pre>
 "#;
             assert_eq!(render_markdown(input, false), expected);
             assert_eq!(render_markdown(input, true), expected);
@@ -399,8 +400,9 @@ more text with spaces
         }
     }
 
-    mod html_munging {
-        use super::super::{id_from_content, normalize_id};
+    #[allow(deprecated)]
+    mod id_from_content {
+        use super::super::id_from_content;
 
         #[test]
         fn it_generates_anchors() {
@@ -410,6 +412,10 @@ more text with spaces
             );
             assert_eq!(id_from_content("## **Bold** title"), "bold-title");
             assert_eq!(id_from_content("## `Code` title"), "code-title");
+            assert_eq!(
+                id_from_content("## title <span dir=rtl>foo</span>"),
+                "title-foo"
+            );
         }
 
         #[test]
@@ -424,6 +430,10 @@ more text with spaces
             );
             assert_eq!(id_from_content("## Über"), "Über");
         }
+    }
+
+    mod html_munging {
+        use super::super::{normalize_id, unique_id_from_content};
 
         #[test]
         fn it_normalizes_ids() {
@@ -442,24 +452,38 @@ more text with spaces
             assert_eq!(normalize_id("한국어"), "한국어");
             assert_eq!(normalize_id(""), "");
         }
+
+        #[test]
+        fn it_generates_unique_ids_from_content() {
+            // Same id if not given shared state
+            assert_eq!(
+                unique_id_from_content("## 中文標題 CJK title", &mut Default::default()),
+                "中文標題-cjk-title"
+            );
+            assert_eq!(
+                unique_id_from_content("## 中文標題 CJK title", &mut Default::default()),
+                "中文標題-cjk-title"
+            );
+
+            // Different id if given shared state
+            let mut id_counter = Default::default();
+            assert_eq!(unique_id_from_content("## Über", &mut id_counter), "Über");
+            assert_eq!(
+                unique_id_from_content("## 中文標題 CJK title", &mut id_counter),
+                "中文標題-cjk-title"
+            );
+            assert_eq!(unique_id_from_content("## Über", &mut id_counter), "Über-1");
+            assert_eq!(unique_id_from_content("## Über", &mut id_counter), "Über-2");
+        }
     }
 
-    mod convert_quotes_to_curly {
-        use super::super::convert_quotes_to_curly;
-
-        #[test]
-        fn it_converts_single_quotes() {
-            assert_eq!(convert_quotes_to_curly("'one', 'two'"), "‘one’, ‘two’");
-        }
-
-        #[test]
-        fn it_converts_double_quotes() {
-            assert_eq!(convert_quotes_to_curly(r#""one", "two""#), "“one”, “two”");
-        }
-
-        #[test]
-        fn it_treats_tab_as_whitespace() {
-            assert_eq!(convert_quotes_to_curly("\t'one'"), "\t‘one’");
-        }
+    #[test]
+    fn escaped_brackets() {
+        assert_eq!(bracket_escape(""), "");
+        assert_eq!(bracket_escape("<"), "&lt;");
+        assert_eq!(bracket_escape(">"), "&gt;");
+        assert_eq!(bracket_escape("<>"), "&lt;&gt;");
+        assert_eq!(bracket_escape("<test>"), "&lt;test&gt;");
+        assert_eq!(bracket_escape("a<test>b"), "a&lt;test&gt;b");
     }
 }

src/utils/string.rs

@@ -1,3 +1,4 @@
+use once_cell::sync::Lazy;
 use regex::Regex;
 use std::ops::Bound::{Excluded, Included, Unbounded};
 use std::ops::RangeBounds;
@@ -23,10 +24,10 @@ pub fn take_lines<R: RangeBounds<usize>>(s: &str, range: R) -> String {
     }
 }
 
-lazy_static! {
-    static ref ANCHOR_START: Regex = Regex::new(r"ANCHOR:\s*(?P<anchor_name>[\w_-]+)").unwrap();
-    static ref ANCHOR_END: Regex = Regex::new(r"ANCHOR_END:\s*(?P<anchor_name>[\w_-]+)").unwrap();
-}
+static ANCHOR_START: Lazy<Regex> =
+    Lazy::new(|| Regex::new(r"ANCHOR:\s*(?P<anchor_name>[\w_-]+)").unwrap());
+static ANCHOR_END: Lazy<Regex> =
+    Lazy::new(|| Regex::new(r"ANCHOR_END:\s*(?P<anchor_name>[\w_-]+)").unwrap());
 
 /// Take anchored lines from a string.
 /// Lines containing anchor are ignored.
@@ -70,7 +71,7 @@ pub fn take_rustdoc_include_lines<R: RangeBounds<usize>>(s: &str, range: R) -> S
             output.push_str("# ");
         }
         output.push_str(line);
-        output.push_str("\n");
+        output.push('\n');
     }
     output.pop();
     output
@@ -95,7 +96,7 @@ pub fn take_rustdoc_include_anchored_lines(s: &str, anchor: &str) -> String {
                 None => {
                     if !ANCHOR_START.is_match(l) {
                         output.push_str(l);
-                        output.push_str("\n");
+                        output.push('\n');
                     }
                 }
             }
@@ -106,7 +107,7 @@ pub fn take_rustdoc_include_anchored_lines(s: &str, anchor: &str) -> String {
         } else if !ANCHOR_END.is_match(l) {
             output.push_str("# ");
             output.push_str(l);
-            output.push_str("\n");
+            output.push('\n');
         }
     }
 
@@ -122,6 +123,7 @@ mod tests {
     };
 
     #[test]
+    #[allow(clippy::reversed_empty_ranges)] // Intentionally checking that those are correctly handled
     fn take_lines_test() {
         let s = "Lorem\nipsum\ndolor\nsit\namet";
         assert_eq!(take_lines(s, 1..3), "ipsum\ndolor");
@@ -163,6 +165,7 @@ mod tests {
     }
 
     #[test]
+    #[allow(clippy::reversed_empty_ranges)] // Intentionally checking that those are correctly handled
     fn take_rustdoc_include_lines_test() {
         let s = "Lorem\nipsum\ndolor\nsit\namet";
         assert_eq!(

src/utils/toml_ext.rs

@@ -53,7 +53,7 @@ impl TomlExt for Value {
 }
 
 fn split(key: &str) -> Option<(&str, &str)> {
-    let ix = key.find(".")?;
+    let ix = key.find('.')?;
 
     let (head, tail) = key.split_at(ix);
     // splitting will leave the "."

test_book/book.toml

@@ -0,0 +1,27 @@
+[book]
+title = "mdBook test book"
+description = "A demo book to test and validate changes"
+authors = ["YJDoc2"]
+language = "en"
+
+[rust]
+edition = "2018"
+
+[output.html]
+mathjax-support = true
+
+[output.html.playground]
+editable = true
+line-numbers = true
+
+[output.html.search]
+limit-results = 20
+use-boolean-and = true
+boost-title = 2
+boost-hierarchy = 2
+boost-paragraph = 1
+expand = true
+heading-split-level = 2
+
+[output.html.redirect]
+"/format/config.html" = "configuration/index.html"

test_book/src/README.md

@@ -0,0 +1,12 @@
+# Demo Book
+
+This is a simple demo book, which is intended to be used for verifying and validating style changes in mdBook.
+This contains dummy examples of various markdown elements and code languages, so that one can check changes made in mdBook styles.
+
+This rough outline is :
+
+- individual : contains basic markdown elements such as headings, paragraphs, links etc.
+- languages : contains a `hello world` in each of supported language to see changes in syntax highlighting
+- rust : contains language examples specific to rust, such as play pen, runnable examples etc.
+
+This is more for checking and fixing style, rather than verifying that correct code is generated for given markdown, that is better handled in tests.

test_book/src/SUMMARY.md

@@ -0,0 +1,33 @@
+# Summary
+
+[Prefix Chapter](prefix.md)
+
+---
+
+- [Introduction](README.md)
+- [Draft Chapter]()
+
+# Actual Markdown Tag Examples
+
+- [Markdown Individual tags](individual/README.md)
+  - [Heading](individual/heading.md)
+  - [Paragraphs](individual/paragraph.md)
+  - [Line Break](individual/linebreak.md)
+  - [Emphasis](individual/emphasis.md)
+  - [Blockquote](individual/blockquote.md)
+  - [List](individual/list.md)
+  - [Code](individual/code.md)
+  - [Image](individual/image.md)
+  - [Links and Horizontal Rule](individual/link_hr.md)
+  - [Tables](individual/table.md)
+  - [Tasks](individual/task.md)
+  - [Strikethrough](individual/strikethrough.md)
+  - [Mixed](individual/mixed.md)
+- [Languages](languages/README.md)
+  - [Syntax Highlight](languages/highlight.md)
+- [Rust Specific](rust/README.md)
+  - [Rust Codeblocks](rust/rust_codeblock.md)
+
+---
+
+[Suffix Chapter](suffix.md)

test_book/src/individual/README.md

@@ -0,0 +1,17 @@
+# Individual Common mark tags
+
+This contains following tags:
+
+- Headings
+- Paragraphs
+- Line breaks
+- Emphasis
+- Blockquotes
+- Lists
+- Code blocks
+- Images
+- Links and Horizontal rules
+- Github tables
+- Github Task Lists
+- Strikethrough
+- Mixed

test_book/src/individual/blockquote.md

@@ -0,0 +1,30 @@
+# Blockquote
+
+> This is a quoted sentence.
+
+> This is a quoted paragraph
+>
+> separated lines  
+> here
+
+> Nested
+>
+> > Quoted  
+> > Paragraph
+
+> ### And now,
+>
+> **Let us _introduce_**
+> All kinds of
+>
+> - tags
+> - etc
+> - stuff
+>
+> 1. In
+> 2. The
+> 3. blockquote
+>
+>    > cause we can
+>    >
+>    > > Cause we can

test_book/src/individual/code.md

@@ -0,0 +1,33 @@
+# Code
+
+This section only does simple code blocks and inline code, detailed syntax highlight and stuff is in the languages section
+
+---
+
+```
+This is a codeblock
+```
+
+---
+
+This line contains `inline code` mixed with some other stuff. (LTR)
+
+ושורה זו מכילה `inline code` אבל עם טקסט בשפה שנכתבת מימין לשמאל. (RTL)
+
+---
+
+````
+escaping ``` in ```, fun, isn't is?
+````
+
+---
+
+```bash,editable
+This is an editable codeblock
+```
+
+---
+
+```rust
+// This links to a playpen
+```

test_book/src/individual/emphasis.md

@@ -0,0 +1,13 @@
+# Emphasis
+
+This has **bold text** in between normal.
+
+This has _italic text_ in between normal.
+
+A **line** having _both_, bold and italic text.
+
+**A bold line _having_ italic text**
+
+_An Italic line having **bold** text_
+
+Now this is going **_out of hands_**.