Merge pull request #1773 from ehuss/bump-version

Update to 0.4.16

.github/workflows/deploy.yml

@@ -15,9 +15,6 @@ jobs:
     - name: Install hub
       run: ci/install-hub.sh ${{ matrix.os }}
       shell: bash
-    - name: Install Rustup
-      run: ci/install-rustup.sh stable
-      shell: bash
     - name: Install Rust
       run: ci/install-rust.sh stable
       shell: bash
@@ -34,12 +31,12 @@ jobs:
     - name: Install Rust (rustup)
       run: rustup update stable --no-self-update && rustup default stable
     - name: Build book
-      run: cargo run -- build book-example
+      run: cargo run -- build guide
     - name: Deploy to GitHub
       env:
         GITHUB_DEPLOY_KEY: ${{ secrets.GITHUB_DEPLOY_KEY }}
       run: |
-        touch book-example/book/.nojekyll
+        touch guide/book/.nojekyll
         curl -LsSf https://raw.githubusercontent.com/rust-lang/simpleinfra/master/setup-deploy-keys/src/deploy.rs | rustc - -o /tmp/deploy
-        cd book-example/book
+        cd guide/book
         /tmp/deploy

.github/workflows/main.yml

@@ -31,11 +31,10 @@ jobs:
             rust: stable
           - build: msrv
             os: ubuntu-latest
-            rust: 1.35.0
+            # sync MSRV with docs: guide/src/guide/installation.md
+            rust: 1.54.0
     steps:
     - uses: actions/checkout@master
-    - name: Install Rustup
-      run: bash ci/install-rustup.sh ${{ matrix.rust }}
     - name: Install Rust
       run: bash ci/install-rust.sh ${{ matrix.rust }}
     - name: Build and run tests
@@ -50,4 +49,4 @@ jobs:
     - uses: actions/checkout@master
     - name: Install Rust
       run: rustup update stable && rustup default stable && rustup component add rustfmt
-    - run: cargo fmt -- --check
+    - run: cargo fmt --check

.gitignore

@@ -4,10 +4,15 @@ target
 .DS_Store
 
 book-test
-book-example/book
+guide/book
 
 .vscode
 tests/dummy_book/book/
+test_book/book/
 
 # Ignore Jetbrains specific files.
 .idea/
+
+# Ignore Vim temporary and swap files.
+*.sw?
+*~

CHANGELOG.md

@@ -1,5 +1,441 @@
 # Changelog
 
+## 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 `cargo 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)
+
+### 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)
+
+## 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)
+
+### Added
+- Added the `output.html.print.enable` configuration value to disable the
+  "print" page.
+  [#1169](https://github.com/rust-lang/mdBook/pull/1169)
+- Added a list of supported languages for syntax-highlighting to the
+  documentation.
+  [#1345](https://github.com/rust-lang/mdBook/pull/1345)
+
+### Fixed
+- Now supports symbolic links for files in the `src` directory.
+  [#1323](https://github.com/rust-lang/mdBook/pull/1323)
+
+## mdBook 0.4.3
+[9278b83...4df9ec9](https://github.com/rust-lang/mdBook/compare/9278b83...4df9ec9)
+
+### Added
+- Added `output.html.cname` option to emit a `CNAME` file which is used by
+  GitHub Pages to know which domain is being used.
+  [#1311](https://github.com/rust-lang/mdBook/pull/1311)
+
+### Changed
+- `mdbook test` no longer stops on the first test failure, but instead will
+  run all the tests.
+  [#1313](https://github.com/rust-lang/mdBook/pull/1313)
+- Removed the `local` font source for Source Code Pro, as the locally
+  installed font may not render properly on FireFox on macOS.
+  [#1307](https://github.com/rust-lang/mdBook/pull/1307)
+
+### Fixed
+- Added newline to end of `.nojekyll` file.
+  [#1310](https://github.com/rust-lang/mdBook/pull/1310)
+- Fixed missing space before draft chapter titles.
+  [#1309](https://github.com/rust-lang/mdBook/pull/1309)
+
+## mdBook 0.4.2
+[649f355...9278b83](https://github.com/rust-lang/mdBook/compare/649f355...9278b83)
+
+### Changed
+- The "show hidden lines" icon has changed from the "expand" icon to an "eye".
+  [#1281](https://github.com/rust-lang/mdBook/pull/1281)
+- Updated highlight.js. This adds several languages: c, c-like (effectively
+  cpp), csharp (replaces cs), kotlin, less, lua, php-template, plaintext,
+  python-repl, r, scss, typescript.
+  [#1277](https://github.com/rust-lang/mdBook/pull/1277)
+
+### Fixed
+- Fixed SUMMARY links that contained newlines.
+  [#1291](https://github.com/rust-lang/mdBook/pull/1291)
+- Fixed SUMMARY links that contain `%20` spaces.
+  [#1293](https://github.com/rust-lang/mdBook/pull/1293)
+- Fixed favicon so that if only the png or svg is overridden, the other is not
+  automatically included in the `<link>` tag.
+  [#1272](https://github.com/rust-lang/mdBook/pull/1272)
+
+## mdBook 0.4.1
+[d4df7e7...649f355](https://github.com/rust-lang/mdBook/compare/d4df7e7...649f355)
+
+### Changed
+- Removed several outdated dev-dependencies.
+  [#1267](https://github.com/rust-lang/mdBook/pull/1267)
+
+### Fixed
+- Fixed sidebar scrolling if the book includes part titles.
+  [#1265](https://github.com/rust-lang/mdBook/pull/1265)
+- Don't include the default favicon if only one of the PNG or SVG is overridden.
+  [#1266](https://github.com/rust-lang/mdBook/pull/1266)
+
+## mdBook 0.4.0
+[99ecd4f...d4df7e7](https://github.com/rust-lang/mdBook/compare/99ecd4f...d4df7e7)
+
+### Breaking Changes
+- Several of the changes in the release have altered the public API of the
+  mdbook library.
+- Many dependencies have been updated or replaced.
+  This also removes the `--websocket-hostname` and `--websocket-port` from
+  the `serve` command.
+  [#1211](https://github.com/rust-lang/mdBook/pull/1211)
+- A new "404" page is now automatically rendered. This requires knowledge of
+  the base URL of your site to work properly. If you decide to use this as
+  your 404 page, you should set the `site-url` setting in the book
+  configuration so mdbook can generate the links correctly. Alternatively you
+  can disable the 404 page generation, or set up your own 404 handling in your
+  web server.
+  [#1221](https://github.com/rust-lang/mdBook/pull/1221)
+- The `debug` and `output` features have been removed as they were unused.
+  [#1211](https://github.com/rust-lang/mdBook/pull/1211)
+- If you are using customized themes, you may want to consider setting the
+  `preferred-dark-theme` config setting, as it now defaults to "navy".
+  [#1199](https://github.com/rust-lang/mdBook/pull/1199)
+- "Playpen" has been renamed to "playground". This is generally backwards
+  compatible for users, but `{{#playpen}}` will now display warnings. This may
+  impact books that have modified the "playpen" elements in the theme.
+  [#1241](https://github.com/rust-lang/mdBook/pull/1241)
+- If a renderer is not installed, it is now treated as an error. If you want
+  the old behavior of ignoring missing renderers, set the `optional` setting
+  for that renderer.
+  [#1122](https://github.com/rust-lang/mdBook/pull/1122)
+- If you have a custom favicon, you may need to look into adding an SVG
+  version, otherwise the default SVG icon will be displayed.
+  [#1230](https://github.com/rust-lang/mdBook/pull/1230)
+
+### Added
+- Added a new `[rust]` configuration section to `book.toml`, which allows
+  setting the default edition with `edition = "2018"`.
+  [#1163](https://github.com/rust-lang/mdBook/pull/1163)
+- Renderers can now be marked as `optional`, so that they will be ignored if
+  the renderer is not installed.
+  [#1122](https://github.com/rust-lang/mdBook/pull/1122)
+- Added `head.hbs` to allow adding content to the `<head>` section in HTML.
+  [#1206](https://github.com/rust-lang/mdBook/pull/1206)
+- Added "draft chapters". These are chapters listed without a link to indicate
+  content yet to be written.
+  [#1153](https://github.com/rust-lang/mdBook/pull/1153)
+- Added "parts" to split a book into different sections. Headers can be added
+  to `SUMMARY.md` to signify different sections.
+  [#1171](https://github.com/rust-lang/mdBook/pull/1171)
+- Added generation of a "404" page for handling missing pages and broken links.
+  [#1221](https://github.com/rust-lang/mdBook/pull/1221)
+- Added configuration section for specifying URL redirects.
+  [#1237](https://github.com/rust-lang/mdBook/pull/1237)
+- Added an SVG favicon that works with light and dark colors schemes.
+  [#1230](https://github.com/rust-lang/mdBook/pull/1230)
+
+### Changed
+- Changed default Rust attribute of `allow(unused_variables)` to `allow(unused)`.
+  [#1195](https://github.com/rust-lang/mdBook/pull/1195)
+- Fonts are now served locally instead of from the Google Fonts CDN. The
+  `copy-fonts` option was added to disable this if you want to supply your own
+  fonts.
+  [#1188](https://github.com/rust-lang/mdBook/pull/1188)
+- Switched the built-in webserver for the `serve` command to a new
+  implementation. This results in some internal differences in how websockets
+  are handled, which removes the separate websocket options. This should also
+  make it easier to serve multiple books at once.
+  [#1211](https://github.com/rust-lang/mdBook/pull/1211)
+- The default dark theme is now "navy".
+  [#1199](https://github.com/rust-lang/mdBook/pull/1199)
+- "Playpen" has been renamed to "playground", matching the actual name of the
+  service which was renamed many years ago.
+  [#1241](https://github.com/rust-lang/mdBook/pull/1241)
+
+### Fixed
+- Links with the `+` symbol should now work.
+  [#1208](https://github.com/rust-lang/mdBook/pull/1208)
+- The `MDBOOK_BOOK` environment variable now correctly allows overriding the
+  entire book configuration.
+  [#1207](https://github.com/rust-lang/mdBook/pull/1207)
+- The sidebar can no longer be dragged outside of the window.
+  [#1229](https://github.com/rust-lang/mdBook/pull/1229)
+- Hide the Rust Playground "play" button for `no_run` code samples.
+  [#1249](https://github.com/rust-lang/mdBook/pull/1249)
+- Fixed the `--dest-dir` command-line option for the `serve` and `watch`
+  commands.
+  [#1228](https://github.com/rust-lang/mdBook/pull/1228)
+- Hotkey handlers are now disabled in `text` input fields (for example, typing
+  `S` in a custom text input field).
+  [#1244](https://github.com/rust-lang/mdBook/pull/1244)
+
+## mdBook 0.3.7
+[88684d8...99ecd4f](https://github.com/rust-lang/mdBook/compare/88684d8...99ecd4f)
+
+### Changed
+- Code spans in headers are no longer highlighted as code.
+  [#1162](https://github.com/rust-lang/mdBook/pull/1162)
+- The sidebar will now scroll the activate page to the middle instead of the top.
+  [#1161](https://github.com/rust-lang/mdBook/pull/1161)
+- Reverted change to reject build output within the `src` directory, and
+  instead add a check that prevents infinite copies.
+  [#1181](https://github.com/rust-lang/mdBook/pull/1181)
+  [#1026](https://github.com/rust-lang/mdBook/pull/1026)
+
+### Fixed
+- Fixed sidebar line-height jumping for collapsed chapters.
+  [#1182](https://github.com/rust-lang/mdBook/pull/1182)
+- Fixed theme selector focus.
+  [#1170](https://github.com/rust-lang/mdBook/pull/1170)
+
+## mdBook 0.3.6
+[efdb832...88684d8](https://github.com/rust-lang/mdBook/compare/efdb832...88684d8)
+
+### Added
+- `MDBook::execute_build_process` is now publicly accessible in the API so
+  that plugins can more easily initiate the build process.
+  [#1099](https://github.com/rust-lang/mdBook/pull/1099)
+
+### Changed
+- Use a different color for Ayu theme's highlighting for Rust attributes (uses
+  a bright color instead of the comment color).
+  [#1133](https://github.com/rust-lang/mdBook/pull/1133)
+- Adjusted spacing of sidebar entries.
+  [#1137](https://github.com/rust-lang/mdBook/pull/1137)
+- Slightly adjusted line-height of `<p>`, `<ul>`, and `<ol>`.
+  [#1136](https://github.com/rust-lang/mdBook/pull/1136)
+- Handlebars updated to 3.0.
+  [#1130](https://github.com/rust-lang/mdBook/pull/1130)
+
+### Fixed
+- Fix an issue with sidebar scroll position on reload.
+  [#1108](https://github.com/rust-lang/mdBook/pull/1108)
+- `mdbook serve` will retain the current scroll position when the page is reloaded.
+  [#1097](https://github.com/rust-lang/mdBook/pull/1097)
+- Fixed the page name if the book didn't have a title to not be prefixed with ` - `.
+  [#1145](https://github.com/rust-lang/mdBook/pull/1145)
+- HTML attributes `rel=next` and `rel=previous` are now supported in "wide"
+  mode (previously they were only set in narrow mode).
+  [#1150](https://github.com/rust-lang/mdBook/pull/1150)
+- Prevent recursive copies when the destination directory is contained in the
+  source directory.
+  [#1135](https://github.com/rust-lang/mdBook/pull/1135)
+- Adjusted the menu bar animation to not immediately obscure the top content.
+  [#989](https://github.com/rust-lang/mdBook/pull/989)
+- Fix for comments in SUMMARY.md that appear between items.
+  [#1167](https://github.com/rust-lang/mdBook/pull/1167)
+
 ## mdBook 0.3.5
 [6e0d0fa...efdb832](https://github.com/rust-lang/mdBook/compare/6e0d0fa...efdb832)
 

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

@@ -6,7 +6,6 @@ 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:
 
 ### Issues to work on
 
@@ -46,7 +45,7 @@ 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
 
@@ -79,7 +78,7 @@ For more information, such as running it from your favourite editor, please see
 
 #### Finding Issues with Clippy
 
-Clippy is a code analyser/linter detecting mistakes, and therfore helps to improve your code.
+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.
 
@@ -106,3 +105,26 @@ 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 higlight.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.

Cargo.toml

@@ -1,6 +1,6 @@
 [package]
 name = "mdbook"
-version = "0.3.5"
+version = "0.4.16"
 authors = [
     "Mathieu David <mathieudavid@mathieudavid.org>",
     "Michael-F-Bryan <michaelfbryan@gmail.com>",
@@ -8,7 +8,7 @@ authors = [
 ]
 documentation = "http://rust-lang.github.io/mdBook/index.html"
 edition = "2018"
-exclude = ["/book-example/*"]
+exclude = ["/guide/*"]
 keywords = ["book", "gitbook", "rustbook", "markdown"]
 license = "MPL-2.0"
 readme = "README.md"
@@ -16,50 +16,51 @@ repository = "https://github.com/rust-lang/mdBook"
 description = "Creates a book from markdown files"
 
 [dependencies]
+anyhow = "1.0.28"
 chrono = "0.4"
-clap = "2.24"
-env_logger = "0.6"
-error-chain = "0.12"
-handlebars = { version = "2.0", default-features = false, features = ["no_dir_source"] }
-itertools = "0.8"
+clap = { version = "3.0", features = ["cargo"] }
+clap_complete = "3.0"
+env_logger = "0.7.1"
+handlebars = "4.0"
 lazy_static = "1.0"
 log = "0.4"
 memchr = "2.0"
-open = "1.1"
-pulldown-cmark = "0.6.1"
-regex = "1.0.0"
+opener = "0.5"
+pulldown-cmark = { version = "0.9.1", default-features = false }
+regex = "1.5.5"
 serde = "1.0"
 serde_derive = "1.0"
 serde_json = "1.0"
-shlex = "0.1"
+shlex = "1"
 tempfile = "3.0"
 toml = "0.5.1"
-toml-query = "0.9"
+topological-sort = "0.1.0"
 
 # Watch feature
 notify = { version = "4.0", optional = true }
 gitignore = { version = "1.0", optional = true }
 
 # Serve feature
-iron = { version = "0.6", optional = true }
-staticfile = { version = "0.5", optional = true }
-ws = { version = "0.9", optional = true}
+futures-util = { version = "0.3.4", optional = true }
+tokio = { version = "1", features = ["macros", "rt-multi-thread"], optional = true }
+warp = { version = "0.3.1", default-features = false, features = ["websocket"], optional = true }
 
 # Search feature
 elasticlunr-rs = { version = "2.3", optional = true, default-features = false }
 ammonia = { version = "3", optional = true }
 
 [dev-dependencies]
-select = "0.4"
+assert_cmd = "1"
+predicates = "2"
+select = "0.5"
+semver = "1.0"
 pretty_assertions = "0.6"
 walkdir = "2.0"
 
 [features]
-default = ["output", "watch", "serve", "search"]
-debug = []
-output = []
+default = ["watch", "serve", "search"]
 watch = ["notify", "gitignore"]
-serve = ["iron", "staticfile", "ws"]
+serve = ["futures-util", "tokio", "warp"]
 search = ["elasticlunr-rs", "ammonia"]
 
 [[bin]]

README.md

@@ -1,230 +1,20 @@
 # mdBook
 
-[![Build Status](https://github.com/rust-lang/mdBook/workflows/CI/badge.svg)](https://github.com/rust-lang/mdBook/actions?workflow=CI)
+[![Build Status](https://github.com/rust-lang/mdBook/workflows/CI/badge.svg?event=push)](https://github.com/rust-lang/mdBook/actions?workflow=CI)
 [![crates.io](https://img.shields.io/crates/v/mdbook.svg)](https://crates.io/crates/mdbook)
 [![LICENSE](https://img.shields.io/github/license/rust-lang/mdBook.svg)](LICENSE)
 
 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] 1.35 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. For example:
-
-   ```
-   cargo install mdbook --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 will primarily be 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
-  `{{# playpen}}` 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 issus 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] who 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

book-example/src/README.md

@@ -1,25 +0,0 @@
-# mdBook
-
-**mdBook** is a command line tool and Rust crate to create books using Markdown
-files. It's very similar to Gitbook but written in
-[Rust](http://www.rust-lang.org).
-
-What you are reading serves as an example of the output of mdBook and at the
-same time as a high-level documentation.
-
-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).
-
-## API docs
-
-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.
-
-## License
-
-mdBook, all the source code, is released under the [Mozilla Public License
-v2.0](https://www.mozilla.org/MPL/2.0/).

book-example/src/cli/README.md

@@ -1,55 +0,0 @@
-# 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.
-
-## Install From Binaries
-
-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.

book-example/src/cli/serve.md

@@ -1,48 +0,0 @@
-# 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
-connection is used to trigger the client-side refresh.
-
-***Note:*** *The `serve` command is for testing a book's HTML output, and is not
-intended to be a complete HTTP server for a website.*
-
-#### Specify a directory
-
-The `serve` command can take a directory as an argument to use as the book's
-root instead of the current working directory.
-
-```bash
-mdbook serve path/to/book
-```
-
-#### 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:
-
-```bash
-mdbook serve path/to/book -p 8000 -n 127.0.0.1 --websocket-hostname 192.168.1.100
-```
-
-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
-default web browser after starting the server.
-
-#### --dest-dir
-
-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`.

book-example/src/continuous-integration.md

@@ -1,89 +0,0 @@
-# Running `mdbook` in Continuous Integration
-
-While the following examples use Travis CI, their principles should
-straightforwardly transfer to other continuous integration providers as well.
-
-## Ensuring Your Book Builds and Tests Pass
-
-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.
-
-```yaml
-language: rust
-sudo: false
-
-cache:
-  - cargo
-
-rust:
-  - stable
-
-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
-
-script:
-  - mdbook build path/to/mybook && mdbook test path/to/mybook
-```
-
-## Deploying Your Book to GitHub Pages
-
-Following these instructions will result in your book being published to GitHub
-pages after a successful CI run on your repository's `master` branch.
-
-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.
-
-Then, append this snippet to your `.travis.yml` and update the path to the
-`book` directory:
-
-```yaml
-deploy:
-  provider: pages
-  skip-cleanup: true
-  github-token: $GITHUB_TOKEN
-  local-dir: path/to/mybook/book
-  keep-history: false
-  on:
-    branch: master
-```
-
-That's it!
-
-### Deploying to GitHub Pages manually
-
-If your CI doesn't support GitHub pages, or you're deploying somewhere else
-with integrations such as Github Pages:
- *note: you may want to use different tmp dirs*:
-
-```console
-$> 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 -
-```
-
-Or put this into a Makefile rule:
-
-```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
-```

book-example/src/format/config.md

@@ -1,333 +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."
-
-[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"
-```
-
-### 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 `{{ #playpen }}`, `{{ #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 the same theme as `default-theme`.
-- **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`.
-- **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.
-- **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.
-- **playpen:** A subtable for configuring various playpen 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`.
-  
-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.playpen]` 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
-google-analytics = "123456"
-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"
-
-[output.html.fold]
-enable = false
-level = 0
-
-[output.html.playpen]
-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
-```
-
-### 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 emtpy 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.
-
-Custom renderers will have access to all configuration within their table
-(i.e. anything under `[output.foo]`), and the command to be invoked can be
-manually specified with the `command` field.
-
-## 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.

book-example/src/format/example.rs

@@ -1,6 +0,0 @@
-fn main() {
-    println!("Hello World!");
-#
-#    // You can even hide lines! :D
-#   println!("I am hidden! Expand the code snippet to see me");
-}

book-example/src/format/summary.md

@@ -1,38 +0,0 @@
-# SUMMARY.md
-
-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.
-
-#### Allowed elements
-
-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.
-   ```markdown
-   [Title of prefix element](relative/path/to/markdown.md)
-   ```
-
-3. ***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.)
-   ```markdown
-   - [Title of the Chapter](relative/path/to/markdown.md)
-   ```
-   You can either use `-` or `*` to indicate a numbered chapter.
-
-4. ***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.
-
-All other elements are unsupported and will be ignored at best or result in an
-error.

book-example/src/format/theme/README.md

@@ -1,34 +0,0 @@
-# Theme
-
-The default renderer uses a [handlebars](http://handlebarsjs.com/) template to
-render your markdown files and comes with a default theme included in the mdBook
-binary.
-
-The theme is totally customizable, you can selectively replace every file from
-the theme by your own by adding a `theme` directory next to `src` folder in your
-project root. Create a new file with the name of the file you want to override
-and now that file will be used instead of the default file.
-
-Here are the files you can override:
-
-- ***index.hbs*** is the handlebars template.
-- ***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.
-- ***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,
-  you should not need to modify this.  
-- ***highlight.css*** is the theme used for the code highlighting
-- ***favicon.png*** the favicon that will be used
-
-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
-overriding all the other files. Because custom files take precedence over
-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
-remove the files you don't want to override.

book-example/src/misc/introduction.md

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

ci/install-hub.sh

@@ -21,4 +21,4 @@ case $1 in
     ;;
 esac
 
-echo "##[add-path]$PWD/hub/bin"
+echo "$PWD/hub/bin" >> $GITHUB_PATH

ci/install-rust.sh

@@ -12,7 +12,7 @@ TOOLCHAIN="$1"
 
 rustup set profile minimal
 rustup component remove --toolchain=$TOOLCHAIN rust-docs || echo "already removed"
-rustup update $TOOLCHAIN
+rustup update --no-self-update $TOOLCHAIN
 rustup default $TOOLCHAIN
 rustup -V
 rustc -Vv

ci/install-rustup.sh

@@ -1,26 +0,0 @@
-#!/usr/bin/env bash
-# Install/update rustup.
-# The first argument should be the toolchain to install.
-#
-# It is helpful to have this as a separate script due to some issues on
-# Windows where immediately after `rustup self update`, rustup can fail with
-# "Device or resource busy".
-
-set -ex
-if [ -z "$1" ]
-then
-    echo "First parameter must be toolchain to install."
-    exit 1
-fi
-TOOLCHAIN="$1"
-
-# Install/update rustup.
-if command -v rustup
-then
-    echo `command -v rustup` `rustup -V` already installed
-    rustup self update
-else
-    # macOS currently does not have rust pre-installed.
-    curl https://sh.rustup.rs -sSf | sh -s -- -y --default-toolchain $TOOLCHAIN --profile=minimal
-    echo "##[add-path]$HOME/.cargo/bin"
-fi

ci/make-release.sh

@@ -11,13 +11,24 @@ fi
 TAG=${GITHUB_REF#*/tags/}
 
 host=$(rustc -Vv | grep ^host: | sed -e "s/host: //g")
-cargo rustc --bin mdbook --release -- -C lto
+export CARGO_PROFILE_RELEASE_LTO=true
+cargo build --bin mdbook --release
 cd target/release
 case $1 in
-  ubuntu* | macos*)
+  ubuntu*)
     asset="mdbook-$TAG-$host.tar.gz"
     tar czf ../../$asset mdbook
     ;;
+  macos*)
+    asset="mdbook-$TAG-$host.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
+    # information. An alternative solution here is to install GNU tar, but
+    # flushing the disk cache seems to work, too.
+    sudo /usr/sbin/purge
+    tar czf ../../$asset mdbook
+    ;;
   windows*)
     asset="mdbook-$TAG-$host.zip"
     7z a ../../$asset mdbook.exe

examples/nop-preprocessor.rs

@@ -1,17 +1,18 @@
 use crate::nop_lib::Nop;
-use clap::{App, Arg, ArgMatches, SubCommand};
+use clap::{App, Arg, ArgMatches};
 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> {
+pub fn make_app() -> App<'static> {
     App::new("nop-preprocessor")
         .about("A mdbook preprocessor which does precisely nothing")
         .subcommand(
-            SubCommand::with_name("supports")
-                .arg(Arg::with_name("renderer").required(true))
+            App::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 {}",
@@ -53,7 +55,7 @@ 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 supported = pre.supports_renderer(renderer);
 
     // Signal whether the renderer is supported by exiting with 1 or 0.
     if supported {
@@ -87,7 +89,7 @@ mod nop_lib {
             // particular config value
             if let Some(nop_cfg) = ctx.config.get_preprocessor(self.name()) {
                 if nop_cfg.contains_key("blow-up") {
-                    return Err("Boom!!1!".into());
+                    anyhow::bail!("Boom!!1!");
                 }
             }
 

guide/book.toml

@@ -4,10 +4,16 @@ description = "Create book from markdown files. Like Gitbook but implemented in
 authors = ["Mathieu David", "Michael-F-Bryan"]
 language = "en"
 
+[rust]
+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.playpen]
+[output.html.playground]
 editable = true
 line-numbers = true
 
@@ -19,3 +25,6 @@ boost-hierarchy = 2
 boost-paragraph = 1
 expand = true
 heading-split-level = 2
+
+[output.html.redirect]
+"/format/config.html" = "configuration/index.html"

guide/src/404.md

@@ -0,0 +1,3 @@
+# Document not found (404)
+
+This URL is invalid, sorry. Try the search instead!

guide/src/README.md

@@ -0,0 +1,41 @@
+# Introduction
+
+**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.
+
+* 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]
+
+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.
+
+[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
+
+## 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
+
+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)
@@ -8,15 +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)
-    - [Configuration](format/config.md)
+        - [Draft chapter]()
+    - [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)
+    - [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

@@ -0,0 +1,14 @@
+# Command Line Tool
+
+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.
+
+This following sections provide in-depth information on the different commands available.
+
+* [`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.
@@ -35,5 +36,5 @@ not specified it will default to the value of the `build.build-dir` key in
 
 -------------------
 
-***Note:*** *Make sure to run the build command in the root directory and not in
-the source directory*
+***Note:*** *The build command copies all files (excluding files with `.md` extension) from the source directory
+into the build directory.*

guide/src/cli/completions.md

@@ -0,0 +1,16 @@
+# 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
+mdbook completions bash > ~/.local/share/bash-completion/completions/mdbook
+```
+
+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

@@ -19,15 +19,15 @@ book-test/
     └── SUMMARY.md
 ```
 
-- The `src` directory is were you write your book in markdown. It contains all
+- The `src` directory is where you write your book in markdown. It contains all
   the source files, configuration files, etc.
 
 - 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 +52,19 @@ 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.
+
+[building]: build.md

guide/src/cli/serve.md

@@ -0,0 +1,56 @@
+# The serve command
+
+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
+intended to be a complete HTTP server for a website.*
+
+#### Specify a directory
+
+The `serve` command can take a directory as an argument to use as the book's
+root instead of the current working directory.
+
+```bash
+mdbook serve path/to/book
+```
+
+### Server options
+
+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 
+```
+
+#### --open
+
+When you use the `--open` (`-o`) flag, mdbook will open the book in your
+default web browser after starting the server.
+
+#### --dest-dir
+
+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`.
+
+#### Specify exclude patterns
+
+The `serve` command will not automatically trigger a build for files listed in
+the `.gitignore` file in the book root directory. The `.gitignore` file may
+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 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

@@ -43,7 +43,17 @@ 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
 

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
 
@@ -25,3 +26,15 @@ 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`.
+
+
+#### Specify exclude patterns
+
+The `watch` command will not automatically trigger a build for files listed in
+the `.gitignore` file in the book root directory. The `.gitignore` file may
+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._

guide/src/continuous-integration.md

@@ -0,0 +1,121 @@
+# Running `mdbook` in Continuous Integration
+
+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.
+
+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.
+
+[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
+
+## Installing mdBook
+
+There are several different strategies for installing mdBook.
+The particular method depends on your needs and preferences.
+
+### Pre-compiled binaries
+
+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:
+
+```sh
+mkdir bin
+curl -sSL https://github.com/rust-lang/mdBook/releases/download/v0.4.16/mdbook-v0.4.16-x86_64-unknown-linux-gnu.tar.gz | tar -xz --directory=bin
+bin/mdbook build
+```
+
+Some considerations for this approach:
+
+* 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.
+
+[releases]: https://github.com/rust-lang/mdBook/releases
+
+### Building from source
+
+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
+```
+
+This includes several recommended options:
+
+* `--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.
+
+You will likely want to investigate caching options, as building mdBook can be somewhat slow.
+
+[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 with 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/"
+```
+
+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.
+
+[`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.
 
@@ -329,7 +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.
 
-
 ## Wrapping Up
 
 Although contrived, hopefully this example was enough to show how you'd create
@@ -342,10 +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/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 +1,110 @@
+# 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"
+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.
+
+```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
+```
+
+- **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.

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 prepocessor 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 +1,299 @@
+# 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:** Copies fonts.css and respective font files to the output directory and use them in the default theme. Defaults to `true`.
+- **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/master/{path}` or for
+  Bitbucket projects set it to
+  `https://bitbucket.org/<owner>/<repo>/src/master/{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 `/`.
+- **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.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

@@ -0,0 +1,6 @@
+fn main() {
+    println!("Hello World!");
+#
+#     // 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

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guide/src/format/markdown.md

@@ -0,0 +1,222 @@
+# 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 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

guide/src/format/mdbook.md

@@ -1,9 +1,10 @@
-# mdBook-specific markdown
+# mdBook-specific features
 
 ## Hiding code lines
 
 There is a feature in mdBook that lets you hide code lines by prepending them
-with a `#` [in the same way that Rustdoc does][rustdoc-hide].
+with a `#` [like you would with Rustdoc][rustdoc-hide].
+This currently only works with Rust language code blocks.
 
 [rustdoc-hide]: https://doc.rust-lang.org/stable/rustdoc/documentation-tests.html#hiding-portions-of-the-example
 
@@ -21,12 +22,73 @@ Will render as
 ```rust
 # fn main() {
     let x = 5;
-    let y = 7;
+    let y = 6;
 
     println!("{}", x + y);
 # }
 ```
 
+The code block has an eyeball icon (<i class="fa fa-eye"></i>) which will toggle the visibility of the hidden lines.
+
+## 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:
@@ -37,10 +99,10 @@ With the following syntax, you can include files into your book:
 
 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
+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 +111,7 @@ 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 +130,8 @@ 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:
@@ -92,17 +154,17 @@ impl System for MySystem { ... }
 Then in the book, all you have to do is:
 ````hbs
 Here is a component:
-```rust,no_run,noplaypen
+```rust,no_run,noplayground
 \{{#include file.rs:component}}
 ```
 
 Here is a system:
-```rust,no_run,noplaypen
+```rust,no_run,noplayground
 \{{#include file.rs:system}}
 ```
 
 This is the full file.
-```rust,no_run,noplaypen
+```rust,no_run,noplayground
 \{{#include file.rs:all}}
 ```
 ````
@@ -156,7 +218,7 @@ 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 +232,7 @@ 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
@@ -178,17 +240,37 @@ That is, it looks like this (click the "expand" icon to see the rest of the file
 With the following syntax, you can insert runnable Rust files into your book:
 
 ```hbs
-\{{#playpen file.rs}}
+\{{#playground file.rs}}
 ```
 
 The path to the Rust file has to be relative from the current source file.
 
-When play is clicked, the code snippet will be sent to the [Rust Playpen] to be
+When play is clicked, the code snippet will be sent to the [Rust Playground] to be
 compiled and run. The result is sent back and displayed directly underneath the
 code.
 
 Here is what a rendered code snippet looks like:
 
-{{#playpen example.rs}}
+{{#playground example.rs}}
 
-[Rust Playpen]: https://play.rust-lang.org/
+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}}
+```

guide/src/format/summary.md

@@ -0,0 +1,99 @@
+# SUMMARY.md
+
+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.
+
+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
+
+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
+   # Summary
+   ```
+
+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 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
+
+   - [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
+
+   - [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
+
+   - [Another Chapter](relative/path/to/markdown4.md)
+   ```
+   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)
+
+   [Title of Suffix Chapter](relative/path/to/markdown2.md)
+   ```
+
+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]()
+   ```
+
+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)
+
+   ---
+
+   - [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

@@ -0,0 +1,50 @@
+# Theme
+
+The default renderer uses a [handlebars](http://handlebarsjs.com/) template to
+render your markdown files and comes with a default theme included in the mdBook
+binary.
+
+The theme is totally customizable, you can selectively replace every file from
+the theme by your own by adding a `theme` directory next to `src` folder in your
+project root. Create a new file with the name of the file you want to override
+and now that file will be used instead of the default file.
+
+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.
+- **_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,
+  you should not need to modify this.
+- **_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].
+
+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
+overriding all the other files. Because custom files take precedence over
+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` 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`]: ../configuration/renderers.md#html-renderer-options
+[newer browsers]: https://caniuse.com/#feat=link-icon-svg

guide/src/format/theme/editor.md

@@ -1,25 +1,27 @@
 # Editor
 
-In addition to providing runnable code playpens, mdBook optionally allows them
+In addition to providing runnable code playgrounds, mdBook optionally allows them
 to be editable. In order to enable editable code blocks, the following needs to
 be added to the ***book.toml***:
 
 ```toml
-[output.html.playpen]
+[output.html.playground]
 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 playpen:
+The above will result in this editable playground:
 
 ```rust,editable
 fn main() {
@@ -28,19 +30,19 @@ fn main() {
 }
 ```
 
-Note the new `Undo Changes` button in the editable playpens.
+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.playpen]
+[output.html.playground]
 editable = true
 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 +19,8 @@ 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 of the book, as specified in `book.toml`
+- ***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`
 
 - ***path*** Relative path to the original markdown file from the source

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

@@ -1,16 +1,67 @@
 # Syntax Highlighting
 
-For syntax highlighting I use [Highlight.js](https://highlightjs.org) with a
-custom theme.
+mdBook uses [Highlight.js](https://highlightjs.org) with a custom theme
+for syntax highlighting.
 
 Automatic language detection has been turned off, so you will probably want to
-specify the programming language you use like this
+specify the programming language you use like this:
 
-<pre><code class="language-markdown">```rust
+~~~markdown
+```rust
 fn main() {
     // Some code
 }
-```</code></pre>
+```
+~~~
+
+## Supported languages
+
+These languages are supported by default, but you can add more by supplying
+your own `highlight.js` file:
+
+- apache
+- armasm
+- bash
+- c
+- coffeescript
+- cpp
+- csharp
+- css
+- d
+- diff
+- go
+- handlebars
+- haskell
+- http
+- ini
+- java
+- javascript
+- json
+- julia
+- kotlin
+- less
+- lua
+- makefile
+- markdown
+- nginx
+- objectivec
+- perl
+- php
+- plaintext
+- properties
+- python
+- r
+- ruby
+- rust
+- scala
+- scss
+- shell
+- sql
+- swift
+- typescript
+- x86asm
+- xml
+- yaml
 
 ## Custom theme
 Like the rest of the theme, the files used for syntax highlighting can be
@@ -61,10 +112,10 @@ 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 `mbdook 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 +1,50 @@
+# 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 1.54.
+
+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).
+
+[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.

src/book/book.rs

@@ -14,14 +14,15 @@ 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)
-        .chain_err(|| "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).chain_err(|| "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).chain_err(|| "Unable to create missing chapters")?;
+        create_missing(src_dir, &summary).with_context(|| "Unable to create missing chapters")?;
     }
 
     load_book_from_disk(&summary, src_dir)
@@ -39,17 +40,21 @@ fn create_missing(src_dir: &Path, summary: &Summary) -> Result<()> {
         let next = items.pop().expect("already checked");
 
         if let SummaryItem::Link(ref link) = *next {
-            let filename = src_dir.join(&link.location);
-            if !filename.exists() {
-                if let Some(parent) = filename.parent() {
-                    if !parent.exists() {
-                        fs::create_dir_all(parent)?;
+            if let Some(ref location) = link.location {
+                let filename = src_dir.join(location);
+                if !filename.exists() {
+                    if let Some(parent) = filename.parent() {
+                        if !parent.exists() {
+                            fs::create_dir_all(parent)?;
+                        }
                     }
-                }
-                debug!("Creating missing file {}", filename.display());
+                    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, "# {}", link.name)?;
+                }
             }
 
             items.extend(&link.nested_items);
@@ -61,7 +66,7 @@ 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()`].
@@ -131,6 +136,8 @@ pub enum BookItem {
     Chapter(Chapter),
     /// A section separator.
     Separator,
+    /// A part title.
+    PartTitle(String),
 }
 
 impl From<Chapter> for BookItem {
@@ -152,8 +159,10 @@ pub struct Chapter {
     /// Nested items.
     pub sub_items: Vec<BookItem>,
     /// The chapter's location, relative to the `SUMMARY.md` file.
-    pub path: PathBuf,
-    /// An ordered list of the names of each chapter above this one, in the hierarchy.
+    pub path: Option<PathBuf>,
+    /// 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>,
 }
 
@@ -162,17 +171,37 @@ 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: 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 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.
+    pub fn is_draft_chapter(&self) -> bool {
+        self.path.is_none()
+    }
 }
 
 /// Use the provided `Summary` to load a `Book` from disk.
@@ -202,16 +231,17 @@ pub(crate) fn load_book_from_disk<P: AsRef<Path>>(summary: &Summary, src_dir: P)
     })
 }
 
-fn load_summary_item<P: AsRef<Path>>(
+fn load_summary_item<P: AsRef<Path> + Clone>(
     item: &SummaryItem,
     src_dir: P,
     parent_names: Vec<String>,
 ) -> Result<BookItem> {
-    match *item {
+    match item {
         SummaryItem::Separator => Ok(BookItem::Separator),
         SummaryItem::Link(ref link) => {
             load_chapter(link, src_dir, parent_names).map(BookItem::Chapter)
         }
+        SummaryItem::PartTitle(title) => Ok(BookItem::PartTitle(title.clone())),
     }
 }
 
@@ -220,28 +250,40 @@ fn load_chapter<P: AsRef<Path>>(
     src_dir: P,
     parent_names: Vec<String>,
 ) -> Result<Chapter> {
-    debug!("Loading {} ({})", link.name, link.location.display());
     let src_dir = src_dir.as_ref();
 
-    let location = if link.location.is_absolute() {
-        link.location.clone()
+    let mut ch = if let Some(ref link_location) = link.location {
+        debug!("Loading {} ({})", link.name, link_location.display());
+
+        let location = if link_location.is_absolute() {
+            link_location.clone()
+        } else {
+            src_dir.join(link_location)
+        };
+
+        let mut f = File::open(&location)
+            .with_context(|| format!("Chapter file not found, {}", link_location.display()))?;
+
+        let mut content = String::new();
+        f.read_to_string(&mut content).with_context(|| {
+            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)
+            .expect("Chapters are always inside a book");
+
+        Chapter::new(&link.name, content, stripped, parent_names.clone())
     } else {
-        src_dir.join(&link.location)
+        Chapter::new_draft(&link.name, parent_names.clone())
     };
 
-    let mut f = File::open(&location)
-        .chain_err(|| format!("Chapter file not found, {}", link.location.display()))?;
+    let mut sub_item_parents = parent_names;
 
-    let mut content = String::new();
-    f.read_to_string(&mut content)
-        .chain_err(|| format!("Unable to read \"{}\" ({})", link.name, location.display()))?;
-
-    let stripped = location
-        .strip_prefix(&src_dir)
-        .expect("Chapters are always inside a book");
-
-    let mut sub_item_parents = parent_names.clone();
-    let mut ch = Chapter::new(&link.name, content, stripped, parent_names);
     ch.number = link.number.clone();
 
     sub_item_parents.push(link.name.clone());
@@ -262,8 +304,6 @@ 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>,
 }
@@ -341,7 +381,7 @@ 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)
     }
@@ -360,6 +400,29 @@ 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");
@@ -376,7 +439,8 @@ And here is some \
             name: String::from("Nested Chapter 1"),
             content: String::from("Hello World!"),
             number: Some(SectionNumber(vec![1, 2])),
-            path: PathBuf::from("second.md"),
+            path: Some(PathBuf::from("second.md")),
+            source_path: Some(PathBuf::from("second.md")),
             parent_names: vec![String::from("Chapter 1")],
             sub_items: Vec::new(),
         };
@@ -384,12 +448,13 @@ And here is some \
             name: String::from("Chapter 1"),
             content: String::from(DUMMY_SRC),
             number: None,
-            path: PathBuf::from("chapter_1.md"),
+            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),
             ],
         });
 
@@ -408,7 +473,8 @@ And here is some \
             sections: vec![BookItem::Chapter(Chapter {
                 name: String::from("Chapter 1"),
                 content: String::from(DUMMY_SRC),
-                path: PathBuf::from("chapter_1.md"),
+                path: Some(PathBuf::from("chapter_1.md")),
+                source_path: Some(PathBuf::from("chapter_1.md")),
                 ..Default::default()
             })],
             ..Default::default()
@@ -448,7 +514,8 @@ And here is some \
                     name: String::from("Chapter 1"),
                     content: String::from(DUMMY_SRC),
                     number: None,
-                    path: PathBuf::from("Chapter_1/index.md"),
+                    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(
@@ -500,7 +567,8 @@ And here is some \
                     name: String::from("Chapter 1"),
                     content: String::from(DUMMY_SRC),
                     number: None,
-                    path: PathBuf::from("Chapter_1/index.md"),
+                    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(
@@ -537,9 +605,10 @@ And here is some \
         let summary = Summary {
             numbered_chapters: vec![SummaryItem::Link(Link {
                 name: String::from("Empty"),
-                location: PathBuf::from(""),
+                location: Some(PathBuf::from("")),
                 ..Default::default()
             })],
+
             ..Default::default()
         };
 
@@ -556,7 +625,7 @@ And here is some \
         let summary = Summary {
             numbered_chapters: vec![SummaryItem::Link(Link {
                 name: String::from("nested"),
-                location: dir,
+                location: Some(dir),
                 ..Default::default()
             })],
             ..Default::default()

src/book/init.rs

@@ -28,7 +28,7 @@ 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
@@ -64,19 +64,19 @@ impl BookBuilder {
         info!("Creating a new book with stub content");
 
         self.create_directory_structure()
-            .chain_err(|| "Unable to create directory structure")?;
+            .with_context(|| "Unable to create directory structure")?;
 
         self.create_stub_files()
-            .chain_err(|| "Unable to create stub files")?;
+            .with_context(|| "Unable to create stub files")?;
 
         if self.create_gitignore {
             self.build_gitignore()
-                .chain_err(|| "Unable to create .gitignore")?;
+                .with_context(|| "Unable to create .gitignore")?;
         }
 
         if self.copy_theme {
             self.copy_across_theme()
-                .chain_err(|| "Unable to copy across the theme")?;
+                .with_context(|| "Unable to copy across the theme")?;
         }
 
         self.write_book_toml()?;
@@ -97,24 +97,20 @@ impl BookBuilder {
     fn write_book_toml(&self) -> Result<()> {
         debug!("Writing book.toml");
         let book_toml = self.root.join("book.toml");
-        let cfg = toml::to_vec(&self.config).chain_err(|| "Unable to serialize the config")?;
+        let cfg = toml::to_vec(&self.config).with_context(|| "Unable to serialize the config")?;
 
         File::create(book_toml)
-            .chain_err(|| "Couldn't create book.toml")?
+            .with_context(|| "Couldn't create book.toml")?
             .write_all(&cfg)
-            .chain_err(|| "Unable to write config to book.toml")?;
+            .with_context(|| "Unable to write config to book.toml")?;
         Ok(())
     }
 
     fn copy_across_theme(&self) -> Result<()> {
         debug!("Copying theme");
 
-        let themedir = self
-            .config
-            .html_config()
-            .and_then(|html| html.theme)
-            .unwrap_or_else(|| self.config.book.src.join("theme"));
-        let themedir = self.root.join(themedir);
+        let html_config = self.config.html_config().unwrap_or_default();
+        let themedir = html_config.theme_dir(&self.root);
 
         if !themedir.exists() {
             debug!(
@@ -128,7 +124,9 @@ 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)?;
@@ -136,14 +134,19 @@ impl BookBuilder {
         let mut chrome_css = File::create(cssdir.join("chrome.css"))?;
         chrome_css.write_all(theme::CHROME_CSS)?;
 
-        let mut print_css = File::create(cssdir.join("print.css"))?;
-        print_css.write_all(theme::PRINT_CSS)?;
+        if html_config.print.enable {
+            let mut print_css = File::create(cssdir.join("print.css"))?;
+            print_css.write_all(theme::PRINT_CSS)?;
+        }
 
         let mut variables_css = File::create(cssdir.join("variables.css"))?;
         variables_css.write_all(theme::VARIABLES_CSS)?;
 
         let mut favicon = File::create(themedir.join("favicon.png"))?;
-        favicon.write_all(theme::FAVICON)?;
+        favicon.write_all(theme::FAVICON_PNG)?;
+
+        let mut favicon = File::create(themedir.join("favicon.svg"))?;
+        favicon.write_all(theme::FAVICON_SVG)?;
 
         let mut js = File::create(themedir.join("book.js"))?;
         js.write_all(theme::JS)?;
@@ -174,13 +177,14 @@ impl BookBuilder {
         let summary = src_dir.join("SUMMARY.md");
         if !summary.exists() {
             trace!("No summary found creating stub summary and chapter_1.md.");
-            let mut f = File::create(&summary).chain_err(|| "Unable to create SUMMARY.md")?;
+            let mut f = File::create(&summary).with_context(|| "Unable to create SUMMARY.md")?;
             writeln!(f, "# Summary")?;
             writeln!(f)?;
             writeln!(f, "- [Chapter 1](./chapter_1.md)")?;
 
             let chapter_1 = src_dir.join("chapter_1.md");
-            let mut f = File::create(&chapter_1).chain_err(|| "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.");

src/book/mod.rs

@@ -5,6 +5,7 @@
 //!
 //! [1]: ../index.html
 
+#[allow(clippy::module_inception)]
 mod book;
 mod init;
 mod summary;
@@ -19,6 +20,7 @@ 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::{
@@ -27,7 +29,7 @@ use crate::preprocess::{
 use crate::renderer::{CmdRenderer, HtmlHandlebars, MarkdownRenderer, RenderContext, Renderer};
 use crate::utils;
 
-use crate::config::Config;
+use crate::config::{Config, RustEdition};
 
 /// The object used to manage and build a book.
 pub struct MDBook {
@@ -39,7 +41,7 @@ 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>>,
 }
 
@@ -68,6 +70,20 @@ 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);
@@ -77,7 +93,7 @@ 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();
 
@@ -96,7 +112,7 @@ 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,
@@ -120,19 +136,18 @@ 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
     /// # use mdbook::MDBook;
     /// # use mdbook::book::BookItem;
-    /// # #[allow(unused_variables)]
-    /// # fn main() {
     /// # let book = MDBook::load("mybook").unwrap();
     /// for item in book.iter() {
     ///     match *item {
     ///         BookItem::Chapter(ref chapter) => {},
     ///         BookItem::Separator => {},
+    ///         BookItem::PartTitle(ref title) => {}
     ///     }
     /// }
     ///
@@ -143,7 +158,6 @@ impl MDBook {
     /// // 2. Chapter 2
     /// //
     /// // etc.
-    /// # }
     /// ```
     pub fn iter(&self) -> BookItems<'_> {
         self.book.iter()
@@ -181,8 +195,8 @@ impl MDBook {
         Ok(())
     }
 
-    /// Run the entire build process for a particular `Renderer`.
-    fn execute_build_process(&self, renderer: &dyn Renderer) -> Result<()> {
+    /// 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();
         let preprocess_ctx = PreprocessorContext::new(
             self.root.clone(),
@@ -197,37 +211,34 @@ impl MDBook {
             }
         }
 
-        info!("Running the {} backend", renderer.name());
-        self.render(&preprocessed_book, renderer)?;
-
-        Ok(())
-    }
-
-    fn render(&self, preprocessed_book: &Book, renderer: &dyn Renderer) -> Result<()> {
         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)
-            .chain_err(|| "Rendering failed")
+            .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
@@ -251,32 +262,55 @@ impl MDBook {
         // Index Preprocessor is disabled so that chapter paths continue to point to the
         // actual markdown files.
 
+        let mut failed = false;
         for item in book.iter() {
             if let BookItem::Chapter(ref ch) = *item {
-                if !ch.path.as_os_str().is_empty() {
-                    let path = self.source_dir().join(&ch.path);
-                    info!("Testing file: {:?}", path);
+                let chapter_path = match ch.path {
+                    Some(ref path) if !path.as_os_str().is_empty() => path,
+                    _ => continue,
+                };
 
-                    // write preprocessed file to tempdir
-                    let path = temp_dir.path().join(&ch.path);
-                    let mut tmpf = utils::fs::create_file(&path)?;
-                    tmpf.write_all(ch.content.as_bytes())?;
+                let path = self.source_dir().join(&chapter_path);
+                info!("Testing file: {:?}", path);
 
-                    let output = Command::new("rustdoc")
-                        .arg(&path)
-                        .arg("--test")
-                        .args(&library_args)
-                        .output()?;
+                // write preprocessed file to tempdir
+                let path = temp_dir.path().join(&chapter_path);
+                let mut tmpf = utils::fs::create_file(&path)?;
+                tmpf.write_all(ch.content.as_bytes())?;
 
-                    if !output.status.success() {
-                        bail!(ErrorKind::Subprocess(
-                            "Rustdoc returned an error".to_string(),
-                            output
-                        ));
+                let mut cmd = Command::new("rustdoc");
+                cmd.arg(&path).arg("--test").args(&library_args);
+
+                if let Some(edition) = self.config.rust.edition {
+                    match edition {
+                        RustEdition::E2015 => {
+                            cmd.args(&["--edition", "2015"]);
+                        }
+                        RustEdition::E2018 => {
+                            cmd.args(&["--edition", "2018"]);
+                        }
+                        RustEdition::E2021 => {
+                            cmd.args(&["--edition", "2021"]);
+                        }
                     }
                 }
+
+                let output = cmd.output()?;
+
+                if !output.status.success() {
+                    failed = true;
+                    error!(
+                        "rustdoc returned an error:\n\
+                        \n--- stdout\n{}\n--- stderr\n{}",
+                        String::from_utf8_lossy(&output.stdout),
+                        String::from_utf8_lossy(&output.stderr)
+                    );
+                }
             }
         }
+        if failed {
+            bail!("One or more tests failed");
+        }
         Ok(())
     }
 
@@ -284,7 +318,7 @@ 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):
@@ -352,12 +386,7 @@ 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: &[&'static str] = &["links", "index"];
 
 fn is_default_preprocessor(pre: &dyn Preprocessor) -> bool {
     let name = pre.name();
@@ -366,36 +395,127 @@ 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.to_string()))
+        .unwrap_or_else(|| format!("mdbook-{}", key))
 }
 
 fn interpret_custom_renderer(key: &str, table: &Value) -> Box<CmdRenderer> {
@@ -408,7 +528,7 @@ fn interpret_custom_renderer(key: &str, table: &Value) -> Box<CmdRenderer> {
 
     let command = table_dot_command.unwrap_or_else(|| format!("mdbook-{}", key));
 
-    Box::new(CmdRenderer::new(key.to_string(), command.to_string()))
+    Box::new(CmdRenderer::new(key.to_string(), command))
 }
 
 /// Check whether we should run a particular `Preprocessor` in combination
@@ -495,8 +615,8 @@ 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]
@@ -543,9 +663,123 @@ 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()
+            .find(|preprocessor| preprocessor.name() == "random")
+            .is_none());
+    }
+
+    #[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()
+            .find(|preprocessor| preprocessor.name() == "links")
+            .is_none());
     }
 
     #[test]

src/book/summary.rs

@@ -1,6 +1,6 @@
 use crate::errors::*;
 use memchr::{self, Memchr};
-use pulldown_cmark::{self, Event, Tag};
+use pulldown_cmark::{self, Event, HeadingLevel, Tag};
 use std::fmt::{self, Display, Formatter};
 use std::iter::FromIterator;
 use std::ops::{Deref, DerefMut};
@@ -25,12 +25,17 @@ use std::path::{Path, PathBuf};
 /// [Title of prefix element](relative/path/to/markdown.md)
 /// ```
 ///
+/// **Part Title:** An optional title for the next collect of numbered chapters. The numbered
+/// chapters can be broken into as many parts as desired.
+///
 /// **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.)
 ///
 /// ```markdown
+/// # Title of Part
+///
 /// - [Title of the Chapter](relative/path/to/markdown.md)
 /// ```
 ///
@@ -55,7 +60,7 @@ pub struct Summary {
     pub title: Option<String>,
     /// Chapters before the main text (e.g. an introduction).
     pub prefix_chapters: Vec<SummaryItem>,
-    /// The main chapters in the document.
+    /// The main numbered chapters of the book, broken into one or more possibly named parts.
     pub numbered_chapters: Vec<SummaryItem>,
     /// Items which come after the main document (e.g. a conclusion).
     pub suffix_chapters: Vec<SummaryItem>,
@@ -71,7 +76,7 @@ pub struct Link {
     pub name: String,
     /// The location of the chapter's source file, taking the book's `src`
     /// directory as the root.
-    pub location: PathBuf,
+    pub location: Option<PathBuf>,
     /// The section number, if this chapter is in the numbered section.
     pub number: Option<SectionNumber>,
     /// Any nested items this chapter may contain.
@@ -83,7 +88,7 @@ impl Link {
     pub fn new<S: Into<String>, P: AsRef<Path>>(name: S, location: P) -> Link {
         Link {
             name: name.into(),
-            location: location.as_ref().to_path_buf(),
+            location: Some(location.as_ref().to_path_buf()),
             number: None,
             nested_items: Vec::new(),
         }
@@ -94,7 +99,7 @@ impl Default for Link {
     fn default() -> Self {
         Link {
             name: String::new(),
-            location: PathBuf::new(),
+            location: Some(PathBuf::new()),
             number: None,
             nested_items: Vec::new(),
         }
@@ -108,6 +113,8 @@ pub enum SummaryItem {
     Link(Link),
     /// A separator (`---`).
     Separator,
+    /// A part title.
+    PartTitle(String),
 }
 
 impl SummaryItem {
@@ -134,12 +141,13 @@ impl From<Link> for SummaryItem {
 ///
 /// ```text
 /// summary           ::= title prefix_chapters numbered_chapters
-/// suffix_chapters
+///                         suffix_chapters
 /// title             ::= "# " TEXT
 ///                     | EPSILON
 /// prefix_chapters   ::= item*
 /// suffix_chapters   ::= item*
-/// numbered_chapters ::= dotted_item+
+/// numbered_chapters ::= part+
+/// part              ::= title dotted_item+
 /// dotted_item       ::= INDENT* DOT_POINT item
 /// item              ::= link
 ///                     | separator
@@ -153,15 +161,19 @@ 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
+    /// here until somebody calls `next_event` again.
+    back: Option<Event<'a>>,
 }
 
 /// Reads `Events` from the provided stream until the corresponding
 /// `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 {
@@ -203,6 +215,7 @@ impl<'a> SummaryParser<'a> {
             src: text,
             stream: pulldown_parser,
             offset: 0,
+            back: None,
         }
     }
 
@@ -223,13 +236,13 @@ impl<'a> SummaryParser<'a> {
 
         let prefix_chapters = self
             .parse_affix(true)
-            .chain_err(|| "There was an error parsing the prefix chapters")?;
+            .with_context(|| "There was an error parsing the prefix chapters")?;
         let numbered_chapters = self
-            .parse_numbered()
-            .chain_err(|| "There was an error parsing the numbered chapters")?;
+            .parse_parts()
+            .with_context(|| "There was an error parsing the numbered chapters")?;
         let suffix_chapters = self
             .parse_affix(false)
-            .chain_err(|| "There was an error parsing the suffix chapters")?;
+            .with_context(|| "There was an error parsing the suffix chapters")?;
 
         Ok(Summary {
             title,
@@ -239,8 +252,7 @@ impl<'a> SummaryParser<'a> {
         })
     }
 
-    /// Parse the affix chapters. This expects the first event (start of
-    /// paragraph) to have already been consumed by the previous parser.
+    /// Parse the affix chapters.
     fn parse_affix(&mut self, is_prefix: bool) -> Result<Vec<SummaryItem>> {
         let mut items = Vec::new();
         debug!(
@@ -250,17 +262,19 @@ impl<'a> SummaryParser<'a> {
 
         loop {
             match self.next_event() {
-                Some(Event::Start(Tag::List(..))) => {
+                Some(ev @ Event::Start(Tag::List(..)))
+                | 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.
+                        self.back(ev);
                         break;
                     } else {
                         bail!(self.parse_error("Suffix chapters cannot be followed by a list"));
                     }
                 }
                 Some(Event::Start(Tag::Link(_type, href, _title))) => {
-                    let link = self.parse_link(href.to_string())?;
+                    let link = self.parse_link(href.to_string());
                     items.push(SummaryItem::Link(link));
                 }
                 Some(Event::Rule) => items.push(SummaryItem::Separator),
@@ -272,52 +286,111 @@ impl<'a> SummaryParser<'a> {
         Ok(items)
     }
 
-    fn parse_link(&mut self, href: String) -> Result<Link> {
+    fn parse_parts(&mut self) -> Result<Vec<SummaryItem>> {
+        let mut parts = vec![];
+
+        // We want the section numbers to be continues through all parts.
+        let mut root_number = SectionNumber::default();
+        let mut root_items = 0;
+
+        loop {
+            // Possibly match a title or the end of the "numbered chapters part".
+            let title = match self.next_event() {
+                Some(ev @ Event::Start(Tag::Paragraph)) => {
+                    // we're starting the suffix chapters
+                    self.back(ev);
+                    break;
+                }
+
+                Some(Event::Start(Tag::Heading(HeadingLevel::H1, ..))) => {
+                    debug!("Found a h1 in the SUMMARY");
+
+                    let tags = collect_events!(self.stream, end Tag::Heading(HeadingLevel::H1, ..));
+                    Some(stringify_events(tags))
+                }
+
+                Some(ev) => {
+                    self.back(ev);
+                    None
+                }
+
+                None => break, // EOF, bail...
+            };
+
+            // Parse the rest of the part.
+            let numbered_chapters = self
+                .parse_numbered(&mut root_items, &mut root_number)
+                .with_context(|| "There was an error parsing the numbered chapters")?;
+
+            if let Some(title) = title {
+                parts.push(SummaryItem::PartTitle(title));
+            }
+            parts.extend(numbered_chapters);
+        }
+
+        Ok(parts)
+    }
+
+    /// Finishes parsing a link once the `Event::Start(Tag::Link(..))` has been opened.
+    fn parse_link(&mut self, href: String) -> Link {
+        let href = href.replace("%20", " ");
         let link_content = collect_events!(self.stream, end Tag::Link(..));
         let name = stringify_events(link_content);
 
-        if href.is_empty() {
-            Err(self.parse_error("You can't have an empty link."))
+        let path = if href.is_empty() {
+            None
         } else {
-            Ok(Link {
-                name,
-                location: PathBuf::from(href.to_string()),
-                number: None,
-                nested_items: Vec::new(),
-            })
+            Some(PathBuf::from(href))
+        };
+
+        Link {
+            name,
+            location: path,
+            number: None,
+            nested_items: Vec::new(),
         }
     }
 
-    /// Parse the numbered chapters. This assumes the opening list tag has
-    /// already been consumed by a previous parser.
-    fn parse_numbered(&mut self) -> Result<Vec<SummaryItem>> {
+    /// Parse the numbered chapters.
+    fn parse_numbered(
+        &mut self,
+        root_items: &mut u32,
+        root_number: &mut SectionNumber,
+    ) -> Result<Vec<SummaryItem>> {
         let mut items = Vec::new();
-        let mut root_items = 0;
-        let root_number = SectionNumber::default();
 
-        // we need to do this funny loop-match-if-let dance because a rule will
-        // close off any currently running list. Therefore we try to read the
-        // list items before the rule, then if we encounter a rule we'll add a
-        // separator and try to resume parsing numbered chapters if we start a
-        // list immediately afterwards.
-        //
-        // If you can think of a better way to do this then please make a PR :)
+        // For the first iteration, we want to just skip any opening paragraph tags, as that just
+        // marks the start of the list. But after that, another opening paragraph indicates that we
+        // have started a new part or the suffix chapters.
+        let mut first = true;
 
         loop {
-            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
-            // them
-            update_section_numbers(&mut bunch_of_items, 0, root_items);
-            root_items += bunch_of_items.len() as u32;
-            items.extend(bunch_of_items);
-
             match self.next_event() {
-                Some(Event::Start(Tag::Paragraph)) => {
-                    // we're starting the suffix chapters
+                Some(ev @ Event::Start(Tag::Paragraph)) => {
+                    if !first {
+                        // we're starting the suffix chapters
+                        self.back(ev);
+                        break;
+                    }
+                }
+                // 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(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)?;
+
+                    // 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
+                    // them
+                    update_section_numbers(&mut bunch_of_items, 0, *root_items);
+                    *root_items += bunch_of_items.len() as u32;
+                    items.extend(bunch_of_items);
+                }
                 Some(Event::Start(other_tag)) => {
                     trace!("Skipping contents of {:?}", other_tag);
 
@@ -327,40 +400,42 @@ impl<'a> SummaryParser<'a> {
                             break;
                         }
                     }
-
-                    if let Some(Event::Start(Tag::List(..))) = self.next_event() {
-                        continue;
-                    } else {
-                        break;
-                    }
                 }
                 Some(Event::Rule) => {
                     items.push(SummaryItem::Separator);
-                    if let Some(Event::Start(Tag::List(..))) = self.next_event() {
-                        continue;
-                    } else {
-                        break;
-                    }
-                }
-                Some(_) => {
-                    // something else... ignore
-                    continue;
                 }
+
+                // something else... ignore
+                Some(_) => {}
+
+                // EOF, bail...
                 None => {
-                    // EOF, bail...
                     break;
                 }
             }
+
+            // From now on, we cannot accept any new paragraph opening tags.
+            first = false;
         }
 
         Ok(items)
     }
 
+    /// Push an event back to the tail of the stream.
+    fn back(&mut self, ev: Event<'a>) {
+        assert!(self.back.is_none());
+        trace!("Back: {:?}", ev);
+        self.back = Some(ev);
+    }
+
     fn next_event(&mut self) -> Option<Event<'a>> {
-        let next = self.stream.next().map(|(ev, range)| {
-            self.offset = range.start;
-            ev
+        let next = self.back.take().or_else(|| {
+            self.stream.next().map(|(ev, range)| {
+                self.offset = range.start;
+                ev
+            })
         });
+
         trace!("Next event: {:?}", next);
 
         next
@@ -377,6 +452,10 @@ impl<'a> SummaryParser<'a> {
                     items.push(item);
                 }
                 Some(Event::Start(Tag::List(..))) => {
+                    // Skip this tag after comment bacause it is not nested.
+                    if items.is_empty() {
+                        continue;
+                    }
                     // recurse to parse the nested list
                     let (_, last_item) = get_last_link(&mut items)?;
                     let last_item_number = last_item
@@ -406,7 +485,7 @@ impl<'a> SummaryParser<'a> {
             match self.next_event() {
                 Some(Event::Start(Tag::Paragraph)) => continue,
                 Some(Event::Start(Tag::Link(_type, href, _title))) => {
-                    let mut link = self.parse_link(href.to_string())?;
+                    let mut link = self.parse_link(href.to_string());
 
                     let mut number = parent.clone();
                     number.0.push(num_existing_items as u32 + 1);
@@ -414,7 +493,10 @@ impl<'a> SummaryParser<'a> {
                         "Found chapter: {} {} ({})",
                         number,
                         link.name,
-                        link.location.display()
+                        link.location
+                            .as_ref()
+                            .map(|p| p.to_str().unwrap_or(""))
+                            .unwrap_or("[draft]")
                     );
 
                     link.number = Some(number);
@@ -433,19 +515,33 @@ impl<'a> SummaryParser<'a> {
 
     fn parse_error<D: Display>(&self, msg: D) -> Error {
         let (line, col) = self.current_location();
-
-        ErrorKind::ParseError(line, col, msg.to_string()).into()
+        anyhow::anyhow!(
+            "failed to parse SUMMARY.md line {}, column {}: {}",
+            line,
+            col,
+            msg
+        )
     }
 
     /// Try to parse the title line.
     fn parse_title(&mut self) -> Option<String> {
-        if let Some(Event::Start(Tag::Heading(1))) = self.next_event() {
-            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))
-        } else {
-            None
+                    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,
+            }
         }
     }
 }
@@ -471,10 +567,9 @@ fn get_last_link(links: &mut [SummaryItem]) -> Result<(usize, &mut Link)> {
         .filter_map(|(i, item)| item.maybe_link_mut().map(|l| (i, l)))
         .rev()
         .next()
-        .ok_or_else(|| {
-            "Unable to get last link because the list of SummaryItems doesn't contain any Links"
-                .into()
-        })
+        .ok_or_else(||
+            anyhow::anyhow!("Unable to get last link because the list of SummaryItems doesn't contain any Links")
+            )
 }
 
 /// Removes the styling from a list of Markdown events and returns just the
@@ -484,6 +579,7 @@ fn stringify_events(events: Vec<Event<'_>>) -> String {
         .into_iter()
         .filter_map(|t| match t {
             Event::Text(text) | Event::Code(text) => Some(text.into_string()),
+            Event::SoftBreak => Some(String::from(" ")),
             _ => None,
         })
         .collect()
@@ -555,6 +651,18 @@ 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";
@@ -585,17 +693,16 @@ mod tests {
         let should_be = vec![
             SummaryItem::Link(Link {
                 name: String::from("First"),
-                location: PathBuf::from("./first.md"),
+                location: Some(PathBuf::from("./first.md")),
                 ..Default::default()
             }),
             SummaryItem::Link(Link {
                 name: String::from("Second"),
-                location: PathBuf::from("./second.md"),
+                location: Some(PathBuf::from("./second.md")),
                 ..Default::default()
             }),
         ];
 
-        let _ = parser.stream.next(); // step past first event
         let got = parser.parse_affix(true).unwrap();
 
         assert_eq!(got, should_be);
@@ -606,7 +713,6 @@ mod tests {
         let src = "[First](./first.md)\n\n---\n\n[Second](./second.md)\n";
         let mut parser = SummaryParser::new(src);
 
-        let _ = parser.stream.next(); // step past first event
         let got = parser.parse_affix(true).unwrap();
 
         assert_eq!(got.len(), 3);
@@ -618,7 +724,6 @@ mod tests {
         let src = "[First](./first.md)\n- [Second](./second.md)\n";
         let mut parser = SummaryParser::new(src);
 
-        let _ = parser.stream.next(); // step past first event
         let got = parser.parse_affix(false);
 
         assert!(got.is_err());
@@ -629,19 +734,19 @@ mod tests {
         let src = "[First](./first.md)";
         let should_be = Link {
             name: String::from("First"),
-            location: PathBuf::from("./first.md"),
+            location: Some(PathBuf::from("./first.md")),
             ..Default::default()
         };
 
         let mut parser = SummaryParser::new(src);
-        let _ = parser.stream.next(); // skip past start of paragraph
+        let _ = parser.stream.next(); // Discard opening paragraph
 
         let href = match parser.stream.next() {
             Some((Event::Start(Tag::Link(_type, href, _title)), _range)) => href.to_string(),
             other => panic!("Unreachable, {:?}", other),
         };
 
-        let got = parser.parse_link(href).unwrap();
+        let got = parser.parse_link(href);
         assert_eq!(got, should_be);
     }
 
@@ -650,16 +755,16 @@ mod tests {
         let src = "- [First](./first.md)\n";
         let link = Link {
             name: String::from("First"),
-            location: PathBuf::from("./first.md"),
+            location: Some(PathBuf::from("./first.md")),
             number: Some(SectionNumber(vec![1])),
             ..Default::default()
         };
         let should_be = vec![SummaryItem::Link(link)];
 
         let mut parser = SummaryParser::new(src);
-        let _ = parser.stream.next();
-
-        let got = parser.parse_numbered().unwrap();
+        let got = parser
+            .parse_numbered(&mut 0, &mut SectionNumber::default())
+            .unwrap();
 
         assert_eq!(got, should_be);
     }
@@ -671,27 +776,92 @@ mod tests {
         let should_be = vec![
             SummaryItem::Link(Link {
                 name: String::from("First"),
-                location: PathBuf::from("./first.md"),
+                location: Some(PathBuf::from("./first.md")),
                 number: Some(SectionNumber(vec![1])),
                 nested_items: vec![SummaryItem::Link(Link {
                     name: String::from("Nested"),
-                    location: PathBuf::from("./nested.md"),
+                    location: Some(PathBuf::from("./nested.md")),
                     number: Some(SectionNumber(vec![1, 1])),
                     nested_items: Vec::new(),
                 })],
             }),
             SummaryItem::Link(Link {
                 name: String::from("Second"),
-                location: PathBuf::from("./second.md"),
+                location: Some(PathBuf::from("./second.md")),
                 number: Some(SectionNumber(vec![2])),
                 nested_items: Vec::new(),
             }),
         ];
 
         let mut parser = SummaryParser::new(src);
-        let _ = parser.stream.next();
+        let got = parser
+            .parse_numbered(&mut 0, &mut SectionNumber::default())
+            .unwrap();
 
-        let got = parser.parse_numbered().unwrap();
+        assert_eq!(got, should_be);
+    }
+
+    #[test]
+    fn parse_numbered_chapters_separated_by_comment() {
+        let src = "- [First](./first.md)\n<!-- this is a comment -->\n- [Second](./second.md)";
+
+        let should_be = vec![
+            SummaryItem::Link(Link {
+                name: String::from("First"),
+                location: Some(PathBuf::from("./first.md")),
+                number: Some(SectionNumber(vec![1])),
+                nested_items: Vec::new(),
+            }),
+            SummaryItem::Link(Link {
+                name: String::from("Second"),
+                location: Some(PathBuf::from("./second.md")),
+                number: Some(SectionNumber(vec![2])),
+                nested_items: Vec::new(),
+            }),
+        ];
+
+        let mut parser = SummaryParser::new(src);
+        let got = parser
+            .parse_numbered(&mut 0, &mut SectionNumber::default())
+            .unwrap();
+
+        assert_eq!(got, should_be);
+    }
+
+    #[test]
+    fn parse_titled_parts() {
+        let src = "- [First](./first.md)\n- [Second](./second.md)\n\
+                   # Title 2\n- [Third](./third.md)\n\t- [Fourth](./fourth.md)";
+
+        let should_be = vec![
+            SummaryItem::Link(Link {
+                name: String::from("First"),
+                location: Some(PathBuf::from("./first.md")),
+                number: Some(SectionNumber(vec![1])),
+                nested_items: Vec::new(),
+            }),
+            SummaryItem::Link(Link {
+                name: String::from("Second"),
+                location: Some(PathBuf::from("./second.md")),
+                number: Some(SectionNumber(vec![2])),
+                nested_items: Vec::new(),
+            }),
+            SummaryItem::PartTitle(String::from("Title 2")),
+            SummaryItem::Link(Link {
+                name: String::from("Third"),
+                location: Some(PathBuf::from("./third.md")),
+                number: Some(SectionNumber(vec![3])),
+                nested_items: vec![SummaryItem::Link(Link {
+                    name: String::from("Fourth"),
+                    location: Some(PathBuf::from("./fourth.md")),
+                    number: Some(SectionNumber(vec![3, 1])),
+                    nested_items: Vec::new(),
+                })],
+            }),
+        ];
+
+        let mut parser = SummaryParser::new(src);
+        let got = parser.parse_parts().unwrap();
 
         assert_eq!(got, should_be);
     }
@@ -706,34 +876,41 @@ mod tests {
         let should_be = vec![
             SummaryItem::Link(Link {
                 name: String::from("First"),
-                location: PathBuf::from("./first.md"),
+                location: Some(PathBuf::from("./first.md")),
                 number: Some(SectionNumber(vec![1])),
                 nested_items: Vec::new(),
             }),
             SummaryItem::Link(Link {
                 name: String::from("Second"),
-                location: PathBuf::from("./second.md"),
+                location: Some(PathBuf::from("./second.md")),
                 number: Some(SectionNumber(vec![2])),
                 nested_items: Vec::new(),
             }),
         ];
 
         let mut parser = SummaryParser::new(src);
-        let _ = parser.stream.next();
-
-        let got = parser.parse_numbered().unwrap();
+        let got = parser
+            .parse_numbered(&mut 0, &mut SectionNumber::default())
+            .unwrap();
 
         assert_eq!(got, should_be);
     }
 
     #[test]
-    fn an_empty_link_location_is_an_error() {
+    fn an_empty_link_location_is_a_draft_chapter() {
         let src = "- [Empty]()\n";
         let mut parser = SummaryParser::new(src);
-        parser.stream.next();
 
-        let got = parser.parse_numbered();
-        assert!(got.is_err());
+        let got = parser.parse_numbered(&mut 0, &mut SectionNumber::default());
+        let should_be = vec![SummaryItem::Link(Link {
+            name: String::from("Empty"),
+            location: None,
+            number: Some(SectionNumber(vec![1])),
+            nested_items: Vec::new(),
+        })];
+
+        assert!(got.is_ok());
+        assert_eq!(got.unwrap(), should_be);
     }
 
     /// Regression test for https://github.com/rust-lang/mdBook/issues/779
@@ -745,31 +922,175 @@ mod tests {
         let should_be = vec![
             SummaryItem::Link(Link {
                 name: String::from("First"),
-                location: PathBuf::from("./first.md"),
+                location: Some(PathBuf::from("./first.md")),
                 number: Some(SectionNumber(vec![1])),
                 nested_items: Vec::new(),
             }),
             SummaryItem::Separator,
             SummaryItem::Link(Link {
                 name: String::from("Second"),
-                location: PathBuf::from("./second.md"),
+                location: Some(PathBuf::from("./second.md")),
                 number: Some(SectionNumber(vec![2])),
                 nested_items: Vec::new(),
             }),
             SummaryItem::Separator,
             SummaryItem::Link(Link {
                 name: String::from("Third"),
-                location: PathBuf::from("./third.md"),
+                location: Some(PathBuf::from("./third.md")),
                 number: Some(SectionNumber(vec![3])),
                 nested_items: Vec::new(),
             }),
         ];
 
         let mut parser = SummaryParser::new(src);
-        let _ = parser.stream.next();
-
-        let got = parser.parse_numbered().unwrap();
+        let got = parser
+            .parse_numbered(&mut 0, &mut SectionNumber::default())
+            .unwrap();
 
         assert_eq!(got, should_be);
     }
+
+    /// Regression test for https://github.com/rust-lang/mdBook/issues/1218
+    /// Ensure chapter names spread across multiple lines have spaces between all the words.
+    #[test]
+    fn add_space_for_multi_line_chapter_names() {
+        let src = "- [Chapter\ntitle](./chapter.md)";
+        let should_be = vec![SummaryItem::Link(Link {
+            name: String::from("Chapter title"),
+            location: Some(PathBuf::from("./chapter.md")),
+            number: Some(SectionNumber(vec![1])),
+            nested_items: Vec::new(),
+        })];
+
+        let mut parser = SummaryParser::new(src);
+        let got = parser
+            .parse_numbered(&mut 0, &mut SectionNumber::default())
+            .unwrap();
+
+        assert_eq!(got, should_be);
+    }
+
+    #[test]
+    fn allow_space_in_link_destination() {
+        let src = "- [test1](./test%20link1.md)\n- [test2](<./test link2.md>)";
+        let should_be = vec![
+            SummaryItem::Link(Link {
+                name: String::from("test1"),
+                location: Some(PathBuf::from("./test link1.md")),
+                number: Some(SectionNumber(vec![1])),
+                nested_items: Vec::new(),
+            }),
+            SummaryItem::Link(Link {
+                name: String::from("test2"),
+                location: Some(PathBuf::from("./test link2.md")),
+                number: Some(SectionNumber(vec![2])),
+                nested_items: Vec::new(),
+            }),
+        ];
+        let mut parser = SummaryParser::new(src);
+        let got = parser
+            .parse_numbered(&mut 0, &mut SectionNumber::default())
+            .unwrap();
+
+        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

@@ -1,22 +1,28 @@
 use crate::{get_book_dir, open};
-use clap::{App, ArgMatches, SubCommand};
+use clap::{arg, App, Arg, ArgMatches};
 use mdbook::errors::Result;
 use mdbook::MDBook;
 
 // Create clap subcommand arguments
-pub fn make_subcommand<'a, 'b>() -> App<'a, 'b> {
-    SubCommand::with_name("build")
+pub fn make_subcommand<'help>() -> App<'help> {
+    App::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(
+            Arg::new("dest-dir")
+                .short('d')
+                .long("dest-dir")
+                .value_name("dest-dir")
+                .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`.",
+                ),
         )
-        .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(arg!([dir]
+            "Root directory for the book{n}\
+            (Defaults to the Current Directory when omitted)"
+        ))
+        .arg(arg!(-o --open "Opens the compiled book in a web browser"))
 }
 
 // Build command implementation

src/cmd/clean.rs

@@ -1,23 +1,28 @@
 use crate::get_book_dir;
-use clap::{App, ArgMatches, SubCommand};
-use mdbook::errors::*;
+use anyhow::Context;
+use clap::{arg, App, Arg, ArgMatches};
 use mdbook::MDBook;
 use std::fs;
 
 // Create clap subcommand arguments
-pub fn make_subcommand<'a, 'b>() -> App<'a, 'b> {
-    SubCommand::with_name("clean")
+pub fn make_subcommand<'help>() -> App<'help> {
+    App::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(
+            Arg::new("dest-dir")
+                .short('d')
+                .long("dest-dir")
+                .value_name("dest-dir")
+                .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`.",
+                ),
         )
+        .arg(arg!([dir]
+            "Root directory for the book{n}\
+            (Defaults to the Current Directory when omitted)"
+        ))
 }
 
 // Clean command implementation
@@ -31,7 +36,8 @@ pub fn execute(args: &ArgMatches) -> mdbook::errors::Result<()> {
     };
 
     if dir_to_remove.exists() {
-        fs::remove_dir_all(&dir_to_remove).chain_err(|| "Unable to remove the build directory")?;
+        fs::remove_dir_all(&dir_to_remove)
+            .with_context(|| "Unable to remove the build directory")?;
     }
 
     Ok(())

src/cmd/init.rs

@@ -1,5 +1,5 @@
 use crate::get_book_dir;
-use clap::{App, ArgMatches, SubCommand};
+use clap::{arg, App, Arg, ArgMatches};
 use mdbook::config;
 use mdbook::errors::Result;
 use mdbook::MDBook;
@@ -8,16 +8,31 @@ 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<'help>() -> App<'help> {
+    App::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)"
+        ))
+        .arg(arg!(--theme "Copies the default theme into your source folder"))
+        .arg(arg!(--force "Skips confirmation prompts"))
+        .arg(
+            Arg::new("title")
+                .long("title")
+                .takes_value(true)
+                .help("Sets the book title")
+                .required(false),
+        )
+        .arg(
+            Arg::new("ignore")
+                .long("ignore")
+                .takes_value(true)
+                .possible_values(&["none", "git"])
+                .help("Creates a VCS ignore file (i.e. .gitignore)")
+                .required(false),
         )
-        .arg_from_usage("--theme 'Copies the default theme into your source folder'")
-        .arg_from_usage("--force 'Skips confirmation prompts'")
 }
 
 // Init command implementation
@@ -25,18 +40,13 @@ 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")?;
+        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.is_present("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 +59,23 @@ 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.value_of("ignore") {
+        match ignore {
+            "git" => builder.create_gitignore(true),
+            _ => builder.create_gitignore(false),
+        };
+    } else {
+        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.is_present("title") {
+        args.value_of("title").map(String::from)
+    } else {
+        request_book_title()
+    };
 
     if let Some(author) = get_author_name() {
         debug!("Obtained user name from gitconfig: {:?}", author);

src/cmd/serve.rs

@@ -1,103 +1,105 @@
 #[cfg(feature = "watch")]
 use super::watch;
 use crate::{get_book_dir, open};
-use clap::{App, Arg, ArgMatches, SubCommand};
-use iron::{status, AfterMiddleware, Chain, Iron, IronError, IronResult, Request, Response, Set};
+use clap::{arg, App, Arg, ArgMatches};
+use futures_util::sink::SinkExt;
+use futures_util::StreamExt;
 use mdbook::errors::*;
 use mdbook::utils;
+use mdbook::utils::fs::get_404_output_file;
 use mdbook::MDBook;
+use std::net::{SocketAddr, ToSocketAddrs};
+use std::path::PathBuf;
+use tokio::sync::broadcast;
+use warp::ws::Message;
+use warp::Filter;
 
-struct ErrorRecover;
+/// The HTTP endpoint for the websocket used to trigger reloads when a file changes.
+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<'help>() -> App<'help> {
+    App::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(
-            Arg::with_name("hostname")
-                .short("n")
+            Arg::new("dest-dir")
+                .short('d')
+                .long("dest-dir")
+                .value_name("dest-dir")
+                .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`.",
+                ),
+        )
+        .arg(arg!([dir]
+            "Root directory for the book{n}\
+            (Defaults to the Current Directory when omitted)"
+        ))
+        .arg(
+            Arg::new("hostname")
+                .short('n')
                 .long("hostname")
                 .takes_value(true)
                 .default_value("localhost")
-                .empty_values(false)
+                .forbid_empty_values(true)
                 .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)
                 .default_value("3000")
-                .empty_values(false)
+                .forbid_empty_values(true)
                 .help("Port to use for HTTP connections"),
         )
-        .arg(
-            Arg::with_name("websocket-hostname")
-                .long("websocket-hostname")
-                .takes_value(true)
-                .empty_values(false)
-                .help(
-                    "Hostname to connect to for WebSockets connections (Defaults to the HTTP hostname)",
-                ),
-        )
-        .arg(
-            Arg::with_name("websocket-port")
-                .short("w")
-                .long("websocket-port")
-                .takes_value(true)
-                .default_value("3001")
-                .empty_values(false)
-                .help("Port to use for WebSockets livereload connections"),
-        )
-        .arg_from_usage("-o, --open 'Opens the book server in a web browser'")
+        .arg(arg!(-o --open "Opens the compiled book in a web browser"))
 }
 
-// Watch command implementation
+// Serve command implementation
 pub fn execute(args: &ArgMatches) -> Result<()> {
     let book_dir = get_book_dir(args);
     let mut book = MDBook::load(&book_dir)?;
 
     let port = args.value_of("port").unwrap();
-    let ws_port = args.value_of("websocket-port").unwrap();
     let hostname = args.value_of("hostname").unwrap();
-    let public_address = args.value_of("websocket-hostname").unwrap_or(hostname);
     let open_browser = args.is_present("open");
 
     let address = format!("{}:{}", hostname, port);
-    let ws_address = format!("{}:{}", hostname, ws_port);
-
-    let livereload_url = format!("ws://{}:{}", public_address, ws_port);
-    book.config
-        .set("output.html.livereload-url", &livereload_url)?;
-
-    if let Some(dest_dir) = args.value_of("dest-dir") {
-        book.config.build.build_dir = dest_dir.into();
-    }
 
+    let update_config = |book: &mut MDBook| {
+        book.config
+            .set("output.html.live-reload-endpoint", &LIVE_RELOAD_ENDPOINT)
+            .expect("live-reload-endpoint update failed");
+        if let Some(dest_dir) = args.value_of("dest-dir") {
+            book.config.build.build_dir = dest_dir.into();
+        }
+        // Override site-url for local serving of the 404 file
+        book.config.set("output.html.site-url", "/").unwrap();
+    };
+    update_config(&mut book);
     book.build()?;
 
-    let mut chain = Chain::new(staticfile::Static::new(book.build_dir_for("html")));
-    chain.link_after(ErrorRecover);
-    let _iron = Iron::new(chain)
-        .http(&*address)
-        .chain_err(|| "Unable to launch the server")?;
+    let sockaddr: SocketAddr = address
+        .to_socket_addrs()?
+        .next()
+        .ok_or_else(|| anyhow::anyhow!("no address found for {}", address))?;
+    let build_dir = book.build_dir_for("html");
+    let input_404 = book
+        .config
+        .get("output.html.input-404")
+        .map(toml::Value::as_str)
+        .and_then(std::convert::identity) // flatten
+        .map(ToString::to_string);
+    let file_404 = get_404_output_file(&input_404);
 
-    let ws_server =
-        ws::WebSocket::new(|_| |_| Ok(())).chain_err(|| "Unable to start the websocket")?;
+    // A channel used to broadcast to any websockets to reload when a file changes.
+    let (tx, _rx) = tokio::sync::broadcast::channel::<Message>(100);
 
-    let broadcaster = ws_server.broadcaster();
-
-    std::thread::spawn(move || {
-        ws_server.listen(&*ws_address).unwrap();
+    let reload_tx = tx.clone();
+    let thread_handle = std::thread::spawn(move || {
+        serve(build_dir, sockaddr, reload_tx, &file_404);
     });
 
     let serving_url = format!("http://{}", address);
@@ -113,32 +115,63 @@ 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| {
-                b.config
-                    .set("output.html.livereload-url", &livereload_url)?;
-                Ok(b)
-            })
-            .and_then(|b| b.build());
+        let result = MDBook::load(&book_dir).and_then(|mut b| {
+            update_config(&mut b);
+            b.build()
+        });
 
         if let Err(e) = result {
             error!("Unable to load the book");
             utils::log_backtrace(&e);
         } else {
-            let _ = broadcaster.send("reload");
+            let _ = tx.send(Message::text("reload"));
         }
     });
 
+    let _ = thread_handle.join();
+
     Ok(())
 }
 
-impl AfterMiddleware for ErrorRecover {
-    fn catch(&self, _: &mut Request, err: IronError) -> IronResult<Response> {
-        match err.response.status {
-            // each error will result in 404 response
-            Some(_) => Ok(err.response.set(status::NotFound)),
-            _ => Err(err),
-        }
-    }
+#[tokio::main]
+async fn serve(
+    build_dir: PathBuf,
+    address: SocketAddr,
+    reload_tx: broadcast::Sender<Message>,
+    file_404: &str,
+) {
+    // A warp Filter which captures `reload_tx` and provides an `rx` copy to
+    // receive reload messages.
+    let sender = warp::any().map(move || reload_tx.subscribe());
+
+    // A warp Filter to handle the livereload endpoint. This upgrades to a
+    // websocket, and then waits for any filesystem change notifications, and
+    // relays them over the websocket.
+    let livereload = warp::path(LIVE_RELOAD_ENDPOINT)
+        .and(warp::ws())
+        .and(sender)
+        .map(|ws: warp::ws::Ws, mut rx: broadcast::Receiver<Message>| {
+            ws.on_upgrade(move |ws| async move {
+                let (mut user_ws_tx, _user_ws_rx) = ws.split();
+                trace!("websocket got connection");
+                if let Ok(m) = rx.recv().await {
+                    trace!("notify of reload");
+                    let _ = user_ws_tx.send(m).await;
+                }
+            })
+        });
+    // A warp Filter that serves from the filesystem.
+    let book_route = warp::fs::dir(build_dir.clone());
+    // The fallback route for 404 errors
+    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

@@ -1,29 +1,37 @@
 use crate::get_book_dir;
-use clap::{App, Arg, ArgMatches, SubCommand};
+use clap::{arg, App, Arg, ArgMatches};
 use mdbook::errors::Result;
 use mdbook::MDBook;
 
 // Create clap subcommand arguments
-pub fn make_subcommand<'a, 'b>() -> App<'a, 'b> {
-    SubCommand::with_name("test")
+pub fn make_subcommand<'help>() -> App<'help> {
+    App::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`.'",
+        .arg(
+            Arg::new("dest-dir")
+                .short('d')
+                .long("dest-dir")
+                .value_name("dest-dir")
+                .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`.",
+                ),
         )
-        .arg_from_usage(
-            "[dir] 'Root directory for the book{n}\
-             (Defaults to the Current Directory when omitted)'",
-        )
-        .arg(Arg::with_name("library-path")
-            .short("L")
+        .arg(arg!([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")
             .takes_value(true)
+            .use_delimiter(true)
             .require_delimiter(true)
-            .multiple(true)
-            .empty_values(false)
+            .multiple_values(true)
+            .multiple_occurrences(true)
+            .forbid_empty_values(true)
             .help("A comma-separated list of directories to add to {n}the crate search path when building tests"))
 }
 

src/cmd/watch.rs

@@ -1,5 +1,5 @@
 use crate::{get_book_dir, open};
-use clap::{App, ArgMatches, SubCommand};
+use clap::{arg, App, Arg, ArgMatches};
 use mdbook::errors::Result;
 use mdbook::utils;
 use mdbook::MDBook;
@@ -10,25 +10,38 @@ 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<'help>() -> App<'help> {
+    App::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(
+            Arg::new("dest-dir")
+                .short('d')
+                .long("dest-dir")
+                .value_name("dest-dir")
+                .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`.",
+                ),
         )
-        .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(arg!([dir]
+            "Root directory for the book{n}\
+            (Defaults to the Current Directory when omitted)"
+        ))
+        .arg(arg!(-o --open "Opens the compiled book in a web browser"))
 }
 
 // Watch command implementation
 pub fn execute(args: &ArgMatches) -> Result<()> {
     let book_dir = get_book_dir(args);
-    let 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") {
+            book.config.build.build_dir = dest_dir.into();
+        }
+    };
+    update_config(&mut book);
 
     if args.is_present("open") {
         book.build()?;
@@ -37,7 +50,10 @@ pub fn execute(args: &ArgMatches) -> Result<()> {
 
     trigger_on_change(&book, |paths, book_dir| {
         info!("Files changed: {:?}\nBuilding book...\n", paths);
-        let result = MDBook::load(&book_dir).and_then(|b| b.build());
+        let result = MDBook::load(&book_dir).and_then(|mut b| {
+            update_config(&mut b);
+            b.build()
+        });
 
         if let Err(e) = result {
             error!("Unable to build the book");
@@ -48,7 +64,7 @@ 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![];
     }
@@ -71,7 +87,7 @@ 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"))

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.
 //!
 //!
@@ -44,12 +44,13 @@
 //! assert_eq!(got, Some(PathBuf::from("./themes")));
 //! # Ok(())
 //! # }
-//! # fn main() { run().unwrap() }
+//! # run().unwrap()
 //! ```
 
 #![deny(missing_docs)]
 
 use serde::{Deserialize, Deserializer, Serialize, Serializer};
+use std::collections::HashMap;
 use std::env;
 use std::fs::File;
 use std::io::Read;
@@ -57,12 +58,9 @@ use std::path::{Path, PathBuf};
 use std::str::FromStr;
 use toml::value::Table;
 use toml::{self, Value};
-use toml_query::delete::TomlValueDeleteExt;
-use toml_query::insert::TomlValueInsertExt;
-use toml_query::read::TomlValueReadExt;
 
 use crate::errors::*;
-use crate::utils;
+use crate::utils::{self, toml_ext::TomlExt};
 
 /// The overall configuration object for MDBook, essentially an in-memory
 /// representation of `book.toml`.
@@ -72,6 +70,8 @@ pub struct Config {
     pub book: BookConfig,
     /// Information about the build environment.
     pub build: BuildConfig,
+    /// Information about Rust language support.
+    pub rust: RustConfig,
     rest: Value,
 }
 
@@ -80,7 +80,7 @@ impl FromStr for Config {
 
     /// Load a `Config` from some string.
     fn from_str(src: &str) -> Result<Self> {
-        toml::from_str(src).chain_err(|| Error::from("Invalid configuration file"))
+        toml::from_str(src).with_context(|| "Invalid configuration file")
     }
 }
 
@@ -89,9 +89,9 @@ impl Config {
     pub fn from_disk<P: AsRef<Path>>(config_file: P) -> Result<Config> {
         let mut buffer = String::new();
         File::open(config_file)
-            .chain_err(|| "Unable to open the configuration file")?
+            .with_context(|| "Unable to open the configuration file")?
             .read_to_string(&mut buffer)
-            .chain_err(|| "Couldn't read the file")?;
+            .with_context(|| "Couldn't read the file")?;
 
         Config::from_str(&buffer)
     }
@@ -122,7 +122,7 @@ impl Config {
     /// > when building the book with something like
     /// >
     /// > ```text
-    /// > $ export MDBOOK_BOOK="{'title': 'My Awesome Book', authors: ['Michael-F-Bryan']}"
+    /// > $ export MDBOOK_BOOK='{"title": "My Awesome Book", "authors": ["Michael-F-Bryan"]}'
     /// > $ mdbook build
     /// > ```
     ///
@@ -140,6 +140,17 @@ impl Config {
             let parsed_value = serde_json::from_str(&value)
                 .unwrap_or_else(|_| serde_json::Value::String(value.to_string()));
 
+            if key == "book" || key == "build" {
+                if let serde_json::Value::Object(ref map) = parsed_value {
+                    // To `set` each `key`, we wrap them as `prefix.key`
+                    for (k, v) in map {
+                        let full_key = format!("{}.{}", key, k);
+                        self.set(&full_key, v).expect("unreachable");
+                    }
+                    return;
+                }
+            }
+
             self.set(key, parsed_value).expect("unreachable");
         }
     }
@@ -147,18 +158,15 @@ impl Config {
     /// Fetch an arbitrary item from the `Config` as a `toml::Value`.
     ///
     /// You can use dotted indices to access nested items (e.g.
-    /// `output.html.playpen` will fetch the "playpen" out of the html output
+    /// `output.html.playground` will fetch the "playground" out of the html output
     /// table).
     pub fn get(&self, key: &str) -> Option<&Value> {
-        self.rest.read(key).unwrap_or(None)
+        self.rest.read(key)
     }
 
     /// Fetch a value from the `Config` so you can mutate it.
     pub fn get_mut(&mut self, key: &str) -> Option<&mut Value> {
-        match self.rest.read_mut(key) {
-            Ok(inner) => inner,
-            Err(_) => None,
-        }
+        self.rest.read_mut(key)
     }
 
     /// Convenience method for getting the html renderer's configuration.
@@ -169,11 +177,14 @@ impl Config {
     /// HTML renderer is refactored to be less coupled to `mdbook` internals.
     #[doc(hidden)]
     pub fn html_config(&self) -> Option<HtmlConfig> {
-        match self.get_deserialized_opt("output.html") {
+        match self
+            .get_deserialized_opt("output.html")
+            .with_context(|| "Parsing configuration [output.html]")
+        {
             Ok(Some(config)) => Some(config),
             Ok(None) => None,
             Err(e) => {
-                utils::log_backtrace(&e.chain_err(|| "Parsing configuration [output.html]"));
+                utils::log_backtrace(&e);
                 None
             }
         }
@@ -201,7 +212,7 @@ impl Config {
                 value
                     .clone()
                     .try_into()
-                    .chain_err(|| "Couldn't deserialize the value")
+                    .with_context(|| "Couldn't deserialize the value")
             })
             .transpose()
     }
@@ -213,17 +224,15 @@ impl Config {
     pub fn set<S: Serialize, I: AsRef<str>>(&mut self, index: I, value: S) -> Result<()> {
         let index = index.as_ref();
 
-        let value =
-            Value::try_from(value).chain_err(|| "Unable to represent the item as a JSON Value")?;
+        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);
         } else {
-            self.rest
-                .insert(index, value)
-                .map_err(ErrorKind::TomlQueryError)?;
+            self.rest.insert(index, value);
         }
 
         Ok(())
@@ -264,7 +273,7 @@ impl Config {
         get_and_insert!(table, "source" => cfg.book.src);
         get_and_insert!(table, "description" => cfg.book.description);
 
-        if let Ok(Some(dest)) = table.delete("output.html.destination") {
+        if let Some(dest) = table.delete("output.html.destination") {
             if let Ok(destination) = dest.try_into() {
                 cfg.build.build_dir = destination;
             }
@@ -280,10 +289,12 @@ impl Default for Config {
         Config {
             book: BookConfig::default(),
             build: BuildConfig::default(),
+            rust: RustConfig::default(),
             rest: Value::Table(Table::default()),
         }
     }
 }
+
 impl<'de> Deserialize<'de> for Config {
     fn deserialize<D: Deserializer<'de>>(de: D) -> std::result::Result<Self, D::Error> {
         let raw = Value::deserialize(de)?;
@@ -300,10 +311,10 @@ impl<'de> Deserialize<'de> for Config {
             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",
                 ));
@@ -312,17 +323,26 @@ 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")
+            .map(|rust| rust.try_into().map_err(D::Error::custom))
+            .transpose()?
             .unwrap_or_default();
 
         Ok(Config {
             book,
             build,
+            rust,
             rest: Value::Table(table),
         })
     }
@@ -330,18 +350,22 @@ impl<'de> Deserialize<'de> for Config {
 
 impl Serialize for Config {
     fn serialize<S: Serializer>(&self, s: S) -> std::result::Result<S::Ok, S::Error> {
-        use serde::ser::Error;
-
+        // TODO: This should probably be removed and use a derive instead.
         let mut table = self.rest.clone();
 
-        let book_config = match Value::try_from(self.book.clone()) {
-            Ok(cfg) => cfg,
-            Err(_) => {
-                return Err(S::Error::custom("Unable to serialize the BookConfig"));
-            }
-        };
+        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);
+        }
 
-        table.insert("book", book_config).expect("unreachable");
         table.serialize(s)
     }
 }
@@ -368,7 +392,7 @@ fn is_legacy_format(table: &Value) -> bool {
     ];
 
     for item in &legacy_items {
-        if let Ok(Some(_)) = table.read(item) {
+        if table.read(item).is_some() {
             return true;
         }
     }
@@ -414,7 +438,7 @@ impl Default for BookConfig {
 pub struct BuildConfig {
     /// Where to put built artefacts relative to the book's root directory.
     pub build_dir: PathBuf,
-    /// Should non-existent markdown files specified in `SETTINGS.md` be created
+    /// Should non-existent markdown files specified in `SUMMARY.md` be created
     /// if they don't exist?
     pub create_missing: bool,
     /// Should the default preprocessors always be used when they are
@@ -432,8 +456,30 @@ impl Default for BuildConfig {
     }
 }
 
+/// Configuration for the Rust compiler(e.g., for playground)
+#[derive(Debug, Default, Clone, PartialEq, Serialize, Deserialize)]
+#[serde(default, rename_all = "kebab-case")]
+pub struct RustConfig {
+    /// Rust edition used in playground
+    pub edition: Option<RustEdition>,
+}
+
+#[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,
+    /// The 2015 edition of Rust
+    #[serde(rename = "2015")]
+    E2015,
+}
+
 /// Configuration for the HTML renderer.
-#[derive(Debug, Clone, Default, PartialEq, Serialize, Deserialize)]
+#[derive(Debug, Clone, PartialEq, Serialize, Deserialize)]
 #[serde(default, rename_all = "kebab-case")]
 pub struct HtmlConfig {
     /// The theme directory, if specified.
@@ -441,12 +487,14 @@ pub struct HtmlConfig {
     /// The default theme to use, defaults to 'light'
     pub default_theme: Option<String>,
     /// The theme to use if the browser requests the dark version of the site.
-    /// Defaults to the same as 'default_theme'
+    /// Defaults to 'navy'.
     pub preferred_dark_theme: Option<String>,
     /// Use "smart quotes" instead of the usual `"` character.
     pub curly_quotes: bool,
     /// Should mathjax be enabled?
     pub mathjax_support: bool,
+    /// Whether to fonts.css and respective font files to the output directory.
+    pub copy_fonts: bool,
     /// An optional google analytics code.
     pub google_analytics: Option<String>,
     /// Additional CSS stylesheets to include in the rendered page's `<head>`.
@@ -456,8 +504,11 @@ pub struct HtmlConfig {
     pub additional_js: Vec<PathBuf>,
     /// Fold settings.
     pub fold: Fold,
-    /// Playpen settings.
-    pub playpen: Playpen,
+    /// Playground settings.
+    #[serde(alias = "playpen")]
+    pub playground: Playground,
+    /// Print settings.
+    pub print: Print,
     /// Don't render section labels.
     pub no_section_label: bool,
     /// Search settings. If `None`, the default will be used.
@@ -467,20 +518,67 @@ pub struct HtmlConfig {
     /// FontAwesome icon class to use for the Git repository link.
     /// Defaults to `fa-github` if `None`.
     pub git_repository_icon: 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.
+    /// Input path for the 404 file, defaults to 404.md, set to "" to disable 404 file output
+    pub input_404: Option<String>,
+    /// Absolute url to site, used to emit correct paths for the 404 page, which might be accessed in a deeply nested directory
+    pub site_url: Option<String>,
+    /// 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
+    pub cname: Option<String>,
+    /// 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 the value [`LIVE_RELOAD_ENDPOINT`]
+    ///
+    /// [`LIVE_RELOAD_ENDPOINT`]: cmd::serve::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>,
+}
+
+impl Default for HtmlConfig {
+    fn default() -> HtmlConfig {
+        HtmlConfig {
+            theme: None,
+            default_theme: None,
+            preferred_dark_theme: None,
+            curly_quotes: false,
+            mathjax_support: false,
+            copy_fonts: true,
+            google_analytics: None,
+            additional_css: Vec::new(),
+            additional_js: Vec::new(),
+            fold: Fold::default(),
+            playground: Playground::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,
+            live_reload_endpoint: None,
+            redirect: HashMap::new(),
+        }
+    }
 }
 
 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"),
@@ -488,6 +586,25 @@ 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")]
+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,
+            page_break: true,
+        }
+    }
+}
+
 /// Configuration for how to fold chapters of sidebar.
 #[derive(Default, Debug, Clone, PartialEq, Serialize, Deserialize)]
 #[serde(default, rename_all = "kebab-case")]
@@ -500,28 +617,31 @@ pub struct Fold {
     pub level: u8,
 }
 
-/// Configuration for tweaking how the the HTML renderer handles the playpen.
+/// Configuration for tweaking how the the HTML renderer handles the playground.
 #[derive(Debug, Clone, PartialEq, Serialize, Deserialize)]
 #[serde(default, rename_all = "kebab-case")]
-pub struct Playpen {
-    /// Should playpen snippets be editable? Default: `false`.
+pub struct Playground {
+    /// Should playground snippets be editable? Default: `false`.
     pub editable: bool,
     /// Display the copy button. Default: `true`.
     pub copyable: bool,
     /// Copy JavaScript files for the editor to the output directory?
     /// Default: `true`.
     pub copy_js: bool,
-    /// Display line numbers on playpen snippets. Default: `false`.
+    /// Display line numbers on playground snippets. Default: `false`.
     pub line_numbers: bool,
+    /// Display the run button. Default: `true`
+    pub runnable: bool,
 }
 
-impl Default for Playpen {
-    fn default() -> Playpen {
-        Playpen {
+impl Default for Playground {
+    fn default() -> Playground {
+        Playground {
             editable: false,
             copyable: true,
             copy_js: true,
             line_numbers: false,
+            runnable: true,
         }
     }
 }
@@ -551,7 +671,7 @@ 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?
@@ -603,6 +723,7 @@ impl<'de, T> Updateable<'de> for T where T: Serialize + Deserialize<'de> {}
 #[cfg(test)]
 mod tests {
     use super::*;
+    use crate::utils::fs::get_404_output_file;
 
     const COMPLEX_CONFIG: &str = r#"
         [book]
@@ -627,10 +748,14 @@ mod tests {
         git-repository-url = "https://foo.com/"
         git-repository-icon = "fa-code-fork"
 
-        [output.html.playpen]
+        [output.html.playground]
         editable = true
         editor = "ace"
 
+        [output.html.redirect]
+        "index.html" = "overview.html"
+        "nexted/page.md" = "https://rust-lang.org/"
+
         [preprocessor.first]
 
         [preprocessor.second]
@@ -653,11 +778,13 @@ mod tests {
             create_missing: false,
             use_default_preprocessors: true,
         };
-        let playpen_should_be = Playpen {
+        let rust_should_be = RustConfig { edition: None };
+        let playground_should_be = Playground {
             editable: true,
             copyable: true,
             copy_js: true,
             line_numbers: false,
+            runnable: true,
         };
         let html_should_be = HtmlConfig {
             curly_quotes: true,
@@ -665,9 +792,18 @@ mod tests {
             additional_css: vec![PathBuf::from("./foo/bar/baz.css")],
             theme: Some(PathBuf::from("./themedir")),
             default_theme: Some(String::from("rust")),
-            playpen: playpen_should_be,
+            playground: playground_should_be,
             git_repository_url: Some(String::from("https://foo.com/")),
             git_repository_icon: Some(String::from("fa-code-fork")),
+            redirect: vec![
+                (String::from("index.html"), String::from("overview.html")),
+                (
+                    String::from("nexted/page.md"),
+                    String::from("https://rust-lang.org/"),
+                ),
+            ]
+            .into_iter()
+            .collect(),
             ..Default::default()
         };
 
@@ -675,9 +811,98 @@ mod tests {
 
         assert_eq!(got.book, book_should_be);
         assert_eq!(got.build, build_should_be);
+        assert_eq!(got.rust, rust_should_be);
         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_eq!(got.html_config().unwrap().playground.runnable, false);
+    }
+
+    #[test]
+    fn edition_2015() {
+        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 = "2015"
+        "#;
+
+        let book_should_be = BookConfig {
+            title: Some(String::from("mdBook Documentation")),
+            description: Some(String::from(
+                "Create book from markdown files. Like Gitbook but implemented in Rust",
+            )),
+            authors: vec![String::from("Mathieu David")],
+            src: PathBuf::from("./source"),
+            ..Default::default()
+        };
+
+        let got = Config::from_str(src).unwrap();
+        assert_eq!(got.book, book_should_be);
+
+        let rust_should_be = RustConfig {
+            edition: Some(RustEdition::E2015),
+        };
+        let got = Config::from_str(src).unwrap();
+        assert_eq!(got.rust, rust_should_be);
+    }
+
+    #[test]
+    fn edition_2018() {
+        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 = "2018"
+        "#;
+
+        let rust_should_be = RustConfig {
+            edition: Some(RustEdition::E2018),
+        };
+
+        let got = Config::from_str(src).unwrap();
+        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)]
@@ -720,7 +945,7 @@ mod tests {
         // is happy...
         let src = COMPLEX_CONFIG;
         let mut config = Config::from_str(src).unwrap();
-        let key = "output.html.playpen.editable";
+        let key = "output.html.playground.editable";
 
         assert_eq!(config.get(key).unwrap(), &Value::Boolean(true));
         *config.get_mut(key).unwrap() = Value::Boolean(false);
@@ -870,4 +1095,84 @@ mod tests {
 
         assert_eq!(cfg.book.title, Some(should_be));
     }
+
+    #[test]
+    fn file_404_default() {
+        let src = r#"
+        [output.html]
+        destination = "my-book"
+        "#;
+
+        let got = Config::from_str(src).unwrap();
+        let html_config = got.html_config().unwrap();
+        assert_eq!(html_config.input_404, None);
+        assert_eq!(&get_404_output_file(&html_config.input_404), "404.html");
+    }
+
+    #[test]
+    fn file_404_custom() {
+        let src = r#"
+        [output.html]
+        input-404= "missing.md"
+        output-404= "missing.html"
+        "#;
+
+        let got = Config::from_str(src).unwrap();
+        let html_config = got.html_config().unwrap();
+        assert_eq!(html_config.input_404, Some("missing.md".to_string()));
+        assert_eq!(&get_404_output_file(&html_config.input_404), "missing.html");
+    }
+
+    #[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();
+    }
 }

src/lib.rs

@@ -76,15 +76,14 @@
 //! 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 error_chain;
 #[macro_use]
 extern crate lazy_static;
 #[macro_use]
@@ -118,48 +117,6 @@ pub use crate::renderer::Renderer;
 
 /// The error types used through out this crate.
 pub mod errors {
-    use std::path::PathBuf;
-
-    error_chain! {
-        foreign_links {
-            Io(std::io::Error) #[doc = "A wrapper around `std::io::Error`"];
-            HandlebarsRender(handlebars::RenderError) #[doc = "Handlebars rendering failed"];
-            HandlebarsTemplate(Box<handlebars::TemplateError>) #[doc = "Unable to parse the template"];
-            Utf8(std::string::FromUtf8Error) #[doc = "Invalid UTF-8"];
-            SerdeJson(serde_json::Error) #[doc = "JSON conversion failed"];
-        }
-
-        errors {
-            /// A subprocess exited with an unsuccessful return code.
-            Subprocess(message: String, output: std::process::Output) {
-                description("A subprocess failed")
-                display("{}: {}", message, String::from_utf8_lossy(&output.stdout))
-            }
-
-            /// An error was encountered while parsing the `SUMMARY.md` file.
-            ParseError(line: usize, col: usize, message: String) {
-                description("A SUMMARY.md parsing error")
-                display("Error at line {}, column {}: {}", line, col, message)
-            }
-
-            /// The user tried to use a reserved filename.
-            ReservedFilenameError(filename: PathBuf) {
-                description("Reserved Filename")
-                display("{} is reserved for internal use", filename.display())
-            }
-
-            /// Error with a TOML file.
-            TomlQueryError(inner: toml_query::error::Error) {
-                description("toml_query error")
-                display("{}", inner)
-            }
-        }
-    }
-
-    // Box to halve the size of Error
-    impl From<handlebars::TemplateError> for Error {
-        fn from(e: handlebars::TemplateError) -> Error {
-            From::from(Box::new(e))
-        }
-    }
+    pub(crate) use anyhow::{bail, ensure, Context};
+    pub use anyhow::{Error, Result};
 }

src/main.rs

@@ -3,8 +3,10 @@ extern crate clap;
 #[macro_use]
 extern crate log;
 
+use anyhow::anyhow;
 use chrono::Local;
-use clap::{App, AppSettings, ArgMatches};
+use clap::{App, AppSettings, Arg, ArgMatches};
+use clap_complete::Shell;
 use env_logger::Builder;
 use log::LevelFilter;
 use mdbook::utils;
@@ -20,39 +22,35 @@ 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());
-
-    #[cfg(feature = "watch")]
-    let app = app.subcommand(cmd::watch::make_subcommand());
-    #[cfg(feature = "serve")]
-    let app = app.subcommand(cmd::serve::make_subcommand());
+    let app = create_clap_app();
 
     // 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),
+        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: Shell = sub_matches
+                .value_of("shell")
+                .ok_or_else(|| anyhow!("Shell name missing."))?
+                .parse()
+                .map_err(|s| anyhow!("Invalid shell: {}", s))?;
+
+            let mut complete_app = create_clap_app();
+            clap_complete::generate(
+                shell,
+                &mut complete_app,
+                "mdbook",
+                &mut std::io::stdout().lock(),
+            );
+            Ok(())
+        })(),
+        _ => unreachable!(),
     };
 
     if let Err(e) = res {
@@ -62,6 +60,43 @@ fn main() {
     }
 }
 
+/// Create a list of valid arguments and sub-commands
+fn create_clap_app() -> App<'static> {
+    let app = App::new(crate_name!())
+        .about(crate_description!())
+        .author("Mathieu David <mathieudavid@mathieudavid.org>")
+        .version(VERSION)
+        .setting(AppSettings::PropagateVersion)
+        .setting(AppSettings::ArgRequiredElseHelp)
+        .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(
+            App::new("completions")
+                .about("Generate shell completions for your shell to stdout")
+                .arg(
+                    Arg::new("shell")
+                        .takes_value(true)
+                        .possible_values(Shell::possible_values())
+                        .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();
 
@@ -103,7 +138,13 @@ 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_app().debug_assert();
+}

src/preprocess/cmd.rs

@@ -43,13 +43,13 @@ impl CmdPreprocessor {
     /// A convenience function custom preprocessors can use to parse the input
     /// written to `stdin` by a `CmdRenderer`.
     pub fn parse_input<R: Read>(reader: R) -> Result<(PreprocessorContext, Book)> {
-        serde_json::from_reader(reader).chain_err(|| "Unable to parse the input")
+        serde_json::from_reader(reader).with_context(|| "Unable to parse the input")
     }
 
     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);
@@ -100,7 +100,7 @@ impl Preprocessor for CmdPreprocessor {
             .stdout(Stdio::piped())
             .stderr(Stdio::inherit())
             .spawn()
-            .chain_err(|| {
+            .with_context(|| {
                 format!(
                     "Unable to start the \"{}\" preprocessor. Is it installed?",
                     self.name()
@@ -109,17 +109,28 @@ impl Preprocessor for CmdPreprocessor {
 
         self.write_input_to_child(&mut child, &book, ctx);
 
-        let output = child
-            .wait_with_output()
-            .chain_err(|| "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).chain_err(|| "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 {
@@ -170,15 +181,15 @@ mod tests {
     use crate::MDBook;
     use std::path::Path;
 
-    fn book_example() -> MDBook {
-        let example = Path::new(env!("CARGO_MANIFEST_DIR")).join("book-example");
+    fn guide() -> MDBook {
+        let example = Path::new(env!("CARGO_MANIFEST_DIR")).join("guide");
         MDBook::load(example).unwrap()
     }
 
     #[test]
     fn round_trip_write_and_parse_input() {
         let cmd = CmdPreprocessor::new("test".to_string(), "test".to_string());
-        let md = book_example();
+        let md = guide();
         let ctx = PreprocessorContext::new(
             md.root.clone(),
             md.config.clone(),

src/preprocess/index.rs

@@ -29,13 +29,15 @@ impl Preprocessor for IndexPreprocessor {
         let source_dir = ctx.root.join(&ctx.config.book.src);
         book.for_each_mut(|section: &mut BookItem| {
             if let BookItem::Chapter(ref mut ch) = *section {
-                if is_readme_file(&ch.path) {
-                    let index_md = source_dir.join(ch.path.with_file_name("index.md"));
-                    if index_md.exists() {
-                        warn_readme_name_conflict(&ch.path, &index_md);
-                    }
+                if let Some(ref mut path) = ch.path {
+                    if is_readme_file(&path) {
+                        let mut index_md = source_dir.join(path.with_file_name("index.md"));
+                        if index_md.exists() {
+                            warn_readme_name_conflict(&path, &&mut index_md);
+                        }
 
-                    ch.path.set_file_name("index.md");
+                        path.set_file_name("index.md");
+                    }
                 }
             }
         });

src/preprocess/links.rs

@@ -22,7 +22,8 @@ const MAX_LINK_NESTED_DEPTH: usize = 10;
 ///.  specified or the lines between specified anchors, and include the rest of the file behind `#`.
 ///   This hides the lines from initial display but shows them when the reader expands the code
 ///   block and provides them to Rustdoc for testing.
-/// - `{{# playpen}}` - Insert runnable Rust files
+/// - `{{# playground}}` - Insert runnable Rust files
+/// - `{{# title}}` - Override \<title\> of a webpage.
 #[derive(Default)]
 pub struct LinkPreprocessor;
 
@@ -45,14 +46,22 @@ impl Preprocessor for LinkPreprocessor {
 
         book.for_each_mut(|section: &mut BookItem| {
             if let BookItem::Chapter(ref mut ch) = *section {
-                let base = ch
-                    .path
-                    .parent()
-                    .map(|dir| src_dir.join(dir))
-                    .expect("All book items have a parent");
+                if let Some(ref chapter_path) = ch.path {
+                    let base = chapter_path
+                        .parent()
+                        .map(|dir| src_dir.join(dir))
+                        .expect("All book items have a parent");
 
-                let content = replace_all(&ch.content, base, &ch.path, 0);
-                ch.content = content;
+                    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);
+                    }
+                }
             }
         });
 
@@ -60,7 +69,13 @@ 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>,
@@ -76,11 +91,17 @@ 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);
                     }
@@ -94,7 +115,7 @@ where
             }
             Err(e) => {
                 error!("Error updating \"{}\", {}", link.link_text, e);
-                for cause in e.iter().skip(1) {
+                for cause in e.chain().skip(1) {
                     warn!("Caused By: {}", cause);
                 }
 
@@ -113,8 +134,9 @@ where
 enum LinkType<'a> {
     Escaped,
     Include(PathBuf, RangeOrAnchor),
-    Playpen(PathBuf, Vec<&'a str>),
+    Playground(PathBuf, Vec<&'a str>),
     RustdocInclude(PathBuf, RangeOrAnchor),
+    Title(&'a str),
 }
 
 #[derive(PartialEq, Debug, Clone)]
@@ -182,8 +204,9 @@ impl<'a> LinkType<'a> {
         match self {
             LinkType::Escaped => None,
             LinkType::Include(p, _) => Some(return_relative_path(base, &p)),
-            LinkType::Playpen(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,
         }
     }
 }
@@ -254,6 +277,9 @@ 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();
@@ -261,7 +287,15 @@ impl<'a> Link<'a> {
 
                 match (typ.as_str(), file_arg) {
                     ("include", Some(pth)) => Some(parse_include_path(pth)),
-                    ("playpen", Some(pth)) => Some(LinkType::Playpen(pth.into(), props)),
+                    ("playground", Some(pth)) => Some(LinkType::Playground(pth.into(), props)),
+                    ("playpen", Some(pth)) => {
+                        warn!(
+                            "the {{{{#playpen}}}} expression has been \
+                            renamed to {{{{#playground}}}}, \
+                            please update your book to use the new name"
+                        );
+                        Some(LinkType::Playground(pth.into(), props))
+                    }
                     ("rustdoc_include", Some(pth)) => Some(parse_rustdoc_include_path(pth)),
                     _ => None,
                 }
@@ -282,7 +316,11 @@ 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
@@ -295,7 +333,7 @@ impl<'a> Link<'a> {
                         RangeOrAnchor::Range(range) => take_lines(&s, range.clone()),
                         RangeOrAnchor::Anchor(anchor) => take_anchored_lines(&s, anchor),
                     })
-                    .chain_err(|| {
+                    .with_context(|| {
                         format!(
                             "Could not read file for link {} ({})",
                             self.link_text,
@@ -315,7 +353,7 @@ impl<'a> Link<'a> {
                             take_rustdoc_include_anchored_lines(&s, anchor)
                         }
                     })
-                    .chain_err(|| {
+                    .with_context(|| {
                         format!(
                             "Could not read file for link {} ({})",
                             self.link_text,
@@ -323,10 +361,10 @@ impl<'a> Link<'a> {
                         )
                     })
             }
-            LinkType::Playpen(ref pat, ref attrs) => {
+            LinkType::Playground(ref pat, ref attrs) => {
                 let target = base.join(pat);
 
-                let contents = fs::read_to_string(&target).chain_err(|| {
+                let mut contents = fs::read_to_string(&target).with_context(|| {
                     format!(
                         "Could not read file for link {} ({})",
                         self.link_text,
@@ -334,13 +372,20 @@ 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())
+            }
         }
     }
 }
@@ -361,17 +406,17 @@ 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]+)\}\}")?;
+    // r"\\\{\{#.*\}\}|\{\{#([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"(?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();
     }
@@ -394,7 +439,21 @@ 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]
@@ -405,7 +464,7 @@ mod tests {
 
     #[test]
     fn test_find_links_partial_link() {
-        let s = "Some random text with {{#playpen...";
+        let s = "Some random text with {{#playground...";
         assert!(find_links(s).collect::<Vec<_>>() == vec![]);
         let s = "Some random text with {{#include...";
         assert!(find_links(s).collect::<Vec<_>>() == vec![]);
@@ -415,19 +474,19 @@ mod tests {
 
     #[test]
     fn test_find_links_empty_link() {
-        let s = "Some random text with {{#playpen}} and {{#playpen   }} {{}} {{#}}...";
+        let s = "Some random text with {{#playground}} and {{#playground   }} {{}} {{#}}...";
         assert!(find_links(s).collect::<Vec<_>>() == vec![]);
     }
 
     #[test]
     fn test_find_links_unknown_link_type() {
-        let s = "Some random text with {{#playpenz ar.rs}} and {{#incn}} {{baz}} {{#bar}}...";
+        let s = "Some random text with {{#playgroundz ar.rs}} and {{#incn}} {{baz}} {{#bar}}...";
         assert!(find_links(s).collect::<Vec<_>>() == vec![]);
     }
 
     #[test]
     fn test_find_links_simple_link() {
-        let s = "Some random text with {{#playpen file.rs}} and {{#playpen test.rs }}...";
+        let s = "Some random text with {{#playground file.rs}} and {{#playground test.rs }}...";
 
         let res = find_links(s).collect::<Vec<_>>();
         println!("\nOUTPUT: {:?}\n", res);
@@ -437,20 +496,38 @@ mod tests {
             vec![
                 Link {
                     start_index: 22,
-                    end_index: 42,
-                    link_type: LinkType::Playpen(PathBuf::from("file.rs"), vec![]),
-                    link_text: "{{#playpen file.rs}}",
+                    end_index: 45,
+                    link_type: LinkType::Playground(PathBuf::from("file.rs"), vec![]),
+                    link_text: "{{#playground file.rs}}",
                 },
                 Link {
-                    start_index: 47,
-                    end_index: 68,
-                    link_type: LinkType::Playpen(PathBuf::from("test.rs"), vec![]),
-                    link_text: "{{#playpen test.rs }}",
+                    start_index: 50,
+                    end_index: 74,
+                    link_type: LinkType::Playground(PathBuf::from("test.rs"), vec![]),
+                    link_text: "{{#playground test.rs }}",
                 },
             ]
         );
     }
 
+    #[test]
+    fn test_find_links_with_special_characters() {
+        let s = "Some random text with {{#playground foo-bar\\baz/_c++.rs}}...";
+
+        let res = find_links(s).collect::<Vec<_>>();
+        println!("\nOUTPUT: {:?}\n", res);
+
+        assert_eq!(
+            res,
+            vec![Link {
+                start_index: 22,
+                end_index: 57,
+                link_type: LinkType::Playground(PathBuf::from("foo-bar\\baz/_c++.rs"), vec![]),
+                link_text: "{{#playground foo-bar\\baz/_c++.rs}}",
+            },]
+        );
+    }
+
     #[test]
     fn test_find_links_with_range() {
         let s = "Some random text with {{#include file.rs:10:20}}...";
@@ -586,7 +663,7 @@ mod tests {
 
     #[test]
     fn test_find_links_escaped_link() {
-        let s = "Some random text with escaped playpen \\{{#playpen file.rs editable}} ...";
+        let s = "Some random text with escaped playground \\{{#playground file.rs editable}} ...";
 
         let res = find_links(s).collect::<Vec<_>>();
         println!("\nOUTPUT: {:?}\n", res);
@@ -594,18 +671,19 @@ mod tests {
         assert_eq!(
             res,
             vec![Link {
-                start_index: 38,
-                end_index: 68,
+                start_index: 41,
+                end_index: 74,
                 link_type: LinkType::Escaped,
-                link_text: "\\{{#playpen file.rs editable}}",
+                link_text: "\\{{#playground file.rs editable}}",
             }]
         );
     }
 
     #[test]
-    fn test_find_playpens_with_properties() {
-        let s = "Some random text with escaped playpen {{#playpen file.rs editable }} and some \
-                 more\n text {{#playpen my.rs editable no_run should_panic}} ...";
+    fn test_find_playgrounds_with_properties() {
+        let s =
+            "Some random text with escaped playground {{#playground file.rs editable }} and some \
+                 more\n text {{#playground my.rs editable no_run should_panic}} ...";
 
         let res = find_links(s).collect::<Vec<_>>();
         println!("\nOUTPUT: {:?}\n", res);
@@ -613,19 +691,19 @@ mod tests {
             res,
             vec![
                 Link {
-                    start_index: 38,
-                    end_index: 68,
-                    link_type: LinkType::Playpen(PathBuf::from("file.rs"), vec!["editable"]),
-                    link_text: "{{#playpen file.rs editable }}",
+                    start_index: 41,
+                    end_index: 74,
+                    link_type: LinkType::Playground(PathBuf::from("file.rs"), vec!["editable"]),
+                    link_text: "{{#playground file.rs editable }}",
                 },
                 Link {
-                    start_index: 89,
-                    end_index: 136,
-                    link_type: LinkType::Playpen(
+                    start_index: 95,
+                    end_index: 145,
+                    link_type: LinkType::Playground(
                         PathBuf::from("my.rs"),
                         vec!["editable", "no_run", "should_panic"],
                     ),
-                    link_text: "{{#playpen my.rs editable no_run should_panic}}",
+                    link_text: "{{#playground my.rs editable no_run should_panic}}",
                 },
             ]
         );
@@ -633,8 +711,9 @@ mod tests {
 
     #[test]
     fn test_find_all_link_types() {
-        let s = "Some random text with escaped playpen {{#include file.rs}} and \\{{#contents are \
-                 insignifficant in escaped link}} some more\n text  {{#playpen my.rs editable \
+        let s =
+            "Some random text with escaped playground {{#include file.rs}} and \\{{#contents are \
+                 insignifficant in escaped link}} some more\n text  {{#playground my.rs editable \
                  no_run should_panic}} ...";
 
         let res = find_links(s).collect::<Vec<_>>();
@@ -643,8 +722,8 @@ mod tests {
         assert_eq!(
             res[0],
             Link {
-                start_index: 38,
-                end_index: 58,
+                start_index: 41,
+                end_index: 61,
                 link_type: LinkType::Include(
                     PathBuf::from("file.rs"),
                     RangeOrAnchor::Range(LineRange::from(..))
@@ -655,8 +734,8 @@ mod tests {
         assert_eq!(
             res[1],
             Link {
-                start_index: 63,
-                end_index: 112,
+                start_index: 66,
+                end_index: 115,
                 link_type: LinkType::Escaped,
                 link_text: "\\{{#contents are insignifficant in escaped link}}",
             }
@@ -664,13 +743,13 @@ mod tests {
         assert_eq!(
             res[2],
             Link {
-                start_index: 130,
-                end_index: 177,
-                link_type: LinkType::Playpen(
+                start_index: 133,
+                end_index: 183,
+                link_type: LinkType::Playground(
                     PathBuf::from("my.rs"),
                     vec!["editable", "no_run", "should_panic"]
                 ),
-                link_text: "{{#playpen my.rs editable no_run should_panic}}",
+                link_text: "{{#playground my.rs editable no_run should_panic}}",
             }
         );
     }

src/preprocess/mod.rs

@@ -12,6 +12,8 @@ use crate::book::Book;
 use crate::config::Config;
 use crate::errors::*;
 
+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 +29,8 @@ 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 +42,7 @@ 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

@@ -1,17 +1,18 @@
 use crate::book::{Book, BookItem};
-use crate::config::{Config, HtmlConfig, Playpen};
+use crate::config::{BookConfig, Config, HtmlConfig, Playground, RustEdition};
 use crate::errors::*;
 use crate::renderer::html_handlebars::helpers;
 use crate::renderer::{RenderContext, Renderer};
-use crate::theme::{self, playpen_editor, Theme};
+use crate::theme::{self, playground_editor, Theme};
 use crate::utils;
 
 use std::borrow::Cow;
 use std::collections::BTreeMap;
 use std::collections::HashMap;
-use std::fs;
+use std::fs::{self, File};
 use std::path::{Path, PathBuf};
 
+use crate::utils::fs::get_404_output_file;
 use handlebars::Handlebars;
 use regex::{Captures, Regex};
 
@@ -30,82 +31,172 @@ impl HtmlHandlebars {
         print_content: &mut String,
     ) -> Result<()> {
         // FIXME: This should be made DRY-er and rely less on mutable state
-        if let BookItem::Chapter(ref ch) = *item {
-            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(&ch.path),
-            );
-            print_content.push_str(&fixed_content);
+        let (ch, path) = match item {
+            BookItem::Chapter(ch) if !ch.is_draft_chapter() => (ch, ch.path.as_ref().unwrap()),
+            _ => return Ok(()),
+        };
 
-            // Update the context with data for this file
-            let path = ch
-                .path
-                .to_str()
-                .chain_err(|| "Could not convert path to str")?;
-            let filepath = Path::new(&ch.path).with_extension("html");
+        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();
 
-            // "print.html" is used for the print page.
-            if ch.path == Path::new("print.md") {
-                bail!(ErrorKind::ReservedFilenameError(ch.path.clone()));
-            };
+            let edit_url = edit_url_template.replace("{path}", &full_path);
+            ctx.data
+                .insert("git_repository_edit_url".to_owned(), json!(edit_url));
+        }
 
-            // Non-lexical lifetimes needed :'(
-            let title: String;
-            {
-                let book_title = ctx
-                    .data
-                    .get("book_title")
-                    .and_then(serde_json::Value::as_str)
-                    .unwrap_or("");
-                title = ch.name.clone() + " - " + book_title;
-            }
+        let content = ch.content.clone();
+        let content = utils::render_markdown(&content, ctx.html_config.curly_quotes);
 
-            ctx.data.insert("path".to_owned(), json!(path));
-            ctx.data.insert("content".to_owned(), json!(content));
-            ctx.data.insert("chapter_title".to_owned(), json!(ch.name));
-            ctx.data.insert("title".to_owned(), json!(title));
-            ctx.data.insert(
-                "path_to_root".to_owned(),
-                json!(utils::fs::path_to_root(&ch.path)),
-            );
-            if let Some(ref section) = ch.number {
-                ctx.data
-                    .insert("section".to_owned(), json!(section.to_string()));
-            }
+        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);
 
-            // Render the handlebars template with the data
-            debug!("Render template");
-            let rendered = ctx.handlebars.render("index", &ctx.data)?;
+        // Update the context with data for this file
+        let ctx_path = path
+            .to_str()
+            .with_context(|| "Could not convert path to str")?;
+        let filepath = Path::new(&ctx_path).with_extension("html");
 
-            let rendered = self.post_process(rendered, &ctx.html_config.playpen);
+        // "print.html" is used for the print page.
+        if path == Path::new("print.md") {
+            bail!("{} is reserved for internal use", path.display());
+        };
 
-            // Write to file
-            debug!("Creating {}", filepath.display());
-            utils::fs::write_file(&ctx.destination, &filepath, rendered.as_bytes())?;
+        let book_title = ctx
+            .data
+            .get("book_title")
+            .and_then(serde_json::Value::as_str)
+            .unwrap_or("");
 
-            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"));
-                let rendered_index = ctx.handlebars.render("index", &ctx.data)?;
-                let rendered_index = self.post_process(rendered_index, &ctx.html_config.playpen);
-                debug!("Creating index.html from {}", path);
-                utils::fs::write_file(&ctx.destination, "index.html", rendered_index.as_bytes())?;
-            }
+        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));
+        ctx.data.insert("content".to_owned(), json!(content));
+        ctx.data.insert("chapter_title".to_owned(), json!(ch.name));
+        ctx.data.insert("title".to_owned(), json!(title));
+        ctx.data.insert(
+            "path_to_root".to_owned(),
+            json!(utils::fs::path_to_root(&path)),
+        );
+        if let Some(ref section) = ch.number {
+            ctx.data
+                .insert("section".to_owned(), json!(section.to_string()));
+        }
+
+        // Render the handlebars template with the data
+        debug!("Render template");
+        let rendered = ctx.handlebars.render("index", &ctx.data)?;
+
+        let rendered = self.post_process(rendered, &ctx.html_config.playground, ctx.edition);
+
+        // Write to file
+        debug!("Creating {}", filepath.display());
+        utils::fs::write_file(&ctx.destination, &filepath, rendered.as_bytes())?;
+
+        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"));
+            let rendered_index = ctx.handlebars.render("index", &ctx.data)?;
+            let rendered_index =
+                self.post_process(rendered_index, &ctx.html_config.playground, ctx.edition);
+            debug!("Creating index.html from {}", ctx_path);
+            utils::fs::write_file(&ctx.destination, "index.html", rendered_index.as_bytes())?;
         }
 
         Ok(())
     }
 
+    fn render_404(
+        &self,
+        ctx: &RenderContext,
+        html_config: &HtmlConfig,
+        src_dir: &Path,
+        handlebars: &mut Handlebars<'_>,
+        data: &mut serde_json::Map<String, serde_json::Value>,
+    ) -> Result<()> {
+        let destination = &ctx.destination;
+        let content_404 = if let Some(ref filename) = html_config.input_404 {
+            let path = src_dir.join(filename);
+            std::fs::read_to_string(&path)
+                .with_context(|| format!("unable to open 404 input file {:?}", path))?
+        } else {
+            // 404 input not explicitly configured try the default file 404.md
+            let default_404_location = src_dir.join("404.md");
+            if default_404_location.exists() {
+                std::fs::read_to_string(&default_404_location).with_context(|| {
+                    format!("unable to open 404 input file {:?}", default_404_location)
+                })?
+            } else {
+                "# Document not found (404)\n\nThis URL is invalid, sorry. Please use the \
+                navigation bar or search to continue."
+                    .to_string()
+            }
+        };
+        let html_content_404 = utils::render_markdown(&content_404, html_config.curly_quotes);
+
+        let mut data_404 = data.clone();
+        let base_url = if let Some(site_url) = &html_config.site_url {
+            site_url
+        } else {
+            debug!(
+                "HTML 'site-url' parameter not set, defaulting to '/'. Please configure \
+                this to ensure the 404 page work correctly, especially if your site is hosted in a \
+                subdirectory on the HTTP server."
+            );
+            "/"
+        };
+        data_404.insert("base_url".to_owned(), json!(base_url));
+        // 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 output_file = get_404_output_file(&html_config.input_404);
+        utils::fs::write_file(destination, output_file, rendered.as_bytes())?;
+        debug!("Creating 404.html ✓");
+        Ok(())
+    }
+
     #[cfg_attr(feature = "cargo-clippy", allow(clippy::let_and_return))]
-    fn post_process(&self, rendered: String, playpen_config: &Playpen) -> String {
+    fn post_process(
+        &self,
+        rendered: String,
+        playground_config: &Playground,
+        edition: Option<RustEdition>,
+    ) -> String {
         let rendered = build_header_links(&rendered);
         let rendered = fix_code_blocks(&rendered);
-        let rendered = add_playpen_pre(&rendered, playpen_config);
+        let rendered = add_playground_pre(&rendered, playground_config, edition);
 
         rendered
     }
@@ -121,15 +212,26 @@ impl HtmlHandlebars {
         write_file(
             destination,
             ".nojekyll",
-            b"This file makes sure that Github Pages doesn't process mdBook's output.",
+            b"This file makes sure that Github Pages doesn't process mdBook's output.\n",
         )?;
 
+        if let Some(cname) = &html_config.cname {
+            write_file(destination, "CNAME", format!("{}\n", cname).as_bytes())?;
+        }
+
         write_file(destination, "book.js", &theme.js)?;
         write_file(destination, "css/general.css", &theme.general_css)?;
         write_file(destination, "css/chrome.css", &theme.chrome_css)?;
-        write_file(destination, "css/print.css", &theme.print_css)?;
+        if html_config.print.enable {
+            write_file(destination, "css/print.css", &theme.print_css)?;
+        }
         write_file(destination, "css/variables.css", &theme.variables_css)?;
-        write_file(destination, "favicon.png", &theme.favicon)?;
+        if let Some(contents) = &theme.favicon_png {
+            write_file(destination, "favicon.png", contents)?;
+        }
+        if let Some(contents) = &theme.favicon_svg {
+            write_file(destination, "favicon.svg", contents)?;
+        }
         write_file(destination, "highlight.css", &theme.highlight_css)?;
         write_file(destination, "tomorrow-night.css", &theme.tomorrow_night_css)?;
         write_file(destination, "ayu-highlight.css", &theme.ayu_highlight_css)?;
@@ -170,20 +272,38 @@ impl HtmlHandlebars {
             "FontAwesome/fonts/FontAwesome.ttf",
             theme::FONT_AWESOME_TTF,
         )?;
+        if html_config.copy_fonts {
+            write_file(destination, "fonts/fonts.css", theme::fonts::CSS)?;
+            for (file_name, contents) in theme::fonts::LICENSES.iter() {
+                write_file(destination, file_name, contents)?;
+            }
+            for (file_name, contents) in theme::fonts::OPEN_SANS.iter() {
+                write_file(destination, file_name, contents)?;
+            }
+            write_file(
+                destination,
+                theme::fonts::SOURCE_CODE_PRO.0,
+                theme::fonts::SOURCE_CODE_PRO.1,
+            )?;
+        }
 
-        let playpen_config = &html_config.playpen;
+        let playground_config = &html_config.playground;
 
         // Ace is a very large dependency, so only load it when requested
-        if playpen_config.editable && playpen_config.copy_js {
+        if playground_config.editable && playground_config.copy_js {
             // Load the editor
-            write_file(destination, "editor.js", playpen_editor::JS)?;
-            write_file(destination, "ace.js", playpen_editor::ACE_JS)?;
-            write_file(destination, "mode-rust.js", playpen_editor::MODE_RUST_JS)?;
-            write_file(destination, "theme-dawn.js", playpen_editor::THEME_DAWN_JS)?;
+            write_file(destination, "editor.js", playground_editor::JS)?;
+            write_file(destination, "ace.js", playground_editor::ACE_JS)?;
+            write_file(destination, "mode-rust.js", playground_editor::MODE_RUST_JS)?;
+            write_file(
+                destination,
+                "theme-dawn.js",
+                playground_editor::THEME_DAWN_JS,
+            )?;
             write_file(
                 destination,
                 "theme-tomorrow_night.js",
-                playpen_editor::THEME_TOMORROW_NIGHT_JS,
+                playground_editor::THEME_TOMORROW_NIGHT_JS,
             )?;
         }
 
@@ -208,7 +328,7 @@ impl HtmlHandlebars {
         );
     }
 
-    fn register_hbs_helpers(&self, handlebars: &mut Handlebars, html_config: &HtmlConfig) {
+    fn register_hbs_helpers(&self, handlebars: &mut Handlebars<'_>, html_config: &HtmlConfig) {
         handlebars.register_helper(
             "toc",
             Box::new(helpers::toc::RenderToc {
@@ -237,7 +357,7 @@ impl HtmlHandlebars {
             let output_location = destination.join(custom_file);
             if let Some(parent) = output_location.parent() {
                 fs::create_dir_all(parent)
-                    .chain_err(|| format!("Unable to create {}", parent.display()))?;
+                    .with_context(|| format!("Unable to create {}", parent.display()))?;
             }
             debug!(
                 "Copying {} -> {}",
@@ -245,7 +365,7 @@ impl HtmlHandlebars {
                 output_location.display()
             );
 
-            fs::copy(&input_location, &output_location).chain_err(|| {
+            fs::copy(&input_location, &output_location).with_context(|| {
                 format!(
                     "Unable to copy {} to {}",
                     input_location.display(),
@@ -256,6 +376,68 @@ impl HtmlHandlebars {
 
         Ok(())
     }
+
+    fn emit_redirects(
+        &self,
+        root: &Path,
+        handlebars: &Handlebars<'_>,
+        redirects: &HashMap<String, String>,
+    ) -> Result<()> {
+        if redirects.is_empty() {
+            return Ok(());
+        }
+
+        log::debug!("Emitting redirects");
+
+        for (original, new) in redirects {
+            log::debug!("Redirecting \"{}\" → \"{}\"", original, new);
+            // 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 filename = root.join(original);
+            self.emit_redirect(handlebars, &filename, new)?;
+        }
+
+        Ok(())
+    }
+
+    fn emit_redirect(
+        &self,
+        handlebars: &Handlebars<'_>,
+        original: &Path,
+        destination: &str,
+    ) -> Result<()> {
+        if original.exists() {
+            // sanity check to avoid accidentally overwriting a real file.
+            let msg = format!(
+                "Not redirecting \"{}\" to \"{}\" because it already exists. Are you sure it needs to be redirected?",
+                original.display(),
+                destination,
+            );
+            return Err(Error::msg(msg));
+        }
+
+        if let Some(parent) = original.parent() {
+            std::fs::create_dir_all(parent)
+                .with_context(|| format!("Unable to ensure \"{}\" exists", parent.display()))?;
+        }
+
+        let ctx = json!({
+            "url": destination,
+        });
+        let f = File::create(original)?;
+        handlebars
+            .render_to_write("redirect", &ctx, f)
+            .with_context(|| {
+                format!(
+                    "Unable to create a redirect file at \"{}\"",
+                    original.display()
+                )
+            })?;
+
+        Ok(())
+    }
 }
 
 // TODO(mattico): Remove some time after the 0.1.8 release
@@ -283,21 +465,23 @@ 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;
         let book = &ctx.book;
+        let build_dir = ctx.root.join(&ctx.config.build.build_dir);
 
         if destination.exists() {
             utils::fs::remove_dir_content(destination)
-                .chain_err(|| "Unable to remove stale HTML output")?;
+                .with_context(|| "Unable to remove stale HTML output")?;
         }
 
         trace!("render");
         let mut handlebars = Handlebars::new();
 
         let theme_dir = match html_config.theme {
-            Some(ref theme) => theme.to_path_buf(),
+            Some(ref theme) => ctx.root.join(theme),
             None => ctx.root.join("theme"),
         };
 
@@ -316,19 +500,26 @@ impl Renderer for HtmlHandlebars {
         debug!("Register the index handlebars template");
         handlebars.register_template_string("index", String::from_utf8(theme.index.clone())?)?;
 
+        debug!("Register the head handlebars template");
+        handlebars.register_partial("head", String::from_utf8(theme.head.clone())?)?;
+
+        debug!("Register the redirect handlebars template");
+        handlebars
+            .register_template_string("redirect", String::from_utf8(theme.redirect.clone())?)?;
+
         debug!("Register the header handlebars template");
         handlebars.register_partial("header", String::from_utf8(theme.header.clone())?)?;
 
         debug!("Register handlebars helpers");
         self.register_hbs_helpers(&mut handlebars, &html_config);
 
-        let mut data = make_data(&ctx.root, &book, &ctx.config, &html_config)?;
+        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)
-            .chain_err(|| "Unexpected error when constructing destination path")?;
+            .with_context(|| "Unexpected error when constructing destination path")?;
 
         let mut is_index = true;
         for item in book.iter() {
@@ -337,12 +528,20 @@ 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;
         }
 
+        // Render 404 page
+        if html_config.input_404 != Some("".to_string()) {
+            self.render_404(ctx, &html_config, &src_dir, &mut handlebars, &mut data)?;
+        }
+
         // Print version
         self.configure_print_version(&mut data, &print_content);
         if let Some(ref title) = ctx.config.book.title {
@@ -350,31 +549,37 @@ impl Renderer for HtmlHandlebars {
         }
 
         // Render the handlebars template with the data
-        debug!("Render template");
-        let rendered = handlebars.render("index", &data)?;
+        if html_config.print.enable {
+            debug!("Render template");
+            let rendered = handlebars.render("index", &data)?;
 
-        let rendered = self.post_process(rendered, &html_config.playpen);
+            let rendered =
+                self.post_process(rendered, &html_config.playground, ctx.config.rust.edition);
 
-        utils::fs::write_file(&destination, "print.html", rendered.as_bytes())?;
-        debug!("Creating print.html ✓");
+            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)
-            .chain_err(|| "Unable to copy across static files")?;
-        self.copy_additional_css_and_js(&html_config, &ctx.root, &destination)
-            .chain_err(|| "Unable to copy across additional CSS and JS")?;
+        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)
+            .with_context(|| "Unable to copy across additional CSS and JS")?;
 
         // Render search index
         #[cfg(feature = "search")]
         {
             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)?;
             }
         }
 
-        // Copy all remaining files
-        utils::fs::copy_files_except_ext(&src_dir, &destination, true, &["md"])?;
+        self.emit_redirects(&ctx.destination, &handlebars, &html_config.redirect)
+            .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"])?;
 
         Ok(())
     }
@@ -385,6 +590,7 @@ fn make_data(
     book: &Book,
     config: &Config,
     html_config: &HtmlConfig,
+    theme: &Theme,
 ) -> Result<serde_json::Map<String, serde_json::Value>> {
     trace!("make_data");
 
@@ -401,9 +607,17 @@ fn make_data(
         "description".to_owned(),
         json!(config.book.description.clone().unwrap_or_default()),
     );
-    data.insert("favicon".to_owned(), json!("favicon.png"));
-    if let Some(ref livereload) = html_config.livereload_url {
-        data.insert("livereload".to_owned(), json!(livereload));
+    if theme.favicon_png.is_some() {
+        data.insert("favicon_png".to_owned(), json!("favicon.png"));
+    }
+    if theme.favicon_svg.is_some() {
+        data.insert("favicon_svg".to_owned(), json!("favicon.svg"));
+    }
+    if let Some(ref live_reload_endpoint) = html_config.live_reload_endpoint {
+        data.insert(
+            "live_reload_endpoint".to_owned(),
+            json!(live_reload_endpoint),
+        );
     }
 
     let default_theme = match html_config.default_theme {
@@ -414,7 +628,7 @@ fn make_data(
 
     let preferred_dark_theme = match html_config.preferred_dark_theme {
         Some(ref theme) => theme.to_lowercase(),
-        None => default_theme,
+        None => "navy".to_string(),
     };
     data.insert(
         "preferred_dark_theme".to_owned(),
@@ -430,6 +644,10 @@ fn make_data(
         data.insert("mathjax_support".to_owned(), json!(true));
     }
 
+    if html_config.copy_fonts {
+        data.insert("copy_fonts".to_owned(), json!(true));
+    }
+
     // Add check to see if there is an additional style
     if !html_config.additional_css.is_empty() {
         let mut css = Vec::new();
@@ -454,18 +672,19 @@ fn make_data(
         data.insert("additional_js".to_owned(), json!(js));
     }
 
-    if html_config.playpen.editable && html_config.playpen.copy_js {
-        data.insert("playpen_js".to_owned(), json!(true));
-        if html_config.playpen.line_numbers {
-            data.insert("playpen_line_numbers".to_owned(), json!(true));
+    if html_config.playground.editable && html_config.playground.copy_js {
+        data.insert("playground_js".to_owned(), json!(true));
+        if html_config.playground.line_numbers {
+            data.insert("playground_line_numbers".to_owned(), json!(true));
         }
     }
-    if html_config.playpen.copyable {
-        data.insert("playpen_copyable".to_owned(), json!(true));
+    if html_config.playground.copyable {
+        data.insert("playground_copyable".to_owned(), json!(true));
     }
 
-    data.insert("fold_enable".to_owned(), json!((html_config.fold.enable)));
-    data.insert("fold_level".to_owned(), json!((html_config.fold.level)));
+    data.insert("print_enable".to_owned(), json!(html_config.print.enable));
+    data.insert("fold_enable".to_owned(), json!(html_config.fold.enable));
+    data.insert("fold_level".to_owned(), json!(html_config.fold.level));
 
     let search = html_config.search.clone();
     if cfg!(feature = "search") {
@@ -500,6 +719,9 @@ fn make_data(
         let mut chapter = BTreeMap::new();
 
         match *item {
+            BookItem::PartTitle(ref title) => {
+                chapter.insert("part".to_owned(), json!(title));
+            }
             BookItem::Chapter(ref ch) => {
                 if let Some(ref section) = ch.number {
                     chapter.insert("section".to_owned(), json!(section.to_string()));
@@ -511,11 +733,12 @@ fn make_data(
                 );
 
                 chapter.insert("name".to_owned(), json!(ch.name));
-                let path = ch
-                    .path
-                    .to_str()
-                    .chain_err(|| "Could not convert path to str")?;
-                chapter.insert("path".to_owned(), json!(path));
+                if let Some(ref path) = ch.path {
+                    let p = path
+                        .to_str()
+                        .with_context(|| "Could not convert path to str")?;
+                    chapter.insert("path".to_owned(), json!(p));
+                }
             }
             BookItem::Separator => {
                 chapter.insert("spacer".to_owned(), json!("_spacer_"));
@@ -555,19 +778,10 @@ fn insert_link_into_header(
     content: &str,
     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 = utils::unique_id_from_content(content, id_counter);
 
     format!(
-        r##"<h{level}><a class="header" href="#{id}" id="{id}">{text}</a></h{level}>"##,
+        r##"<h{level} id="{id}"><a class="header" href="#{id}">{text}</a></h{level}>"##,
         level = level,
         id = id,
         text = content
@@ -600,7 +814,11 @@ fn fix_code_blocks(html: &str) -> String {
         .into_owned()
 }
 
-fn add_playpen_pre(html: &str, playpen_config: &Playpen) -> String {
+fn add_playground_pre(
+    html: &str,
+    playground_config: &Playground,
+    edition: Option<RustEdition>,
+) -> String {
     let regex = Regex::new(r##"((?s)<code[^>]?class="([^"]+)".*?>(.*?)</code>)"##).unwrap();
     regex
         .replace_all(html, |caps: &Captures<'_>| {
@@ -609,15 +827,34 @@ fn add_playpen_pre(html: &str, playpen_config: &Playpen) -> String {
             let code = &caps[3];
 
             if classes.contains("language-rust") {
-                if (!classes.contains("ignore") && !classes.contains("noplaypen"))
+                if (!classes.contains("ignore")
+                    && !classes.contains("noplayground")
+                    && !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 {
+                        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=\"playpen\"><code class=\"{}\">{}</code></pre>",
+                        "<pre class=\"playground\"><code class=\"{}{}\">{}</code></pre>",
                         classes,
+                        edition_class,
                         {
-                            let content: Cow<'_, str> = if playpen_config.editable
+                            let content: Cow<'_, str> = if playground_config.editable
                                 && classes.contains("editable")
                                 || text.contains("fn main")
                                 || text.contains("quick_main!")
@@ -628,7 +865,7 @@ fn add_playpen_pre(html: &str, playpen_config: &Playpen) -> String {
                                 let (attrs, code) = partition_source(code);
 
                                 format!(
-                                    "\n# #![allow(unused_variables)]\n{}#fn main() {{\n{}#}}",
+                                    "\n# #![allow(unused)]\n{}#fn main() {{\n{}#}}",
                                     attrs, code
                                 )
                                 .into()
@@ -690,10 +927,10 @@ 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');
         }
     }
 
@@ -701,11 +938,14 @@ fn partition_source(s: &str) -> (String, String) {
 }
 
 struct RenderItemContext<'a> {
-    handlebars: &'a Handlebars,
+    handlebars: &'a Handlebars<'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)]
@@ -717,61 +957,134 @@ mod tests {
         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>"##,
             ),
         ];
 
         for (src, should_be) in inputs {
-            let got = build_header_links(&src);
+            let got = build_header_links(src);
             assert_eq!(got, should_be);
         }
     }
 
     #[test]
-    fn add_playpen() {
+    fn add_playground() {
         let inputs = [
           ("<code class=\"language-rust\">x()</code>",
-           "<pre class=\"playpen\"><code class=\"language-rust\">\n<span class=\"boring\">#![allow(unused_variables)]\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\">\n<span class=\"boring\">#![allow(unused)]\n</span><span class=\"boring\">fn main() {\n</span>x()\n<span class=\"boring\">}\n</span></code></pre>"),
           ("<code class=\"language-rust\">fn main() {}</code>",
-           "<pre class=\"playpen\"><code class=\"language-rust\">fn main() {}\n</code></pre>"),
+           "<pre class=\"playground\"><code class=\"language-rust\">fn main() {}\n</code></pre>"),
           ("<code class=\"language-rust editable\">let s = \"foo\n # bar\n\";</code>",
-           "<pre class=\"playpen\"><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<span class=\"boring\"> bar\n</span>\";\n</code></pre>"),
           ("<code class=\"language-rust editable\">let s = \"foo\n ## bar\n\";</code>",
-           "<pre class=\"playpen\"><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\";\n</code></pre>"),
           ("<code class=\"language-rust editable\">let s = \"foo\n # bar\n#\n\";</code>",
-           "<pre class=\"playpen\"><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<span class=\"boring\"> bar\n</span><span class=\"boring\">\n</span>\";\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 editable\">#![no_std]\nlet s = \"foo\";\n #[some_attr]</code>",
-           "<pre class=\"playpen\"><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]\n</code></pre>"),
         ];
         for (src, should_be) in &inputs {
-            let got = add_playpen_pre(
+            let got = add_playground_pre(
                 src,
-                &Playpen {
+                &Playground {
                     editable: true,
-                    ..Playpen::default()
+                    ..Playground::default()
                 },
+                None,
+            );
+            assert_eq!(&*got, *should_be);
+        }
+    }
+    #[test]
+    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>"),
+          ("<code class=\"language-rust\">fn main() {}</code>",
+           "<pre class=\"playground\"><code class=\"language-rust edition2015\">fn main() {}\n</code></pre>"),
+          ("<code class=\"language-rust edition2015\">fn main() {}</code>",
+           "<pre class=\"playground\"><code class=\"language-rust edition2015\">fn main() {}\n</code></pre>"),
+          ("<code class=\"language-rust edition2018\">fn main() {}</code>",
+           "<pre class=\"playground\"><code class=\"language-rust edition2018\">fn main() {}\n</code></pre>"),
+        ];
+        for (src, should_be) in &inputs {
+            let got = add_playground_pre(
+                src,
+                &Playground {
+                    editable: true,
+                    ..Playground::default()
+                },
+                Some(RustEdition::E2015),
+            );
+            assert_eq!(&*got, *should_be);
+        }
+    }
+    #[test]
+    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>"),
+          ("<code class=\"language-rust\">fn main() {}</code>",
+           "<pre class=\"playground\"><code class=\"language-rust edition2018\">fn main() {}\n</code></pre>"),
+          ("<code class=\"language-rust edition2015\">fn main() {}</code>",
+           "<pre class=\"playground\"><code class=\"language-rust edition2015\">fn main() {}\n</code></pre>"),
+          ("<code class=\"language-rust edition2018\">fn main() {}</code>",
+           "<pre class=\"playground\"><code class=\"language-rust edition2018\">fn main() {}\n</code></pre>"),
+        ];
+        for (src, should_be) in &inputs {
+            let got = add_playground_pre(
+                src,
+                &Playground {
+                    editable: true,
+                    ..Playground::default()
+                },
+                Some(RustEdition::E2018),
+            );
+            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\">\n<span class=\"boring\">#![allow(unused)]\n</span><span class=\"boring\">fn main() {\n</span>x()\n<span class=\"boring\">}\n</span></code></pre>"),
+            ("<code class=\"language-rust\">fn main() {}</code>",
+             "<pre class=\"playground\"><code class=\"language-rust edition2021\">fn main() {}\n</code></pre>"),
+            ("<code class=\"language-rust edition2015\">fn main() {}</code>",
+             "<pre class=\"playground\"><code class=\"language-rust edition2015\">fn main() {}\n</code></pre>"),
+            ("<code class=\"language-rust edition2018\">fn main() {}</code>",
+             "<pre class=\"playground\"><code class=\"language-rust edition2018\">fn main() {}\n</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);
         }

src/renderer/html_handlebars/helpers/navigation.rs

@@ -46,7 +46,7 @@ impl Target {
 
 fn find_chapter(
     ctx: &Context,
-    rc: &mut RenderContext<'_>,
+    rc: &mut RenderContext<'_, '_>,
     target: Target,
 ) -> Result<Option<StringMap>, RenderError> {
     debug!("Get data from context");
@@ -75,8 +75,7 @@ fn find_chapter(
                     // Skip things like "spacer"
                     chapter.contains_key("path")
                 })
-                .skip(1)
-                .next()
+                .nth(1)
             {
                 Some(chapter) => return Ok(Some(chapter.clone())),
                 None => return Ok(None),
@@ -92,7 +91,7 @@ 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));
                     }
                 }
@@ -108,9 +107,9 @@ fn find_chapter(
 
 fn render(
     _h: &Helper<'_, '_>,
-    r: &Handlebars,
+    r: &Handlebars<'_>,
     ctx: &Context,
-    rc: &mut RenderContext<'_>,
+    rc: &mut RenderContext<'_, '_>,
     out: &mut dyn Output,
     chapter: &StringMap,
 ) -> Result<(), RenderError> {
@@ -150,7 +149,7 @@ fn render(
     _h.template()
         .ok_or_else(|| RenderError::new("Error with the handlebars template"))
         .and_then(|t| {
-            let mut local_rc = rc.new_for_block();
+            let mut local_rc = rc.clone();
             let local_ctx = Context::wraps(&context)?;
             t.render(r, &local_ctx, &mut local_rc, out)
         })?;
@@ -160,9 +159,9 @@ fn render(
 
 pub fn previous(
     _h: &Helper<'_, '_>,
-    r: &Handlebars,
+    r: &Handlebars<'_>,
     ctx: &Context,
-    rc: &mut RenderContext<'_>,
+    rc: &mut RenderContext<'_, '_>,
     out: &mut dyn Output,
 ) -> Result<(), RenderError> {
     trace!("previous (handlebars helper)");
@@ -176,9 +175,9 @@ pub fn previous(
 
 pub fn next(
     _h: &Helper<'_, '_>,
-    r: &Handlebars,
+    r: &Handlebars<'_>,
     ctx: &Context,
-    rc: &mut RenderContext<'_>,
+    rc: &mut RenderContext<'_, '_>,
     out: &mut dyn Output,
 ) -> Result<(), RenderError> {
     trace!("next (handlebars helper)");

src/renderer/html_handlebars/helpers/theme.rs

@@ -2,9 +2,9 @@ use handlebars::{Context, Handlebars, Helper, Output, RenderContext, RenderError
 
 pub fn theme_option(
     h: &Helper<'_, '_>,
-    _r: &Handlebars,
+    _r: &Handlebars<'_>,
     ctx: &Context,
-    rc: &mut RenderContext<'_>,
+    rc: &mut RenderContext<'_, '_>,
     out: &mut dyn Output,
 ) -> Result<(), RenderError> {
     trace!("theme_option (handlebars helper)");

src/renderer/html_handlebars/helpers/toc.rs

@@ -1,4 +1,5 @@
 use std::collections::BTreeMap;
+use std::io;
 use std::path::Path;
 
 use crate::utils;
@@ -16,9 +17,9 @@ impl HelperDef for RenderToc {
     fn call<'reg: 'rc, 'rc>(
         &self,
         _h: &Helper<'reg, 'rc>,
-        _r: &'reg Handlebars,
+        _r: &'reg Handlebars<'_>,
         ctx: &'rc Context,
-        rc: &mut RenderContext<'reg>,
+        rc: &mut RenderContext<'reg, 'rc>,
         out: &mut dyn Output,
     ) -> Result<(), RenderError> {
         // get value from context data
@@ -32,7 +33,7 @@ impl HelperDef for RenderToc {
             .evaluate(ctx, "@root/path")?
             .as_json()
             .as_str()
-            .ok_or(RenderError::new("Type error for `path`, string expected"))?
+            .ok_or_else(|| RenderError::new("Type error for `path`, string expected"))?
             .replace("\"", "");
 
         let current_section = rc
@@ -46,17 +47,13 @@ impl HelperDef for RenderToc {
             .evaluate(ctx, "@root/fold_enable")?
             .as_json()
             .as_bool()
-            .ok_or(RenderError::new(
-                "Type error for `fold_enable`, bool expected",
-            ))?;
+            .ok_or_else(|| RenderError::new("Type error for `fold_enable`, bool expected"))?;
 
         let fold_level = rc
             .evaluate(ctx, "@root/fold_level")?
             .as_json()
             .as_u64()
-            .ok_or(RenderError::new(
-                "Type error for `fold_level`, u64 expected",
-            ))?;
+            .ok_or_else(|| RenderError::new("Type error for `fold_level`, u64 expected"))?;
 
         out.write("<ol class=\"chapter\">")?;
 
@@ -75,18 +72,15 @@ impl HelperDef for RenderToc {
                 ("", 1)
             };
 
-            let is_expanded = {
-                if !fold_enable {
-                    // Disable fold. Expand all chapters.
-                    true
-                } else if !section.is_empty() && current_section.starts_with(section) {
-                    // The section is ancestor or the current section itself.
+            let is_expanded =
+                if !fold_enable || (!section.is_empty() && current_section.starts_with(section)) {
+                    // Expand if folding is disabled, or if the section is an
+                    // ancestor or the current section itself.
                     true
                 } else {
                     // Levels that are larger than this would be folded.
                     level - 1 < fold_level as usize
-                }
-            };
+                };
 
             if level > current_level {
                 while level > current_level {
@@ -106,33 +100,41 @@ impl HelperDef for RenderToc {
                 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\">")?;
+                write_escaped(out, title)?;
+                out.write("</li>")?;
+                continue;
+            }
+
             // Link
-            let path_exists = if let Some(path) = item.get("path") {
-                if !path.is_empty() {
-                    out.write("<a href=\"")?;
+            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 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("\\", "/");
+                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 {
-                        out.write(" class=\"active\"")?;
-                    }
-
-                    out.write(">")?;
-                    true
-                } else {
-                    false
+                if path == &current_path {
+                    out.write(" class=\"active\"")?;
                 }
+
+                out.write(">")?;
+                true
             } else {
+                out.write("<div>")?;
                 false
             };
 
@@ -140,7 +142,7 @@ impl HelperDef for RenderToc {
                 // 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> ")?;
                 }
             }
@@ -159,11 +161,13 @@ impl HelperDef for RenderToc {
                 html::push_html(&mut markdown_parsed_name, parser);
 
                 // write to the handlebars template
-                out.write(&markdown_parsed_name)?;
+                write_escaped(out, &markdown_parsed_name)?;
             }
 
             if path_exists {
                 out.write("</a>")?;
+            } else {
+                out.write("</div>")?;
             }
 
             // Render expand/collapse toggle
@@ -191,7 +195,7 @@ fn write_li_open_tag(
     is_expanded: bool,
     is_affix: bool,
 ) -> Result<(), std::io::Error> {
-    let mut li = String::from("<li class=\"");
+    let mut li = String::from("<li class=\"chapter-item ");
     if is_expanded {
         li.push_str("expanded ");
     }
@@ -201,3 +205,18 @@ fn write_li_open_tag(
     li.push_str("\">");
     out.write(&li)
 }
+
+fn write_escaped(out: &mut dyn Output, mut title: &str) -> io::Result<()> {
+    let needs_escape: &[char] = &['<', '>'];
+    while let Some(next) = title.find(needs_escape) {
+        out.write(&title[..next])?;
+        match title.as_bytes()[next] {
+            b'<' => out.write("&lt;")?,
+            b'>' => out.write("&gt;")?,
+            _ => unreachable!(),
+        }
+        title = &title[next + 1..];
+    }
+    out.write(title)?;
+    Ok(())
+}

src/renderer/html_handlebars/search.rs

@@ -17,10 +17,10 @@ pub fn create_files(search_config: &Search, destination: &Path, book: &Book) ->
     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());
@@ -71,17 +71,21 @@ fn render_item(
     item: &BookItem,
 ) -> Result<()> {
     let chapter = match *item {
-        BookItem::Chapter(ref ch) => ch,
+        BookItem::Chapter(ref ch) if !ch.is_draft_chapter() => ch,
         _ => return Ok(()),
     };
 
-    let filepath = Path::new(&chapter.path).with_extension("html");
+    let chapter_path = chapter
+        .path
+        .as_ref()
+        .expect("Checked that path exists above");
+    let filepath = Path::new(&chapter_path).with_extension("html");
     let filepath = filepath
         .to_str()
-        .chain_err(|| "Could not convert HTML path to str")?;
+        .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);
@@ -91,9 +95,12 @@ 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
@@ -112,9 +119,9 @@ fn render_item(
 
                 in_heading = true;
             }
-            Event::End(Tag::Heading(i)) if i <= max_section_depth => {
+            Event::End(Tag::Heading(i, ..)) if i as u32 <= max_section_depth => {
                 in_heading = false;
-                section_id = Some(utils::id_from_content(&heading));
+                section_id = Some(utils::unique_id_from_content(&heading, &mut id_counter));
                 breadcrumbs.push(heading.clone());
             }
             Event::Start(Tag::FootnoteDefinition(name)) => {
@@ -128,14 +135,14 @@ 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(' ');
@@ -159,7 +166,12 @@ 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,

src/renderer/markdown_renderer.rs

@@ -28,18 +28,24 @@ impl Renderer for MarkdownRenderer {
 
         if destination.exists() {
             utils::fs::remove_dir_content(destination)
-                .chain_err(|| "Unable to remove stale Markdown output")?;
+                .with_context(|| "Unable to remove stale Markdown output")?;
         }
 
         trace!("markdown render");
         for item in book.iter() {
             if let BookItem::Chapter(ref ch) = *item {
-                utils::fs::write_file(&ctx.destination, &ch.path, ch.content.as_bytes())?;
+                if !ch.is_draft_chapter() {
+                    utils::fs::write_file(
+                        &ctx.destination,
+                        &ch.path.as_ref().expect("Checked path exists before"),
+                        ch.content.as_bytes(),
+                    )?;
+                }
             }
         }
 
         fs::create_dir_all(&destination)
-            .chain_err(|| "Unexpected error when constructing destination path")?;
+            .with_context(|| "Unexpected error when constructing destination path")?;
 
         Ok(())
     }

src/renderer/mod.rs

@@ -18,14 +18,16 @@ mod html_handlebars;
 mod markdown_renderer;
 
 use shlex::Shlex;
+use std::collections::HashMap;
 use std::fs;
-use std::io::{self, Read};
-use std::path::PathBuf;
+use std::io::{self, ErrorKind, Read};
+use std::path::{Path, PathBuf};
 use std::process::{Command, Stdio};
 
 use crate::book::Book;
 use crate::config::Config;
 use crate::errors::*;
+use toml::Value;
 
 /// An arbitrary `mdbook` backend.
 ///
@@ -33,12 +35,9 @@ use crate::errors::*;
 /// 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;
@@ -66,6 +65,8 @@ 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: (),
 }
 
@@ -82,6 +83,7 @@ impl RenderContext {
             version: crate::MDBOOK_VERSION.to_string(),
             root: root.into(),
             destination: destination.into(),
+            chapter_titles: HashMap::new(),
             __non_exhaustive: (),
         }
     }
@@ -93,7 +95,7 @@ impl RenderContext {
 
     /// Load a `RenderContext` from its JSON representation.
     pub fn from_json<R: Read>(reader: R) -> Result<RenderContext> {
-        serde_json::from_reader(reader).chain_err(|| "Unable to deserialize the `RenderContext`")
+        serde_json::from_reader(reader).with_context(|| "Unable to deserialize the `RenderContext`")
     }
 }
 
@@ -132,14 +134,44 @@ 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);
@@ -149,6 +181,40 @@ impl CmdRenderer {
     }
 }
 
+impl CmdRenderer {
+    fn handle_render_command_error(&self, ctx: &RenderContext, error: io::Error) -> Result<()> {
+        if let ErrorKind::NotFound = error.kind() {
+            // Look for "output.{self.name}.optional".
+            // If it exists and is true, treat this as a warning.
+            // Otherwise, fail the build.
+
+            let optional_key = format!("output.{}.optional", self.name);
+
+            let is_optional = match ctx.config.get(&optional_key) {
+                Some(Value::Boolean(value)) => *value,
+                _ => false,
+            };
+
+            if is_optional {
+                warn!(
+                    "The command `{}` for backend `{}` was not found, \
+                    but was marked as optional.",
+                    self.cmd, self.name
+                );
+                return Ok(());
+            } else {
+                error!(
+                    "The command `{0}` wasn't found, is the \"{1}\" backend installed? \
+                    If you want to ignore this error when the \"{1}\" backend is not installed, \
+                    set `optional = true` in the `[output.{1}]` section of the book.toml configuration file.",
+                    self.cmd, self.name
+                );
+            }
+        }
+        Err(error).with_context(|| "Unable to start the backend")?
+    }
+}
+
 impl Renderer for CmdRenderer {
     fn name(&self) -> &str {
         &self.name
@@ -160,7 +226,7 @@ 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())
@@ -168,34 +234,22 @@ impl Renderer for CmdRenderer {
             .spawn()
         {
             Ok(c) => c,
-            Err(ref e) if e.kind() == io::ErrorKind::NotFound => {
-                warn!(
-                    "The command wasn't found, is the \"{}\" backend installed?",
-                    self.name
-                );
-                warn!("\tCommand: {}", self.cmd);
-                return Ok(());
-            }
-            Err(e) => {
-                return Err(e).chain_err(|| "Unable to start the backend")?;
-            }
+            Err(e) => return self.handle_render_command_error(ctx, e),
         };
 
-        {
-            let mut stdin = child.stdin.take().expect("Child has stdin");
-            if let Err(e) = serde_json::to_writer(&mut stdin, &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);
-            }
-
-            // explicitly close the `stdin` file handle
-            drop(stdin);
+        let mut stdin = child.stdin.take().expect("Child has stdin");
+        if let Err(e) = serde_json::to_writer(&mut stdin, &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);
         }
 
+        // explicitly close the `stdin` file handle
+        drop(stdin);
+
         let status = child
             .wait()
-            .chain_err(|| "Error waiting for the backend to complete")?;
+            .with_context(|| "Error waiting for the backend to complete")?;
 
         trace!("{} exited with output: {:?}", self.cmd, status);
 

src/theme/ayu-highlight.css

@@ -12,8 +12,7 @@ Original by Dempfi (https://github.com/dempfi/ayu)
 }
 
 .hljs-comment,
-.hljs-quote,
-.hljs-meta {
+.hljs-quote {
   color: #5c6773;
   font-style: italic;
 }
@@ -30,6 +29,7 @@ Original by Dempfi (https://github.com/dempfi/ayu)
 }
 
 .hljs-number,
+.hljs-meta,
 .hljs-builtin-name,
 .hljs-literal,
 .hljs-type,

src/theme/book.js

@@ -4,8 +4,8 @@
 window.onunload = function () { };
 
 // Global variable, shared between modules
-function playpen_text(playpen) {
-    let code_block = playpen.querySelector("code");
+function playground_text(playground) {
+    let code_block = playground.querySelector("code");
 
     if (window.ace && code_block.classList.contains("editable")) {
         let editor = window.ace.edit(code_block);
@@ -23,8 +23,8 @@ function playpen_text(playpen) {
         ]);
     }
 
-    var playpens = Array.from(document.querySelectorAll(".playpen"));
-    if (playpens.length > 0) {
+    var playgrounds = Array.from(document.querySelectorAll(".playground"));
+    if (playgrounds.length > 0) {
         fetch_with_timeout("https://play.rust-lang.org/meta/crates", {
             headers: {
                 'Content-Type': "application/json",
@@ -36,21 +36,21 @@ function playpen_text(playpen) {
         .then(response => {
             // get list of crates available in the rust playground
             let playground_crates = response.crates.map(item => item["id"]);
-            playpens.forEach(block => handle_crate_list_update(block, playground_crates));
+            playgrounds.forEach(block => handle_crate_list_update(block, playground_crates));
         });
     }
 
-    function handle_crate_list_update(playpen_block, playground_crates) {
+    function handle_crate_list_update(playground_block, playground_crates) {
         // update the play buttons after receiving the response
-        update_play_button(playpen_block, playground_crates);
+        update_play_button(playground_block, playground_crates);
 
         // and install on change listener to dynamically update ACE editors
         if (window.ace) {
-            let code_block = playpen_block.querySelector("code");
+            let code_block = playground_block.querySelector("code");
             if (code_block.classList.contains("editable")) {
                 let editor = window.ace.edit(code_block);
                 editor.addEventListener("change", function (e) {
-                    update_play_button(playpen_block, playground_crates);
+                    update_play_button(playground_block, playground_crates);
                 });
                 // add Ctrl-Enter command to execute rust code
                 editor.commands.addCommand({
@@ -59,7 +59,7 @@ function playpen_text(playpen) {
                         win: "Ctrl-Enter",
                         mac: "Ctrl-Enter"
                     },
-                    exec: _editor => run_rust_code(playpen_block)
+                    exec: _editor => run_rust_code(playground_block)
                 });
             }
         }
@@ -77,7 +77,7 @@ function playpen_text(playpen) {
         }
 
         // get list of `extern crate`'s from snippet
-        var txt = playpen_text(pre_block);
+        var txt = playground_text(pre_block);
         var re = /extern\s+crate\s+([a-zA-Z_0-9]+)\s*;/g;
         var snippet_crates = [];
         var item;
@@ -106,11 +106,14 @@ function playpen_text(playpen) {
             code_block.append(result_block);
         }
 
-        let text = playpen_text(code_block);
+        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 +136,15 @@ function playpen_text(playpen) {
             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);
     }
 
@@ -143,27 +154,29 @@ function playpen_text(playpen) {
         languages: [],      // Languages used for auto-detection
     });
 
+    let code_nodes = Array
+        .from(document.querySelectorAll('code'))
+        // Don't highlight `inline code` blocks in headers.
+        .filter(function (node) {return !node.parentElement.classList.contains("header"); });
+
     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 {
-        Array
-            .from(document.querySelectorAll('code'))
-            .forEach(function (block) { hljs.highlightBlock(block); });
+        code_nodes.forEach(function (block) { hljs.highlightBlock(block); });
     }
 
     // Adding the hljs class gives code blocks the color css
     // even if highlighting doesn't apply
-    Array
-        .from(document.querySelectorAll('code'))
-        .forEach(function (block) { block.classList.add('hljs'); });
+    code_nodes.forEach(function (block) { block.classList.add('hljs'); });
 
     Array.from(document.querySelectorAll("code.language-rust")).forEach(function (block) {
 
@@ -174,23 +187,23 @@ function playpen_text(playpen) {
 
         var buttons = document.createElement('div');
         buttons.className = 'buttons';
-        buttons.innerHTML = "<button class=\"fa fa-expand\" title=\"Show hidden lines\" aria-label=\"Show hidden lines\"></button>";
+        buttons.innerHTML = "<button class=\"fa fa-eye\" title=\"Show hidden lines\" aria-label=\"Show hidden lines\"></button>";
 
         // add expand button
         var pre_block = block.parentNode;
         pre_block.insertBefore(buttons, pre_block.firstChild);
 
         pre_block.querySelector('.buttons').addEventListener('click', function (e) {
-            if (e.target.classList.contains('fa-expand')) {
-                e.target.classList.remove('fa-expand');
-                e.target.classList.add('fa-compress');
+            if (e.target.classList.contains('fa-eye')) {
+                e.target.classList.remove('fa-eye');
+                e.target.classList.add('fa-eye-slash');
                 e.target.title = 'Hide lines';
                 e.target.setAttribute('aria-label', e.target.title);
 
                 block.classList.remove('hide-boring');
-            } else if (e.target.classList.contains('fa-compress')) {
-                e.target.classList.remove('fa-compress');
-                e.target.classList.add('fa-expand');
+            } else if (e.target.classList.contains('fa-eye-slash')) {
+                e.target.classList.remove('fa-eye-slash');
+                e.target.classList.add('fa-eye');
                 e.target.title = 'Show hidden lines';
                 e.target.setAttribute('aria-label', e.target.title);
 
@@ -199,10 +212,10 @@ function playpen_text(playpen) {
         });
     });
 
-    if (window.playpen_copyable) {
+    if (window.playground_copyable) {
         Array.from(document.querySelectorAll('pre code')).forEach(function (block) {
             var pre_block = block.parentNode;
-            if (!pre_block.classList.contains('playpen')) {
+            if (!pre_block.classList.contains('playground')) {
                 var buttons = pre_block.querySelector(".buttons");
                 if (!buttons) {
                     buttons = document.createElement('div');
@@ -221,8 +234,8 @@ function playpen_text(playpen) {
         });
     }
 
-    // Process playpen code blocks
-    Array.from(document.querySelectorAll(".playpen")).forEach(function (pre_block) {
+    // Process playground code blocks
+    Array.from(document.querySelectorAll(".playground")).forEach(function (pre_block) {
         // Add play button
         var buttons = pre_block.querySelector(".buttons");
         if (!buttons) {
@@ -242,7 +255,7 @@ function playpen_text(playpen) {
             run_rust_code(pre_block);
         });
 
-        if (window.playpen_copyable) {
+        if (window.playground_copyable) {
             var copyCodeClipboardButton = document.createElement('button');
             copyCodeClipboardButton.className = 'fa fa-copy clip-button';
             copyCodeClipboardButton.innerHTML = '<i class="tooltiptext"></i>';
@@ -284,7 +297,7 @@ function playpen_text(playpen) {
     function showThemes() {
         themePopup.style.display = 'block';
         themeToggleButton.setAttribute('aria-expanded', true);
-        themePopup.querySelector("button#" + document.body.className).focus();
+        themePopup.querySelector("button#" + get_theme()).focus();
     }
 
     function hideThemes() {
@@ -293,6 +306,16 @@ function playpen_text(playpen) {
         themeToggleButton.focus();
     }
 
+    function get_theme() {
+        var theme;
+        try { theme = localStorage.getItem('mdbook-theme'); } catch (e) { }
+        if (theme === null || theme === undefined) {
+            return default_theme;
+        } else {
+            return theme;
+        }
+    }
+
     function set_theme(theme, store = true) {
         let ace_theme;
 
@@ -324,9 +347,7 @@ function playpen_text(playpen) {
             });
         }
 
-        var previousTheme;
-        try { previousTheme = localStorage.getItem('mdbook-theme'); } catch (e) { }
-        if (previousTheme === null || previousTheme === undefined) { previousTheme = default_theme; }
+        var previousTheme = get_theme();
 
         if (store) {
             try { localStorage.setItem('mdbook-theme', theme); } catch (e) { }
@@ -337,9 +358,7 @@ function playpen_text(playpen) {
     }
 
     // Set theme
-    var theme;
-    try { theme = localStorage.getItem('mdbook-theme'); } catch(e) { }
-    if (theme === null || theme === undefined) { theme = default_theme; }
+    var theme = get_theme();
 
     set_theme(theme, false);
 
@@ -352,7 +371,14 @@ function playpen_text(playpen) {
     });
 
     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);
     });
 
@@ -408,7 +434,6 @@ function playpen_text(playpen) {
 (function sidebar() {
     var html = document.querySelector("html");
     var sidebar = document.getElementById("sidebar");
-    var sidebarScrollBox = document.getElementById("sidebar-scrollbox");
     var sidebarLinks = document.querySelectorAll('#sidebar a');
     var sidebarToggleButton = document.getElementById("sidebar-toggle");
     var sidebarResizeHandle = document.getElementById("sidebar-resize-handle");
@@ -450,6 +475,11 @@ function playpen_text(playpen) {
     // Toggle sidebar
     sidebarToggleButton.addEventListener('click', function sidebarToggle() {
         if (html.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")) {
             hideSidebar();
@@ -470,7 +500,16 @@ function playpen_text(playpen) {
         html.classList.add('sidebar-resizing');
     }
     function resize(e) {
-        document.documentElement.style.setProperty('--sidebar-width', (e.clientX - sidebar.offsetLeft) + 'px');
+        var pos = (e.clientX - sidebar.offsetLeft);
+        if (pos < 20) {
+            hideSidebar();
+        } else {
+            if (html.classList.contains("sidebar-hidden")) {
+                showSidebar();
+            }
+            pos = Math.min(pos, window.innerWidth - 100);
+            document.documentElement.style.setProperty('--sidebar-width', pos + 'px');
+        }
     }
     //on mouseup remove windows functions mousemove & mouseup
     function stopResize(e) {
@@ -505,9 +544,10 @@ function playpen_text(playpen) {
     }, { passive: true });
 
     // Scroll sidebar to current active section
-    var activeSection = sidebar.querySelector(".active");
+    var activeSection = document.getElementById("sidebar").querySelector(".active");
     if (activeSection) {
-        sidebarScrollBox.scrollTop = activeSection.offsetTop;
+        // https://developer.mozilla.org/en-US/docs/Web/API/Element/scrollIntoView
+        activeSection.scrollIntoView({ block: 'center' });
     }
 })();
 
@@ -551,8 +591,8 @@ function playpen_text(playpen) {
     var clipboardSnippets = new ClipboardJS('.clip-button', {
         text: function (trigger) {
             hideTooltip(trigger);
-            let playpen = trigger.closest("pre");
-            return playpen_text(playpen);
+            let playground = trigger.closest("pre");
+            return playground_text(playground);
         }
     });
 
@@ -580,26 +620,60 @@ function playpen_text(playpen) {
     });
 })();
 
-(function autoHideMenu() {
+(function controllMenu() {
     var menu = document.getElementById('menu-bar');
 
-    var previousScrollTop = document.scrollingElement.scrollTop;
-
-    document.addEventListener('scroll', function () {
-        if (menu.classList.contains('folded') && document.scrollingElement.scrollTop < previousScrollTop) {
-            menu.classList.remove('folded');
-        } else if (!menu.classList.contains('folded') && document.scrollingElement.scrollTop > previousScrollTop) {
-            menu.classList.add('folded');
-        }
-
-        if (!menu.classList.contains('bordered') && document.scrollingElement.scrollTop > 0) {
-            menu.classList.add('bordered');
-        }
-
-        if (menu.classList.contains('bordered') && document.scrollingElement.scrollTop === 0) {
-            menu.classList.remove('bordered');
-        }
-
-        previousScrollTop = Math.max(document.scrollingElement.scrollTop, 0);
-    }, { passive: true });
+    (function controllPosition() {
+        var scrollTop = document.scrollingElement.scrollTop;
+        var prevScrollTop = scrollTop;
+        var minMenuY = -menu.clientHeight - 50;
+        // When the script loads, the page can be at any scroll (e.g. if you reforesh it).
+        menu.style.top = scrollTop + 'px';
+        // Same as parseInt(menu.style.top.slice(0, -2), but faster
+        var topCache = menu.style.top.slice(0, -2);
+        menu.classList.remove('sticky');
+        var stickyCache = false; // Same as menu.classList.contains('sticky'), but faster
+        document.addEventListener('scroll', function () {
+            scrollTop = Math.max(document.scrollingElement.scrollTop, 0);
+            // `null` means that it doesn't need to be updated
+            var nextSticky = null;
+            var nextTop = null;
+            var scrollDown = scrollTop > prevScrollTop;
+            var menuPosAbsoluteY = topCache - scrollTop;
+            if (scrollDown) {
+                nextSticky = false;
+                if (menuPosAbsoluteY > 0) {
+                    nextTop = prevScrollTop;
+                }
+            } else {
+                if (menuPosAbsoluteY > 0) {
+                    nextSticky = true;
+                } else if (menuPosAbsoluteY < minMenuY) {
+                    nextTop = prevScrollTop + minMenuY;
+                }
+            }
+            if (nextSticky === true && stickyCache === false) {
+                menu.classList.add('sticky');
+                stickyCache = true;
+            } else if (nextSticky === false && stickyCache === true) {
+                menu.classList.remove('sticky');
+                stickyCache = false;
+            }
+            if (nextTop !== null) {
+                menu.style.top = nextTop + 'px';
+                topCache = nextTop;
+            }
+            prevScrollTop = scrollTop;
+        }, { passive: true });
+    })();
+    (function controllBorder() {
+        menu.classList.remove('bordered');
+        document.addEventListener('scroll', function () {
+            if (menu.offsetTop === 0) {
+                menu.classList.remove('bordered');
+            } else {
+                menu.classList.add('bordered');
+            }
+        }, { passive: true });
+    })();
 })();

src/theme/css/chrome.css

@@ -20,14 +20,13 @@ a > .hljs {
 
 /* Menu Bar */
 
-#menu-bar {
-    position: -webkit-sticky;
-    position: sticky;
-    top: 0;
+#menu-bar,
+#menu-bar-hover-placeholder {
     z-index: 101;
     margin: auto calc(0px - var(--page-padding));
 }
-#menu-bar > #menu-bar-sticky-container {
+#menu-bar {
+    position: relative;
     display: flex;
     flex-wrap: wrap;
     background-color: var(--bg);
@@ -35,10 +34,21 @@ a > .hljs {
     border-bottom-width: 1px;
     border-bottom-style: solid;
 }
-.js #menu-bar > #menu-bar-sticky-container {
-    transition: transform 0.3s;
+#menu-bar.sticky,
+.js #menu-bar-hover-placeholder:hover + #menu-bar,
+.js #menu-bar:hover,
+.js.sidebar-visible #menu-bar {
+    position: -webkit-sticky;
+    position: sticky;
+    top: 0 !important;
 }
-#menu-bar.bordered > #menu-bar-sticky-container  {
+#menu-bar-hover-placeholder {
+    position: sticky;
+    position: -webkit-sticky;
+    top: 0;
+    height: var(--menu-bar-height);
+}
+#menu-bar.bordered {
     border-bottom-color: var(--table-border-color);
 }
 #menu-bar i, #menu-bar .icon-button {
@@ -72,10 +82,6 @@ a > .hljs {
     text-decoration: none;
 }
 
-html:not(.sidebar-visible) #menu-bar:not(:hover).folded > #menu-bar-sticky-container {
-    transform: translateY(calc(-10px - var(--menu-bar-height)));
-}
-
 .left-buttons {
     display: flex;
     margin: 0 5px;
@@ -87,7 +93,7 @@ html:not(.sidebar-visible) #menu-bar:not(:hover).folded > #menu-bar-sticky-conta
 .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;
@@ -417,6 +423,11 @@ ul#searchresults span.teaser em {
     display: none;
 }
 
+.chapter li.chapter-item {
+    line-height: 1.5em;
+    margin-top: 0.6em;
+}
+
 .chapter li.expanded > a.toggle div {
     transform: rotate(90deg);
 }

src/theme/css/general.css

@@ -12,6 +12,7 @@ html {
     color: var(--fg);
     background-color: var(--bg);
     text-size-adjust: none;
+    -webkit-text-size-adjust: none;
 }
 
 body {
@@ -25,11 +26,16 @@ code {
     font-size: 0.875em; /* please adjust the ace font size accordingly in editor.js */
 }
 
+/* Don't change font size in headers. */
+h1 code, h2 code, h3 code, h4 code, h5 code, h6 code {
+    font-size: unset;
+}
+
 .left { float: left; }
 .right { float: right; }
 .boring { opacity: 0.6; }
 .hide-boring .boring { display: none; }
-.hidden { display: none; }
+.hidden { display: none !important; }
 
 h2, h3 { margin-top: 2.5em; }
 h4, h5 { margin-top: 2em; }
@@ -40,26 +46,30 @@ h4, h5 { margin-top: 2em; }
     margin-top: 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;
     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 {
     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 */
 }
 .page-wrapper {
     box-sizing: border-box;
@@ -78,9 +88,12 @@ h4 a.header:target {
     margin-right: auto;
     max-width: var(--content-max-width);
 }
+.content p { line-height: 1.45em; }
+.content ol { line-height: 1.45em; }
+.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);
@@ -157,3 +170,13 @@ blockquote {
 .tooltipped .tooltiptext {
     visibility: visible;
 }
+
+.chapter li.part-title {
+    color: var(--sidebar-fg);
+    margin: 5px 0px;
+    font-weight: bold;
+}
+
+.result-no-output {
+    font-style: italic;
+}

src/theme/css/variables.css

@@ -67,7 +67,7 @@
 
     --links: #2b79a2;
 
-    --inline-code-color: #c5c8c6;;
+    --inline-code-color: #c5c8c6;
 
     --theme-popup-bg: #141617;
     --theme-popup-border: #43484d;
@@ -92,22 +92,22 @@
 
 .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;
@@ -147,7 +147,7 @@
 
     --links: #2b79a2;
 
-    --inline-code-color: #c5c8c6;;
+    --inline-code-color: #c5c8c6;
 
     --theme-popup-bg: #161923;
     --theme-popup-border: #737480;
@@ -228,7 +228,7 @@
 
         --links: #2b79a2;
 
-        --inline-code-color: #c5c8c6;;
+        --inline-code-color: #c5c8c6;
 
         --theme-popup-bg: #141617;
         --theme-popup-border: #43484d;

src/theme/favicon.svg

@@ -0,0 +1,22 @@
+<svg xmlns="http://www.w3.org/2000/svg" viewBox="0 0 199.7 184.2">
+  <style>
+    @media (prefers-color-scheme: dark) {
+      svg { fill: white; }
+    }
+  </style>
+<path d="M189.5,36.8c0.2,2.8,0,5.1-0.6,6.8L153,162c-0.6,2.1-2,3.7-4.2,5c-2.2,1.2-4.4,1.9-6.7,1.9H31.4c-9.6,0-15.3-2.8-17.3-8.4
+  c-0.8-2.2-0.8-3.9,0.1-5.2c0.9-1.2,2.4-1.8,4.6-1.8H123c7.4,0,12.6-1.4,15.4-4.1s5.7-8.9,8.6-18.4l32.9-108.6
+  c1.8-5.9,1-11.1-2.2-15.6S169.9,0,164,0H72.7c-1,0-3.1,0.4-6.1,1.1l0.1-0.4C64.5,0.2,62.6,0,61,0.1s-3,0.5-4.3,1.4
+  c-1.3,0.9-2.4,1.8-3.2,2.8S52,6.5,51.2,8.1c-0.8,1.6-1.4,3-1.9,4.3s-1.1,2.7-1.8,4.2c-0.7,1.5-1.3,2.7-2,3.7c-0.5,0.6-1.2,1.5-2,2.5
+  s-1.6,2-2.2,2.8s-0.9,1.5-1.1,2.2c-0.2,0.7-0.1,1.8,0.2,3.2c0.3,1.4,0.4,2.4,0.4,3.1c-0.3,3-1.4,6.9-3.3,11.6
+  c-1.9,4.7-3.6,8.1-5.1,10.1c-0.3,0.4-1.2,1.3-2.6,2.7c-1.4,1.4-2.3,2.6-2.6,3.7c-0.3,0.4-0.3,1.5-0.1,3.4c0.3,1.8,0.4,3.1,0.3,3.8
+  c-0.3,2.7-1.3,6.3-3,10.8c-1.7,4.5-3.4,8.2-5,11c-0.2,0.5-0.9,1.4-2,2.8c-1.1,1.4-1.8,2.5-2,3.4c-0.2,0.6-0.1,1.8,0.1,3.4
+  c0.2,1.6,0.2,2.8-0.1,3.6c-0.6,3-1.8,6.7-3.6,11c-1.8,4.3-3.6,7.9-5.4,11c-0.5,0.8-1.1,1.7-2,2.8c-0.8,1.1-1.5,2-2,2.8
+  s-0.8,1.6-1,2.5c-0.1,0.5,0,1.3,0.4,2.3c0.3,1.1,0.4,1.9,0.4,2.6c-0.1,1.1-0.2,2.6-0.5,4.4c-0.2,1.8-0.4,2.9-0.4,3.2
+  c-1.8,4.8-1.7,9.9,0.2,15.2c2.2,6.2,6.2,11.5,11.9,15.8c5.7,4.3,11.7,6.4,17.8,6.4h110.7c5.2,0,10.1-1.7,14.7-5.2s7.7-7.8,9.2-12.9
+  l33-108.6c1.8-5.8,1-10.9-2.2-15.5C194.9,39.7,192.6,38,189.5,36.8z M59.6,122.8L73.8,80c0,0,7,0,10.8,0s28.8-1.7,25.4,17.5
+  c-3.4,19.2-18.8,25.2-36.8,25.4S59.6,122.8,59.6,122.8z M78.6,116.8c4.7-0.1,18.9-2.9,22.1-17.1S89.2,86.3,89.2,86.3l-8.9,0
+  l-10.2,30.5C70.2,116.9,74,116.9,78.6,116.8z M75.3,68.7L89,26.2h9.8l0.8,34l23.6-34h9.9l-13.6,42.5h-7.1l12.5-35.4l-24.5,35.4h-6.8
+  l-0.8-35L82,68.7H75.3z"/>
+</svg>
+<!-- Original image Copyright Dave Gandy — CC BY 4.0 License -->

src/theme/fonts/OPEN-SANS-LICENSE.txt

@@ -0,0 +1,202 @@
+
+                                 Apache License
+                           Version 2.0, January 2004
+                        http://www.apache.org/licenses/
+
+   TERMS AND CONDITIONS FOR USE, REPRODUCTION, AND DISTRIBUTION
+
+   1. Definitions.
+
+      "License" shall mean the terms and conditions for use, reproduction,
+      and distribution as defined by Sections 1 through 9 of this document.
+
+      "Licensor" shall mean the copyright owner or entity authorized by
+      the copyright owner that is granting the License.
+
+      "Legal Entity" shall mean the union of the acting entity and all
+      other entities that control, are controlled by, or are under common
+      control with that entity. For the purposes of this definition,
+      "control" means (i) the power, direct or indirect, to cause the
+      direction or management of such entity, whether by contract or
+      otherwise, or (ii) ownership of fifty percent (50%) or more of the
+      outstanding shares, or (iii) beneficial ownership of such entity.
+
+      "You" (or "Your") shall mean an individual or Legal Entity
+      exercising permissions granted by this License.
+
+      "Source" form shall mean the preferred form for making modifications,
+      including but not limited to software source code, documentation
+      source, and configuration files.
+
+      "Object" form shall mean any form resulting from mechanical
+      transformation or translation of a Source form, including but
+      not limited to compiled object code, generated documentation,
+      and conversions to other media types.
+
+      "Work" shall mean the work of authorship, whether in Source or
+      Object form, made available under the License, as indicated by a
+      copyright notice that is included in or attached to the work
+      (an example is provided in the Appendix below).
+
+      "Derivative Works" shall mean any work, whether in Source or Object
+      form, that is based on (or derived from) the Work and for which the
+      editorial revisions, annotations, elaborations, or other modifications
+      represent, as a whole, an original work of authorship. For the purposes
+      of this License, Derivative Works shall not include works that remain
+      separable from, or merely link (or bind by name) to the interfaces of,
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+
+      "Contribution" shall mean any work of authorship, including
+      the original version of the Work and any modifications or additions
+      to that Work or Derivative Works thereof, that is intentionally
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+      communication on electronic mailing lists, source code control systems,
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+      on behalf of whom a Contribution has been received by Licensor and
+      subsequently incorporated within the Work.
+
+   2. Grant of Copyright License. Subject to the terms and conditions of
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+      institute patent litigation against any entity (including a
+      cross-claim or counterclaim in a lawsuit) alleging that the Work
+      or a Contribution incorporated within the Work constitutes direct
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+      granted to You under this License for that Work shall terminate
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+
+   4. Redistribution. You may reproduce and distribute copies of the
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+
+      (a) You must give any other recipients of the Work or
+          Derivative Works a copy of this License; and
+
+      (b) You must cause any modified files to carry prominent notices
+          stating that You changed the files; and
+
+      (c) You must retain, in the Source form of any Derivative Works
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+
+      (d) If the Work includes a "NOTICE" text file as part of its
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src/theme/fonts/SOURCE-CODE-PRO-LICENSE.txt

@@ -0,0 +1,93 @@
+Copyright 2010, 2012 Adobe Systems Incorporated (http://www.adobe.com/), with Reserved Font Name 'Source'. All Rights Reserved. Source is a trademark of Adobe Systems Incorporated in the United States and/or other countries.
+
+This Font Software is licensed under the SIL Open Font License, Version 1.1.
+This license is copied below, and is also available with a FAQ at:
+http://scripts.sil.org/OFL
+
+
+-----------------------------------------------------------
+SIL OPEN FONT LICENSE Version 1.1 - 26 February 2007
+-----------------------------------------------------------
+
+PREAMBLE
+The goals of the Open Font License (OFL) are to stimulate worldwide
+development of collaborative font projects, to support the font creation
+efforts of academic and linguistic communities, and to provide a free and
+open framework in which fonts may be shared and improved in partnership
+with others.
+
+The OFL allows the licensed fonts to be used, studied, modified and
+redistributed freely as long as they are not sold by themselves. The
+fonts, including any derivative works, can be bundled, embedded, 
+redistributed and/or sold with any software provided that any reserved
+names are not used by derivative works. The fonts and derivatives,
+however, cannot be released under any other type of license. The
+requirement for fonts to remain under this license does not apply
+to any document created using the fonts or their derivatives.
+
+DEFINITIONS
+"Font Software" refers to the set of files released by the Copyright
+Holder(s) under this license and clearly marked as such. This may
+include source files, build scripts and documentation.
+
+"Reserved Font Name" refers to any names specified as such after the
+copyright statement(s).
+
+"Original Version" refers to the collection of Font Software components as
+distributed by the Copyright Holder(s).
+
+"Modified Version" refers to any derivative made by adding to, deleting,
+or substituting -- in part or in whole -- any of the components of the
+Original Version, by changing formats or by porting the Font Software to a
+new environment.
+
+"Author" refers to any designer, engineer, programmer, technical
+writer or other person who contributed to the Font Software.
+
+PERMISSION & CONDITIONS
+Permission is hereby granted, free of charge, to any person obtaining
+a copy of the Font Software, to use, study, copy, merge, embed, modify,
+redistribute, and sell modified and unmodified copies of the Font
+Software, subject to the following conditions:
+
+1) Neither the Font Software nor any of its individual components,
+in Original or Modified Versions, may be sold by itself.
+
+2) Original or Modified Versions of the Font Software may be bundled,
+redistributed and/or sold with any software, provided that each copy
+contains the above copyright notice and this license. These can be
+included either as stand-alone text files, human-readable headers or
+in the appropriate machine-readable metadata fields within text or
+binary files as long as those fields can be easily viewed by the user.
+
+3) No Modified Version of the Font Software may use the Reserved Font
+Name(s) unless explicit written permission is granted by the corresponding
+Copyright Holder. This restriction only applies to the primary font name as
+presented to the users.
+
+4) The name(s) of the Copyright Holder(s) or the Author(s) of the Font
+Software shall not be used to promote, endorse or advertise any
+Modified Version, except to acknowledge the contribution(s) of the
+Copyright Holder(s) and the Author(s) or with their explicit written
+permission.
+
+5) The Font Software, modified or unmodified, in part or in whole,
+must be distributed entirely under this license, and must not be
+distributed under any other license. The requirement for fonts to
+remain under this license does not apply to any document created
+using the Font Software.
+
+TERMINATION
+This license becomes null and void if any of the above conditions are
+not met.
+
+DISCLAIMER
+THE FONT SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
+EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO ANY WARRANTIES OF
+MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT
+OF COPYRIGHT, PATENT, TRADEMARK, OR OTHER RIGHT. IN NO EVENT SHALL THE
+COPYRIGHT HOLDER BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY,
+INCLUDING ANY GENERAL, SPECIAL, INDIRECT, INCIDENTAL, OR CONSEQUENTIAL
+DAMAGES, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
+FROM, OUT OF THE USE OR INABILITY TO USE THE FONT SOFTWARE OR FROM
+OTHER DEALINGS IN THE FONT SOFTWARE.

src/theme/fonts/fonts.css

@@ -0,0 +1,100 @@
+/* Open Sans is licensed under the Apache License, Version 2.0. See http://www.apache.org/licenses/LICENSE-2.0 */
+/* Source Code Pro is under the Open Font License. See https://scripts.sil.org/cms/scripts/page.php?site_id=nrsi&id=OFL */
+
+/* open-sans-300 - latin_vietnamese_latin-ext_greek-ext_greek_cyrillic-ext_cyrillic */
+@font-face {
+  font-family: 'Open Sans';
+  font-style: normal;
+  font-weight: 300;
+  src: local('Open Sans Light'), local('OpenSans-Light'),
+       url('open-sans-v17-all-charsets-300.woff2') format('woff2');
+}
+
+/* open-sans-300italic - latin_vietnamese_latin-ext_greek-ext_greek_cyrillic-ext_cyrillic */
+@font-face {
+  font-family: 'Open Sans';
+  font-style: italic;
+  font-weight: 300;
+  src: local('Open Sans Light Italic'), local('OpenSans-LightItalic'),
+       url('open-sans-v17-all-charsets-300italic.woff2') format('woff2');
+}
+
+/* open-sans-regular - latin_vietnamese_latin-ext_greek-ext_greek_cyrillic-ext_cyrillic */
+@font-face {
+  font-family: 'Open Sans';
+  font-style: normal;
+  font-weight: 400;
+  src: local('Open Sans Regular'), local('OpenSans-Regular'),
+       url('open-sans-v17-all-charsets-regular.woff2') format('woff2');
+}
+
+/* open-sans-italic - latin_vietnamese_latin-ext_greek-ext_greek_cyrillic-ext_cyrillic */
+@font-face {
+  font-family: 'Open Sans';
+  font-style: italic;
+  font-weight: 400;
+  src: local('Open Sans Italic'), local('OpenSans-Italic'),
+       url('open-sans-v17-all-charsets-italic.woff2') format('woff2');
+}
+
+/* open-sans-600 - latin_vietnamese_latin-ext_greek-ext_greek_cyrillic-ext_cyrillic */
+@font-face {
+  font-family: 'Open Sans';
+  font-style: normal;
+  font-weight: 600;
+  src: local('Open Sans SemiBold'), local('OpenSans-SemiBold'),
+       url('open-sans-v17-all-charsets-600.woff2') format('woff2');
+}
+
+/* open-sans-600italic - latin_vietnamese_latin-ext_greek-ext_greek_cyrillic-ext_cyrillic */
+@font-face {
+  font-family: 'Open Sans';
+  font-style: italic;
+  font-weight: 600;
+  src: local('Open Sans SemiBold Italic'), local('OpenSans-SemiBoldItalic'),
+       url('open-sans-v17-all-charsets-600italic.woff2') format('woff2');
+}
+
+/* open-sans-700 - latin_vietnamese_latin-ext_greek-ext_greek_cyrillic-ext_cyrillic */
+@font-face {
+  font-family: 'Open Sans';
+  font-style: normal;
+  font-weight: 700;
+  src: local('Open Sans Bold'), local('OpenSans-Bold'),
+       url('open-sans-v17-all-charsets-700.woff2') format('woff2');
+}
+
+/* open-sans-700italic - latin_vietnamese_latin-ext_greek-ext_greek_cyrillic-ext_cyrillic */
+@font-face {
+  font-family: 'Open Sans';
+  font-style: italic;
+  font-weight: 700;
+  src: local('Open Sans Bold Italic'), local('OpenSans-BoldItalic'),
+       url('open-sans-v17-all-charsets-700italic.woff2') format('woff2');
+}
+
+/* open-sans-800 - latin_vietnamese_latin-ext_greek-ext_greek_cyrillic-ext_cyrillic */
+@font-face {
+  font-family: 'Open Sans';
+  font-style: normal;
+  font-weight: 800;
+  src: local('Open Sans ExtraBold'), local('OpenSans-ExtraBold'),
+       url('open-sans-v17-all-charsets-800.woff2') format('woff2');
+}
+
+/* open-sans-800italic - latin_vietnamese_latin-ext_greek-ext_greek_cyrillic-ext_cyrillic */
+@font-face {
+  font-family: 'Open Sans';
+  font-style: italic;
+  font-weight: 800;
+  src: local('Open Sans ExtraBold Italic'), local('OpenSans-ExtraBoldItalic'),
+       url('open-sans-v17-all-charsets-800italic.woff2') format('woff2');
+}
+
+/* source-code-pro-500 - latin_vietnamese_latin-ext_greek_cyrillic-ext_cyrillic */
+@font-face {
+  font-family: 'Source Code Pro';
+  font-style: normal;
+  font-weight: 500;
+  src: url('source-code-pro-v11-all-charsets-500.woff2') format('woff2');
+}

src/theme/fonts/mod.rs

@@ -0,0 +1,61 @@
+pub static CSS: &[u8] = include_bytes!("fonts.css");
+// An array of (file_name, file_contents) pairs
+pub static LICENSES: [(&str, &[u8]); 2] = [
+    (
+        "fonts/OPEN-SANS-LICENSE.txt",
+        include_bytes!("OPEN-SANS-LICENSE.txt"),
+    ),
+    (
+        "fonts/SOURCE-CODE-PRO-LICENSE.txt",
+        include_bytes!("SOURCE-CODE-PRO-LICENSE.txt"),
+    ),
+];
+// An array of (file_name, file_contents) pairs
+pub static OPEN_SANS: [(&str, &[u8]); 10] = [
+    (
+        "fonts/open-sans-v17-all-charsets-300.woff2",
+        include_bytes!("open-sans-v17-all-charsets-300.woff2"),
+    ),
+    (
+        "fonts/open-sans-v17-all-charsets-300italic.woff2",
+        include_bytes!("open-sans-v17-all-charsets-300italic.woff2"),
+    ),
+    (
+        "fonts/open-sans-v17-all-charsets-regular.woff2",
+        include_bytes!("open-sans-v17-all-charsets-regular.woff2"),
+    ),
+    (
+        "fonts/open-sans-v17-all-charsets-italic.woff2",
+        include_bytes!("open-sans-v17-all-charsets-italic.woff2"),
+    ),
+    (
+        "fonts/open-sans-v17-all-charsets-600.woff2",
+        include_bytes!("open-sans-v17-all-charsets-600.woff2"),
+    ),
+    (
+        "fonts/open-sans-v17-all-charsets-600italic.woff2",
+        include_bytes!("open-sans-v17-all-charsets-600italic.woff2"),
+    ),
+    (
+        "fonts/open-sans-v17-all-charsets-700.woff2",
+        include_bytes!("open-sans-v17-all-charsets-700.woff2"),
+    ),
+    (
+        "fonts/open-sans-v17-all-charsets-700italic.woff2",
+        include_bytes!("open-sans-v17-all-charsets-700italic.woff2"),
+    ),
+    (
+        "fonts/open-sans-v17-all-charsets-800.woff2",
+        include_bytes!("open-sans-v17-all-charsets-800.woff2"),
+    ),
+    (
+        "fonts/open-sans-v17-all-charsets-800italic.woff2",
+        include_bytes!("open-sans-v17-all-charsets-800italic.woff2"),
+    ),
+];
+
+// A (file_name, file_contents) pair
+pub static SOURCE_CODE_PRO: (&str, &[u8]) = (
+    "fonts/source-code-pro-v11-all-charsets-500.woff2",
+    include_bytes!("source-code-pro-v11-all-charsets-500.woff2"),
+);