Bump 0.4.5

Thanks to Kamil Vavra for responsibly disclosing the vulnerability
according to Rust's Security Policy.

.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 +31,9 @@ jobs:
             rust: stable
           - build: msrv
             os: ubuntu-latest
-            rust: 1.35.0
+            rust: 1.39.0
     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

.gitignore

@@ -4,10 +4,14 @@ target
 .DS_Store
 
 book-test
-book-example/book
+guide/book
 
 .vscode
 tests/dummy_book/book/
 
 # Ignore Jetbrains specific files.
 .idea/
+
+# Ignore Vim temporary and swap files.
+*.sw?
+*~

CHANGELOG.md

@@ -1,5 +1,222 @@
 # Changelog
 
+## 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)
 

Cargo.toml

@@ -1,6 +1,6 @@
 [package]
 name = "mdbook"
-version = "0.3.5"
+version = "0.4.5"
 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"
@@ -16,17 +16,16 @@ 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"
+env_logger = "0.7.1"
+handlebars = "3.0"
 lazy_static = "1.0"
 log = "0.4"
 memchr = "2.0"
 open = "1.1"
-pulldown-cmark = "0.6.1"
+pulldown-cmark = "0.7.0"
 regex = "1.0.0"
 serde = "1.0"
 serde_derive = "1.0"
@@ -34,32 +33,29 @@ serde_json = "1.0"
 shlex = "0.1"
 tempfile = "3.0"
 toml = "0.5.1"
-toml-query = "0.9"
 
 # 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 = "0.2.18", features = ["macros"], optional = true }
+warp = { version = "0.2.2", 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"
+select = "0.5"
 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

@@ -1,6 +1,6 @@
 # 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)
 
@@ -24,7 +24,7 @@ There are multiple ways to install mdBook.
 
 2. **From Crates.io**
 
-   This requires at least [Rust] 1.35 and Cargo to be installed. Once you have installed
+   This requires at least [Rust] 1.39 and Cargo to be installed. Once you have installed
    Rust, type the following in the terminal:
 
    ```
@@ -42,10 +42,14 @@ There are multiple ways to install mdBook.
 
    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:
+   we released a new version.
+
+   You can also disable default features to speed up compile time.
+
+   Example:
 
    ```
-   cargo install mdbook --vers "^0.1.0"
+   cargo install mdbook --no-default-features --features output --vers "^0.1.0"
    ```
 
 3. **From Git**
@@ -81,7 +85,7 @@ There are multiple ways to install mdBook.
 
 ## Usage
 
-mdBook will primarily be used as a command line tool, even though it exposes
+mdBook is primarily used as a command line tool, even though it exposes
 all its functionality as a Rust crate for integration in other projects.
 
 Here are the main commands you will want to run. For a more exhaustive
@@ -144,7 +148,7 @@ preprocessors are:
   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.
+  `{{# playground}}` and `{{# include}}` helpers in a chapter.
 
 Renderers are given the final book so they can do something with it. This is
 typically used for, as the name suggests, rendering the document in a particular
@@ -200,12 +204,12 @@ 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
+If you are just starting out with Rust, there are a series of issues that are
 tagged [E-Easy] and **we will gladly mentor you** so that you can successfully
 go through the process of fixing a bug or adding a new feature! Let us know if
 you need any help.
 
-For more info about contributing, check out our [contribution guide] who helps
+For more info about contributing, check out our [contribution guide] which helps
 you go through the build and contribution process!
 
 There is also a [rendered version][master-docs] of the latest API docs

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

@@ -87,7 +87,7 @@ 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 +4,14 @@ 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/"
 
-[output.html.playpen]
+[output.html.playground]
 editable = true
 line-numbers = true
 

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

@@ -1,8 +1,8 @@
 # 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).
+(as by the [CommonMark](https://commonmark.org/) specification) 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.

guide/src/SUMMARY.md

@@ -10,13 +10,14 @@
     - [clean](cli/clean.md)
 - [Format](format/README.md)
     - [SUMMARY.md](format/summary.md)
+        - [Draft chapter]()
     - [Configuration](format/config.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)
 - [Continuous Integration](continuous-integration.md)
 - [For Developers](for_developers/README.md)
     - [Preprocessors](for_developers/preprocessors.md)

guide/src/cli/build.md

@@ -35,5 +35,5 @@ 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/init.md

@@ -19,7 +19,7 @@ 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

guide/src/cli/serve.md

@@ -46,3 +46,14 @@ 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 `.gitignore` from book root directory is used. Global
+`$HOME/.gitignore` or `.gitignore` files in parent directories are not used._

guide/src/cli/watch.md

@@ -25,3 +25,15 @@ 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/for_developers/backends.md

@@ -329,6 +329,38 @@ generation or a warning).
 All environment variables are passed through to the backend, allowing you to use
 the usual `RUST_LOG` to control logging verbosity.
 
+## Handling missing backends
+
+If you enable a backend that isn't installed, the default behavior is to throw an error:
+
+```text
+The command `mdbook-wordcount` wasn't found, is the "wordcount" backend installed?
+If you want to ignore this error when the "wordcount" backend is not installed,
+set `optional = true` in the `[output.wordcount]` section of the book.toml configuration file.
+```
+
+This behavior can be changed by marking the backend as optional.
+
+```diff
+  [book]
+  title = "mdBook Documentation"
+  description = "Create book from markdown files. Like Gitbook but implemented in Rust"
+  authors = ["Mathieu David", "Michael-F-Bryan"]
+
+  [output.html]
+
+  [output.wordcount]
+  command = "python /path/to/wordcount.py"
++ optional = true
+```
+
+This demotes the error to a warning, and it will instead look like this:
+
+```text
+The command was not found, but was marked as optional.
+    Command: wordcount
+```
+
 
 ## Wrapping Up
 

guide/src/format/config.md

@@ -10,6 +10,9 @@ title = "Example book"
 author = "John Doe"
 description = "The example book covers examples."
 
+[rust]
+edition = "2018"
+
 [build]
 build-dir = "my-example-book"
 create-missing = false
@@ -54,6 +57,22 @@ src = "my-src"  # the source files will be found in `root/my-src` instead of `ro
 language = "en"
 ```
 
+### Rust options
+
+Options for the Rust language, relevant to running tests and playground
+integration.
+
+- **edition**: Rust edition to use by default for the code snippets. Default
+  is "2015". Individual code blocks can be controlled with the `edition2015`
+  or `edition2018` annotations, such as:
+
+  ~~~text
+  ```rust,edition2015
+  // This only works in 2015.
+  let try = true;
+  ```
+  ~~~
+
 ### Build options
 
 This controls the build process of your book.
@@ -81,7 +100,7 @@ This controls the build process of your book.
 
 The following preprocessors are available and included by default:
 
-- `links`: Expand the `{{ #playpen }}`, `{{ #include }}`, and `{{ #rustdoc_include }}` handlebars
+- `links`: Expand the `{{ #playground }}`, `{{ #include }}`, and `{{ #rustdoc_include }}` handlebars
   helpers in a chapter to include the contents of a file.
 - `index`: Convert all chapter files named `README.md` into `index.md`. That is
   to say, all `README.md` would be rendered to an index file `index.html` in the
@@ -153,11 +172,12 @@ The following configuration options are available:
 - **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`.
+  CSS media query. Defaults to `navy`.
 - **curly-quotes:** Convert straight quotes to curly quotes, except for those
   that occur in code blocks and code spans. Defaults to `false`.
 - **mathjax-support:** Adds support for [MathJax](mathjax.md). Defaults to
   `false`.
+- **copy-fonts:** Copies fonts.css and respective font files to the output directory and use them in the default theme. Defaults to `true`.
 - **google-analytics:** If you use Google Analytics, this option lets you enable
   it by simply specifying your ID in the configuration file.
 - **additional-css:** If you need to slightly change the appearance of your book
@@ -167,18 +187,44 @@ The following configuration options are available:
 - **additional-js:** If you need to add some behaviour to your book without
   removing the current behaviour, you can specify a set of JavaScript files that
   will be loaded alongside the default one.
+- **print:** A subtable for configuration print settings. mdBook by default adds
+  support for printing out the book as a single page. This is accessed using the
+  print icon on the top right of the book.
 - **no-section-label:** mdBook by defaults adds section label in table of
   contents column. For example, "1.", "2.1". Set this option to true to disable
   those labels. Defaults to `false`.
 - **fold:** A subtable for configuring sidebar section-folding behavior.
-- **playpen:** A subtable for configuring various playpen settings.
+- **playground:** A subtable for configuring various playground settings.
 - **search:** A subtable for configuring the in-browser search functionality.
   mdBook must be compiled with the `search` feature enabled (on by default).
 - **git-repository-url:**  A url to the git repository for the book. If provided
   an icon link will be output in the menu bar of the book.
 - **git-repository-icon:** The FontAwesome icon class to use for the git
   repository link. Defaults to `fa-github`.
-  
+- **redirect:** A subtable used for generating redirects when a page is moved.
+  The table contains key-value pairs where the key is where the redirect file
+  needs to be created, as an absolute path from the build directory, (e.g.
+  `/appendices/bibliography.html`). The value can be any valid URI the
+  browser should navigate to (e.g. `https://rust-lang.org/`,
+  `/overview.html`, or `../bibliography.html`).
+- **input-404:** The name of the markdown file used for misssing files.
+  The corresponding output file will be the same, with the extension replaced with `html`.
+  Defaults to `404.md`.
+- **site-url:** The url where the book will be hosted. This is required to ensure
+  navigation links and script/css imports in the 404 file work correctly, even when accessing
+  urls in subdirectories. Defaults to `/`.
+- **cname:** The DNS subdomain or apex domain at which your book will be hosted.
+  This string will be written to a file named CNAME in the root of your site, as
+  required by GitHub Pages (see [*Managing a custom domain for your GitHub Pages
+  site*][custom domain]).
+
+[custom domain]: https://docs.github.com/en/github/working-with-github-pages/managing-a-custom-domain-for-your-github-pages-site
+
+Available configuration options for the `[output.html.print]` table:
+
+- **enable:** Enable print support. When `false`, all print support will not be
+  rendered. Defaults to `true`.
+
 Available configuration options for the `[output.html.fold]` table:
 
 - **enable:** Enable section-folding. When off, all folds are open.
@@ -186,7 +232,7 @@ Available configuration options for the `[output.html.fold]` table:
 - **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:
+Available configuration options for the `[output.html.playground]` table:
 
 - **editable:** Allow editing the source code. Defaults to `false`.
 - **copyable:** Display the copy button on code snippets. Defaults to `true`.
@@ -233,18 +279,25 @@ default-theme = "light"
 preferred-dark-theme = "navy"
 curly-quotes = true
 mathjax-support = false
-google-analytics = "123456"
+copy-fonts = true
+google-analytics = "UA-123456-7"
 additional-css = ["custom.css", "custom2.css"]
 additional-js = ["custom.js"]
 no-section-label = false
 git-repository-url = "https://github.com/rust-lang/mdBook"
 git-repository-icon = "fa-github"
+site-url = "/example-book/"
+cname = "myproject.rs"
+input-404 = "not-found.md"
+
+[output.html.print]
+enable = true
 
 [output.html.fold]
 enable = false
 level = 0
 
-[output.html.playpen]
+[output.html.playground]
 editable = false
 copy-js = true
 line-numbers = false
@@ -260,6 +313,10 @@ boost-paragraph = 1
 expand = true
 heading-split-level = 3
 copy-js = true
+
+[output.html.redirect]
+"/appendices/bibliography.html" = "https://rustc-dev-guide.rust-lang.org/appendix/bibliography.html"
+"/other-installation-methods.html" = "../infra/other-installation-methods.html"
 ```
 
 ### Markdown Renderer
@@ -270,7 +327,7 @@ 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:
+Enable it by adding an empty table to your `book.toml` as follows:
 
 ```toml
 [output.markdown]
@@ -287,11 +344,17 @@ specify which preprocessors should run before the Markdown renderer.
 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.
+rendering. See the [alternative backends] chapter for more detail.
 
-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.
+The custom renderer has access to all the fields within its table (i.e.
+anything under `[output.foo]`). mdBook checks for two common fields:
+
+- **command:** The command to execute for this custom renderer. Defaults to
+  the name of the renderer with the `mdbook-` prefix (such as `mdbook-foo`).
+- **optional:** If `true`, then the command will be ignored if it is not
+  installed, otherwise mdBook will fail with an error. Defaults to `false`.
+
+[alternative backends]: ../for_developers/backends.md
 
 ## Environment Variables
 

guide/src/format/mdbook.md

@@ -1,9 +1,9 @@
-# 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].
 
 [rustdoc-hide]: https://doc.rust-lang.org/stable/rustdoc/documentation-tests.html#hiding-portions-of-the-example
 
@@ -37,7 +37,7 @@ 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.
@@ -92,17 +92,17 @@ 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}}
 ```
 ````
@@ -178,17 +178,17 @@ 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/
+[Rust Playground]: https://play.rust-lang.org/

guide/src/format/summary.md

@@ -7,7 +7,7 @@ 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
+#### Structure
 
 1. ***Title*** It's common practice to begin with a title, generally <code
    class="language-markdown"># Summary</code>. But it is not mandatory, the
@@ -22,17 +22,45 @@ allow for easy parsing. Let's see how you should format your `SUMMARY.md` file.
    [Title of prefix element](relative/path/to/markdown.md)
    ```
 
-3. ***Numbered Chapter*** Numbered chapters are the main content of the book,
+3. ***Part Title:*** Headers can be used as a title for the following numbered
+   chapters. This can be used to logically separate different sections
+   of book. The title is rendered as unclickable text.
+   Titles are optional, and the numbered chapters can be broken into as many
+   parts as desired.
+
+4. ***Numbered Chapter*** Numbered chapters are the main content of the book,
    they will be numbered and can be nested, resulting in a nice hierarchy
    (chapters, sub-chapters, etc.)
    ```markdown
+   # Title of Part
+
    - [Title of the Chapter](relative/path/to/markdown.md)
+
+   # Title of Another Part
+
+   - [More Chapters](relative/path/to/markdown2.md)
    ```
    You can either use `-` or `*` to indicate a numbered chapter.
 
-4. ***Suffix Chapter*** After the numbered chapters you can add a couple of
+5. ***Suffix Chapter*** After the numbered chapters you can add a couple of
    non-numbered chapters. They are the same as prefix chapters but come after
    the numbered chapters instead of before.
 
 All other elements are unsupported and will be ignored at best or result in an
 error.
+
+#### Other elements
+
+- ***Separators*** In between chapters you can add a separator. In the HTML renderer
+  this will result in a line being rendered in the table of contents. A separator is
+  a line containing exclusively dashes and at least three of them: `---`.
+- ***Draft chapters*** Draft chapters are chapters without a file and thus content.
+  The purpose of a draft chapter is to signal future chapters still to be written.
+  Or when still laying out the structure of the book to avoid creating the files
+  while you are still changing the structure of the book a lot.
+  Draft chapters will be rendered in the HTML renderer as disabled links in the table
+  of contents, as you can see for the next chapter in the table of contents on the left.
+  Draft chapters are written like normal chapters but without writing the path to the file
+  ```markdown
+  - [Draft chapter]()
+  ```

guide/src/format/theme/README.md

@@ -11,16 +11,19 @@ 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
+- **_index.hbs_** is the handlebars template.
+- **_head.hbs_** is appended to the HTML `<head>` section.
+- **_header.hbs_** content is appended on top of every book page.
+- **_book.css_** is the style used in the output. If you want to change the
   design of your book, this is probably the file you want to modify. Sometimes
   in conjunction with `index.hbs` when you want to radically change the layout.
-- ***book.js*** is mostly used to add client side functionality, like hiding /
+- **_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
+- **_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
@@ -32,3 +35,10 @@ 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.
+
+If you completely replace all built-in themes, be sure to also set
+[`output.html.preferred-dark-theme`] in the config, which defaults to the
+built-in `navy` theme.
+
+[`output.html.preferred-dark-theme`]: ../config.md#html-renderer-options
+[newer browsers]: https://caniuse.com/#feat=link-icon-svg

guide/src/format/theme/editor.md

@@ -1,11 +1,11 @@
 # 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
 ```
 
@@ -19,7 +19,7 @@ fn main() {
 }
 ```</code></pre>
 
-The above will result in this editable playpen:
+The above will result in this editable playground:
 
 ```rust,editable
 fn main() {
@@ -28,7 +28,7 @@ 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
 
@@ -36,7 +36,7 @@ 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:
 
 ```toml
-[output.html.playpen]
+[output.html.playground]
 editable = true
 editor = "/path/to/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 `{{ book_title }} - {{ chapter_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

src/book/book.rs

@@ -15,13 +15,13 @@ pub fn load_book<P: AsRef<Path>>(src_dir: P, cfg: &BuildConfig) -> Result<Book>
 
     let mut summary_content = String::new();
     File::open(summary_md)
-        .chain_err(|| "Couldn't open SUMMARY.md")?
+        .with_context(|| "Couldn't open SUMMARY.md")?
         .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(|| "Summary parsing failed")?;
 
     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 +39,19 @@ 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)?;
+                    writeln!(f, "# {}", link.name)?;
+                }
             }
 
             items.extend(&link.nested_items);
@@ -131,6 +133,8 @@ pub enum BookItem {
     Chapter(Chapter),
     /// A section separator.
     Separator,
+    /// A part title.
+    PartTitle(String),
 }
 
 impl From<Chapter> for BookItem {
@@ -152,7 +156,7 @@ pub struct Chapter {
     /// Nested items.
     pub sub_items: Vec<BookItem>,
     /// The chapter's location, relative to the `SUMMARY.md` file.
-    pub path: PathBuf,
+    pub path: Option<PathBuf>,
     /// An ordered list of the names of each chapter above this one, in the hierarchy.
     pub parent_names: Vec<String>,
 }
@@ -168,11 +172,31 @@ impl Chapter {
         Chapter {
             name: name.to_string(),
             content,
-            path: path.into(),
+            path: Some(path.into()),
             parent_names,
             ..Default::default()
         }
     }
+
+    /// Create a new draft chapter that is not attached to a source markdown file and has
+    /// thus no content.
+    pub fn new_draft(name: &str, parent_names: Vec<String>) -> Self {
+        Chapter {
+            name: name.to_string(),
+            content: String::new(),
+            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 {
+        match self.path {
+            Some(_) => false,
+            None => true,
+        }
+    }
 }
 
 /// Use the provided `Summary` to load a `Book` from disk.
@@ -202,16 +226,17 @@ 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 +245,36 @@ 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())
+        })?;
+
+        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 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());
@@ -376,7 +409,7 @@ 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")),
             parent_names: vec![String::from("Chapter 1")],
             sub_items: Vec::new(),
         };
@@ -384,7 +417,7 @@ 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")),
             parent_names: Vec::new(),
             sub_items: vec![
                 BookItem::Chapter(nested.clone()),
@@ -408,7 +441,7 @@ 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")),
                 ..Default::default()
             })],
             ..Default::default()
@@ -448,7 +481,7 @@ 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")),
                     parent_names: Vec::new(),
                     sub_items: vec![
                         BookItem::Chapter(Chapter::new(
@@ -500,7 +533,7 @@ 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")),
                     parent_names: Vec::new(),
                     sub_items: vec![
                         BookItem::Chapter(Chapter::new(
@@ -537,9 +570,10 @@ 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 +590,7 @@ 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

@@ -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()?;
@@ -97,22 +97,21 @@ 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)
+        let html_config = self.config.html_config().unwrap_or_default();
+        let themedir = html_config
+            .theme
             .unwrap_or_else(|| self.config.book.src.join("theme"));
         let themedir = self.root.join(themedir);
 
@@ -136,14 +135,19 @@ 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 +178,14 @@ 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;
@@ -27,7 +28,7 @@ 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 {
@@ -126,13 +127,12 @@ impl MDBook {
     /// ```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 +143,6 @@ impl MDBook {
     /// // 2. Chapter 2
     /// //
     /// // etc.
-    /// # }
     /// ```
     pub fn iter(&self) -> BookItems<'_> {
         self.book.iter()
@@ -182,7 +181,7 @@ impl MDBook {
     }
 
     /// Run the entire build process for a particular `Renderer`.
-    fn execute_build_process(&self, renderer: &dyn Renderer) -> Result<()> {
+    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(),
@@ -216,7 +215,7 @@ impl MDBook {
 
         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.
@@ -251,32 +250,52 @@ 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"]);
+                        }
                     }
                 }
+
+                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(())
     }
 
@@ -395,7 +414,7 @@ fn interpret_custom_preprocessor(key: &str, table: &Value) -> Box<CmdPreprocesso
         .map(ToString::to_string)
         .unwrap_or_else(|| format!("mdbook-{}", key));
 
-    Box::new(CmdPreprocessor::new(key.to_string(), command.to_string()))
+    Box::new(CmdPreprocessor::new(key.to_string(), command))
 }
 
 fn interpret_custom_renderer(key: &str, table: &Value) -> Box<CmdRenderer> {
@@ -408,7 +427,7 @@ 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

src/book/summary.rs

@@ -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
@@ -155,6 +163,10 @@ struct SummaryParser<'a> {
     src: &'a str,
     stream: pulldown_cmark::OffsetIter<'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
@@ -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(1))) => {
                     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(1))) => {
+                    debug!("Found a h1 in the SUMMARY");
+
+                    let tags = collect_events!(self.stream, end Tag::Heading(1));
+                    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(1))) => {
+                    // 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 +515,24 @@ 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");
+        match self.next_event() {
+            Some(Event::Start(Tag::Heading(1))) => {
+                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(1));
+                Some(stringify_events(tags))
+            }
+            _ => None,
         }
     }
 }
@@ -471,10 +558,9 @@ 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 +570,7 @@ 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()
@@ -585,17 +672,16 @@ 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 +692,6 @@ 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 +703,6 @@ 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 +713,19 @@ 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 +734,16 @@ 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 +755,92 @@ 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 +855,41 @@ 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
@@ -745,30 +901,75 @@ 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(&mut 0, &mut SectionNumber::default())
+            .unwrap();
 
-        let got = parser.parse_numbered().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);
     }

src/cmd/clean.rs

@@ -1,6 +1,6 @@
 use crate::get_book_dir;
+use anyhow::Context;
 use clap::{App, ArgMatches, SubCommand};
-use mdbook::errors::*;
 use mdbook::MDBook;
 use std::fs;
 
@@ -31,7 +31,8 @@ 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/serve.rs

@@ -2,12 +2,20 @@
 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 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> {
@@ -40,64 +48,53 @@ pub fn make_subcommand<'a, 'b>() -> App<'a, 'b> {
                 .empty_values(false)
                 .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'")
 }
 
-// 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 livereload_url = format!("ws://{}/{}", address, LIVE_RELOAD_ENDPOINT);
+    let update_config = |book: &mut MDBook| {
+        book.config
+            .set("output.html.livereload-url", &livereload_url)
+            .expect("livereload-url update failed");
+        if let Some(dest_dir) = args.value_of("dest-dir") {
+            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 +110,56 @@ 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);
+    warp::serve(routes).run(address).await;
 }

src/cmd/watch.rs

@@ -28,7 +28,14 @@ pub fn make_subcommand<'a, 'b>() -> App<'a, 'b> {
 // 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 +44,10 @@ 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");

src/config.rs

@@ -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;
             }
@@ -280,6 +289,7 @@ impl Default for Config {
         Config {
             book: BookConfig::default(),
             build: BuildConfig::default(),
+            rust: RustConfig::default(),
             rest: Value::Table(Table::default()),
         }
     }
@@ -320,9 +330,15 @@ impl<'de> Deserialize<'de> for Config {
             .and_then(|value| value.try_into().ok())
             .unwrap_or_default();
 
+        let rust: RustConfig = table
+            .remove("rust")
+            .and_then(|value| value.try_into().ok())
+            .unwrap_or_default();
+
         Ok(Config {
             book,
             build,
+            rust,
             rest: Value::Table(table),
         })
     }
@@ -330,18 +346,17 @@ 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.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 +383,7 @@ 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 +429,7 @@ 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 +447,27 @@ 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 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 +475,14 @@ 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 +492,11 @@ 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.
@@ -467,6 +506,17 @@ 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>,
+    /// 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>,
     /// 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
@@ -475,6 +525,37 @@ pub struct HtmlConfig {
     /// This config item *should not be edited* by the end user.
     #[doc(hidden)]
     pub livereload_url: 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,
+            input_404: None,
+            site_url: None,
+            cname: None,
+            livereload_url: None,
+            redirect: HashMap::new(),
+        }
+    }
 }
 
 impl HtmlConfig {
@@ -488,6 +569,20 @@ impl HtmlConfig {
     }
 }
 
+/// Configuration for how to render the print icon, print.html, and print.css.
+#[derive(Debug, Clone, PartialEq, Serialize, Deserialize)]
+#[serde(rename_all = "kebab-case")]
+pub struct Print {
+    /// Whether print support is enabled.
+    pub enable: bool,
+}
+
+impl Default for Print {
+    fn default() -> Self {
+        Self { enable: true }
+    }
+}
+
 /// Configuration for how to fold chapters of sidebar.
 #[derive(Default, Debug, Clone, PartialEq, Serialize, Deserialize)]
 #[serde(default, rename_all = "kebab-case")]
@@ -500,24 +595,24 @@ 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,
 }
 
-impl Default for Playpen {
-    fn default() -> Playpen {
-        Playpen {
+impl Default for Playground {
+    fn default() -> Playground {
+        Playground {
             editable: false,
             copyable: true,
             copy_js: true,
@@ -603,6 +698,7 @@ 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 +723,14 @@ 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]
@@ -653,7 +753,8 @@ 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,
@@ -665,9 +766,18 @@ 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 +785,62 @@ 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 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 load_arbitrary_output_type() {
         #[derive(Debug, Deserialize, PartialEq)]
@@ -720,7 +883,7 @@ 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 +1033,31 @@ 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");
+    }
 }

src/lib.rs

@@ -82,9 +82,8 @@
 
 #![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/preprocess/cmd.rs

@@ -43,7 +43,7 @@ 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) {
@@ -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()
@@ -111,7 +111,7 @@ impl Preprocessor for CmdPreprocessor {
 
         let output = child
             .wait_with_output()
-            .chain_err(|| "Error waiting for the preprocessor to complete")?;
+            .with_context(|| "Error waiting for the preprocessor to complete")?;
 
         trace!("{} exited with output: {:?}", self.cmd, output);
         ensure!(
@@ -119,7 +119,8 @@ impl Preprocessor for CmdPreprocessor {
             "The preprocessor exited unsuccessfully"
         );
 
-        serde_json::from_slice(&output.stdout).chain_err(|| "Unable to parse the preprocessed book")
+        serde_json::from_slice(&output.stdout)
+            .with_context(|| "Unable to parse the preprocessed book")
     }
 
     fn supports_renderer(&self, renderer: &str) -> bool {
@@ -170,15 +171,15 @@ 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 +22,7 @@ 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
 #[derive(Default)]
 pub struct LinkPreprocessor;
 
@@ -45,14 +45,15 @@ 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 content = replace_all(&ch.content, base, chapter_path, 0);
+                    ch.content = content;
+                }
             }
         });
 
@@ -94,7 +95,7 @@ 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);
                 }
 
@@ -113,7 +114,7 @@ where
 enum LinkType<'a> {
     Escaped,
     Include(PathBuf, RangeOrAnchor),
-    Playpen(PathBuf, Vec<&'a str>),
+    Playground(PathBuf, Vec<&'a str>),
     RustdocInclude(PathBuf, RangeOrAnchor),
 }
 
@@ -182,7 +183,7 @@ 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)),
         }
     }
@@ -261,7 +262,15 @@ 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,
                 }
@@ -295,7 +304,7 @@ 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 +324,7 @@ 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 +332,10 @@ 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 contents = fs::read_to_string(&target).with_context(|| {
                     format!(
                         "Could not read file for link {} ({})",
                         self.link_text,
@@ -364,14 +373,14 @@ fn find_links(contents: &str) -> LinkIter<'_> {
     // r"\\\{\{#.*\}\}|\{\{#([a-zA-Z0-9]+)\s*([a-zA-Z0-9_.\-:/\\\s]+)\}\}")?;
     lazy_static! {
         static ref RE: Regex = Regex::new(
-            r"(?x)                     # insignificant whitespace mode
-            \\\{\{\#.*\}\}             # match escaped link
-            |                          # or
-            \{\{\s*                    # link opening parens and whitespace
-            \#([a-zA-Z0-9_]+)          # link type
-            \s+                        # separating whitespace
-            ([a-zA-Z0-9\s_.\-:/\\]+)   # link target path and space separated properties
-            \s*\}\}                    # whitespace and link closing parens"
+            r"(?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"
         )
         .unwrap();
     }
@@ -405,7 +414,7 @@ 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 +424,19 @@ 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 +446,38 @@ 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 +613,7 @@ 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 +621,19 @@ 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 +641,19 @@ 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 +661,9 @@ 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 +672,8 @@ 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 +684,8 @@ 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 +693,13 @@ 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/renderer/html_handlebars/hbs_renderer.rs

@@ -1,17 +1,18 @@
 use crate::book::{Book, BookItem};
-use crate::config::{Config, HtmlConfig, Playpen};
+use crate::config::{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 +31,144 @@ 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");
+        let content = ch.content.clone();
+        let content = utils::render_markdown(&content, ctx.html_config.curly_quotes);
 
-            // "print.html" is used for the print page.
-            if ch.path == Path::new("print.md") {
-                bail!(ErrorKind::ReservedFilenameError(ch.path.clone()));
-            };
+        let fixed_content = utils::render_markdown_with_path(
+            &ch.content,
+            ctx.html_config.curly_quotes,
+            Some(&path),
+        );
+        print_content.push_str(&fixed_content);
 
-            // 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;
-            }
+        // 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");
 
-            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()));
-            }
+        // "print.html" is used for the print page.
+        if path == Path::new("print.md") {
+            bail!("{} is reserved for internal use", path.display());
+        };
 
-            // Render the handlebars template with the data
-            debug!("Render template");
-            let rendered = ctx.handlebars.render("index", &ctx.data)?;
+        let book_title = ctx
+            .data
+            .get("book_title")
+            .and_then(serde_json::Value::as_str)
+            .unwrap_or("");
 
-            let rendered = self.post_process(rendered, &ctx.html_config.playpen);
+        let title = match book_title {
+            "" => ch.name.clone(),
+            _ => ch.name.clone() + " - " + book_title,
+        };
 
-            // Write to file
-            debug!("Creating {}", filepath.display());
-            utils::fs::write_file(&ctx.destination, &filepath, rendered.as_bytes())?;
+        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()));
+        }
 
-            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())?;
-            }
+        // 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: &PathBuf,
+        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 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 +184,26 @@ 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 +244,38 @@ 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 +300,7 @@ 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 +329,7 @@ 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 +337,7 @@ 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 +348,68 @@ 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
@@ -287,10 +441,11 @@ impl Renderer for HtmlHandlebars {
         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");
@@ -316,19 +471,26 @@ 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() {
@@ -338,11 +500,17 @@ impl Renderer for HtmlHandlebars {
                 data: data.clone(),
                 is_index,
                 html_config: html_config.clone(),
+                edition: ctx.config.rust.edition,
             };
             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 {
@@ -350,19 +518,22 @@ 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")?;
+            .with_context(|| "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")?;
+            .with_context(|| "Unable to copy across additional CSS and JS")?;
 
         // Render search index
         #[cfg(feature = "search")]
@@ -373,8 +544,11 @@ impl Renderer for HtmlHandlebars {
             }
         }
 
-        // 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 +559,7 @@ fn make_data(
     book: &Book,
     config: &Config,
     html_config: &HtmlConfig,
+    theme: &Theme,
 ) -> Result<serde_json::Map<String, serde_json::Value>> {
     trace!("make_data");
 
@@ -401,7 +576,12 @@ fn make_data(
         "description".to_owned(),
         json!(config.book.description.clone().unwrap_or_default()),
     );
-    data.insert("favicon".to_owned(), json!("favicon.png"));
+    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 livereload) = html_config.livereload_url {
         data.insert("livereload".to_owned(), json!(livereload));
     }
@@ -414,7 +594,7 @@ 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 +610,10 @@ 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 +638,19 @@ 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 +685,9 @@ 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 +699,12 @@ 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_"));
@@ -600,7 +789,11 @@ 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 +802,31 @@ 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"))
                     || classes.contains("mdbook-runnable")
                 {
+                    let contains_e2015 = classes.contains("edition2015");
+                    let contains_e2018 = classes.contains("edition2018");
+                    let edition_class = if contains_e2015 || contains_e2018 {
+                        // the user forced edition, we should not overwrite it
+                        ""
+                    } else {
+                        match edition {
+                            Some(RustEdition::E2015) => " edition2015",
+                            Some(RustEdition::E2018) => " edition2018",
+                            None => "",
+                        }
+                    };
+
                     // wrap the contents in an external pre block
                     format!(
-                        "<pre class=\"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 +837,7 @@ 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()
@@ -701,11 +910,12 @@ 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,
     html_config: HtmlConfig,
+    edition: Option<RustEdition>,
 }
 
 #[cfg(test)]
@@ -748,30 +958,79 @@ mod tests {
     }
 
     #[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);
         }

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),
@@ -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

@@ -16,9 +16,9 @@ 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 +32,7 @@ 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 +46,13 @@ 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 +71,15 @@ 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 +99,41 @@ 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\">")?;
+                out.write(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
             };
 
@@ -164,6 +165,8 @@ impl HelperDef for RenderToc {
 
             if path_exists {
                 out.write("</a>")?;
+            } else {
+                out.write("</div>")?;
             }
 
             // Render expand/collapse toggle
@@ -191,7 +194,7 @@ 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 ");
     }

src/renderer/html_handlebars/search.rs

@@ -71,14 +71,18 @@ 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();

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

@@ -19,13 +19,14 @@ mod markdown_renderer;
 
 use shlex::Shlex;
 use std::fs;
-use std::io::{self, Read};
+use std::io::{self, ErrorKind, Read};
 use std::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.
 ///
@@ -93,7 +94,7 @@ 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`")
     }
 }
 
@@ -149,6 +150,40 @@ 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
@@ -168,34 +203,22 @@ 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;
@@ -106,7 +106,7 @@ 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";
@@ -143,6 +143,11 @@ 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
@@ -154,16 +159,12 @@ function playpen_text(playpen) {
             .from(document.querySelectorAll('code:not(.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 +175,23 @@ 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 +200,10 @@ 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 +222,8 @@ 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 +243,7 @@ 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 +285,7 @@ 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 +294,16 @@ 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 +335,7 @@ 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 +346,7 @@ 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);
 
@@ -408,7 +415,6 @@ 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 +456,11 @@ 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 +481,16 @@ 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 +525,10 @@ 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 +572,8 @@ 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 +601,60 @@ 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;
@@ -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

@@ -25,11 +25,16 @@ 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; }
@@ -60,6 +65,7 @@ h4 a.header:target {
 .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;
@@ -78,6 +84,9 @@ 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%; }
@@ -157,3 +166,9 @@ blockquote {
 .tooltipped .tooltiptext {
     visibility: visible;
 }
+
+.chapter li.part-title {
+    color: var(--sidebar-fg);
+    margin: 5px 0px;
+    font-weight: bold;
+}

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.
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+      "License" shall mean the terms and conditions for use, reproduction,
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+
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+   See the License for the specific language governing permissions and
+   limitations under the License.

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"),
+);

src/theme/head.hbs

@@ -0,0 +1 @@
+{{!-- Put your head HTML text here --}}

src/theme/index.hbs

@@ -7,22 +7,37 @@
         {{#if is_print }}
         <meta name="robots" content="noindex" />
         {{/if}}
+        {{#if base_url}}
+        <base href="{{ base_url }}">
+        {{/if}}
+
+
+        <!-- Custom HTML head -->
+        {{> head}}
 
         <meta content="text/html; charset=utf-8" http-equiv="Content-Type">
         <meta name="description" content="{{ description }}">
         <meta name="viewport" content="width=device-width, initial-scale=1">
         <meta name="theme-color" content="#ffffff" />
 
-        <link rel="shortcut icon" href="{{ path_to_root }}{{ favicon }}">
+        {{#if favicon_svg}}
+        <link rel="icon" href="{{ path_to_root }}favicon.svg">
+        {{/if}}
+        {{#if favicon_png}}
+        <link rel="shortcut icon" href="{{ path_to_root }}favicon.png">
+        {{/if}}
         <link rel="stylesheet" href="{{ path_to_root }}css/variables.css">
         <link rel="stylesheet" href="{{ path_to_root }}css/general.css">
         <link rel="stylesheet" href="{{ path_to_root }}css/chrome.css">
+        {{#if print_enable}}
         <link rel="stylesheet" href="{{ path_to_root }}css/print.css" media="print">
+        {{/if}}
 
         <!-- Fonts -->
         <link rel="stylesheet" href="{{ path_to_root }}FontAwesome/css/font-awesome.css">
-        <link href="https://fonts.googleapis.com/css?family=Open+Sans:300italic,400italic,600italic,700italic,800italic,400,300,600,700,800" rel="stylesheet" type="text/css">
-        <link href="https://fonts.googleapis.com/css?family=Source+Code+Pro:500" rel="stylesheet" type="text/css">
+        {{#if copy_fonts}}
+        <link rel="stylesheet" href="{{ path_to_root }}fonts/fonts.css">
+        {{/if}}
 
         <!-- Highlight.js Stylesheets -->
         <link rel="stylesheet" href="{{ path_to_root }}highlight.css">
@@ -87,7 +102,7 @@
         </script>
 
         <nav id="sidebar" class="sidebar" aria-label="Table of contents">
-            <div id="sidebar-scrollbox" class="sidebar-scrollbox">
+            <div class="sidebar-scrollbox">
                 {{#toc}}{{/toc}}
             </div>
             <div id="sidebar-resize-handle" class="sidebar-resize-handle"></div>
@@ -97,41 +112,42 @@
 
             <div class="page">
                 {{> header}}
-                <div id="menu-bar" class="menu-bar">
-                    <div id="menu-bar-sticky-container">
-                        <div class="left-buttons">
-                            <button id="sidebar-toggle" class="icon-button" type="button" title="Toggle Table of Contents" aria-label="Toggle Table of Contents" aria-controls="sidebar">
-                                <i class="fa fa-bars"></i>
-                            </button>
-                            <button id="theme-toggle" class="icon-button" type="button" title="Change theme" aria-label="Change theme" aria-haspopup="true" aria-expanded="false" aria-controls="theme-list">
-                                <i class="fa fa-paint-brush"></i>
-                            </button>
-                            <ul id="theme-list" class="theme-popup" aria-label="Themes" role="menu">
-                                <li role="none"><button role="menuitem" class="theme" id="light">{{ theme_option "Light" }}</button></li>
-                                <li role="none"><button role="menuitem" class="theme" id="rust">{{ theme_option "Rust" }}</button></li>
-                                <li role="none"><button role="menuitem" class="theme" id="coal">{{ theme_option "Coal" }}</button></li>
-                                <li role="none"><button role="menuitem" class="theme" id="navy">{{ theme_option "Navy" }}</button></li>
-                                <li role="none"><button role="menuitem" class="theme" id="ayu">{{ theme_option "Ayu" }}</button></li>
-                            </ul>
-                            {{#if search_enabled}}
-                            <button id="search-toggle" class="icon-button" type="button" title="Search. (Shortkey: s)" aria-label="Toggle Searchbar" aria-expanded="false" aria-keyshortcuts="S" aria-controls="searchbar">
-                                <i class="fa fa-search"></i>
-                            </button>
-                            {{/if}}
-                        </div>
+                <div id="menu-bar-hover-placeholder"></div>
+                <div id="menu-bar" class="menu-bar sticky bordered">
+                    <div class="left-buttons">
+                        <button id="sidebar-toggle" class="icon-button" type="button" title="Toggle Table of Contents" aria-label="Toggle Table of Contents" aria-controls="sidebar">
+                            <i class="fa fa-bars"></i>
+                        </button>
+                        <button id="theme-toggle" class="icon-button" type="button" title="Change theme" aria-label="Change theme" aria-haspopup="true" aria-expanded="false" aria-controls="theme-list">
+                            <i class="fa fa-paint-brush"></i>
+                        </button>
+                        <ul id="theme-list" class="theme-popup" aria-label="Themes" role="menu">
+                            <li role="none"><button role="menuitem" class="theme" id="light">{{ theme_option "Light" }}</button></li>
+                            <li role="none"><button role="menuitem" class="theme" id="rust">{{ theme_option "Rust" }}</button></li>
+                            <li role="none"><button role="menuitem" class="theme" id="coal">{{ theme_option "Coal" }}</button></li>
+                            <li role="none"><button role="menuitem" class="theme" id="navy">{{ theme_option "Navy" }}</button></li>
+                            <li role="none"><button role="menuitem" class="theme" id="ayu">{{ theme_option "Ayu" }}</button></li>
+                        </ul>
+                        {{#if search_enabled}}
+                        <button id="search-toggle" class="icon-button" type="button" title="Search. (Shortkey: s)" aria-label="Toggle Searchbar" aria-expanded="false" aria-keyshortcuts="S" aria-controls="searchbar">
+                            <i class="fa fa-search"></i>
+                        </button>
+                        {{/if}}
+                    </div>
 
-                        <h1 class="menu-title">{{ book_title }}</h1>
+                    <h1 class="menu-title">{{ book_title }}</h1>
 
-                        <div class="right-buttons">
-                            <a href="{{ path_to_root }}print.html" title="Print this book" aria-label="Print this book">
-                                <i id="print-button" class="fa fa-print"></i>
-                            </a>
-                            {{#if git_repository_url}}
-                            <a href="{{git_repository_url}}" title="Git repository" aria-label="Git repository">
-                                <i id="git-repository-button" class="fa {{git_repository_icon}}"></i>
-                            </a>
-                            {{/if}}
-                        </div>
+                    <div class="right-buttons">
+                        {{#if print_enable}}
+                        <a href="{{ path_to_root }}print.html" title="Print this book" aria-label="Print this book">
+                            <i id="print-button" class="fa fa-print"></i>
+                        </a>
+                        {{/if}}
+                        {{#if git_repository_url}}
+                        <a href="{{git_repository_url}}" title="Git repository" aria-label="Git repository">
+                            <i id="git-repository-button" class="fa {{git_repository_icon}}"></i>
+                        </a>
+                        {{/if}}
                     </div>
                 </div>
 
@@ -183,13 +199,13 @@
 
             <nav class="nav-wide-wrapper" aria-label="Page navigation">
                 {{#previous}}
-                    <a href="{{ path_to_root }}{{link}}" class="nav-chapters previous" title="Previous chapter" aria-label="Previous chapter" aria-keyshortcuts="Left">
+                    <a rel="prev" href="{{ path_to_root }}{{link}}" class="nav-chapters previous" title="Previous chapter" aria-label="Previous chapter" aria-keyshortcuts="Left">
                         <i class="fa fa-angle-left"></i>
                     </a>
                 {{/previous}}
 
                 {{#next}}
-                    <a href="{{ path_to_root }}{{link}}" class="nav-chapters next" title="Next chapter" aria-label="Next chapter" aria-keyshortcuts="Right">
+                    <a rel="next" href="{{ path_to_root }}{{link}}" class="nav-chapters next" title="Next chapter" aria-label="Next chapter" aria-keyshortcuts="Right">
                         <i class="fa fa-angle-right"></i>
                     </a>
                 {{/next}}
@@ -204,7 +220,7 @@
             socket.onmessage = function (event) {
                 if (event.data === "reload") {
                     socket.close();
-                    location.reload(true); // force reload from server (not from cache)
+                    location.reload();
                 }
             };
 
@@ -233,19 +249,19 @@
         </script>
         {{/if}}
 
-        {{#if playpen_line_numbers}}
+        {{#if playground_line_numbers}}
         <script type="text/javascript">
-            window.playpen_line_numbers = true;
-        </script>
-        {{/if}}
-        
-        {{#if playpen_copyable}}
-        <script type="text/javascript">
-            window.playpen_copyable = true;
+            window.playground_line_numbers = true;
         </script>
         {{/if}}
 
-        {{#if playpen_js}}
+        {{#if playground_copyable}}
+        <script type="text/javascript">
+            window.playground_copyable = true;
+        </script>
+        {{/if}}
+
+        {{#if playground_js}}
         <script src="{{ path_to_root }}ace.js" type="text/javascript" charset="utf-8"></script>
         <script src="{{ path_to_root }}editor.js" type="text/javascript" charset="utf-8"></script>
         <script src="{{ path_to_root }}mode-rust.js" type="text/javascript" charset="utf-8"></script>

src/theme/mod.rs

@@ -1,6 +1,8 @@
 #![allow(missing_docs)]
 
-pub mod playpen_editor;
+pub mod playground_editor;
+
+pub mod fonts;
 
 #[cfg(feature = "search")]
 pub mod searcher;
@@ -12,12 +14,15 @@ use std::path::Path;
 use crate::errors::*;
 
 pub static INDEX: &[u8] = include_bytes!("index.hbs");
+pub static HEAD: &[u8] = include_bytes!("head.hbs");
+pub static REDIRECT: &[u8] = include_bytes!("redirect.hbs");
 pub static HEADER: &[u8] = include_bytes!("header.hbs");
 pub static CHROME_CSS: &[u8] = include_bytes!("css/chrome.css");
 pub static GENERAL_CSS: &[u8] = include_bytes!("css/general.css");
 pub static PRINT_CSS: &[u8] = include_bytes!("css/print.css");
 pub static VARIABLES_CSS: &[u8] = include_bytes!("css/variables.css");
-pub static FAVICON: &[u8] = include_bytes!("favicon.png");
+pub static FAVICON_PNG: &[u8] = include_bytes!("favicon.png");
+pub static FAVICON_SVG: &[u8] = include_bytes!("favicon.svg");
 pub static JS: &[u8] = include_bytes!("book.js");
 pub static HIGHLIGHT_JS: &[u8] = include_bytes!("highlight.js");
 pub static TOMORROW_NIGHT_CSS: &[u8] = include_bytes!("tomorrow-night.css");
@@ -42,12 +47,15 @@ pub static FONT_AWESOME_OTF: &[u8] = include_bytes!("FontAwesome/fonts/FontAweso
 #[derive(Debug, PartialEq)]
 pub struct Theme {
     pub index: Vec<u8>,
+    pub head: Vec<u8>,
+    pub redirect: Vec<u8>,
     pub header: Vec<u8>,
     pub chrome_css: Vec<u8>,
     pub general_css: Vec<u8>,
     pub print_css: Vec<u8>,
     pub variables_css: Vec<u8>,
-    pub favicon: Vec<u8>,
+    pub favicon_png: Option<Vec<u8>>,
+    pub favicon_svg: Option<Vec<u8>>,
     pub js: Vec<u8>,
     pub highlight_css: Vec<u8>,
     pub tomorrow_night_css: Vec<u8>,
@@ -72,6 +80,8 @@ impl Theme {
         {
             let files = vec![
                 (theme_dir.join("index.hbs"), &mut theme.index),
+                (theme_dir.join("head.hbs"), &mut theme.head),
+                (theme_dir.join("redirect.hbs"), &mut theme.redirect),
                 (theme_dir.join("header.hbs"), &mut theme.header),
                 (theme_dir.join("book.js"), &mut theme.js),
                 (theme_dir.join("css/chrome.css"), &mut theme.chrome_css),
@@ -81,7 +91,6 @@ impl Theme {
                     theme_dir.join("css/variables.css"),
                     &mut theme.variables_css,
                 ),
-                (theme_dir.join("favicon.png"), &mut theme.favicon),
                 (theme_dir.join("highlight.js"), &mut theme.highlight_js),
                 (theme_dir.join("clipboard.min.js"), &mut theme.clipboard_js),
                 (theme_dir.join("highlight.css"), &mut theme.highlight_css),
@@ -95,13 +104,36 @@ impl Theme {
                 ),
             ];
 
-            for (filename, dest) in files {
+            let load_with_warn = |filename: &Path, dest| {
                 if !filename.exists() {
-                    continue;
+                    // Don't warn if the file doesn't exist.
+                    return false;
                 }
-
-                if let Err(e) = load_file_contents(&filename, dest) {
+                if let Err(e) = load_file_contents(filename, dest) {
                     warn!("Couldn't load custom file, {}: {}", filename.display(), e);
+                    false
+                } else {
+                    true
+                }
+            };
+
+            for (filename, dest) in files {
+                load_with_warn(&filename, dest);
+            }
+
+            // If the user overrides one favicon, but not the other, do not
+            // copy the default for the other.
+            let favicon_png = &mut theme.favicon_png.as_mut().unwrap();
+            let png = load_with_warn(&theme_dir.join("favicon.png"), favicon_png);
+            let favicon_svg = &mut theme.favicon_svg.as_mut().unwrap();
+            let svg = load_with_warn(&theme_dir.join("favicon.svg"), favicon_svg);
+            match (png, svg) {
+                (true, true) | (false, false) => {}
+                (true, false) => {
+                    theme.favicon_svg = None;
+                }
+                (false, true) => {
+                    theme.favicon_png = None;
                 }
             }
         }
@@ -114,12 +146,15 @@ impl Default for Theme {
     fn default() -> Theme {
         Theme {
             index: INDEX.to_owned(),
+            head: HEAD.to_owned(),
+            redirect: REDIRECT.to_owned(),
             header: HEADER.to_owned(),
             chrome_css: CHROME_CSS.to_owned(),
             general_css: GENERAL_CSS.to_owned(),
             print_css: PRINT_CSS.to_owned(),
             variables_css: VARIABLES_CSS.to_owned(),
-            favicon: FAVICON.to_owned(),
+            favicon_png: Some(FAVICON_PNG.to_owned()),
+            favicon_svg: Some(FAVICON_SVG.to_owned()),
             js: JS.to_owned(),
             highlight_css: HIGHLIGHT_CSS.to_owned(),
             tomorrow_night_css: TOMORROW_NIGHT_CSS.to_owned(),
@@ -168,9 +203,13 @@ mod tests {
     fn theme_dir_overrides_defaults() {
         let files = [
             "index.hbs",
+            "head.hbs",
+            "redirect.hbs",
             "header.hbs",
             "favicon.png",
+            "favicon.svg",
             "css/chrome.css",
+            "css/fonts.css",
             "css/general.css",
             "css/print.css",
             "css/variables.css",
@@ -194,12 +233,15 @@ mod tests {
 
         let empty = Theme {
             index: Vec::new(),
+            head: Vec::new(),
+            redirect: Vec::new(),
             header: Vec::new(),
             chrome_css: Vec::new(),
             general_css: Vec::new(),
             print_css: Vec::new(),
             variables_css: Vec::new(),
-            favicon: Vec::new(),
+            favicon_png: Some(Vec::new()),
+            favicon_svg: Some(Vec::new()),
             js: Vec::new(),
             highlight_css: Vec::new(),
             tomorrow_night_css: Vec::new(),
@@ -210,4 +252,19 @@ mod tests {
 
         assert_eq!(got, empty);
     }
+
+    #[test]
+    fn favicon_override() {
+        let temp = TempFileBuilder::new().prefix("mdbook-").tempdir().unwrap();
+        fs::write(temp.path().join("favicon.png"), "1234").unwrap();
+        let got = Theme::new(temp.path());
+        assert_eq!(got.favicon_png.as_ref().unwrap(), b"1234");
+        assert_eq!(got.favicon_svg, None);
+
+        let temp = TempFileBuilder::new().prefix("mdbook-").tempdir().unwrap();
+        fs::write(temp.path().join("favicon.svg"), "4567").unwrap();
+        let got = Theme::new(temp.path());
+        assert_eq!(got.favicon_png, None);
+        assert_eq!(got.favicon_svg.as_ref().unwrap(), b"4567");
+    }
 }

src/theme/playground_editor/editor.js

@@ -6,7 +6,7 @@ window.editors = [];
     }
 
     Array.from(document.querySelectorAll('.editable')).forEach(function(editable) {
-        let display_line_numbers = window.playpen_line_numbers || false;
+        let display_line_numbers = window.playground_line_numbers || false;
 
         let editor = ace.edit(editable);
             editor.setOptions({

src/theme/playground_editor/mod.rs

@@ -1,4 +1,4 @@
-//! Theme dependencies for the playpen editor.
+//! Theme dependencies for the playground editor.
 
 pub static JS: &[u8] = include_bytes!("editor.js");
 pub static ACE_JS: &[u8] = include_bytes!("ace.js");

src/theme/redirect.hbs

@@ -0,0 +1,12 @@
+<!DOCTYPE html>
+<html lang="en">
+  <head>
+    <meta charset="utf-8">
+    <title>Redirecting...</title>
+    <meta http-equiv="refresh" content="0;URL='{{url}}'">
+    <meta rel="canonical" href="{{url}}">
+  </head>
+  <body>
+      <p>Redirecting to... <a href="{{url}}">{{url}}</a>.</p>
+  </body>
+</html>

src/theme/searcher/searcher.js

@@ -145,6 +145,11 @@ window.search = window.search || {};
             url.push("");
         }
 
+        // encodeURIComponent escapes all chars that could allow an XSS except
+        // for '. Due to that we also manually replace ' with its url-encoded
+        // representation (%27).
+        var searchterms = encodeURIComponent(searchterms.join(" ")).replace(/\'/g, "%27");
+
         return '<a href="' + path_to_root + url[0] + '?' + URL_MARK_PARAM + '=' + searchterms + '#' + url[1]
             + '" aria-details="teaser_' + teaser_count + '">' + result.doc.breadcrumbs + '</a>'
             + '<span class="teaser" id="teaser_' + teaser_count + '" aria-label="Search Result Teaser">' 
@@ -311,7 +316,7 @@ window.search = window.search || {};
     
     // Eventhandler for keyevents on `document`
     function globalKeyHandler(e) {
-        if (e.altKey || e.ctrlKey || e.metaKey || e.shiftKey || e.target.type === 'textarea') { return; }
+        if (e.altKey || e.ctrlKey || e.metaKey || e.shiftKey || e.target.type === 'textarea' || e.target.type === 'text') { return; }
 
         if (e.keyCode === ESCAPE_KEYCODE) {
             e.preventDefault();

src/utils/fs.rs

@@ -28,11 +28,8 @@ pub fn write_file<P: AsRef<Path>>(build_dir: &Path, filename: P, content: &[u8])
 /// ```rust
 /// # use std::path::Path;
 /// # use mdbook::utils::fs::path_to_root;
-/// #
-/// # fn main() {
 /// let path = Path::new("some/relative/path");
 /// assert_eq!(path_to_root(path), "../../");
-/// # }
 /// ```
 ///
 /// **note:** it's not very fool-proof, if you find a situation where
@@ -95,13 +92,15 @@ pub fn copy_files_except_ext(
     from: &Path,
     to: &Path,
     recursive: bool,
+    avoid_dir: Option<&PathBuf>,
     ext_blacklist: &[&str],
 ) -> Result<()> {
     debug!(
-        "Copying all files from {} to {} (blacklist: {:?})",
+        "Copying all files from {} to {} (blacklist: {:?}), avoiding {:?}",
         from.display(),
         to.display(),
-        ext_blacklist
+        ext_blacklist,
+        avoid_dir
     );
 
     // Check that from and to are different
@@ -111,7 +110,7 @@ pub fn copy_files_except_ext(
 
     for entry in fs::read_dir(from)? {
         let entry = entry?;
-        let metadata = entry.metadata()?;
+        let metadata = entry.path().metadata()?;
 
         // If the entry is a dir and the recursive option is enabled, call itself
         if metadata.is_dir() && recursive {
@@ -119,6 +118,12 @@ pub fn copy_files_except_ext(
                 continue;
             }
 
+            if let Some(avoid) = avoid_dir {
+                if entry.path() == *avoid {
+                    continue;
+                }
+            }
+
             // check if output dir already exists
             if !to.join(entry.file_name()).exists() {
                 fs::create_dir(&to.join(entry.file_name()))?;
@@ -128,6 +133,7 @@ pub fn copy_files_except_ext(
                 &from.join(entry.file_name()),
                 &to.join(entry.file_name()),
                 true,
+                avoid_dir,
                 ext_blacklist,
             )?;
         } else if metadata.is_file() {
@@ -171,10 +177,27 @@ pub fn copy_files_except_ext(
     Ok(())
 }
 
+pub fn get_404_output_file(input_404: &Option<String>) -> String {
+    input_404
+        .as_ref()
+        .unwrap_or(&"404.md".to_string())
+        .replace(".md", ".html")
+}
+
 #[cfg(test)]
 mod tests {
     use super::copy_files_except_ext;
-    use std::fs;
+    use std::{fs, io::Result, path::Path};
+
+    #[cfg(target_os = "windows")]
+    fn symlink<P: AsRef<Path>, Q: AsRef<Path>>(src: P, dst: Q) -> Result<()> {
+        std::os::windows::fs::symlink_file(src, dst)
+    }
+
+    #[cfg(not(target_os = "windows"))]
+    fn symlink<P: AsRef<Path>, Q: AsRef<Path>>(src: P, dst: Q) -> Result<()> {
+        std::os::unix::fs::symlink(src, dst)
+    }
 
     #[test]
     fn copy_files_except_ext_test() {
@@ -205,6 +228,12 @@ mod tests {
         if let Err(err) = fs::File::create(&tmp.path().join("sub_dir_exists/file.txt")) {
             panic!("Could not create sub_dir_exists/file.txt: {}", err);
         }
+        if let Err(err) = symlink(
+            &tmp.path().join("file.png"),
+            &tmp.path().join("symlink.png"),
+        ) {
+            panic!("Could not symlink file.png: {}", err);
+        }
 
         // Create output dir
         if let Err(err) = fs::create_dir(&tmp.path().join("output")) {
@@ -215,7 +244,7 @@ mod tests {
         }
 
         if let Err(e) =
-            copy_files_except_ext(&tmp.path(), &tmp.path().join("output"), true, &["md"])
+            copy_files_except_ext(&tmp.path(), &tmp.path().join("output"), true, None, &["md"])
         {
             panic!("Error while executing the function:\n{:?}", e);
         }
@@ -236,5 +265,8 @@ mod tests {
         if !(&tmp.path().join("output/sub_dir_exists/file.txt")).exists() {
             panic!("output/sub_dir/file.png should exist")
         }
+        if !(&tmp.path().join("output/symlink.png")).exists() {
+            panic!("output/symlink.png should exist")
+        }
     }
 }

src/utils/mod.rs

@@ -2,10 +2,11 @@
 
 pub mod fs;
 mod string;
+pub(crate) mod toml_ext;
 use crate::errors::Error;
 use regex::Regex;
 
-use pulldown_cmark::{html, CowStr, Event, Options, Parser, Tag};
+use pulldown_cmark::{html, CodeBlockKind, CowStr, Event, Options, Parser, Tag};
 
 use std::borrow::Cow;
 use std::fmt::Write;
@@ -226,10 +227,10 @@ impl EventQuoteConverter {
 
 fn clean_codeblock_headers(event: Event<'_>) -> Event<'_> {
     match event {
-        Event::Start(Tag::CodeBlock(ref info)) => {
+        Event::Start(Tag::CodeBlock(CodeBlockKind::Fenced(ref info))) => {
             let info: String = info.chars().filter(|ch| !ch.is_whitespace()).collect();
 
-            Event::Start(Tag::CodeBlock(CowStr::from(info)))
+            Event::Start(Tag::CodeBlock(CodeBlockKind::Fenced(CowStr::from(info))))
         }
         _ => event,
     }
@@ -271,7 +272,7 @@ fn convert_quotes_to_curly(original_text: &str) -> String {
 pub fn log_backtrace(e: &Error) {
     error!("Error: {}", e);
 
-    for cause in e.iter().skip(1) {
+    for cause in e.chain().skip(1) {
         error!("\tCaused By: {}", cause);
     }
 }
@@ -358,8 +359,7 @@ more text with spaces
 ```
 "#;
 
-            let expected =
-                r#"<pre><code class="language-rust,no_run,should_panic,property_3"></code></pre>
+            let expected = r#"<pre><code class="language-rust,no_run,should_panic,property_3"></code></pre>
 "#;
             assert_eq!(render_markdown(input, false), expected);
             assert_eq!(render_markdown(input, true), expected);
@@ -372,8 +372,7 @@ more text with spaces
 ```
 "#;
 
-            let expected =
-                r#"<pre><code class="language-rust,no_run,,,should_panic,,property_3"></code></pre>
+            let expected = r#"<pre><code class="language-rust,no_run,,,should_panic,,property_3"></code></pre>
 "#;
             assert_eq!(render_markdown(input, false), expected);
             assert_eq!(render_markdown(input, true), expected);

src/utils/string.rs

@@ -1,4 +1,3 @@
-use itertools::Itertools;
 use regex::Regex;
 use std::ops::Bound::{Excluded, Included, Unbounded};
 use std::ops::RangeBounds;
@@ -10,11 +9,17 @@ pub fn take_lines<R: RangeBounds<usize>>(s: &str, range: R) -> String {
         Included(&n) => n,
         Unbounded => 0,
     };
-    let mut lines = s.lines().skip(start);
+    let lines = s.lines().skip(start);
     match range.end_bound() {
-        Excluded(end) => lines.take(end.saturating_sub(start)).join("\n"),
-        Included(end) => lines.take((end + 1).saturating_sub(start)).join("\n"),
-        Unbounded => lines.join("\n"),
+        Excluded(end) => lines
+            .take(end.saturating_sub(start))
+            .collect::<Vec<_>>()
+            .join("\n"),
+        Included(end) => lines
+            .take((end + 1).saturating_sub(start))
+            .collect::<Vec<_>>()
+            .join("\n"),
+        Unbounded => lines.collect::<Vec<_>>().join("\n"),
     }
 }
 
@@ -43,11 +48,9 @@ pub fn take_anchored_lines(s: &str, anchor: &str) -> String {
                     }
                 }
             }
-        } else {
-            if let Some(cap) = ANCHOR_START.captures(l) {
-                if &cap["anchor_name"] == anchor {
-                    anchor_found = true;
-                }
+        } else if let Some(cap) = ANCHOR_START.captures(l) {
+            if &cap["anchor_name"] == anchor {
+                anchor_found = true;
             }
         }
     }
@@ -96,16 +99,14 @@ pub fn take_rustdoc_include_anchored_lines(s: &str, anchor: &str) -> String {
                     }
                 }
             }
-        } else {
-            if let Some(cap) = ANCHOR_START.captures(l) {
-                if &cap["anchor_name"] == anchor {
-                    within_anchored_section = true;
-                }
-            } else if !ANCHOR_END.is_match(l) {
-                output.push_str("# ");
-                output.push_str(l);
-                output.push_str("\n");
+        } else if let Some(cap) = ANCHOR_START.captures(l) {
+            if &cap["anchor_name"] == anchor {
+                within_anchored_section = true;
             }
+        } else if !ANCHOR_END.is_match(l) {
+            output.push_str("# ");
+            output.push_str(l);
+            output.push_str("\n");
         }
     }
 

src/utils/toml_ext.rs

@@ -0,0 +1,130 @@
+use toml::value::{Table, Value};
+
+pub(crate) trait TomlExt {
+    fn read(&self, key: &str) -> Option<&Value>;
+    fn read_mut(&mut self, key: &str) -> Option<&mut Value>;
+    fn insert(&mut self, key: &str, value: Value);
+    fn delete(&mut self, key: &str) -> Option<Value>;
+}
+
+impl TomlExt for Value {
+    fn read(&self, key: &str) -> Option<&Value> {
+        if let Some((head, tail)) = split(key) {
+            self.get(head)?.read(tail)
+        } else {
+            self.get(key)
+        }
+    }
+
+    fn read_mut(&mut self, key: &str) -> Option<&mut Value> {
+        if let Some((head, tail)) = split(key) {
+            self.get_mut(head)?.read_mut(tail)
+        } else {
+            self.get_mut(key)
+        }
+    }
+
+    fn insert(&mut self, key: &str, value: Value) {
+        if !self.is_table() {
+            *self = Value::Table(Table::new());
+        }
+
+        let table = self.as_table_mut().expect("unreachable");
+
+        if let Some((head, tail)) = split(key) {
+            table
+                .entry(head)
+                .or_insert_with(|| Value::Table(Table::new()))
+                .insert(tail, value);
+        } else {
+            table.insert(key.to_string(), value);
+        }
+    }
+
+    fn delete(&mut self, key: &str) -> Option<Value> {
+        if let Some((head, tail)) = split(key) {
+            self.get_mut(head)?.delete(tail)
+        } else if let Some(table) = self.as_table_mut() {
+            table.remove(key)
+        } else {
+            None
+        }
+    }
+}
+
+fn split(key: &str) -> Option<(&str, &str)> {
+    let ix = key.find(".")?;
+
+    let (head, tail) = key.split_at(ix);
+    // splitting will leave the "."
+    let tail = &tail[1..];
+
+    Some((head, tail))
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+    use std::str::FromStr;
+
+    #[test]
+    fn read_simple_table() {
+        let src = "[table]";
+        let value = Value::from_str(src).unwrap();
+
+        let got = value.read("table").unwrap();
+
+        assert!(got.is_table());
+    }
+
+    #[test]
+    fn read_nested_item() {
+        let src = "[table]\nnested=true";
+        let value = Value::from_str(src).unwrap();
+
+        let got = value.read("table.nested").unwrap();
+
+        assert_eq!(got, &Value::Boolean(true));
+    }
+
+    #[test]
+    fn insert_item_at_top_level() {
+        let mut value = Value::Table(Table::default());
+        let item = Value::Boolean(true);
+
+        value.insert("first", item.clone());
+
+        assert_eq!(value.get("first").unwrap(), &item);
+    }
+
+    #[test]
+    fn insert_nested_item() {
+        let mut value = Value::Table(Table::default());
+        let item = Value::Boolean(true);
+
+        value.insert("first.second", item.clone());
+
+        let inserted = value.read("first.second").unwrap();
+        assert_eq!(inserted, &item);
+    }
+
+    #[test]
+    fn delete_a_top_level_item() {
+        let src = "top = true";
+        let mut value = Value::from_str(src).unwrap();
+
+        let got = value.delete("top").unwrap();
+
+        assert_eq!(got, Value::Boolean(true));
+    }
+
+    #[test]
+    fn delete_a_nested_item() {
+        let src = "[table]\n nested = true";
+        let mut value = Value::from_str(src).unwrap();
+
+        let got = value.delete("table.nested").unwrap();
+
+        assert_eq!(got, Value::Boolean(true));
+    }
+}

tests/alternative_backends.rs

@@ -8,28 +8,33 @@ use tempfile::{Builder as TempFileBuilder, TempDir};
 
 #[test]
 fn passing_alternate_backend() {
-    let (md, _temp) = dummy_book_with_backend("passing", success_cmd());
+    let (md, _temp) = dummy_book_with_backend("passing", success_cmd(), false);
 
     md.build().unwrap();
 }
 
 #[test]
 fn failing_alternate_backend() {
-    let (md, _temp) = dummy_book_with_backend("failing", fail_cmd());
+    let (md, _temp) = dummy_book_with_backend("failing", fail_cmd(), false);
 
     md.build().unwrap_err();
 }
 
 #[test]
-fn missing_backends_arent_fatal() {
-    let (md, _temp) = dummy_book_with_backend("missing", "trduyvbhijnorgevfuhn");
+fn missing_backends_are_fatal() {
+    let (md, _temp) = dummy_book_with_backend("missing", "trduyvbhijnorgevfuhn", false);
+    assert!(md.build().is_err());
+}
 
+#[test]
+fn missing_optional_backends_are_not_fatal() {
+    let (md, _temp) = dummy_book_with_backend("missing", "trduyvbhijnorgevfuhn", true);
     assert!(md.build().is_ok());
 }
 
 #[test]
 fn alternate_backend_with_arguments() {
-    let (md, _temp) = dummy_book_with_backend("arguments", "echo Hello World!");
+    let (md, _temp) = dummy_book_with_backend("arguments", "echo Hello World!", false);
 
     md.build().unwrap();
 }
@@ -56,7 +61,7 @@ fn backends_receive_render_context_via_stdin() {
     let out_file = temp.path().join("out.txt");
     let cmd = tee_command(&out_file);
 
-    let (md, _temp) = dummy_book_with_backend("cat-to-file", &cmd);
+    let (md, _temp) = dummy_book_with_backend("cat-to-file", &cmd, false);
 
     assert!(!out_file.exists());
     md.build().unwrap();
@@ -66,7 +71,11 @@ fn backends_receive_render_context_via_stdin() {
     assert!(got.is_ok());
 }
 
-fn dummy_book_with_backend(name: &str, command: &str) -> (MDBook, TempDir) {
+fn dummy_book_with_backend(
+    name: &str,
+    command: &str,
+    backend_is_optional: bool,
+) -> (MDBook, TempDir) {
     let temp = TempFileBuilder::new().prefix("mdbook").tempdir().unwrap();
 
     let mut config = Config::default();
@@ -74,6 +83,12 @@ fn dummy_book_with_backend(name: &str, command: &str) -> (MDBook, TempDir) {
         .set(format!("output.{}.command", name), command)
         .unwrap();
 
+    if backend_is_optional {
+        config
+            .set(format!("output.{}.optional", name), true)
+            .unwrap();
+    }
+
     let md = MDBook::init(temp.path())
         .with_config(config)
         .build()

tests/dummy_book/mod.rs

@@ -4,12 +4,12 @@
 // Not all features are used in all test crates, so...
 #![allow(dead_code, unused_variables, unused_imports, unused_extern_crates)]
 
+use anyhow::Context;
 use mdbook::errors::*;
+use mdbook::MDBook;
 use std::fs::{self, File};
 use std::io::{Read, Write};
 use std::path::Path;
-
-use mdbook::MDBook;
 use tempfile::{Builder as TempFileBuilder, TempDir};
 use walkdir::WalkDir;
 
@@ -43,10 +43,10 @@ impl DummyBook {
         let temp = TempFileBuilder::new()
             .prefix("dummy_book-")
             .tempdir()
-            .chain_err(|| "Unable to create temp directory")?;
+            .with_context(|| "Unable to create temp directory")?;
 
         let dummy_book_root = Path::new(env!("CARGO_MANIFEST_DIR")).join("tests/dummy_book");
-        recursive_copy(&dummy_book_root, temp.path()).chain_err(|| {
+        recursive_copy(&dummy_book_root, temp.path()).with_context(|| {
             "Couldn't copy files into a \
              temporary directory"
         })?;
@@ -113,7 +113,7 @@ fn recursive_copy<A: AsRef<Path>, B: AsRef<Path>>(from: A, to: B) -> Result<()>
     let to = to.as_ref();
 
     for entry in WalkDir::new(&from) {
-        let entry = entry.chain_err(|| "Unable to inspect directory entry")?;
+        let entry = entry.with_context(|| "Unable to inspect directory entry")?;
 
         let original_location = entry.path();
         let relative = original_location
@@ -123,11 +123,11 @@ fn recursive_copy<A: AsRef<Path>, B: AsRef<Path>>(from: A, to: B) -> Result<()>
 
         if original_location.is_file() {
             if let Some(parent) = new_location.parent() {
-                fs::create_dir_all(parent).chain_err(|| "Couldn't create directory")?;
+                fs::create_dir_all(parent).with_context(|| "Couldn't create directory")?;
             }
 
             fs::copy(&original_location, &new_location)
-                .chain_err(|| "Unable to copy file contents")?;
+                .with_context(|| "Unable to copy file contents")?;
         }
     }
 
@@ -135,11 +135,11 @@ fn recursive_copy<A: AsRef<Path>, B: AsRef<Path>>(from: A, to: B) -> Result<()>
 }
 
 pub fn new_copy_of_example_book() -> Result<TempDir> {
-    let temp = TempFileBuilder::new().prefix("book-example").tempdir()?;
+    let temp = TempFileBuilder::new().prefix("guide").tempdir()?;
 
-    let book_example = Path::new(env!("CARGO_MANIFEST_DIR")).join("book-example");
+    let guide = Path::new(env!("CARGO_MANIFEST_DIR")).join("guide");
 
-    recursive_copy(book_example, temp.path())?;
+    recursive_copy(guide, temp.path())?;
 
     Ok(temp)
 }

tests/dummy_book/src/second.md

@@ -2,4 +2,4 @@
 
 This makes sure you can insert runnable Rust files.
 
-{{#playpen example.rs}}
+{{#playground example.rs}}

tests/init.rs

@@ -24,6 +24,12 @@ fn base_mdbook_init_should_create_default_content() {
         println!("{}", target.display());
         assert!(target.exists(), "{} doesn't exist", file);
     }
+
+    let contents = fs::read_to_string(temp.path().join("book.toml")).unwrap();
+    assert_eq!(
+        contents,
+        "[book]\nauthors = []\nlanguage = \"en\"\nmultilingual = false\nsrc = \"src\"\n"
+    );
 }
 
 /// Run `mdbook init` in a directory containing a SUMMARY.md should create the