Merge branch 'rust-lang:master' into #1564

.github/workflows/main.yml

@@ -31,7 +31,7 @@ jobs:
             rust: stable
           - build: msrv
             os: ubuntu-latest
-            rust: 1.45.0
+            rust: 1.46.0
     steps:
     - uses: actions/checkout@master
     - name: Install Rust

CHANGELOG.md

@@ -1,5 +1,72 @@
 # Changelog
 
+## mdBook 0.4.13
+[e6629cd...f55028b](https://github.com/rust-lang/mdBook/compare/e6629cd...f55028b)
+
+### Added
+
+- Added the ability to specify the preprocessor order.
+  [#1607](https://github.com/rust-lang/mdBook/pull/1607)
+
+### Fixed
+
+- Include chapters with no headers in the search index
+  [#1637](https://github.com/rust-lang/mdBook/pull/1637)
+- Switched to the `opener` crate for opening a web browser, which should fix
+  some issues with blocking.
+  [#1656](https://github.com/rust-lang/mdBook/pull/1656)
+- Fixed clicking the border of the theme switcher breaking the theme selection.
+  [#1651](https://github.com/rust-lang/mdBook/pull/1651)
+
+## mdBook 0.4.12
+[14add9c...8b4e488](https://github.com/rust-lang/mdBook/compare/14add9c...8b4e488)
+
+### Changed
+- Reverted the change to update to highlight.js 11, as it broke hidden code lines.
+  [#1597](https://github.com/rust-lang/mdBook/pull/1621)
+ 
+## mdBook 0.4.11
+[e440094...2cf00d0](https://github.com/rust-lang/mdBook/compare/e440094...2cf00d0)
+
+### Added
+- Added support for Rust 2021 edition.
+  [#1596](https://github.com/rust-lang/mdBook/pull/1596)
+- Added `mdbook completions` subcommand which provides shell completions.
+  [#1425](https://github.com/rust-lang/mdBook/pull/1425)
+- Added `--title` and `--ignore` flags to `mdbook init` to avoid the
+  interactive input.
+  [#1559](https://github.com/rust-lang/mdBook/pull/1559)
+
+### Changed
+- If running a Rust example does not have any output, it now displays the text
+  "No output" instead of not showing anything.
+  [#1599](https://github.com/rust-lang/mdBook/pull/1599)
+- Code block language tags can now be separated by space or tab (along with
+  commas) to match the behavior of other sites like GitHub and rustdoc.
+  [#1469](https://github.com/rust-lang/mdBook/pull/1469)
+- Updated `warp` (the web server) to the latest version.
+  This also updates the minimum supported Rust version to 1.46.
+  [#1612](https://github.com/rust-lang/mdBook/pull/1612)
+- Updated to highlight.js 11. This has various highlighting improvements.
+  [#1597](https://github.com/rust-lang/mdBook/pull/1597)
+
+### Fixed
+- Inline code blocks inside a header are no longer highlighted when
+  `output.html.playground.editable` is `true`.
+  [#1613](https://github.com/rust-lang/mdBook/pull/1613)
+
+## mdBook 0.4.10
+[2f7293a...dc2062a](https://github.com/rust-lang/mdBook/compare/2f7293a...dc2062a)
+
+### Changed
+- Reverted breaking change in 0.4.9 that removed the `__non_exhaustive` marker
+  on the `Book` struct.
+  [#1572](https://github.com/rust-lang/mdBook/pull/1572)
+- Updated handlebars to 4.0.
+  [#1550](https://github.com/rust-lang/mdBook/pull/1550)
+- Removed the `chapter_begin` id on the print page's chapter separators.
+  [#1541](https://github.com/rust-lang/mdBook/pull/1541)
+
 ## mdBook 0.4.9
 [7e01cf9...d325c60](https://github.com/rust-lang/mdBook/compare/7e01cf9...d325c60)
 

CODE_OF_CONDUCT.md

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

CONTRIBUTING.md

@@ -6,7 +6,6 @@ If you have come here to learn how to contribute to mdBook, we have some tips fo
 
 First of all, don't hesitate to ask questions!
 Use the [issue tracker](https://github.com/rust-lang/mdBook/issues), no question is too simple.
-If we don't respond in a couple of days, ping us @Michael-F-Bryan, @budziq, @steveklabnik, @frewsxcv it might just be that we forgot. :wink:
 
 ### Issues to work on
 
@@ -46,7 +45,7 @@ mdBook builds on stable Rust, if you want to build mdBook from source, here are
 0. Navigate into the newly created `mdBook` directory
 0. Run `cargo build`
 
-The resulting binary can be found in `mdBook/target/debug/` under the name `mdBook` or `mdBook.exe`.
+The resulting binary can be found in `mdBook/target/debug/` under the name `mdbook` or `mdbook.exe`.
 
 ### Code Quality
 
@@ -106,3 +105,26 @@ and [rustfmt](https://github.com/rust-lang/rustfmt) on the code first.
 This is not a requirement though and will never block a pull-request from being merged.
 
 That's it, happy contributions! :tada: :tada: :tada:
+
+## Browser compatibility and testing
+
+Currently we don't have a strict browser compatibility matrix due to our limited resources.
+We generally strive to keep mdBook compatible with a relatively recent browser on all of the most major platforms.
+That is, supporting Chrome, Safari, Firefox, Edge on Windows, macOS, Linux, iOS, and Android.
+If possible, do your best to avoid breaking older browser releases.
+
+Any change to the HTML or styling is encouraged to manually check on as many browsers and platforms that you can.
+Unfortunately at this time we don't have any automated UI or browser testing, so your assistance in testing is appreciated.
+
+## Updating higlight.js
+
+The following are instructions for updating [highlight.js](https://highlightjs.org/).
+
+1. Clone the repository at <https://github.com/highlightjs/highlight.js>
+1. Check out a tagged release (like `10.1.1`).
+1. Run `npm install`
+1. Run `node tools/build.js :common apache armasm coffeescript d handlebars haskell http julia nginx properties r scala x86asm yaml`
+1. Compare the language list that it spits out to the one in [`syntax-highlighting.md`](https://github.com/camelid/mdBook/blob/master/guide/src/format/theme/syntax-highlighting.md). If any are missing, add them to the list and rebuild (and update these docs). If any are added to the common set, add them to `syntax-highlighting.md`.
+1. Copy `build/highlight.min.js` to mdbook's directory [`highlight.js`](https://github.com/rust-lang/mdBook/blob/master/src/theme/highlight.js).
+1. Be sure to check the highlight.js [CHANGES](https://github.com/highlightjs/highlight.js/blob/main/CHANGES.md) for any breaking changes. Breaking changes that would affect users will need to wait until the next major release.
+1. Build mdbook with the new file and build some books with the new version and compare the output with a variety of languages to see if anything changes. (TODO: It would be nice to have a demo file in the repo to help with this.)

Cargo.toml

@@ -1,6 +1,6 @@
 [package]
 name = "mdbook"
-version = "0.4.9"
+version = "0.4.13"
 authors = [
     "Mathieu David <mathieudavid@mathieudavid.org>",
     "Michael-F-Bryan <michaelfbryan@gmail.com>",
@@ -24,7 +24,7 @@ handlebars = "4.0"
 lazy_static = "1.0"
 log = "0.4"
 memchr = "2.0"
-open = "1.1"
+opener = "0.5"
 pulldown-cmark = "0.7.0"
 regex = "1.0.0"
 serde = "1.0"
@@ -33,6 +33,7 @@ serde_json = "1.0"
 shlex = "1"
 tempfile = "3.0"
 toml = "0.5.1"
+topological-sort = "0.1.0"
 
 # Watch feature
 notify = { version = "4.0", optional = true }
@@ -40,14 +41,16 @@ gitignore = { version = "1.0", optional = true }
 
 # Serve feature
 futures-util = { version = "0.3.4", optional = true }
-tokio = { version = "0.2.18", features = ["macros"], optional = true }
+tokio = { version = "1", features = ["macros", "rt-multi-thread"], optional = true }
-warp = { version = "0.2.2", default-features = false, features = ["websocket"], optional = true }
+warp = { version = "0.3.1", default-features = false, features = ["websocket"], optional = true }
 
 # Search feature
 elasticlunr-rs = { version = "2.3", optional = true, default-features = false }
 ammonia = { version = "3", optional = true }
 
 [dev-dependencies]
+assert_cmd = "1"
+predicates = "2"
 select = "0.5"
 semver = "0.11.0"
 pretty_assertions = "0.6"

README.md

@@ -163,6 +163,7 @@ of a book in order to validate links or run tests. Some existing renderers are:
   preprocessors.
 - [`linkcheck`] - a backend which will check that all links are valid
 - [`epub`] - an experimental EPUB generator
+- [`man`] - a backend that generates manual pages from the book
 
 > **Note for Developers:** Feel free to send us a PR if you've developed your
 > own plugin and want it mentioned here.
@@ -234,3 +235,4 @@ All the code in this repository is released under the ***Mozilla Public License
 [master-docs]: http://rust-lang.github.io/mdBook/
 [`linkcheck`]: https://crates.io/crates/mdbook-linkcheck
 [`epub`]: https://crates.io/crates/mdbook-epub
+[`man`]: https://crates.io/crates/mdbook-man

examples/nop-preprocessor.rs

@@ -37,7 +37,7 @@ fn handle_preprocessing(pre: &dyn Preprocessor) -> Result<(), Error> {
     let book_version = Version::parse(&ctx.mdbook_version)?;
     let version_req = VersionReq::parse(mdbook::MDBOOK_VERSION)?;
 
-    if version_req.matches(&book_version) != true {
+    if !version_req.matches(&book_version) {
         eprintln!(
             "Warning: The {} plugin was built against version {} of mdbook, \
              but we're being called from version {}",
@@ -55,7 +55,7 @@ fn handle_preprocessing(pre: &dyn Preprocessor) -> Result<(), Error> {
 
 fn handle_supports(pre: &dyn Preprocessor, sub_args: &ArgMatches) -> ! {
     let renderer = sub_args.value_of("renderer").expect("Required argument");
-    let supported = pre.supports_renderer(&renderer);
+    let supported = pre.supports_renderer(renderer);
 
     // Signal whether the renderer is supported by exiting with 1 or 0.
     if supported {

guide/src/README.md

@@ -1,25 +1,40 @@
-# mdBook
+# Introduction
 
-**mdBook** is a command line tool and Rust crate to create books using Markdown
+**mdBook** is a command line tool and Rust crate to create books with Markdown. The output resembles tools like Gitbook,
-(as by the [CommonMark](https://commonmark.org/) specification) files. It's very
+and is ideal for creating product or API documentation, tutorials, course materials or anything that requires a clean,
-similar to Gitbook but written in [Rust](http://www.rust-lang.org).
+easily navigable and customizable presentation. mdBook is written in [Rust](https://www.rust-lang.org); its performance
+and simplicity made it ideal for use as a tool to publish directly to hosted websites such
+as [GitHub Pages](https://pages.github.com) via automation. This guide, in fact, serves as both the mdBook documentation
+and a fine example of what mdBook produces.
 
-What you are reading serves as an example of the output of mdBook and at the
+mdBook includes built in support for both preprocessing your Markdown and alternative renderers for producing formats
-same time as a high-level documentation.
+other than HTML. These facilities also enable other functionality such as
+validation. [Searching](https://crates.io/search?q=mdbook&sort=relevance) Rust's [crates.io](https://crates.io) is a
+great way to discover more extensions.
 
-mdBook is free and open source, you can find the source code on
+## API Documentation
-[GitHub](https://github.com/rust-lang/mdBook). Issues and feature
-requests can be posted on the [GitHub issue
-tracker](https://github.com/rust-lang/mdBook/issues).
 
-## API docs
+In addition to the above features, mdBook also has a Rust [API](https://docs.rs/mdbook/*/mdbook/). This allows you to
+write your own preprocessor or renderer, as well as incorporate mdBook features into other applications.
+The [For Developers](for_developers) section of this guide contains more information and some examples.
 
-Alongside this book you can also read the [API
+## Markdown
-docs](https://docs.rs/mdbook/*/mdbook/) generated by Rustdoc if you would like
+
-to use mdBook as a crate or write a new renderer and need a more low-level
+mdBook's [parser](https://github.com/raphlinus/pulldown-cmark) adheres to the [CommonMark](https://commonmark.org/)
-overview.
+specification. You can take a quick [tutorial](https://commonmark.org/help/tutorial/),
+or [try out](https://spec.commonmark.org/dingus/) CommonMark in real time. For a more in-depth experience, check out the
+[Markdown Guide](https://www.markdownguide.org).
+
+## Contributing
+
+mdBook is free and open source. You can find the source code on
+[GitHub](https://github.com/rust-lang/mdBook) and issues and feature requests can be posted on
+the [GitHub issue tracker](https://github.com/rust-lang/mdBook/issues). mdBook relies on the community to fix bugs and
+add features: if you'd like to contribute, please read
+the [CONTRIBUTING](https://github.com/rust-lang/mdBook/blob/master/CONTRIBUTING.md) guide and consider opening
+a [pull request](https://github.com/rust-lang/mdBook/pulls).
 
 ## License
 
-mdBook, all the source code, is released under the [Mozilla Public License
+The mdBook source and documentation are released under
-v2.0](https://www.mozilla.org/MPL/2.0/).
+the [Mozilla Public License v2.0](https://www.mozilla.org/MPL/2.0/).

guide/src/SUMMARY.md

@@ -1,6 +1,6 @@
 # Summary
 
-- [mdBook](README.md)
+- [Introduction](README.md)
 - [Command Line Tool](cli/README.md)
     - [init](cli/init.md)
     - [build](cli/build.md)

guide/src/cli/init.md

@@ -52,3 +52,19 @@ directory called `theme` in your source directory so that you can modify it.
 
 The theme is selectively overwritten, this means that if you don't want to
 overwrite a specific file, just delete it and the default file will be used.
+
+#### --title
+
+Specify a title for the book. If not supplied, an interactive prompt will ask for 
+a title. 
+
+```bash
+mdbook init --title="my amazing book"
+```
+
+#### --ignore
+
+Create a `.gitignore` file configured to ignore the `book` directory created when [building] a book. 
+If not supplied, an interactive prompt will ask whether it should be created.
+
+[building]: build.md

guide/src/cli/test.md

@@ -43,7 +43,17 @@ mdbook test path/to/book
 The `--library-path` (`-L`) option allows you to add directories to the library
 search path used by `rustdoc` when it builds and tests the examples. Multiple
 directories can be specified with multiple options (`-L foo -L bar`) or with a
-comma-delimited list (`-L foo,bar`).
+comma-delimited list (`-L foo,bar`). The path should point to the Cargo 
+[build cache](https://doc.rust-lang.org/cargo/guide/build-cache.html) `deps` directory that
+contains the build output of your project. For example, if your Rust project's book is in a directory
+named `my-book`, the following command would include the crate's dependencies when running `test`:
+
+```shell
+mdbook test my-book -L target/debug/deps/
+```
+
+See the `rustdoc` command-line [documentation](https://doc.rust-lang.org/rustdoc/command-line-arguments.html#-l--library-path-where-to-look-for-dependencies)
+for more information.
 
 #### --dest-dir
 

guide/src/continuous-integration.md

@@ -26,7 +26,7 @@ before_script:
   - cargo install-update -a
 
 script:
-  - mdbook build path/to/mybook && mdbook test path/to/mybook
+  - mdbook build && mdbook test # In case of custom book path: mdbook build path/to/mybook && mdbook test path/to/mybook
 ```
 
 ## Deploying Your Book to GitHub Pages
@@ -50,10 +50,10 @@ deploy:
   provider: pages
   skip-cleanup: true
   github-token: $GITHUB_TOKEN
-  local-dir: path/to/mybook/book
+  local-dir: book # In case of custom book path: path/to/mybook/book
   keep-history: false
   on:
-    branch: master
+    branch: main
 ```
 
 That's it!
@@ -77,7 +77,7 @@ before_script:
   - cargo install-update -a
 
 script:
-  - mdbook build path/to/mybook && mdbook test path/to/mybook
+  - mdbook build && mdbook test # In case of custom book path: mdbook build path/to/mybook && mdbook test path/to/mybook
   
 deploy:
   provider: pages
@@ -85,10 +85,10 @@ deploy:
   edge: true
   cleanup: false
   github-token: $GITHUB_TOKEN
-  local-dir: path/to/mybook/book
+  local-dir: book # In case of custom book path: path/to/mybook/book
   keep-history: false
   on:
-    branch: master
+    branch: main
   target_branch: gh-pages
 ```
 
@@ -141,8 +141,8 @@ pages:
     - mdbook --version || cargo install mdbook
   script:
     - mdbook build -d public
-  only:
+  rules:
-      - master 
+    - if: '$CI_COMMIT_REF_NAME == "master"'
   artifacts:
     paths:
       - public

guide/src/for_developers/backends.md

@@ -13,6 +13,7 @@ rough example of how this is accomplished in practice.
 - [mdbook-epub] - an EPUB renderer
 - [mdbook-test] - a program to run the book's contents through [rust-skeptic] to
   verify everything compiles and runs correctly (similar to `rustdoc --test`)
+- [mdbook-man] - generate manual pages from the book
 
 This page will step you through creating your own alternative backend in the form
 of a simple word counting program. Although it will be written in Rust, there's
@@ -377,6 +378,7 @@ the source code or ask questions.
 [mdbook-linkcheck]: https://github.com/Michael-F-Bryan/mdbook-linkcheck
 [mdbook-epub]: https://github.com/Michael-F-Bryan/mdbook-epub
 [mdbook-test]: https://github.com/Michael-F-Bryan/mdbook-test
+[mdbook-man]: https://github.com/vv9k/mdbook-man
 [rust-skeptic]: https://github.com/budziq/rust-skeptic
 [`RenderContext`]: https://docs.rs/mdbook/*/mdbook/renderer/struct.RenderContext.html
 [`RenderContext::from_json()`]: https://docs.rs/mdbook/*/mdbook/renderer/struct.RenderContext.html#method.from_json

guide/src/for_developers/preprocessors.md

@@ -34,8 +34,15 @@ command = "python3 /path/to/foo.py"
 renderer = ["html", "epub"]
 ```
 
-In typical unix style, all inputs to the plugin will be written to `stdin` as
+Once the preprocessor has been defined and the build process starts, mdBook executes the command defined in the `preprocessor.foo.command` key twice.
-JSON and `mdbook` will read from `stdout` if it is expecting output.
+The first time it runs the preprocessor to determine if it supports the given renderer.
+mdBook passes two arguments to the process: the first argument is the string `supports` and the second argument is the renderer name.
+The preprocessor should exit with a status code 0 if it supports the given renderer, or return a non-zero exit code if it does not.
+
+If the preprocessor supports the renderer, then mdbook runs it a second time, passing JSON data into stdin.
+The JSON consists of an array of `[context, book]` where `context` is the serialized object [`PreprocessorContext`] and `book` is a [`Book`] object containing the content of the book.
+
+The preprocessor should return the JSON format of the [`Book`] object to stdout, with any modifications it wishes to perform.
 
 The easiest way to get started is by creating your own implementation of the
 `Preprocessor` trait (e.g. in `lib.rs`) and then creating a shell binary which
@@ -106,6 +113,33 @@ fn remove_emphasis(
 
 For everything else, have a look [at the complete example][example].
 
+## Implementing a preprocessor with a different language
+
+The fact that mdBook utilizes stdin and stdout to communicate with the preprocessors makes it easy to implement them in a language other than Rust.
+The following code shows how to implement a simple preprocessor in Python, which will modify the content of the first chapter.
+The example below follows the configuration shown above with `preprocessor.foo.command` actually pointing to a Python script.
+
+```python
+import json
+import sys
+
+
+if __name__ == '__main__':
+    if len(sys.argv) > 1: # we check if we received any argument
+        if sys.argv[1] == "supports": 
+            # then we are good to return an exit status code of 0, since the other argument will just be the renderer's name
+            sys.exit(0)
+
+    # load both the context and the book representations from stdin
+    context, book = json.load(sys.stdin)
+    # and now, we can just modify the content of the first chapter
+    book['sections'][0]['Chapter']['content'] = '# Hello'
+    # we are done with the book's modification, we can just print it to stdout, 
+    print(json.dumps(book))
+```
+
+
+
 [preprocessor-docs]: https://docs.rs/mdbook/latest/mdbook/preprocess/trait.Preprocessor.html
 [pc]: https://crates.io/crates/pulldown-cmark
 [pctc]: https://crates.io/crates/pulldown-cmark-to-cmark
@@ -113,3 +147,5 @@ For everything else, have a look [at the complete example][example].
 [an example no-op preprocessor]: https://github.com/rust-lang/mdBook/blob/master/examples/nop-preprocessor.rs
 [`CmdPreprocessor::parse_input()`]: https://docs.rs/mdbook/latest/mdbook/preprocess/trait.Preprocessor.html#method.parse_input
 [`Book::for_each_mut()`]: https://docs.rs/mdbook/latest/mdbook/book/struct.Book.html#method.for_each_mut
+[`PreprocessorContext`]: https://docs.rs/mdbook/latest/mdbook/preprocess/struct.PreprocessorContext.html
+[`Book`]: https://docs.rs/mdbook/latest/mdbook/book/struct.Book.html

guide/src/format/configuration/general.md

@@ -63,8 +63,8 @@ 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`
+  is "2015". Individual code blocks can be controlled with the `edition2015`, 
-  or `edition2018` annotations, such as:
+  `edition2018` or `edition2021` annotations, such as:
 
   ~~~text
   ```rust,edition2015

guide/src/format/configuration/preprocessors.md

@@ -56,3 +56,25 @@ be overridden by adding a `command` field.
 [preprocessor.random]
 command = "python random.py"
 ```
+
+### Require A Certain Order
+
+The order in which preprocessors are run can be controlled with the `before` and `after` fields.
+For example, suppose you want your `linenos` preprocessor to process lines that may have been `{{#include}}`d; then you want it to run after the built-in `links` preprocessor, which you can require using either the `before` or `after` field:
+
+```toml
+[preprocessor.linenos]
+after = [ "links" ]
+```
+
+or
+
+```toml
+[preprocessor.links]
+before = [ "linenos" ]
+```
+
+It would also be possible, though redundant, to specify both of the above in the same config file.
+
+Preprocessors having the same priority specified through `before` and `after` are sorted by name.
+Any infinite loops will be detected and produce an error.

guide/src/format/configuration/renderers.md

@@ -188,13 +188,13 @@ Enable it by adding an empty table to your `book.toml` as follows:
 There are no configuration options for the Markdown renderer at this time;
 only whether it is enabled or disabled.
 
-See [the preprocessors documentation](#configuring-preprocessors) for how to
+See [the preprocessors documentation](preprocessors.md) for how to
 specify which preprocessors should run before the Markdown renderer.
 
 ### Custom Renderers
 
 A custom renderer can be enabled by adding a `[output.foo]` table to your
-`book.toml`. Similar to [preprocessors](#configuring-preprocessors) this will
+`book.toml`. Similar to [preprocessors](preprocessors.md) this will
 instruct `mdbook` to pass a representation of the book to `mdbook-foo` for
 rendering. See the [alternative backends] chapter for more detail.
 

guide/src/format/mdbook.md

@@ -21,7 +21,7 @@ Will render as
 ```rust
 # fn main() {
     let x = 5;
-    let y = 7;
+    let y = 6;
 
     println!("{}", x + y);
 # }

guide/src/misc/contributors.md

@@ -15,8 +15,10 @@ shout-out to them!
 - [projektir](https://github.com/projektir)
 - [Phaiax](https://github.com/Phaiax)
 - Matt Ickstadt ([mattico](https://github.com/mattico))
-- Weihang Lo ([@weihanglo](https://github.com/weihanglo))
+- Weihang Lo ([weihanglo](https://github.com/weihanglo))
-- Avision Ho ([@avisionh](https://github.com/avisionh))
+- Avision Ho ([avisionh](https://github.com/avisionh))
-- Vivek Akupatni ([@apatniv](https://github.com/apatniv))
+- Vivek Akupatni ([apatniv](https://github.com/apatniv))
+- Eric Huss ([ehuss](https://github.com/ehuss))
+- Josh Rotenberg ([joshrotenberg](https://github.com/joshrotenberg))
 
 If you feel you're missing from this list, feel free to add yourself in a PR.

src/book/book.rs

@@ -22,7 +22,7 @@ pub fn load_book<P: AsRef<Path>>(src_dir: P, cfg: &BuildConfig) -> Result<Book>
         .with_context(|| format!("Summary parsing failed for file={:?}", summary_md))?;
 
     if cfg.create_missing {
-        create_missing(&src_dir, &summary).with_context(|| "Unable to create missing chapters")?;
+        create_missing(src_dir, &summary).with_context(|| "Unable to create missing chapters")?;
     }
 
     load_book_from_disk(&summary, src_dir)
@@ -74,10 +74,10 @@ fn create_missing(src_dir: &Path, summary: &Summary) -> Result<()> {
 /// [`iter()`]: #method.iter
 /// [`for_each_mut()`]: #method.for_each_mut
 #[derive(Debug, Clone, Default, PartialEq, Serialize, Deserialize)]
-#[non_exhaustive]
 pub struct Book {
     /// The sections in this book.
     pub sections: Vec<BookItem>,
+    __non_exhaustive: (),
 }
 
 impl Book {
@@ -225,7 +225,10 @@ pub(crate) fn load_book_from_disk<P: AsRef<Path>>(summary: &Summary, src_dir: P)
         chapters.push(chapter);
     }
 
-    Ok(Book { sections: chapters })
+    Ok(Book {
+        sections: chapters,
+        __non_exhaustive: (),
+    })
 }
 
 fn load_summary_item<P: AsRef<Path> + Clone>(
@@ -378,7 +381,7 @@ And here is some \
 
         root.nested_items.push(second.clone().into());
         root.nested_items.push(SummaryItem::Separator);
-        root.nested_items.push(second.clone().into());
+        root.nested_items.push(second.into());
 
         (root, temp_dir)
     }
@@ -451,7 +454,7 @@ And here is some \
             sub_items: vec![
                 BookItem::Chapter(nested.clone()),
                 BookItem::Separator,
-                BookItem::Chapter(nested.clone()),
+                BookItem::Chapter(nested),
             ],
         });
 

src/book/mod.rs

@@ -20,6 +20,7 @@ use std::process::Command;
 use std::string::ToString;
 use tempfile::Builder as TempFileBuilder;
 use toml::Value;
+use topological_sort::TopologicalSort;
 
 use crate::errors::*;
 use crate::preprocess::{
@@ -274,6 +275,10 @@ impl MDBook {
                         RustEdition::E2018 => {
                             cmd.args(&["--edition", "2018"]);
                         }
+                        RustEdition::E2021 => {
+                            cmd.args(&["--edition", "2021"])
+                                .args(&["-Z", "unstable-options"]);
+                        }
                     }
                 }
 
@@ -368,12 +373,7 @@ fn determine_renderers(config: &Config) -> Vec<Box<dyn Renderer>> {
     renderers
 }
 
-fn default_preprocessors() -> Vec<Box<dyn Preprocessor>> {
+const DEFAULT_PREPROCESSORS: &[&'static str] = &["links", "index"];
-    vec![
-        Box::new(LinkPreprocessor::new()),
-        Box::new(IndexPreprocessor::new()),
-    ]
-}
 
 fn is_default_preprocessor(pre: &dyn Preprocessor) -> bool {
     let name = pre.name();
@@ -382,36 +382,127 @@ fn is_default_preprocessor(pre: &dyn Preprocessor) -> bool {
 
 /// Look at the `MDBook` and try to figure out what preprocessors to run.
 fn determine_preprocessors(config: &Config) -> Result<Vec<Box<dyn Preprocessor>>> {
-    let mut preprocessors = Vec::new();
+    // Collect the names of all preprocessors intended to be run, and the order
+    // in which they should be run.
+    let mut preprocessor_names = TopologicalSort::<String>::new();
 
     if config.build.use_default_preprocessors {
-        preprocessors.extend(default_preprocessors());
+        for name in DEFAULT_PREPROCESSORS {
+            preprocessor_names.insert(name.to_string());
+        }
     }
 
     if let Some(preprocessor_table) = config.get("preprocessor").and_then(Value::as_table) {
-        for key in preprocessor_table.keys() {
+        for (name, table) in preprocessor_table.iter() {
-            match key.as_ref() {
+            preprocessor_names.insert(name.to_string());
-                "links" => preprocessors.push(Box::new(LinkPreprocessor::new())),
+
-                "index" => preprocessors.push(Box::new(IndexPreprocessor::new())),
+            let exists = |name| {
-                name => preprocessors.push(interpret_custom_preprocessor(
+                (config.build.use_default_preprocessors && DEFAULT_PREPROCESSORS.contains(&name))
-                    name,
+                    || preprocessor_table.contains_key(name)
-                    &preprocessor_table[name],
+            };
-                )),
+
+            if let Some(before) = table.get("before") {
+                let before = before.as_array().ok_or_else(|| {
+                    Error::msg(format!(
+                        "Expected preprocessor.{}.before to be an array",
+                        name
+                    ))
+                })?;
+                for after in before {
+                    let after = after.as_str().ok_or_else(|| {
+                        Error::msg(format!(
+                            "Expected preprocessor.{}.before to contain strings",
+                            name
+                        ))
+                    })?;
+
+                    if !exists(after) {
+                        // Only warn so that preprocessors can be toggled on and off (e.g. for
+                        // troubleshooting) without having to worry about order too much.
+                        warn!(
+                            "preprocessor.{}.after contains \"{}\", which was not found",
+                            name, after
+                        );
+                    } else {
+                        preprocessor_names.add_dependency(name, after);
                     }
                 }
             }
 
+            if let Some(after) = table.get("after") {
+                let after = after.as_array().ok_or_else(|| {
+                    Error::msg(format!(
+                        "Expected preprocessor.{}.after to be an array",
+                        name
+                    ))
+                })?;
+                for before in after {
+                    let before = before.as_str().ok_or_else(|| {
+                        Error::msg(format!(
+                            "Expected preprocessor.{}.after to contain strings",
+                            name
+                        ))
+                    })?;
+
+                    if !exists(before) {
+                        // See equivalent warning above for rationale
+                        warn!(
+                            "preprocessor.{}.before contains \"{}\", which was not found",
+                            name, before
+                        );
+                    } else {
+                        preprocessor_names.add_dependency(before, name);
+                    }
+                }
+            }
+        }
+    }
+
+    // Now that all links have been established, queue preprocessors in a suitable order
+    let mut preprocessors = Vec::with_capacity(preprocessor_names.len());
+    // `pop_all()` returns an empty vector when no more items are not being depended upon
+    for mut names in std::iter::repeat_with(|| preprocessor_names.pop_all())
+        .take_while(|names| !names.is_empty())
+    {
+        // The `topological_sort` crate does not guarantee a stable order for ties, even across
+        // runs of the same program. Thus, we break ties manually by sorting.
+        // Careful: `str`'s default sorting, which we are implicitly invoking here, uses code point
+        // values ([1]), which may not be an alphabetical sort.
+        // As mentioned in [1], doing so depends on locale, which is not desirable for deciding
+        // preprocessor execution order.
+        // [1]: https://doc.rust-lang.org/stable/std/cmp/trait.Ord.html#impl-Ord-14
+        names.sort();
+        for name in names {
+            let preprocessor: Box<dyn Preprocessor> = match name.as_str() {
+                "links" => Box::new(LinkPreprocessor::new()),
+                "index" => Box::new(IndexPreprocessor::new()),
+                _ => {
+                    // The only way to request a custom preprocessor is through the `preprocessor`
+                    // table, so it must exist, be a table, and contain the key.
+                    let table = &config.get("preprocessor").unwrap().as_table().unwrap()[&name];
+                    let command = get_custom_preprocessor_cmd(&name, table);
+                    Box::new(CmdPreprocessor::new(name, command))
+                }
+            };
+            preprocessors.push(preprocessor);
+        }
+    }
+
+    // "If `pop_all` returns an empty vector and `len` is not 0, there are cyclic dependencies."
+    // Normally, `len() == 0` is equivalent to `is_empty()`, so we'll use that.
+    if preprocessor_names.is_empty() {
         Ok(preprocessors)
+    } else {
+        Err(Error::msg("Cyclic dependency detected in preprocessors"))
+    }
 }
 
-fn interpret_custom_preprocessor(key: &str, table: &Value) -> Box<CmdPreprocessor> {
+fn get_custom_preprocessor_cmd(key: &str, table: &Value) -> String {
-    let command = table
+    table
         .get("command")
         .and_then(Value::as_str)
         .map(ToString::to_string)
-        .unwrap_or_else(|| format!("mdbook-{}", key));
+        .unwrap_or_else(|| format!("mdbook-{}", key))
-
-    Box::new(CmdPreprocessor::new(key.to_string(), command))
 }
 
 fn interpret_custom_renderer(key: &str, table: &Value) -> Box<CmdRenderer> {
@@ -511,8 +602,8 @@ mod tests {
 
         assert!(got.is_ok());
         assert_eq!(got.as_ref().unwrap().len(), 2);
-        assert_eq!(got.as_ref().unwrap()[0].name(), "links");
+        assert_eq!(got.as_ref().unwrap()[0].name(), "index");
-        assert_eq!(got.as_ref().unwrap()[1].name(), "index");
+        assert_eq!(got.as_ref().unwrap()[1].name(), "links");
     }
 
     #[test]
@@ -559,9 +650,123 @@ mod tests {
 
         // make sure the `preprocessor.random` table exists
         let random = cfg.get_preprocessor("random").unwrap();
-        let random = interpret_custom_preprocessor("random", &Value::Table(random.clone()));
+        let random = get_custom_preprocessor_cmd("random", &Value::Table(random.clone()));
 
-        assert_eq!(random.cmd(), "python random.py");
+        assert_eq!(random, "python random.py");
+    }
+
+    #[test]
+    fn preprocessor_before_must_be_array() {
+        let cfg_str = r#"
+        [preprocessor.random]
+        before = 0
+        "#;
+
+        let cfg = Config::from_str(cfg_str).unwrap();
+
+        assert!(determine_preprocessors(&cfg).is_err());
+    }
+
+    #[test]
+    fn preprocessor_after_must_be_array() {
+        let cfg_str = r#"
+        [preprocessor.random]
+        after = 0
+        "#;
+
+        let cfg = Config::from_str(cfg_str).unwrap();
+
+        assert!(determine_preprocessors(&cfg).is_err());
+    }
+
+    #[test]
+    fn preprocessor_order_is_honored() {
+        let cfg_str = r#"
+        [preprocessor.random]
+        before = [ "last" ]
+        after = [ "index" ]
+
+        [preprocessor.last]
+        after = [ "links", "index" ]
+        "#;
+
+        let cfg = Config::from_str(cfg_str).unwrap();
+
+        let preprocessors = determine_preprocessors(&cfg).unwrap();
+        let index = |name| {
+            preprocessors
+                .iter()
+                .enumerate()
+                .find(|(_, preprocessor)| preprocessor.name() == name)
+                .unwrap()
+                .0
+        };
+        let assert_before = |before, after| {
+            if index(before) >= index(after) {
+                eprintln!("Preprocessor order:");
+                for preprocessor in &preprocessors {
+                    eprintln!("  {}", preprocessor.name());
+                }
+                panic!("{} should come before {}", before, after);
+            }
+        };
+
+        assert_before("index", "random");
+        assert_before("index", "last");
+        assert_before("random", "last");
+        assert_before("links", "last");
+    }
+
+    #[test]
+    fn cyclic_dependencies_are_detected() {
+        let cfg_str = r#"
+        [preprocessor.links]
+        before = [ "index" ]
+
+        [preprocessor.index]
+        before = [ "links" ]
+        "#;
+
+        let cfg = Config::from_str(cfg_str).unwrap();
+
+        assert!(determine_preprocessors(&cfg).is_err());
+    }
+
+    #[test]
+    fn dependencies_dont_register_undefined_preprocessors() {
+        let cfg_str = r#"
+        [preprocessor.links]
+        before = [ "random" ]
+        "#;
+
+        let cfg = Config::from_str(cfg_str).unwrap();
+
+        let preprocessors = determine_preprocessors(&cfg).unwrap();
+
+        assert!(preprocessors
+            .iter()
+            .find(|preprocessor| preprocessor.name() == "random")
+            .is_none());
+    }
+
+    #[test]
+    fn dependencies_dont_register_builtin_preprocessors_if_disabled() {
+        let cfg_str = r#"
+        [preprocessor.random]
+        before = [ "links" ]
+
+        [build]
+        use-default-preprocessors = false
+        "#;
+
+        let cfg = Config::from_str(cfg_str).unwrap();
+
+        let preprocessors = determine_preprocessors(&cfg).unwrap();
+
+        assert!(preprocessors
+            .iter()
+            .find(|preprocessor| preprocessor.name() == "links")
+            .is_none());
     }
 
     #[test]

src/book/summary.rs

@@ -382,7 +382,7 @@ impl<'a> SummaryParser<'a> {
                 }
                 Some(ev @ Event::Start(Tag::List(..))) => {
                     self.back(ev);
-                    let mut bunch_of_items = self.parse_nested_numbered(&root_number)?;
+                    let mut bunch_of_items = self.parse_nested_numbered(root_number)?;
 
                     // if we've resumed after something like a rule the root sections
                     // will be numbered from 1. We need to manually go back and update

src/cmd/init.rs

@@ -1,5 +1,5 @@
 use crate::get_book_dir;
-use clap::{App, ArgMatches, SubCommand};
+use clap::{App, Arg, ArgMatches, SubCommand};
 use mdbook::config;
 use mdbook::errors::Result;
 use mdbook::MDBook;
@@ -18,6 +18,21 @@ pub fn make_subcommand<'a, 'b>() -> App<'a, 'b> {
         )
         .arg_from_usage("--theme 'Copies the default theme into your source folder'")
         .arg_from_usage("--force 'Skips confirmation prompts'")
+        .arg(
+            Arg::with_name("title")
+                .long("title")
+                .takes_value(true)
+                .help("Sets the book title")
+                .required(false),
+        )
+        .arg(
+            Arg::with_name("ignore")
+                .long("ignore")
+                .takes_value(true)
+                .possible_values(&["none", "git"])
+                .help("Creates a VCS ignore file (i.e. .gitignore)")
+                .required(false),
+        )
 }
 
 // Init command implementation
@@ -25,7 +40,6 @@ pub fn execute(args: &ArgMatches) -> Result<()> {
     let book_dir = get_book_dir(args);
     let mut builder = MDBook::init(&book_dir);
     let mut config = config::Config::default();
-
     // If flag `--theme` is present, copy theme to src
     if args.is_present("theme") {
         let theme_dir = book_dir.join("theme");
@@ -45,13 +59,23 @@ pub fn execute(args: &ArgMatches) -> Result<()> {
         }
     }
 
+    if let Some(ignore) = args.value_of("ignore") {
+        match ignore {
+            "git" => builder.create_gitignore(true),
+            _ => builder.create_gitignore(false),
+        };
+    } else {
         println!("\nDo you want a .gitignore to be created? (y/n)");
-
         if confirm() {
             builder.create_gitignore(true);
         }
+    }
 
-    config.book.title = request_book_title();
+    config.book.title = if args.is_present("title") {
+        args.value_of("title").map(String::from)
+    } else {
+        request_book_title()
+    };
 
     if let Some(author) = get_author_name() {
         debug!("Obtained user name from gitconfig: {:?}", author);

src/config.rs

@@ -467,6 +467,9 @@ pub struct RustConfig {
 #[derive(Debug, Copy, Clone, PartialEq, Serialize, Deserialize)]
 /// Rust edition to use for the code.
 pub enum RustEdition {
+    /// The 2021 edition of Rust
+    #[serde(rename = "2021")]
+    E2021,
     /// The 2018 edition of Rust
     #[serde(rename = "2018")]
     E2018,
@@ -855,6 +858,26 @@ mod tests {
         assert_eq!(got.rust, rust_should_be);
     }
 
+    #[test]
+    fn edition_2021() {
+        let src = r#"
+        [book]
+        title = "mdBook Documentation"
+        description = "Create book from markdown files. Like Gitbook but implemented in Rust"
+        authors = ["Mathieu David"]
+        src = "./source"
+        [rust]
+        edition = "2021"
+        "#;
+
+        let rust_should_be = RustConfig {
+            edition: Some(RustEdition::E2021),
+        };
+
+        let got = Config::from_str(src).unwrap();
+        assert_eq!(got.rust, rust_should_be);
+    }
+
     #[test]
     fn load_arbitrary_output_type() {
         #[derive(Debug, Deserialize, PartialEq)]

src/main.rs

@@ -3,8 +3,9 @@ extern crate clap;
 #[macro_use]
 extern crate log;
 
+use anyhow::anyhow;
 use chrono::Local;
-use clap::{App, AppSettings, ArgMatches};
+use clap::{App, AppSettings, Arg, ArgMatches, Shell, SubCommand};
 use env_logger::Builder;
 use log::LevelFilter;
 use mdbook::utils;
@@ -20,7 +21,40 @@ const VERSION: &str = concat!("v", crate_version!());
 fn main() {
     init_logger();
 
-    // Create a list of valid arguments and sub-commands
+    let app = create_clap_app();
+
+    // Check which subcomamnd the user ran...
+    let res = match app.get_matches().subcommand() {
+        ("init", Some(sub_matches)) => cmd::init::execute(sub_matches),
+        ("build", Some(sub_matches)) => cmd::build::execute(sub_matches),
+        ("clean", Some(sub_matches)) => cmd::clean::execute(sub_matches),
+        #[cfg(feature = "watch")]
+        ("watch", Some(sub_matches)) => cmd::watch::execute(sub_matches),
+        #[cfg(feature = "serve")]
+        ("serve", Some(sub_matches)) => cmd::serve::execute(sub_matches),
+        ("test", Some(sub_matches)) => cmd::test::execute(sub_matches),
+        ("completions", Some(sub_matches)) => (|| {
+            let shell: Shell = sub_matches
+                .value_of("shell")
+                .ok_or_else(|| anyhow!("Shell name missing."))?
+                .parse()
+                .map_err(|s| anyhow!("Invalid shell: {}", s))?;
+
+            create_clap_app().gen_completions_to("mdbook", shell, &mut std::io::stdout().lock());
+            Ok(())
+        })(),
+        (_, _) => unreachable!(),
+    };
+
+    if let Err(e) = res {
+        utils::log_backtrace(&e);
+
+        std::process::exit(101);
+    }
+}
+
+/// Create a list of valid arguments and sub-commands
+fn create_clap_app<'a, 'b>() -> App<'a, 'b> {
     let app = App::new(crate_name!())
         .about(crate_description!())
         .author("Mathieu David <mathieudavid@mathieudavid.org>")
@@ -35,31 +69,26 @@ fn main() {
         .subcommand(cmd::init::make_subcommand())
         .subcommand(cmd::build::make_subcommand())
         .subcommand(cmd::test::make_subcommand())
-        .subcommand(cmd::clean::make_subcommand());
+        .subcommand(cmd::clean::make_subcommand())
+        .subcommand(
+            SubCommand::with_name("completions")
+                .about("Generate shell completions for your shell to stdout")
+                .arg(
+                    Arg::with_name("shell")
+                        .takes_value(true)
+                        .possible_values(&Shell::variants())
+                        .help("the shell to generate completions for")
+                        .value_name("SHELL")
+                        .required(true),
+                ),
+        );
 
     #[cfg(feature = "watch")]
     let app = app.subcommand(cmd::watch::make_subcommand());
     #[cfg(feature = "serve")]
     let app = app.subcommand(cmd::serve::make_subcommand());
 
-    // Check which subcomamnd the user ran...
+    app
-    let res = match app.get_matches().subcommand() {
-        ("init", Some(sub_matches)) => cmd::init::execute(sub_matches),
-        ("build", Some(sub_matches)) => cmd::build::execute(sub_matches),
-        ("clean", Some(sub_matches)) => cmd::clean::execute(sub_matches),
-        #[cfg(feature = "watch")]
-        ("watch", Some(sub_matches)) => cmd::watch::execute(sub_matches),
-        #[cfg(feature = "serve")]
-        ("serve", Some(sub_matches)) => cmd::serve::execute(sub_matches),
-        ("test", Some(sub_matches)) => cmd::test::execute(sub_matches),
-        (_, _) => unreachable!(),
-    };
-
-    if let Err(e) = res {
-        utils::log_backtrace(&e);
-
-        std::process::exit(101);
-    }
 }
 
 fn init_logger() {
@@ -103,7 +132,8 @@ fn get_book_dir(args: &ArgMatches) -> PathBuf {
 }
 
 fn open<P: AsRef<OsStr>>(path: P) {
-    if let Err(e) = open::that(path) {
+    info!("Opening web browser");
+    if let Err(e) = opener::open(path) {
         error!("Error opening web browser: {}", e);
     }
 }

src/preprocess/cmd.rs

@@ -49,7 +49,7 @@ impl CmdPreprocessor {
     fn write_input_to_child(&self, child: &mut Child, book: &Book, ctx: &PreprocessorContext) {
         let stdin = child.stdin.take().expect("Child has stdin");
 
-        if let Err(e) = self.write_input(stdin, &book, &ctx) {
+        if let Err(e) = self.write_input(stdin, book, ctx) {
             // Looks like the backend hung up before we could finish
             // sending it the render context. Log the error and keep going
             warn!("Error writing the RenderContext to the backend, {}", e);

src/renderer/html_handlebars/hbs_renderer.rs

@@ -54,16 +54,14 @@ impl HtmlHandlebars {
         let content = ch.content.clone();
         let content = utils::render_markdown(&content, ctx.html_config.curly_quotes);
 
-        let fixed_content = utils::render_markdown_with_path(
+        let fixed_content =
-            &ch.content,
+            utils::render_markdown_with_path(&ch.content, ctx.html_config.curly_quotes, Some(path));
-            ctx.html_config.curly_quotes,
-            Some(&path),
-        );
         if !ctx.is_index {
             // Add page break between chapters
             // See https://developer.mozilla.org/en-US/docs/Web/CSS/break-before and https://developer.mozilla.org/en-US/docs/Web/CSS/page-break-before
             // Add both two CSS properties because of the compatibility issue
-            print_content.push_str(r#"<div id="chapter_begin" style="break-before: page; page-break-before: always;"></div>"#);
+            print_content
+                .push_str(r#"<div style="break-before: page; page-break-before: always;"></div>"#);
         }
         print_content.push_str(&fixed_content);
 
@@ -177,7 +175,7 @@ impl HtmlHandlebars {
         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())?;
+        utils::fs::write_file(destination, output_file, rendered.as_bytes())?;
         debug!("Creating 404.html ✓");
         Ok(())
     }
@@ -222,10 +220,10 @@ impl HtmlHandlebars {
         }
         write_file(destination, "css/variables.css", &theme.variables_css)?;
         if let Some(contents) = &theme.favicon_png {
-            write_file(destination, "favicon.png", &contents)?;
+            write_file(destination, "favicon.png", contents)?;
         }
         if let Some(contents) = &theme.favicon_svg {
-            write_file(destination, "favicon.svg", &contents)?;
+            write_file(destination, "favicon.svg", contents)?;
         }
         write_file(destination, "highlight.css", &theme.highlight_css)?;
         write_file(destination, "tomorrow-night.css", &theme.tomorrow_night_css)?;
@@ -508,7 +506,7 @@ impl Renderer for HtmlHandlebars {
         debug!("Register handlebars helpers");
         self.register_hbs_helpers(&mut handlebars, &html_config);
 
-        let mut data = make_data(&ctx.root, &book, &ctx.config, &html_config, &theme)?;
+        let mut data = make_data(&ctx.root, book, &ctx.config, &html_config, &theme)?;
 
         // Print version
         let mut print_content = String::new();
@@ -551,14 +549,14 @@ impl Renderer for HtmlHandlebars {
             let rendered =
                 self.post_process(rendered, &html_config.playground, ctx.config.rust.edition);
 
-            utils::fs::write_file(&destination, "print.html", rendered.as_bytes())?;
+            utils::fs::write_file(destination, "print.html", rendered.as_bytes())?;
             debug!("Creating print.html ✓");
         }
 
         debug!("Copy static files");
-        self.copy_static_files(&destination, &theme, &html_config)
+        self.copy_static_files(destination, &theme, &html_config)
             .with_context(|| "Unable to copy across static files")?;
-        self.copy_additional_css_and_js(&html_config, &ctx.root, &destination)
+        self.copy_additional_css_and_js(&html_config, &ctx.root, destination)
             .with_context(|| "Unable to copy across additional CSS and JS")?;
 
         // Render search index
@@ -566,7 +564,7 @@ impl Renderer for HtmlHandlebars {
         {
             let search = html_config.search.unwrap_or_default();
             if search.enable {
-                super::search::create_files(&search, &destination, &book)?;
+                super::search::create_files(&search, destination, book)?;
             }
         }
 
@@ -574,7 +572,7 @@ impl Renderer for HtmlHandlebars {
             .context("Unable to emit redirects")?;
 
         // Copy all remaining files, avoid a recursive copy from/to the book build dir
-        utils::fs::copy_files_except_ext(&src_dir, &destination, true, Some(&build_dir), &["md"])?;
+        utils::fs::copy_files_except_ext(&src_dir, destination, true, Some(&build_dir), &["md"])?;
 
         Ok(())
     }
@@ -835,13 +833,15 @@ fn add_playground_pre(
                 {
                     let contains_e2015 = classes.contains("edition2015");
                     let contains_e2018 = classes.contains("edition2018");
-                    let edition_class = if contains_e2015 || contains_e2018 {
+                    let contains_e2021 = classes.contains("edition2021");
+                    let edition_class = if contains_e2015 || contains_e2018 || contains_e2021 {
                         // the user forced edition, we should not overwrite it
                         ""
                     } else {
                         match edition {
                             Some(RustEdition::E2015) => " edition2015",
                             Some(RustEdition::E2018) => " edition2018",
+                            Some(RustEdition::E2021) => " edition2021",
                             None => "",
                         }
                     };
@@ -980,7 +980,7 @@ mod tests {
         ];
 
         for (src, should_be) in inputs {
-            let got = build_header_links(&src);
+            let got = build_header_links(src);
             assert_eq!(got, should_be);
         }
     }
@@ -1063,4 +1063,28 @@ mod tests {
             assert_eq!(&*got, *should_be);
         }
     }
+    #[test]
+    fn add_playground_edition2021() {
+        let inputs = [
+            ("<code class=\"language-rust\">x()</code>",
+             "<pre class=\"playground\"><code class=\"language-rust edition2021\">\n<span class=\"boring\">#![allow(unused)]\n</span><span class=\"boring\">fn main() {\n</span>x()\n<span class=\"boring\">}\n</span></code></pre>"),
+            ("<code class=\"language-rust\">fn main() {}</code>",
+             "<pre class=\"playground\"><code class=\"language-rust edition2021\">fn main() {}\n</code></pre>"),
+            ("<code class=\"language-rust edition2015\">fn main() {}</code>",
+             "<pre class=\"playground\"><code class=\"language-rust edition2015\">fn main() {}\n</code></pre>"),
+            ("<code class=\"language-rust edition2018\">fn main() {}</code>",
+             "<pre class=\"playground\"><code class=\"language-rust edition2018\">fn main() {}\n</code></pre>"),
+        ];
+        for (src, should_be) in &inputs {
+            let got = add_playground_pre(
+                src,
+                &Playground {
+                    editable: true,
+                    ..Playground::default()
+                },
+                Some(RustEdition::E2021),
+            );
+            assert_eq!(&*got, *should_be);
+        }
+    }
 }

src/renderer/html_handlebars/helpers/navigation.rs

@@ -91,7 +91,7 @@ fn find_chapter(
         match item.get("path") {
             Some(path) if !path.is_empty() => {
                 if let Some(previous) = previous {
-                    if let Some(item) = target.find(&base_path, &path, &item, &previous)? {
+                    if let Some(item) = target.find(&base_path, path, &item, &previous)? {
                         return Ok(Some(item));
                     }
                 }

src/renderer/html_handlebars/helpers/toc.rs

@@ -142,7 +142,7 @@ impl HelperDef for RenderToc {
                 // Section does not necessarily exist
                 if let Some(section) = item.get("section") {
                     out.write("<strong aria-hidden=\"true\">")?;
-                    out.write(&section)?;
+                    out.write(section)?;
                     out.write("</strong> ")?;
                 }
             }

src/renderer/html_handlebars/search.rs

@@ -17,10 +17,10 @@ pub fn create_files(search_config: &Search, destination: &Path, book: &Book) ->
     let mut doc_urls = Vec::with_capacity(book.sections.len());
 
     for item in book.iter() {
-        render_item(&mut index, &search_config, &mut doc_urls, item)?;
+        render_item(&mut index, search_config, &mut doc_urls, item)?;
     }
 
-    let index = write_to_json(index, &search_config, doc_urls)?;
+    let index = write_to_json(index, search_config, doc_urls)?;
     debug!("Writing search index ✓");
     if index.len() > 10_000_000 {
         warn!("searchindex.json is very large ({} bytes)", index.len());
@@ -134,7 +134,7 @@ fn render_item(
                 // in an HtmlBlock tag. We must collect consecutive Html events
                 // into a block ourselves.
                 while let Some(Event::Html(html)) = p.peek() {
-                    html_block.push_str(&html);
+                    html_block.push_str(html);
                     p.next();
                 }
 
@@ -165,7 +165,12 @@ fn render_item(
         }
     }
 
-    if !heading.is_empty() {
+    if !body.is_empty() || !heading.is_empty() {
+        if heading.is_empty() {
+            if let Some(chapter) = breadcrumbs.first() {
+                heading = chapter.clone();
+            }
+        }
         // Make sure the last section is added to the index
         add_doc(
             index,

src/theme/book.js

@@ -108,9 +108,12 @@ function playground_text(playground) {
 
         let text = playground_text(code_block);
         let classes = code_block.querySelector('code').classList;
-        let has_2018 = classes.contains("edition2018");
+        let edition = "2015";
-        let edition = has_2018 ? "2018" : "2015";
+        if(classes.contains("edition2018")) {
-
+            edition = "2018";
+        } else if(classes.contains("edition2021")) {
+            edition = "2021";
+        }
         var params = {
             version: "stable",
             optimize: "0",
@@ -133,7 +136,15 @@ function playground_text(playground) {
             body: JSON.stringify(params)
         })
         .then(response => response.json())
-        .then(response => result_block.innerText = response.result)
+        .then(response => {
+            if (response.result.trim() === '') {
+                result_block.innerText = "No output";
+                result_block.classList.add("result-no-output");
+            } else {
+                result_block.innerText = response.result;
+                result_block.classList.remove("result-no-output");
+            }
+        })
         .catch(error => result_block.innerText = "Playground Communication: " + error.message);
     }
 
@@ -151,12 +162,13 @@ function playground_text(playground) {
     if (window.ace) {
         // language-rust class needs to be removed for editable
         // blocks or highlightjs will capture events
-        Array
+        code_nodes
-            .from(document.querySelectorAll('code.editable'))
+            .filter(function (node) {return node.classList.contains("editable"); })
             .forEach(function (block) { block.classList.remove('language-rust'); });
 
         Array
-            .from(document.querySelectorAll('code:not(.editable)'))
+        code_nodes
+            .filter(function (node) {return !node.classList.contains("editable"); })
             .forEach(function (block) { hljs.highlightBlock(block); });
     } else {
         code_nodes.forEach(function (block) { hljs.highlightBlock(block); });
@@ -359,7 +371,14 @@ function playground_text(playground) {
     });
 
     themePopup.addEventListener('click', function (e) {
-        var theme = e.target.id || e.target.parentElement.id;
+        var theme;
+        if (e.target.className === "theme") {
+            theme = e.target.id;
+        } else if (e.target.parentElement.className === "theme") {
+            theme = e.target.parentElement.id;
+        } else {
+            return;
+        }
         set_theme(theme);
     });
 

src/theme/css/general.css

@@ -175,3 +175,7 @@ blockquote {
     margin: 5px 0px;
     font-weight: bold;
 }
+
+.result-no-output {
+    font-style: italic;
+}

src/theme/css/variables.css

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

src/utils/fs.rs

@@ -247,7 +247,7 @@ mod tests {
         }
 
         if let Err(e) =
-            copy_files_except_ext(&tmp.path(), &tmp.path().join("output"), true, None, &["md"])
+            copy_files_except_ext(tmp.path(), &tmp.path().join("output"), true, None, &["md"])
         {
             panic!("Error while executing the function:\n{:?}", e);
         }

src/utils/mod.rs

@@ -228,7 +228,14 @@ impl EventQuoteConverter {
 fn clean_codeblock_headers(event: Event<'_>) -> Event<'_> {
     match event {
         Event::Start(Tag::CodeBlock(CodeBlockKind::Fenced(ref info))) => {
-            let info: String = info.chars().filter(|ch| !ch.is_whitespace()).collect();
+            let info: String = info
+                .chars()
+                .map(|x| match x {
+                    ' ' | '\t' => ',',
+                    _ => x,
+                })
+                .filter(|ch| !ch.is_whitespace())
+                .collect();
 
             Event::Start(Tag::CodeBlock(CodeBlockKind::Fenced(CowStr::from(info))))
         }
@@ -372,7 +379,7 @@ 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);

tests/cli/build.rs

@@ -0,0 +1,29 @@
+use crate::dummy_book::DummyBook;
+
+use assert_cmd::Command;
+
+#[test]
+fn mdbook_cli_dummy_book_generates_index_html() {
+    let temp = DummyBook::new().build().unwrap();
+
+    // doesn't exist before
+    assert!(!temp.path().join("book").exists());
+
+    let mut cmd = Command::cargo_bin("mdbook").unwrap();
+    cmd.arg("build").current_dir(temp.path());
+    cmd.assert()
+        .success()
+        .stderr(
+            predicates::str::is_match(r##"Stack depth exceeded in first[\\/]recursive.md."##)
+                .unwrap(),
+        )
+        .stderr(predicates::str::contains(
+            r##"[INFO] (mdbook::book): Running the html backend"##,
+        ));
+
+    // exists afterward
+    assert!(temp.path().join("book").exists());
+
+    let index_file = temp.path().join("book/index.html");
+    assert!(index_file.exists());
+}

tests/cli/mod.rs

@@ -0,0 +1,2 @@
+mod build;
+mod test;

tests/cli/test.rs

@@ -0,0 +1,34 @@
+use crate::dummy_book::DummyBook;
+
+use assert_cmd::Command;
+use predicates::boolean::PredicateBooleanExt;
+
+#[test]
+fn mdbook_cli_can_correctly_test_a_passing_book() {
+    let temp = DummyBook::new().with_passing_test(true).build().unwrap();
+
+    let mut cmd = Command::cargo_bin("mdbook").unwrap();
+    cmd.arg("test").current_dir(temp.path());
+    cmd.assert().success()
+      .stderr(predicates::str::is_match(r##"Testing file: "([^"]+)[\\/]README.md""##).unwrap())
+      .stderr(predicates::str::is_match(r##"Testing file: "([^"]+)[\\/]intro.md""##).unwrap())
+      .stderr(predicates::str::is_match(r##"Testing file: "([^"]+)[\\/]first[\\/]index.md""##).unwrap())
+      .stderr(predicates::str::is_match(r##"Testing file: "([^"]+)[\\/]first[\\/]nested.md""##).unwrap())
+      .stderr(predicates::str::is_match(r##"rustdoc returned an error:\n\n"##).unwrap().not())
+      .stderr(predicates::str::is_match(r##"Nested_Chapter::Rustdoc_include_works_with_anchors_too \(line \d+\) ... FAILED"##).unwrap().not());
+}
+
+#[test]
+fn mdbook_cli_detects_book_with_failing_tests() {
+    let temp = DummyBook::new().with_passing_test(false).build().unwrap();
+
+    let mut cmd = Command::cargo_bin("mdbook").unwrap();
+    cmd.arg("test").current_dir(temp.path());
+    cmd.assert().failure()
+      .stderr(predicates::str::is_match(r##"Testing file: "([^"]+)[\\/]README.md""##).unwrap())
+      .stderr(predicates::str::is_match(r##"Testing file: "([^"]+)[\\/]intro.md""##).unwrap())
+      .stderr(predicates::str::is_match(r##"Testing file: "([^"]+)[\\/]first[\\/]index.md""##).unwrap())
+      .stderr(predicates::str::is_match(r##"Testing file: "([^"]+)[\\/]first[\\/]nested.md""##).unwrap())
+      .stderr(predicates::str::is_match(r##"rustdoc returned an error:\n\n"##).unwrap())
+      .stderr(predicates::str::is_match(r##"Nested_Chapter::Rustdoc_include_works_with_anchors_too \(line \d+\) ... FAILED"##).unwrap());
+}

tests/cli_tests.rs

@@ -0,0 +1,2 @@
+mod cli;
+mod dummy_book;

tests/dummy_book/src/SUMMARY.md

@@ -12,6 +12,7 @@
     - [Recursive](first/recursive.md)
     - [Markdown](first/markdown.md)
     - [Unicode](first/unicode.md)
+    - [No Headers](first/no-headers.md)
 - [Second Chapter](second.md)
     - [Nested Chapter](second/nested.md)
 

tests/dummy_book/src/first/no-headers.md

@@ -0,0 +1,3 @@
+Capybara capybara capybara.
+
+Capybara capybara capybara.

tests/rendered_output.rs

@@ -34,6 +34,7 @@ const TOC_SECOND_LEVEL: &[&str] = &[
     "1.3. Recursive",
     "1.4. Markdown",
     "1.5. Unicode",
+    "1.6. No Headers",
     "2.1. Nested Chapter",
 ];
 
@@ -264,7 +265,7 @@ fn root_index_html() -> Result<Document> {
 fn check_second_toc_level() {
     let doc = root_index_html().unwrap();
     let mut should_be = Vec::from(TOC_SECOND_LEVEL);
-    should_be.sort();
+    should_be.sort_unstable();
 
     let pred = descendants!(
         Class("chapter"),
@@ -288,7 +289,7 @@ fn check_first_toc_level() {
     let mut should_be = Vec::from(TOC_TOP_LEVEL);
 
     should_be.extend(TOC_SECOND_LEVEL);
-    should_be.sort();
+    should_be.sort_unstable();
 
     let pred = descendants!(
         Class("chapter"),
@@ -535,7 +536,7 @@ fn redirects_are_emitted_correctly() {
         let mut redirect_file = md.build_dir_for("html");
         // append everything except the bits that make it absolute
         // (e.g. "/" or "C:\")
-        redirect_file.extend(remove_absolute_components(&original));
+        redirect_file.extend(remove_absolute_components(original));
         let contents = fs::read_to_string(&redirect_file).unwrap();
         assert!(contents.contains(redirect));
     }
@@ -552,7 +553,7 @@ fn edit_url_has_default_src_dir_edit_url() {
         edit-url-template = "https://github.com/rust-lang/mdBook/edit/master/guide/{path}"    
         "#;
 
-    write_file(&temp.path(), "book.toml", book_toml.as_bytes()).unwrap();
+    write_file(temp.path(), "book.toml", book_toml.as_bytes()).unwrap();
 
     let md = MDBook::load(temp.path()).unwrap();
     md.build().unwrap();
@@ -560,7 +561,7 @@ fn edit_url_has_default_src_dir_edit_url() {
     let index_html = temp.path().join("book").join("index.html");
     assert_contains_strings(
         index_html,
-        &vec![
+        &[
             r#"href="https://github.com/rust-lang/mdBook/edit/master/guide/src/README.md" title="Suggest an edit""#,
         ],
     );
@@ -578,7 +579,7 @@ fn edit_url_has_configured_src_dir_edit_url() {
         edit-url-template = "https://github.com/rust-lang/mdBook/edit/master/guide/{path}"    
         "#;
 
-    write_file(&temp.path(), "book.toml", book_toml.as_bytes()).unwrap();
+    write_file(temp.path(), "book.toml", book_toml.as_bytes()).unwrap();
 
     let md = MDBook::load(temp.path()).unwrap();
     md.build().unwrap();
@@ -586,7 +587,7 @@ fn edit_url_has_configured_src_dir_edit_url() {
     let index_html = temp.path().join("book").join("index.html");
     assert_contains_strings(
         index_html,
-        &vec![
+        &[
             r#"href="https://github.com/rust-lang/mdBook/edit/master/guide/src2/README.md" title="Suggest an edit""#,
         ],
     );
@@ -611,7 +612,7 @@ mod search {
         let index = fs::read_to_string(index).unwrap();
         let index = index.trim_start_matches("Object.assign(window.search, ");
         let index = index.trim_end_matches(");");
-        serde_json::from_str(&index).unwrap()
+        serde_json::from_str(index).unwrap()
     }
 
     #[test]
@@ -631,6 +632,7 @@ mod search {
         let introduction = get_doc_ref("intro.html#introduction");
         let some_section = get_doc_ref("first/index.html#some-section");
         let summary = get_doc_ref("first/includes.html#summary");
+        let no_headers = get_doc_ref("first/no-headers.html");
         let conclusion = get_doc_ref("conclusion.html#conclusion");
 
         let bodyidx = &index["index"]["index"]["body"]["root"];
@@ -644,13 +646,21 @@ mod search {
         assert_eq!(docs[&some_section]["body"], "");
         assert_eq!(
             docs[&summary]["body"],
-            "Dummy Book Introduction First Chapter Nested Chapter Includes Recursive Markdown Unicode Second Chapter Nested Chapter Conclusion"
+            "Dummy Book Introduction First Chapter Nested Chapter Includes Recursive Markdown Unicode No Headers Second Chapter Nested Chapter Conclusion"
         );
         assert_eq!(
             docs[&summary]["breadcrumbs"],
             "First Chapter » Includes » Summary"
         );
         assert_eq!(docs[&conclusion]["body"], "I put &lt;HTML&gt; in here!");
+        assert_eq!(
+            docs[&no_headers]["breadcrumbs"],
+            "First Chapter » No Headers"
+        );
+        assert_eq!(
+            docs[&no_headers]["body"],
+            "Capybara capybara capybara. Capybara capybara capybara."
+        );
     }
 
     // Setting this to `true` may cause issues with `cargo watch`,