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| <main> |
| <h1 id="rustdoc-overview"><a class="header" href="#rustdoc-overview">Rustdoc overview</a></h1> |
| <p><code>rustdoc</code> lives in-tree with the compiler and standard library. |
| This chapter is about how it works. |
| For information about Rustdoc’s features and how to use them, see |
| the <a href="https://doc.rust-lang.org/nightly/rustdoc/">Rustdoc book</a>. |
| For more details about how rustdoc works, see the <a href="./rustdoc-internals.html">“Rustdoc internals” chapter</a>.</p> |
| <p><code>rustdoc</code> uses <code>rustc</code> internals (and, of course, the standard library), so you |
| will have to build the compiler and <code>std</code> once before you can build <code>rustdoc</code>.</p> |
| <p>Rustdoc is implemented entirely within the crate <a href="https://github.com/rust-lang/rust/tree/HEAD/src/librustdoc"><code>librustdoc</code></a>. |
| It runs the compiler up to the point where we have an internal representation of a |
| crate (HIR) and the ability to run some queries about the types of items. |
| <a href="./hir.html">HIR</a> and <a href="./query.html">queries</a> are discussed in the linked chapters.</p> |
| <p><code>librustdoc</code> performs two major steps after that to render a set of documentation:</p> |
| <ul> |
| <li>“Clean” the AST into a form that’s more suited to creating documentation (and |
| slightly more resistant to churn in the compiler).</li> |
| <li>Use this cleaned AST to render a crate’s documentation, one page at a time.</li> |
| </ul> |
| <p>Naturally, there’s more than just this, and those descriptions simplify out |
| lots of details, but that’s the high-level overview.</p> |
| <p>(Side note: <code>librustdoc</code> is a library crate! |
| The <code>rustdoc</code> binary is created using the project in <a href="https://github.com/rust-lang/rust/tree/HEAD/src/tools/rustdoc"><code>src/tools/rustdoc</code></a>. |
| Note that literally all that does is call the <code>main()</code> that’s in this crate’s <code>lib.rs</code>, though.)</p> |
| <h2 id="cheat-sheet"><a class="header" href="#cheat-sheet">Cheat sheet</a></h2> |
| <ul> |
| <li>Run <code>./x setup tools</code> before getting started. This will configure <code>x</code> |
| with nice settings for developing rustdoc and other tools, including |
| downloading a copy of rustc rather than building it.</li> |
| <li>Use <code>./x check rustdoc</code> to quickly check for compile errors.</li> |
| <li>Use <code>./x build library rustdoc</code> to make a usable |
| rustdoc you can run on other projects. |
| <ul> |
| <li>Add <code>library/test</code> to be able to use <code>rustdoc --test</code>.</li> |
| <li>Run <code>rustup toolchain link stage2 build/host/stage2</code> to add a |
| custom toolchain called <code>stage2</code> to your rustup environment. |
| After running that, <code>cargo +stage2 doc</code> in any directory will build with |
| your locally-compiled rustdoc.</li> |
| </ul> |
| </li> |
| <li>Use <code>./x doc library</code> to use this rustdoc to generate the |
| standard library docs. |
| <ul> |
| <li>The completed docs will be available in <code>build/host/doc</code> (under <code>core</code>, <code>alloc</code>, and <code>std</code>).</li> |
| <li>If you want to copy those docs to a webserver, copy all of |
| <code>build/host/doc</code>, since that’s where the CSS, JS, fonts, and landing page are.</li> |
| <li>For frontend debugging, disable the <code>rust.docs-minification</code> option in <a href="./building/how-to-build-and-run.html"><code>bootstrap.toml</code></a>.</li> |
| </ul> |
| </li> |
| <li>Use <code>./x test tests/rustdoc*</code> to run the tests using a stage1 |
| rustdoc. |
| <ul> |
| <li>See <a href="./rustdoc-internals.html">Rustdoc internals</a> for more information about tests.</li> |
| </ul> |
| </li> |
| <li>Use <code>./x.py test tidy --extra-checks=js</code> to run rustdoc’s JavaScript checks (<code>eslint</code>, <code>es-check</code>, and <code>tsc</code>).</li> |
| </ul> |
| <blockquote> |
| <p><strong>Note:</strong> <code>./x.py test tidy</code> already runs these checks automatically when JS/TS sources changed; <code>--extra-checks=js</code> forces them explicitly.</p> |
| </blockquote> |
| <h3 id="javascript-ci-checks"><a class="header" href="#javascript-ci-checks">JavaScript CI checks</a></h3> |
| <p>Rustdoc’s JavaScript and TypeScript are checked during CI by <code>eslint</code>, <code>es-check</code>, and <code>tsc</code> (not by compiletest). |
| These run as part of the <code>tidy</code> job.</p> |
| <pre><code class="language-console">./x.py test tidy --extra-checks=js |
| </code></pre> |
| <p>The <code>--extra-checks=js</code> flag enables the frontend linting that runs in CI.</p> |
| <h2 id="code-structure"><a class="header" href="#code-structure">Code structure</a></h2> |
| <p>All paths in this section are relative to <code>src/librustdoc/</code> in the rust-lang/rust repository.</p> |
| <ul> |
| <li>Most of the HTML printing code is in <code>html/format.rs</code> and <code>html/render/mod.rs</code>. |
| It’s in a bunch of functions returning <code>impl std::fmt::Display</code>.</li> |
| <li>The data types that get rendered by the functions mentioned above are defined in <code>clean/types.rs</code>. |
| The functions responsible for creating them from the <code>HIR</code> and the <code>rustc_middle::ty</code> IR |
| live in <code>clean/mod.rs</code>.</li> |
| <li>The bits specific to using rustdoc as a test harness are in |
| <code>doctest.rs</code>.</li> |
| <li>The Markdown renderer is loaded up in <code>html/markdown.rs</code>, including functions |
| for extracting doctests from a given block of Markdown.</li> |
| <li>Frontend CSS and JavaScript are stored in <code>html/static/</code>. |
| <ul> |
| <li>Re. JavaScript, type annotations are written using <a href="https://www.typescriptlang.org/docs/handbook/jsdoc-supported-types.html">TypeScript-flavored JSDoc</a> |
| comments and an external <code>.d.ts</code> file. |
| This way, the code itself remains plain, valid JavaScript. |
| We only use <code>tsc</code> as a linter.</li> |
| </ul> |
| </li> |
| </ul> |
| <h2 id="tests"><a class="header" href="#tests">Tests</a></h2> |
| <p><code>rustdoc</code>’s integration tests are split across several test suites. |
| See <a href="tests/compiletest.html#rustdoc-test-suites">Rustdoc tests suites</a> for more details.</p> |
| <h2 id="constraints"><a class="header" href="#constraints">Constraints</a></h2> |
| <p>We try to make rustdoc work reasonably well with JavaScript disabled, and when browsing local files. |
| We have <a href="https://rust-lang.github.io/rfcs/1985-tiered-browser-support.html#supported-browsers">a list of supported browsers</a>.</p> |
| <p>Supporting local files (<code>file:///</code> URLs) brings some surprising restrictions. |
| Certain browser features that require secure origins, like <code>localStorage</code> and |
| Service Workers, don’t work reliably. |
| We can still use such features, but we should make sure pages are still usable without them.</p> |
| <p>Rustdoc <a href="https://doc.rust-lang.org/rustdoc/advanced-features.html#interactions-between-platform-specific-docs">does not type-check function bodies</a>. |
| This works by <a href="https://github.com/rust-lang/rust/blob/52bf0cf795dfecc8b929ebb1c1e2545c3f41d4c9/src/librustdoc/core.rs#L299-L323">overriding the built-in queries for typeck</a>, |
| by <a href="https://github.com/rust-lang/rust/blob/52bf0cf795dfecc8b929ebb1c1e2545c3f41d4c9/compiler/rustc_resolve/src/late.rs#L4517">silencing name resolution errors</a>, and by <a href="https://github.com/rust-lang/rust/blob/52bf0cf795dfecc8b929ebb1c1e2545c3f41d4c9/compiler/rustc_hir_analysis/src/check/check.rs#L188-L194">not resolving opaque types</a>. |
| This comes with several caveats: in particular, rustdoc <em>cannot</em> run any parts of the compiler that |
| require type-checking bodies; |
| for example, it cannot generate <code>.rlib</code> files or run most lints. |
| We want to move away from this model eventually, but we need some alternative for |
| <a href="https://github.com/rust-lang/rust/issues/75100">the people using it</a>; |
| see <a href="https://rust-lang.zulipchat.com/#narrow/stream/266220-rustdoc/topic/stop.20accepting.20broken.20code">various</a> |
| <a href="https://rust-lang.zulipchat.com/#narrow/channel/393423-t-rustdoc.2Fmeetings/topic/meeting.202024-07-08/near/449969836">previous</a> <a href="https://rust-lang.zulipchat.com/#narrow/channel/238009-t-compiler.2Fmeetings/topic/.5Bweekly.5D.202023-01-26/near/323755789">Zulip</a> <a href="https://rust-lang.zulipchat.com/#narrow/channel/266220-t-rustdoc/topic/Pre-RFC.3A.20stop.20accepting.20broken.20code">discussions</a>. |
| For examples of code that breaks if this hack is removed, see |
| <a href="https://github.com/rust-lang/rust/tree/163cb4ea3f0ae3bc7921cc259a08a7bf92e73ee6/tests/rustdoc-ui/error-in-impl-trait"><code>tests/rustdoc-ui/error-in-impl-trait</code></a>.</p> |
| <h2 id="multiple-runs-same-output-directory"><a class="header" href="#multiple-runs-same-output-directory">Multiple runs, same output directory</a></h2> |
| <p>Rustdoc can be run multiple times for varying inputs, with its output set to the same directory. |
| That’s how cargo produces documentation for dependencies of the current crate. |
| It can also be done manually if a user wants a big |
| documentation bundle with all of the docs they care about.</p> |
| <p>HTML is generated independently for each crate, but there is some cross-crate |
| information that we update as we add crates to the output directory:</p> |
| <ul> |
| <li><code>crates<SUFFIX>.js</code> holds a list of all crates in the output directory.</li> |
| <li><code>search-index<SUFFIX>.js</code> holds a list of all searchable items.</li> |
| <li>For each trait, there is a file under <code>implementors/.../trait.TraitName.js</code> |
| containing a list of implementors of that trait. |
| The implementors may be in |
| different crates than the trait, and the JS file is updated as we discover new ones.</li> |
| </ul> |
| <h2 id="use-cases"><a class="header" href="#use-cases">Use cases</a></h2> |
| <p>There are a few major use cases for rustdoc that you should keep in mind when working on it:</p> |
| <h3 id="standard-library-docs"><a class="header" href="#standard-library-docs">Standard library docs</a></h3> |
| <p>These are published at <a href="https://doc.rust-lang.org/std">https://doc.rust-lang.org/std</a> as part of the Rust release process. |
| Stable releases are also uploaded to specific versioned URLs like |
| <a href="https://doc.rust-lang.org/1.57.0/std/">https://doc.rust-lang.org/1.57.0/std/</a>. |
| Beta and nightly docs are published to |
| <a href="https://doc.rust-lang.org/beta/std/">https://doc.rust-lang.org/beta/std/</a> and <a href="https://doc.rust-lang.org/nightly/std/">https://doc.rust-lang.org/nightly/std/</a>. |
| The docs are uploaded with the <a href="https://github.com/rust-lang/promote-release">promote-release |
| tool</a> and served from S3 with CloudFront.</p> |
| <p>The standard library docs contain five crates: alloc, core, proc_macro, std, and test.</p> |
| <h3 id="docsrs"><a class="header" href="#docsrs">docs.rs</a></h3> |
| <p>When crates are published to crates.io, docs.rs automatically builds |
| and publishes their documentation, for instance at <a href="https://docs.rs/serde/latest/serde/">https://docs.rs/serde/latest/serde/</a>. |
| It always builds with the current nightly |
| rustdoc, so any changes you land in rustdoc are “insta-stable” in that they will |
| have an immediate public effect on docs.rs. |
| Old documentation is only sometimes rebuilt, so |
| you will see some variation in UI when browsing old releases in docs.rs. |
| Crate authors can request rebuilds, which will be run with the latest rustdoc.</p> |
| <p>Docs.rs performs some transformations on rustdoc’s output in order to save |
| storage and display a navigation bar at the top. |
| In particular, certain static |
| files, like main.js and rustdoc.css, may be shared across multiple invocations |
| of the same version of rustdoc. |
| Others, like crates.js and sidebar-items.js, are different for different invocations. |
| Still others, like fonts, will never change. |
| These categories are distinguished using the <code>SharedResource</code> enum in |
| <code>src/librustdoc/html/render/write_shared.rs</code></p> |
| <p>Documentation on docs.rs is always generated for a single crate at a time, so |
| the search and sidebar functionality don’t include dependencies of the current crate.</p> |
| <h3 id="locally-generated-docs"><a class="header" href="#locally-generated-docs">Locally generated docs</a></h3> |
| <p>Crate authors can run <code>cargo doc --open</code> in crates they have checked out locally to see the docs. |
| This is useful to check that the docs they are writing are useful and display correctly. |
| It can also be useful for people to view documentation on crates they aren’t authors of, but want to |
| use. |
| In both cases, people may use <code>--document-private-items</code> Cargo flag to |
| see private methods, fields, and so on, which are normally not displayed.</p> |
| <p>By default, <code>cargo doc</code> will generate documentation for a crate and all of its dependencies. |
| That can result in a very large documentation bundle, with a large (and slow) search corpus. |
| The Cargo flag <code>--no-deps</code> inhibits that behavior and generates docs for just the crate.</p> |
| <h3 id="self-hosted-project-docs"><a class="header" href="#self-hosted-project-docs">Self-hosted project docs</a></h3> |
| <p>Some projects host their own documentation. |
| This is easy to do by locally generating docs, and simply copying them to a web server. |
| Rustdoc’s HTML output can be extensively customized by flags. |
| Users can add a theme, set the default theme, and inject arbitrary HTML. |
| See <code>rustdoc --help</code> for details.</p> |
| |
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