2 [contributing-to-rust]: #contributing-to-rust
4 Thank you for your interest in contributing to Rust! There are many ways to
5 contribute, and we appreciate all of them. This document is a bit long, so here's
6 links to the major sections:
8 * [Feature Requests](#feature-requests)
9 * [Bug Reports](#bug-reports)
10 * [The Build System](#the-build-system)
11 * [Pull Requests](#pull-requests)
12 * [Writing Documentation](#writing-documentation)
13 * [Issue Triage](#issue-triage)
14 * [Out-of-tree Contributions](#out-of-tree-contributions)
15 * [Helpful Links and Information](#helpful-links-and-information)
17 If you have questions, please make a post on [internals.rust-lang.org][internals] or
18 hop on the [Rust Discord server][rust-discord] or [Rust Zulip server][rust-zulip].
20 As a reminder, all contributors are expected to follow our [Code of Conduct][coc].
22 The [rustc-guide] is your friend! It describes how the compiler works and how
23 to contribute to it in more detail than this document.
25 If this is your first time contributing, the [walkthrough] chapter of the guide
26 can give you a good example of how a typical contribution would go.
28 [internals]: https://internals.rust-lang.org
29 [rust-discord]: http://discord.gg/rust-lang
30 [rust-zulip]: https://rust-lang.zulipchat.com
31 [coc]: https://www.rust-lang.org/conduct.html
32 [rustc-guide]: https://rust-lang.github.io/rustc-guide/
33 [walkthrough]: https://rust-lang.github.io/rustc-guide/walkthrough.html
36 [feature-requests]: #feature-requests
38 To request a change to the way the Rust language works, please head over
39 to the [RFCs repository](https://github.com/rust-lang/rfcs) and view the
40 [README](https://github.com/rust-lang/rfcs/blob/master/README.md)
44 [bug-reports]: #bug-reports
46 While bugs are unfortunate, they're a reality in software. We can't fix what we
47 don't know about, so please report liberally. If you're not sure if something
48 is a bug or not, feel free to file a bug anyway.
50 **If you believe reporting your bug publicly represents a security risk to Rust users,
51 please follow our [instructions for reporting security vulnerabilities](https://www.rust-lang.org/policies/security)**.
53 If you have the chance, before reporting a bug, please [search existing
54 issues](https://github.com/rust-lang/rust/search?q=&type=Issues&utf8=%E2%9C%93),
55 as it's possible that someone else has already reported your error. This doesn't
56 always work, and sometimes it's hard to know what to search for, so consider this
57 extra credit. We won't mind if you accidentally file a duplicate report.
59 Similarly, to help others who encountered the bug find your issue,
60 consider filing an issue with a descriptive title, which contains information that might be unique to it.
61 This can be the language or compiler feature used, the conditions that trigger the bug,
62 or part of the error message if there is any.
63 An example could be: **"impossible case reached" on lifetime inference for impl Trait in return position**.
65 Opening an issue is as easy as following [this
66 link](https://github.com/rust-lang/rust/issues/new) and filling out the fields.
67 Here's a template that you can use to file a bug, though it's not necessary to
70 <short summary of the bug>
74 <code sample that causes the bug>
76 I expected to see this happen: <explanation>
78 Instead, this happened: <explanation>
82 `rustc --version --verbose`:
86 All three components are important: what you did, what you expected, what
87 happened instead. Please include the output of `rustc --version --verbose`,
88 which includes important information about what platform you're on, what
89 version of Rust you're using, etc.
91 Sometimes, a backtrace is helpful, and so including that is nice. To get
92 a backtrace, set the `RUST_BACKTRACE` environment variable to a value
93 other than `0`. The easiest way
94 to do this is to invoke `rustc` like this:
97 $ RUST_BACKTRACE=1 rustc ...
102 For info on how to configure and build the compiler, please see [this
103 chapter][rustcguidebuild] of the rustc-guide. This chapter contains info for
104 contributions to the compiler and the standard library. It also lists some
105 really useful commands to the build system (`./x.py`), which could save you a
108 [rustcguidebuild]: https://rust-lang.github.io/rustc-guide/how-to-build-and-run.html
111 [pull-requests]: #pull-requests
113 Pull requests are the primary mechanism we use to change Rust. GitHub itself
114 has some [great documentation][about-pull-requests] on using the Pull Request feature.
115 We use the "fork and pull" model [described here][development-models], where
116 contributors push changes to their personal fork and create pull requests to
117 bring those changes into the source repository.
119 [about-pull-requests]: https://help.github.com/articles/about-pull-requests/
120 [development-models]: https://help.github.com/articles/about-collaborative-development-models/
122 Please make pull requests against the `master` branch.
124 Rust follows a no merge policy, meaning, when you encounter merge
125 conflicts you are expected to always rebase instead of merge.
126 E.g. always use rebase when bringing the latest changes from
127 the master branch to your feature branch.
128 Also, please make sure that fixup commits are squashed into other related
129 commits with meaningful commit messages.
131 Please make sure your pull request is in compliance with Rust's style
132 guidelines by running
134 $ python x.py test src/tools/tidy
136 Make this check before every pull request (and every new commit in a pull
137 request); you can add [git hooks](https://git-scm.com/book/en/v2/Customizing-Git-Git-Hooks)
138 before every push to make sure you never forget to make this check.
140 All pull requests are reviewed by another person. We have a bot,
141 [@rust-highfive][rust-highfive], that will automatically assign a random person to review your
144 If you want to request that a specific person reviews your pull request,
145 you can add an `r?` to the message. For example, [Steve][steveklabnik] usually reviews
146 documentation changes. So if you were to make a documentation change, add
150 to the end of the message, and @rust-highfive will assign [@steveklabnik][steveklabnik] instead
151 of a random person. This is entirely optional.
153 After someone has reviewed your pull request, they will leave an annotation
154 on the pull request with an `r+`. It will look something like this:
158 This tells [@bors][bors], our lovable integration bot, that your pull request has
159 been approved. The PR then enters the [merge queue][merge-queue], where [@bors][bors]
160 will run all the tests on every platform we support. If it all works out,
161 [@bors][bors] will merge your code into `master` and close the pull request.
163 Depending on the scale of the change, you may see a slightly different form of `r+`:
167 The additional `rollup` tells [@bors][bors] that this change is eligible for to be
168 "rolled up". Changes that are rolled up are tested and merged at the same time, to
169 speed the process up. Typically only small changes that are expected not to conflict
170 with one another are rolled up.
172 [rust-highfive]: https://github.com/rust-highfive
173 [steveklabnik]: https://github.com/steveklabnik
174 [bors]: https://github.com/bors
175 [merge-queue]: https://buildbot2.rust-lang.org/homu/queue/rust
177 Speaking of tests, Rust has a comprehensive test suite. More information about
178 it can be found [here][rctd].
180 ### External Dependencies
182 Currently building Rust will also build the following external projects:
184 * [clippy](https://github.com/rust-lang/rust-clippy)
185 * [miri](https://github.com/rust-lang/miri)
186 * [rustfmt](https://github.com/rust-lang/rustfmt)
187 * [rls](https://github.com/rust-lang/rls/)
189 We allow breakage of these tools in the nightly channel. Maintainers of these
190 projects will be notified of the breakages and should fix them as soon as
193 After the external is fixed, one could add the changes with
196 git add path/to/submodule
199 outside the submodule.
201 In order to prepare your tool-fixing PR, you can run the build locally by doing
202 `./x.py build src/tools/TOOL`. If you will be editing the sources
203 there, you may wish to set `submodules = false` in the `config.toml`
204 to prevent `x.py` from resetting to the original branch.
206 Breakage is not allowed in the beta and stable channels, and must be addressed
207 before the PR is merged.
209 #### Breaking Tools Built With The Compiler
211 Rust's build system builds a number of tools that make use of the
212 internals of the compiler. This includes
213 [Clippy](https://github.com/rust-lang/rust-clippy),
214 [RLS](https://github.com/rust-lang/rls) and
215 [rustfmt](https://github.com/rust-lang/rustfmt). If these tools
216 break because of your changes, you may run into a sort of "chicken and egg"
217 problem. These tools rely on the latest compiler to be built so you can't update
218 them to reflect your changes to the compiler until those changes are merged into
219 the compiler. At the same time, you can't get your changes merged into the compiler
220 because the rust-lang/rust build won't pass until those tools build and pass their
223 That means that, in the default state, you can't update the compiler without first
224 fixing rustfmt, rls and the other tools that the compiler builds.
226 Luckily, a feature was [added to Rust's build](https://github.com/rust-lang/rust/issues/45861)
227 to make all of this easy to handle. The idea is that we allow these tools to be "broken",
228 so that the rust-lang/rust build passes without trying to build them, then land the change
229 in the compiler, wait for a nightly, and go update the tools that you broke. Once you're done
230 and the tools are working again, you go back in the compiler and update the tools
231 so they can be distributed again.
233 This should avoid a bunch of synchronization dances and is also much easier on contributors as
234 there's no need to block on rls/rustfmt/other tools changes going upstream.
236 Here are those same steps in detail:
238 1. (optional) First, if it doesn't exist already, create a `config.toml` by copying
239 `config.toml.example` in the root directory of the Rust repository.
240 Set `submodules = false` in the `[build]` section. This will prevent `x.py`
241 from resetting to the original branch after you make your changes. If you
242 need to [update any submodules to their latest versions](#updating-submodules),
243 see the section of this file about that for more information.
244 2. (optional) Run `./x.py test src/tools/rustfmt` (substituting the submodule
245 that broke for `rustfmt`). Fix any errors in the submodule (and possibly others).
246 3. (optional) Make commits for your changes and send them to upstream repositories as a PR.
247 4. (optional) Maintainers of these submodules will **not** merge the PR. The PR can't be
248 merged because CI will be broken. You'll want to write a message on the PR referencing
249 your change, and how the PR should be merged once your change makes it into a nightly.
250 5. Wait for your PR to merge.
251 6. Wait for a nightly
252 7. (optional) Help land your PR on the upstream repository now that your changes are in nightly.
253 8. (optional) Send a PR to rust-lang/rust updating the submodule.
255 #### Updating submodules
257 These instructions are specific to updating `rustfmt`, however they may apply
258 to the other submodules as well. Please help by improving these instructions
259 if you find any discrepancies or special cases that need to be addressed.
261 To update the `rustfmt` submodule, start by running the appropriate
262 [`git submodule` command](https://git-scm.com/book/en/v2/Git-Tools-Submodules).
263 For example, to update to the latest commit on the remote master branch,
266 git submodule update --remote src/tools/rustfmt
268 If you run `./x.py build` now, and you are lucky, it may just work. If you see
269 an error message about patches that did not resolve to any crates, you will need
270 to complete a few more steps which are outlined with their rationale below.
272 *(This error may change in the future to include more information.)*
274 error: failed to resolve patches for `https://github.com/rust-lang/rustfmt`
277 patch for `rustfmt-nightly` in `https://github.com/rust-lang/rustfmt` did not resolve to any crates
278 failed to run: ~/rust/build/x86_64-unknown-linux-gnu/stage0/bin/cargo build --manifest-path ~/rust/src/bootstrap/Cargo.toml
281 If you haven't used the `[patch]`
282 section of `Cargo.toml` before, there is [some relevant documentation about it
283 in the cargo docs](http://doc.crates.io/manifest.html#the-patch-section). In
284 addition to that, you should read the
285 [Overriding dependencies](http://doc.crates.io/specifying-dependencies.html#overriding-dependencies)
286 section of the documentation as well.
288 Specifically, the following [section in Overriding dependencies](http://doc.crates.io/specifying-dependencies.html#testing-a-bugfix) reveals what the problem is:
290 > Next up we need to ensure that our lock file is updated to use this new version of uuid so our project uses the locally checked out copy instead of one from crates.io. The way [patch] works is that it'll load the dependency at ../path/to/uuid and then whenever crates.io is queried for versions of uuid it'll also return the local version.
292 > This means that the version number of the local checkout is significant and will affect whether the patch is used. Our manifest declared uuid = "1.0" which means we'll only resolve to >= 1.0.0, < 2.0.0, and Cargo's greedy resolution algorithm also means that we'll resolve to the maximum version within that range. Typically this doesn't matter as the version of the git repository will already be greater or match the maximum version published on crates.io, but it's important to keep this in mind!
294 This says that when we updated the submodule, the version number in our
295 `src/tools/rustfmt/Cargo.toml` changed. The new version is different from
296 the version in `Cargo.lock`, so the build can no longer continue.
298 To resolve this, we need to update `Cargo.lock`. Luckily, cargo provides a
299 command to do this easily.
302 $ cargo update -p rustfmt-nightly
305 This should change the version listed in `Cargo.lock` to the new version you updated
306 the submodule to. Running `./x.py build` should work now.
308 ## Writing Documentation
310 Documentation improvements are very welcome. The source of `doc.rust-lang.org`
311 is located in `src/doc` in the tree, and standard API documentation is generated
312 from the source code itself. Documentation pull requests function in the same way
313 as other pull requests.
315 To find documentation-related issues, sort by the [T-doc label][tdoc].
317 [tdoc]: https://github.com/rust-lang/rust/issues?q=is%3Aopen%20is%3Aissue%20label%3AT-doc
319 You can find documentation style guidelines in [RFC 1574][rfc1574].
321 [rfc1574]: https://github.com/rust-lang/rfcs/blob/master/text/1574-more-api-documentation-conventions.md#appendix-a-full-conventions-text
323 In many cases, you don't need a full `./x.py doc`. You can use `rustdoc` directly
324 to check small fixes. For example, `rustdoc src/doc/reference.md` will render
325 reference to `doc/reference.html`. The CSS might be messed up, but you can
326 verify that the HTML is right.
328 Additionally, contributions to the [rustc-guide] are always welcome. Contributions
329 can be made directly at [the
330 rust-lang/rustc-guide](https://github.com/rust-lang/rustc-guide) repo. The issue
331 tracker in that repo is also a great way to find things that need doing. There
332 are issues for beginners and advanced compiler devs alike!
336 Sometimes, an issue will stay open, even though the bug has been fixed. And
337 sometimes, the original bug may go stale because something has changed in the
340 It can be helpful to go through older bug reports and make sure that they are
341 still valid. Load up an older issue, double check that it's still true, and
342 leave a comment letting us know if it is or is not. The [least recently
343 updated sort][lru] is good for finding issues like this.
345 Contributors with sufficient permissions on the Rust repo can help by adding
346 labels to triage issues:
348 * Yellow, **A**-prefixed labels state which **area** of the project an issue
351 * Magenta, **B**-prefixed labels identify bugs which are **blockers**.
353 * Dark blue, **beta-** labels track changes which need to be backported into
356 * Light purple, **C**-prefixed labels represent the **category** of an issue.
358 * Green, **E**-prefixed labels explain the level of **experience** necessary
361 * The dark blue **final-comment-period** label marks bugs that are using the
362 RFC signoff functionality of [rfcbot][rfcbot] and are currently in the final
365 * Red, **I**-prefixed labels indicate the **importance** of the issue. The
366 [I-nominated][inom] label indicates that an issue has been nominated for
367 prioritizing at the next triage meeting.
369 * The purple **metabug** label marks lists of bugs collected by other
372 * Purple gray, **O**-prefixed labels are the **operating system** or platform
373 that this issue is specific to.
375 * Orange, **P**-prefixed labels indicate a bug's **priority**. These labels
376 are only assigned during triage meetings, and replace the [I-nominated][inom]
379 * The gray **proposed-final-comment-period** label marks bugs that are using
380 the RFC signoff functionality of [rfcbot][rfcbot] and are currently awaiting
381 signoff of all team members in order to enter the final comment period.
383 * Pink, **regression**-prefixed labels track regressions from stable to the
386 * The light orange **relnotes** label marks issues that should be documented in
387 the release notes of the next release.
389 * Gray, **S**-prefixed labels are used for tracking the **status** of pull
392 * Blue, **T**-prefixed bugs denote which **team** the issue belongs to.
394 If you're looking for somewhere to start, check out the [E-easy][eeasy] tag.
396 [inom]: https://github.com/rust-lang/rust/issues?q=is%3Aopen+is%3Aissue+label%3AI-nominated
397 [eeasy]: https://github.com/rust-lang/rust/issues?q=is%3Aopen+is%3Aissue+label%3AE-easy
398 [lru]: https://github.com/rust-lang/rust/issues?q=is%3Aissue+is%3Aopen+sort%3Aupdated-asc
399 [rfcbot]: https://github.com/anp/rfcbot-rs/
401 ## Out-of-tree Contributions
403 There are a number of other ways to contribute to Rust that don't deal with
406 Answer questions in the _Get Help!_ channels from the [Rust Discord server][rust-discord], on [users.rust-lang.org][users],
407 or on [StackOverflow][so].
409 Participate in the [RFC process](https://github.com/rust-lang/rfcs).
411 Find a [requested community library][community-library], build it, and publish
412 it to [Crates.io](http://crates.io). Easier said than done, but very, very
415 [rust-discord]: https://discord.gg/rust-lang
416 [users]: https://users.rust-lang.org/
417 [so]: http://stackoverflow.com/questions/tagged/rust
418 [community-library]: https://github.com/rust-lang/rfcs/labels/A-community-library
420 ## Helpful Links and Information
422 For people new to Rust, and just starting to contribute, or even for
423 more seasoned developers, some useful places to look for information
426 * The [rustc guide] contains information about how various parts of the compiler work and how to contribute to the compiler
427 * [Rust Forge][rustforge] contains additional documentation, including write-ups of how to achieve common tasks
428 * The [Rust Internals forum][rif], a place to ask questions and
429 discuss Rust's internals
430 * The [generated documentation for rust's compiler][gdfrustc]
431 * The [rust reference][rr], even though it doesn't specifically talk about Rust's internals, it's a great resource nonetheless
432 * Although out of date, [Tom Lee's great blog article][tlgba] is very helpful
433 * [rustaceans.org][ro] is helpful, but mostly dedicated to IRC
434 * The [Rust Compiler Testing Docs][rctd]
435 * For [@bors][bors], [this cheat sheet][cheatsheet] is helpful
436 (though you'll need to replace `@homu` with `@bors` in any commands)
437 * **Google!** ([search only in Rust Documentation][gsearchdocs] to find types, traits, etc. quickly)
438 * Don't be afraid to ask! The Rust community is friendly and helpful.
440 [rustc guide]: https://rust-lang.github.io/rustc-guide/about-this-guide.html
441 [gdfrustc]: https://doc.rust-lang.org/nightly/nightly-rustc/rustc/
442 [gsearchdocs]: https://www.google.com/search?q=site:doc.rust-lang.org+your+query+here
443 [rif]: http://internals.rust-lang.org
444 [rr]: https://doc.rust-lang.org/book/README.html
445 [rustforge]: https://forge.rust-lang.org/
446 [tlgba]: http://tomlee.co/2014/04/a-more-detailed-tour-of-the-rust-compiler/
447 [ro]: http://www.rustaceans.org/
448 [rctd]: https://rust-lang.github.io/rustc-guide/tests/intro.html
449 [cheatsheet]: https://buildbot2.rust-lang.org/homu/