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], [Rust Zulip server][rust-zulip] or [#rust-internals][pound-rust-internals].
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 [pound-rust-internals]: https://chat.mibbit.com/?server=irc.mozilla.org&channel=%23rust-internals
29 [internals]: https://internals.rust-lang.org
30 [rust-discord]: http://discord.gg/rust-lang
31 [rust-zulip]: https://rust-lang.zulipchat.com
32 [coc]: https://www.rust-lang.org/conduct.html
33 [rustc-guide]: https://rust-lang.github.io/rustc-guide/
34 [walkthrough]: https://rust-lang.github.io/rustc-guide/walkthrough.html
37 [feature-requests]: #feature-requests
39 To request a change to the way the Rust language works, please head over
40 to the [RFCs repository](https://github.com/rust-lang/rfcs) and view the
41 [README](https://github.com/rust-lang/rfcs/blob/master/README.md)
45 [bug-reports]: #bug-reports
47 While bugs are unfortunate, they're a reality in software. We can't fix what we
48 don't know about, so please report liberally. If you're not sure if something
49 is a bug or not, feel free to file a bug anyway.
51 **If you believe reporting your bug publicly represents a security risk to Rust users,
52 please follow our [instructions for reporting security vulnerabilities](https://www.rust-lang.org/policies/security)**.
54 If you have the chance, before reporting a bug, please [search existing
55 issues](https://github.com/rust-lang/rust/search?q=&type=Issues&utf8=%E2%9C%93),
56 as it's possible that someone else has already reported your error. This doesn't
57 always work, and sometimes it's hard to know what to search for, so consider this
58 extra credit. We won't mind if you accidentally file a duplicate report.
60 Similarly, to help others who encountered the bug find your issue,
61 consider filing an issue with a descriptive title, which contains information that might be unique to it.
62 This can be the language or compiler feature used, the conditions that trigger the bug,
63 or part of the error message if there is any.
64 An example could be: **"impossible case reached" on lifetime inference for impl Trait in return position**.
66 Opening an issue is as easy as following [this
67 link](https://github.com/rust-lang/rust/issues/new) and filling out the fields.
68 Here's a template that you can use to file a bug, though it's not necessary to
71 <short summary of the bug>
75 <code sample that causes the bug>
77 I expected to see this happen: <explanation>
79 Instead, this happened: <explanation>
83 `rustc --version --verbose`:
87 All three components are important: what you did, what you expected, what
88 happened instead. Please include the output of `rustc --version --verbose`,
89 which includes important information about what platform you're on, what
90 version of Rust you're using, etc.
92 Sometimes, a backtrace is helpful, and so including that is nice. To get
93 a backtrace, set the `RUST_BACKTRACE` environment variable to a value
94 other than `0`. The easiest way
95 to do this is to invoke `rustc` like this:
98 $ RUST_BACKTRACE=1 rustc ...
103 For info on how to configure and build the compiler, please see [this
104 chapter][rustcguidebuild] of the rustc-guide. This chapter contains info for
105 contributions to the compiler and the standard library. It also lists some
106 really useful commands to the build system (`./x.py`), which could save you a
109 [rustcguidebuild]: https://rust-lang.github.io/rustc-guide/how-to-build-and-run.html
112 [pull-requests]: #pull-requests
114 Pull requests are the primary mechanism we use to change Rust. GitHub itself
115 has some [great documentation][about-pull-requests] on using the Pull Request feature.
116 We use the "fork and pull" model [described here][development-models], where
117 contributors push changes to their personal fork and create pull requests to
118 bring those changes into the source repository.
120 [about-pull-requests]: https://help.github.com/articles/about-pull-requests/
121 [development-models]: https://help.github.com/articles/about-collaborative-development-models/
123 Please make pull requests against the `master` branch.
125 Rust follows a no merge policy, meaning, when you encounter merge
126 conflicts you are expected to always rebase instead of merge.
127 E.g. always use rebase when bringing the latest changes from
128 the master branch to your feature branch.
129 Also, please make sure that fixup commits are squashed into other related
130 commits with meaningful commit messages.
132 Please make sure your pull request is in compliance with Rust's style
133 guidelines by running
135 $ python x.py test src/tools/tidy
137 Make this check before every pull request (and every new commit in a pull
138 request); you can add [git hooks](https://git-scm.com/book/en/v2/Customizing-Git-Git-Hooks)
139 before every push to make sure you never forget to make this check.
141 All pull requests are reviewed by another person. We have a bot,
142 [@rust-highfive][rust-highfive], that will automatically assign a random person to review your
145 If you want to request that a specific person reviews your pull request,
146 you can add an `r?` to the message. For example, [Steve][steveklabnik] usually reviews
147 documentation changes. So if you were to make a documentation change, add
151 to the end of the message, and @rust-highfive will assign [@steveklabnik][steveklabnik] instead
152 of a random person. This is entirely optional.
154 After someone has reviewed your pull request, they will leave an annotation
155 on the pull request with an `r+`. It will look something like this:
159 This tells [@bors][bors], our lovable integration bot, that your pull request has
160 been approved. The PR then enters the [merge queue][merge-queue], where [@bors][bors]
161 will run all the tests on every platform we support. If it all works out,
162 [@bors][bors] will merge your code into `master` and close the pull request.
164 Depending on the scale of the change, you may see a slightly different form of `r+`:
168 The additional `rollup` tells [@bors][bors] that this change is eligible for to be
169 "rolled up". Changes that are rolled up are tested and merged at the same time, to
170 speed the process up. Typically only small changes that are expected not to conflict
171 with one another are rolled up.
173 [rust-highfive]: https://github.com/rust-highfive
174 [steveklabnik]: https://github.com/steveklabnik
175 [bors]: https://github.com/bors
176 [merge-queue]: https://buildbot2.rust-lang.org/homu/queue/rust
178 Speaking of tests, Rust has a comprehensive test suite. More information about
179 it can be found [here][rctd].
181 ### External Dependencies
183 Currently building Rust will also build the following external projects:
185 * [clippy](https://github.com/rust-lang/rust-clippy)
186 * [miri](https://github.com/rust-lang/miri)
187 * [rustfmt](https://github.com/rust-lang/rustfmt)
188 * [rls](https://github.com/rust-lang/rls/)
190 We allow breakage of these tools in the nightly channel. Maintainers of these
191 projects will be notified of the breakages and should fix them as soon as
194 After the external is fixed, one could add the changes with
197 git add path/to/submodule
200 outside the submodule.
202 In order to prepare your tool-fixing PR, you can run the build locally by doing
203 `./x.py build src/tools/TOOL`. If you will be editing the sources
204 there, you may wish to set `submodules = false` in the `config.toml`
205 to prevent `x.py` from resetting to the original branch.
207 Breakage is not allowed in the beta and stable channels, and must be addressed
208 before the PR is merged.
210 #### Breaking Tools Built With The Compiler
212 Rust's build system builds a number of tools that make use of the
213 internals of the compiler. This includes
214 [Clippy](https://github.com/rust-lang/rust-clippy),
215 [RLS](https://github.com/rust-lang/rls) and
216 [rustfmt](https://github.com/rust-lang/rustfmt). If these tools
217 break because of your changes, you may run into a sort of "chicken and egg"
218 problem. These tools rely on the latest compiler to be built so you can't update
219 them to reflect your changes to the compiler until those changes are merged into
220 the compiler. At the same time, you can't get your changes merged into the compiler
221 because the rust-lang/rust build won't pass until those tools build and pass their
224 That means that, in the default state, you can't update the compiler without first
225 fixing rustfmt, rls and the other tools that the compiler builds.
227 Luckily, a feature was [added to Rust's build](https://github.com/rust-lang/rust/issues/45861)
228 to make all of this easy to handle. The idea is that we allow these tools to be "broken",
229 so that the rust-lang/rust build passes without trying to build them, then land the change
230 in the compiler, wait for a nightly, and go update the tools that you broke. Once you're done
231 and the tools are working again, you go back in the compiler and update the tools
232 so they can be distributed again.
234 This should avoid a bunch of synchronization dances and is also much easier on contributors as
235 there's no need to block on rls/rustfmt/other tools changes going upstream.
237 Here are those same steps in detail:
239 1. (optional) First, if it doesn't exist already, create a `config.toml` by copying
240 `config.toml.example` in the root directory of the Rust repository.
241 Set `submodules = false` in the `[build]` section. This will prevent `x.py`
242 from resetting to the original branch after you make your changes. If you
243 need to [update any submodules to their latest versions](#updating-submodules),
244 see the section of this file about that for more information.
245 2. (optional) Run `./x.py test src/tools/rustfmt` (substituting the submodule
246 that broke for `rustfmt`). Fix any errors in the submodule (and possibly others).
247 3. (optional) Make commits for your changes and send them to upstream repositories as a PR.
248 4. (optional) Maintainers of these submodules will **not** merge the PR. The PR can't be
249 merged because CI will be broken. You'll want to write a message on the PR referencing
250 your change, and how the PR should be merged once your change makes it into a nightly.
251 5. Wait for your PR to merge.
252 6. Wait for a nightly
253 7. (optional) Help land your PR on the upstream repository now that your changes are in nightly.
254 8. (optional) Send a PR to rust-lang/rust updating the submodule.
256 #### Updating submodules
258 These instructions are specific to updating `rustfmt`, however they may apply
259 to the other submodules as well. Please help by improving these instructions
260 if you find any discrepancies or special cases that need to be addressed.
262 To update the `rustfmt` submodule, start by running the appropriate
263 [`git submodule` command](https://git-scm.com/book/en/v2/Git-Tools-Submodules).
264 For example, to update to the latest commit on the remote master branch,
267 git submodule update --remote src/tools/rustfmt
269 If you run `./x.py build` now, and you are lucky, it may just work. If you see
270 an error message about patches that did not resolve to any crates, you will need
271 to complete a few more steps which are outlined with their rationale below.
273 *(This error may change in the future to include more information.)*
275 error: failed to resolve patches for `https://github.com/rust-lang/rustfmt`
278 patch for `rustfmt-nightly` in `https://github.com/rust-lang/rustfmt` did not resolve to any crates
279 failed to run: ~/rust/build/x86_64-unknown-linux-gnu/stage0/bin/cargo build --manifest-path ~/rust/src/bootstrap/Cargo.toml
282 If you haven't used the `[patch]`
283 section of `Cargo.toml` before, there is [some relevant documentation about it
284 in the cargo docs](http://doc.crates.io/manifest.html#the-patch-section). In
285 addition to that, you should read the
286 [Overriding dependencies](http://doc.crates.io/specifying-dependencies.html#overriding-dependencies)
287 section of the documentation as well.
289 Specifically, the following [section in Overriding dependencies](http://doc.crates.io/specifying-dependencies.html#testing-a-bugfix) reveals what the problem is:
291 > 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.
293 > 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!
295 This says that when we updated the submodule, the version number in our
296 `src/tools/rustfmt/Cargo.toml` changed. The new version is different from
297 the version in `Cargo.lock`, so the build can no longer continue.
299 To resolve this, we need to update `Cargo.lock`. Luckily, cargo provides a
300 command to do this easily.
303 $ cargo update -p rustfmt-nightly
306 This should change the version listed in `Cargo.lock` to the new version you updated
307 the submodule to. Running `./x.py build` should work now.
309 ## Writing Documentation
311 Documentation improvements are very welcome. The source of `doc.rust-lang.org`
312 is located in `src/doc` in the tree, and standard API documentation is generated
313 from the source code itself. Documentation pull requests function in the same way
314 as other pull requests.
316 To find documentation-related issues, sort by the [T-doc label][tdoc].
318 [tdoc]: https://github.com/rust-lang/rust/issues?q=is%3Aopen%20is%3Aissue%20label%3AT-doc
320 You can find documentation style guidelines in [RFC 1574][rfc1574].
322 [rfc1574]: https://github.com/rust-lang/rfcs/blob/master/text/1574-more-api-documentation-conventions.md#appendix-a-full-conventions-text
324 In many cases, you don't need a full `./x.py doc`. You can use `rustdoc` directly
325 to check small fixes. For example, `rustdoc src/doc/reference.md` will render
326 reference to `doc/reference.html`. The CSS might be messed up, but you can
327 verify that the HTML is right.
329 Additionally, contributions to the [rustc-guide] are always welcome. Contributions
330 can be made directly at [the
331 rust-lang/rustc-guide](https://github.com/rust-lang/rustc-guide) repo. The issue
332 tracker in that repo is also a great way to find things that need doing. There
333 are issues for beginners and advanced compiler devs alike!
337 Sometimes, an issue will stay open, even though the bug has been fixed. And
338 sometimes, the original bug may go stale because something has changed in the
341 It can be helpful to go through older bug reports and make sure that they are
342 still valid. Load up an older issue, double check that it's still true, and
343 leave a comment letting us know if it is or is not. The [least recently
344 updated sort][lru] is good for finding issues like this.
346 Contributors with sufficient permissions on the Rust repo can help by adding
347 labels to triage issues:
349 * Yellow, **A**-prefixed labels state which **area** of the project an issue
352 * Magenta, **B**-prefixed labels identify bugs which are **blockers**.
354 * Dark blue, **beta-** labels track changes which need to be backported into
357 * Light purple, **C**-prefixed labels represent the **category** of an issue.
359 * Green, **E**-prefixed labels explain the level of **experience** necessary
362 * The dark blue **final-comment-period** label marks bugs that are using the
363 RFC signoff functionality of [rfcbot][rfcbot] and are currently in the final
366 * Red, **I**-prefixed labels indicate the **importance** of the issue. The
367 [I-nominated][inom] label indicates that an issue has been nominated for
368 prioritizing at the next triage meeting.
370 * The purple **metabug** label marks lists of bugs collected by other
373 * Purple gray, **O**-prefixed labels are the **operating system** or platform
374 that this issue is specific to.
376 * Orange, **P**-prefixed labels indicate a bug's **priority**. These labels
377 are only assigned during triage meetings, and replace the [I-nominated][inom]
380 * The gray **proposed-final-comment-period** label marks bugs that are using
381 the RFC signoff functionality of [rfcbot][rfcbot] and are currently awaiting
382 signoff of all team members in order to enter the final comment period.
384 * Pink, **regression**-prefixed labels track regressions from stable to the
387 * The light orange **relnotes** label marks issues that should be documented in
388 the release notes of the next release.
390 * Gray, **S**-prefixed labels are used for tracking the **status** of pull
393 * Blue, **T**-prefixed bugs denote which **team** the issue belongs to.
395 If you're looking for somewhere to start, check out the [E-easy][eeasy] tag.
397 [inom]: https://github.com/rust-lang/rust/issues?q=is%3Aopen+is%3Aissue+label%3AI-nominated
398 [eeasy]: https://github.com/rust-lang/rust/issues?q=is%3Aopen+is%3Aissue+label%3AE-easy
399 [lru]: https://github.com/rust-lang/rust/issues?q=is%3Aissue+is%3Aopen+sort%3Aupdated-asc
400 [rfcbot]: https://github.com/anp/rfcbot-rs/
402 ## Out-of-tree Contributions
404 There are a number of other ways to contribute to Rust that don't deal with
407 Answer questions in [#rust][pound-rust], or on [users.rust-lang.org][users],
408 or on [StackOverflow][so].
410 Participate in the [RFC process](https://github.com/rust-lang/rfcs).
412 Find a [requested community library][community-library], build it, and publish
413 it to [Crates.io](http://crates.io). Easier said than done, but very, very
416 [pound-rust]: http://chat.mibbit.com/?server=irc.mozilla.org&channel=%23rust
417 [users]: https://users.rust-lang.org/
418 [so]: http://stackoverflow.com/questions/tagged/rust
419 [community-library]: https://github.com/rust-lang/rfcs/labels/A-community-library
421 ## Helpful Links and Information
423 For people new to Rust, and just starting to contribute, or even for
424 more seasoned developers, some useful places to look for information
427 * The [rustc guide] contains information about how various parts of the compiler work and how to contribute to the compiler
428 * [Rust Forge][rustforge] contains additional documentation, including write-ups of how to achieve common tasks
429 * The [Rust Internals forum][rif], a place to ask questions and
430 discuss Rust's internals
431 * The [generated documentation for rust's compiler][gdfrustc]
432 * The [rust reference][rr], even though it doesn't specifically talk about Rust's internals, it's a great resource nonetheless
433 * Although out of date, [Tom Lee's great blog article][tlgba] is very helpful
434 * [rustaceans.org][ro] is helpful, but mostly dedicated to IRC
435 * The [Rust Compiler Testing Docs][rctd]
436 * For [@bors][bors], [this cheat sheet][cheatsheet] is helpful
437 (though you'll need to replace `@homu` with `@bors` in any commands)
438 * **Google!** ([search only in Rust Documentation][gsearchdocs] to find types, traits, etc. quickly)
439 * Don't be afraid to ask! The Rust community is friendly and helpful.
441 [rustc guide]: https://rust-lang.github.io/rustc-guide/about-this-guide.html
442 [gdfrustc]: https://doc.rust-lang.org/nightly/nightly-rustc/rustc/
443 [gsearchdocs]: https://www.google.com/search?q=site:doc.rust-lang.org+your+query+here
444 [rif]: http://internals.rust-lang.org
445 [rr]: https://doc.rust-lang.org/book/README.html
446 [rustforge]: https://forge.rust-lang.org/
447 [tlgba]: http://tomlee.co/2014/04/a-more-detailed-tour-of-the-rust-compiler/
448 [ro]: http://www.rustaceans.org/
449 [rctd]: https://rust-lang.github.io/rustc-guide/tests/intro.html
450 [cheatsheet]: https://buildbot2.rust-lang.org/homu/