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 [#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 [coc]: https://www.rust-lang.org/conduct.html
31 [walkthrough]: https://rust-lang.github.io/rustc-guide/walkthrough.html
34 [feature-requests]: #feature-requests
36 To request a change to the way the Rust language works, please head over
37 to the [RFCs repository](https://github.com/rust-lang/rfcs) and view the
38 [README](https://github.com/rust-lang/rfcs/blob/master/README.md)
42 [bug-reports]: #bug-reports
44 While bugs are unfortunate, they're a reality in software. We can't fix what we
45 don't know about, so please report liberally. If you're not sure if something
46 is a bug or not, feel free to file a bug anyway.
48 **If you believe reporting your bug publicly represents a security risk to Rust users,
49 please follow our [instructions for reporting security vulnerabilities](https://www.rust-lang.org/policies/security)**.
51 If you have the chance, before reporting a bug, please [search existing
52 issues](https://github.com/rust-lang/rust/search?q=&type=Issues&utf8=%E2%9C%93),
53 as it's possible that someone else has already reported your error. This doesn't
54 always work, and sometimes it's hard to know what to search for, so consider this
55 extra credit. We won't mind if you accidentally file a duplicate report.
57 Similarly, to help others who encountered the bug find your issue,
58 consider filing an issue with a descriptive title, which contains information that might be unique to it.
59 This can be the language or compiler feature used, the conditions that trigger the bug,
60 or part of the error message if there is any.
61 An example could be: **"impossible case reached" on lifetime inference for impl Trait in return position**.
63 Opening an issue is as easy as following [this
64 link](https://github.com/rust-lang/rust/issues/new) and filling out the fields.
65 Here's a template that you can use to file a bug, though it's not necessary to
68 <short summary of the bug>
72 <code sample that causes the bug>
74 I expected to see this happen: <explanation>
76 Instead, this happened: <explanation>
80 `rustc --version --verbose`:
84 All three components are important: what you did, what you expected, what
85 happened instead. Please include the output of `rustc --version --verbose`,
86 which includes important information about what platform you're on, what
87 version of Rust you're using, etc.
89 Sometimes, a backtrace is helpful, and so including that is nice. To get
90 a backtrace, set the `RUST_BACKTRACE` environment variable to a value
91 other than `0`. The easiest way
92 to do this is to invoke `rustc` like this:
95 $ RUST_BACKTRACE=1 rustc ...
100 For info on how to configure and build the compiler, please see [this
101 chapter][rustcguidebuild] of the rustc-guide. This chapter contains info for
102 contributions to the compiler and the standard library. It also lists some
103 really useful commands to the build system (`./x.py`), which could save you a
106 [rustcguidebuild]: https://rust-lang.github.io/rustc-guide/how-to-build-and-run.html
109 [pull-requests]: #pull-requests
111 Pull requests are the primary mechanism we use to change Rust. GitHub itself
112 has some [great documentation][about-pull-requests] on using the Pull Request feature.
113 We use the "fork and pull" model [described here][development-models], where
114 contributors push changes to their personal fork and create pull requests to
115 bring those changes into the source repository.
117 [about-pull-requests]: https://help.github.com/articles/about-pull-requests/
118 [development-models]: https://help.github.com/articles/about-collaborative-development-models/
120 Please make pull requests against the `master` branch.
122 Please make sure your pull request is in compliance with Rust's style
123 guidelines by running
125 $ python x.py test src/tools/tidy
127 Make this check before every pull request (and every new commit in a pull
128 request); you can add [git hooks](https://git-scm.com/book/en/v2/Customizing-Git-Git-Hooks)
129 before every push to make sure you never forget to make this check.
131 All pull requests are reviewed by another person. We have a bot,
132 @rust-highfive, that will automatically assign a random person to review your
135 If you want to request that a specific person reviews your pull request,
136 you can add an `r?` to the message. For example, Steve usually reviews
137 documentation changes. So if you were to make a documentation change, add
141 to the end of the message, and @rust-highfive will assign @steveklabnik instead
142 of a random person. This is entirely optional.
144 After someone has reviewed your pull request, they will leave an annotation
145 on the pull request with an `r+`. It will look something like this:
149 This tells @bors, our lovable integration bot, that your pull request has
150 been approved. The PR then enters the [merge queue][merge-queue], where @bors
151 will run all the tests on every platform we support. If it all works out,
152 @bors will merge your code into `master` and close the pull request.
154 [merge-queue]: https://buildbot2.rust-lang.org/homu/queue/rust
156 Speaking of tests, Rust has a comprehensive test suite. More information about
157 it can be found [here][rctd].
159 ### External Dependencies
160 [external-dependencies]: #external-dependencies
162 Currently building Rust will also build the following external projects:
164 * [clippy](https://github.com/rust-lang-nursery/rust-clippy)
165 * [miri](https://github.com/solson/miri)
166 * [rustfmt](https://github.com/rust-lang-nursery/rustfmt)
167 * [rls](https://github.com/rust-lang-nursery/rls/)
169 We allow breakage of these tools in the nightly channel. Maintainers of these
170 projects will be notified of the breakages and should fix them as soon as
173 After the external is fixed, one could add the changes with
176 git add path/to/submodule
179 outside the submodule.
181 In order to prepare your tool-fixing PR, you can run the build locally by doing
182 `./x.py build src/tools/TOOL`. If you will be editing the sources
183 there, you may wish to set `submodules = false` in the `config.toml`
184 to prevent `x.py` from resetting to the original branch.
186 Breakage is not allowed in the beta and stable channels, and must be addressed
187 before the PR is merged.
189 #### Breaking Tools Built With The Compiler
190 [breaking-tools-built-with-the-compiler]: #breaking-tools-built-with-the-compiler
192 Rust's build system builds a number of tools that make use of the
193 internals of the compiler. This includes
194 [Clippy](https://github.com/rust-lang-nursery/rust-clippy),
195 [RLS](https://github.com/rust-lang-nursery/rls) and
196 [rustfmt](https://github.com/rust-lang-nursery/rustfmt). If these tools
197 break because of your changes, you may run into a sort of "chicken and egg"
198 problem. These tools rely on the latest compiler to be built so you can't update
199 them to reflect your changes to the compiler until those changes are merged into
200 the compiler. At the same time, you can't get your changes merged into the compiler
201 because the rust-lang/rust build won't pass until those tools build and pass their
204 That means that, in the default state, you can't update the compiler without first
205 fixing rustfmt, rls and the other tools that the compiler builds.
207 Luckily, a feature was [added to Rust's build](https://github.com/rust-lang/rust/issues/45861)
208 to make all of this easy to handle. The idea is that we allow these tools to be "broken",
209 so that the rust-lang/rust build passes without trying to build them, then land the change
210 in the compiler, wait for a nightly, and go update the tools that you broke. Once you're done
211 and the tools are working again, you go back in the compiler and update the tools
212 so they can be distributed again.
214 This should avoid a bunch of synchronization dances and is also much easier on contributors as
215 there's no need to block on rls/rustfmt/other tools changes going upstream.
217 Here are those same steps in detail:
219 1. (optional) First, if it doesn't exist already, create a `config.toml` by copying
220 `config.toml.example` in the root directory of the Rust repository.
221 Set `submodules = false` in the `[build]` section. This will prevent `x.py`
222 from resetting to the original branch after you make your changes. If you
223 need to [update any submodules to their latest versions][updating-submodules],
224 see the section of this file about that for more information.
225 2. (optional) Run `./x.py test src/tools/rustfmt` (substituting the submodule
226 that broke for `rustfmt`). Fix any errors in the submodule (and possibly others).
227 3. (optional) Make commits for your changes and send them to upstream repositories as a PR.
228 4. (optional) Maintainers of these submodules will **not** merge the PR. The PR can't be
229 merged because CI will be broken. You'll want to write a message on the PR referencing
230 your change, and how the PR should be merged once your change makes it into a nightly.
231 5. Wait for your PR to merge.
232 6. Wait for a nightly
233 7. (optional) Help land your PR on the upstream repository now that your changes are in nightly.
234 8. (optional) Send a PR to rust-lang/rust updating the submodule.
236 #### Updating submodules
237 [updating-submodules]: #updating-submodules
239 These instructions are specific to updating `rustfmt`, however they may apply
240 to the other submodules as well. Please help by improving these instructions
241 if you find any discrepancies or special cases that need to be addressed.
243 To update the `rustfmt` submodule, start by running the appropriate
244 [`git submodule` command](https://git-scm.com/book/en/v2/Git-Tools-Submodules).
245 For example, to update to the latest commit on the remote master branch,
248 git submodule update --remote src/tools/rustfmt
250 If you run `./x.py build` now, and you are lucky, it may just work. If you see
251 an error message about patches that did not resolve to any crates, you will need
252 to complete a few more steps which are outlined with their rationale below.
254 *(This error may change in the future to include more information.)*
256 error: failed to resolve patches for `https://github.com/rust-lang-nursery/rustfmt`
259 patch for `rustfmt-nightly` in `https://github.com/rust-lang-nursery/rustfmt` did not resolve to any crates
260 failed to run: ~/rust/build/x86_64-unknown-linux-gnu/stage0/bin/cargo build --manifest-path ~/rust/src/bootstrap/Cargo.toml
263 If you haven't used the `[patch]`
264 section of `Cargo.toml` before, there is [some relevant documentation about it
265 in the cargo docs](http://doc.crates.io/manifest.html#the-patch-section). In
266 addition to that, you should read the
267 [Overriding dependencies](http://doc.crates.io/specifying-dependencies.html#overriding-dependencies)
268 section of the documentation as well.
270 Specifically, the following [section in Overriding dependencies](http://doc.crates.io/specifying-dependencies.html#testing-a-bugfix) reveals what the problem is:
272 > 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.
274 > 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!
276 This says that when we updated the submodule, the version number in our
277 `src/tools/rustfmt/Cargo.toml` changed. The new version is different from
278 the version in `Cargo.lock`, so the build can no longer continue.
280 To resolve this, we need to update `Cargo.lock`. Luckily, cargo provides a
281 command to do this easily.
284 $ cargo update -p rustfmt-nightly
287 This should change the version listed in `Cargo.lock` to the new version you updated
288 the submodule to. Running `./x.py build` should work now.
290 ## Writing Documentation
291 [writing-documentation]: #writing-documentation
293 Documentation improvements are very welcome. The source of `doc.rust-lang.org`
294 is located in `src/doc` in the tree, and standard API documentation is generated
295 from the source code itself.
297 Documentation pull requests function in the same way as other pull requests,
298 though you may see a slightly different form of `r+`:
300 @bors: r+ 38fe8d2 rollup
302 That additional `rollup` tells @bors that this change is eligible for a 'rollup'.
303 To save @bors some work, and to get small changes through more quickly, when
304 @bors attempts to merge a commit that's rollup-eligible, it will also merge
305 the other rollup-eligible patches too, and they'll get tested and merged at
308 To find documentation-related issues, sort by the [T-doc label][tdoc].
310 [tdoc]: https://github.com/rust-lang/rust/issues?q=is%3Aopen%20is%3Aissue%20label%3AT-doc
312 You can find documentation style guidelines in [RFC 1574][rfc1574].
314 [rfc1574]: https://github.com/rust-lang/rfcs/blob/master/text/1574-more-api-documentation-conventions.md#appendix-a-full-conventions-text
316 In many cases, you don't need a full `./x.py doc`. You can use `rustdoc` directly
317 to check small fixes. For example, `rustdoc src/doc/reference.md` will render
318 reference to `doc/reference.html`. The CSS might be messed up, but you can
319 verify that the HTML is right.
321 Additionally, contributions to the [rustc-guide] are always welcome. Contributions
322 can be made directly at [the
323 rust-lang/rustc-guide](https://github.com/rust-lang/rustc-guide) repo. The issue
324 tracker in that repo is also a great way to find things that need doing. There
325 are issues for beginners and advanced compiler devs alike!
328 [issue-triage]: #issue-triage
330 Sometimes, an issue will stay open, even though the bug has been fixed. And
331 sometimes, the original bug may go stale because something has changed in the
334 It can be helpful to go through older bug reports and make sure that they are
335 still valid. Load up an older issue, double check that it's still true, and
336 leave a comment letting us know if it is or is not. The [least recently
337 updated sort][lru] is good for finding issues like this.
339 Contributors with sufficient permissions on the Rust repo can help by adding
340 labels to triage issues:
342 * Yellow, **A**-prefixed labels state which **area** of the project an issue
345 * Magenta, **B**-prefixed labels identify bugs which are **blockers**.
347 * Dark blue, **beta-** labels track changes which need to be backported into
350 * Light purple, **C**-prefixed labels represent the **category** of an issue.
352 * Green, **E**-prefixed labels explain the level of **experience** necessary
355 * The dark blue **final-comment-period** label marks bugs that are using the
356 RFC signoff functionality of [rfcbot][rfcbot] and are currently in the final
359 * Red, **I**-prefixed labels indicate the **importance** of the issue. The
360 [I-nominated][inom] label indicates that an issue has been nominated for
361 prioritizing at the next triage meeting.
363 * The purple **metabug** label marks lists of bugs collected by other
366 * Purple gray, **O**-prefixed labels are the **operating system** or platform
367 that this issue is specific to.
369 * Orange, **P**-prefixed labels indicate a bug's **priority**. These labels
370 are only assigned during triage meetings, and replace the [I-nominated][inom]
373 * The gray **proposed-final-comment-period** label marks bugs that are using
374 the RFC signoff functionality of [rfcbot][rfcbot] and are currently awaiting
375 signoff of all team members in order to enter the final comment period.
377 * Pink, **regression**-prefixed labels track regressions from stable to the
380 * The light orange **relnotes** label marks issues that should be documented in
381 the release notes of the next release.
383 * Gray, **S**-prefixed labels are used for tracking the **status** of pull
386 * Blue, **T**-prefixed bugs denote which **team** the issue belongs to.
388 If you're looking for somewhere to start, check out the [E-easy][eeasy] tag.
390 [inom]: https://github.com/rust-lang/rust/issues?q=is%3Aopen+is%3Aissue+label%3AI-nominated
391 [eeasy]: https://github.com/rust-lang/rust/issues?q=is%3Aopen+is%3Aissue+label%3AE-easy
392 [lru]: https://github.com/rust-lang/rust/issues?q=is%3Aissue+is%3Aopen+sort%3Aupdated-asc
393 [rfcbot]: https://github.com/anp/rfcbot-rs/
395 ## Out-of-tree Contributions
396 [out-of-tree-contributions]: #out-of-tree-contributions
398 There are a number of other ways to contribute to Rust that don't deal with
401 Answer questions in [#rust][pound-rust], or on [users.rust-lang.org][users],
402 or on [StackOverflow][so].
404 Participate in the [RFC process](https://github.com/rust-lang/rfcs).
406 Find a [requested community library][community-library], build it, and publish
407 it to [Crates.io](http://crates.io). Easier said than done, but very, very
410 [pound-rust]: http://chat.mibbit.com/?server=irc.mozilla.org&channel=%23rust
411 [users]: https://users.rust-lang.org/
412 [so]: http://stackoverflow.com/questions/tagged/rust
413 [community-library]: https://github.com/rust-lang/rfcs/labels/A-community-library
415 ## Helpful Links and Information
416 [helpful-info]: #helpful-info
418 For people new to Rust, and just starting to contribute, or even for
419 more seasoned developers, some useful places to look for information
422 * The [rustc guide] contains information about how various parts of the compiler work and how to contribute to the compiler
423 * [Rust Forge][rustforge] contains additional documentation, including write-ups of how to achieve common tasks
424 * The [Rust Internals forum][rif], a place to ask questions and
425 discuss Rust's internals
426 * The [generated documentation for rust's compiler][gdfrustc]
427 * The [rust reference][rr], even though it doesn't specifically talk about Rust's internals, it's a great resource nonetheless
428 * Although out of date, [Tom Lee's great blog article][tlgba] is very helpful
429 * [rustaceans.org][ro] is helpful, but mostly dedicated to IRC
430 * The [Rust Compiler Testing Docs][rctd]
431 * For @bors, [this cheat sheet][cheatsheet] is helpful (Remember to replace `@homu` with `@bors` in the commands that you use.)
432 * **Google!** ([search only in Rust Documentation][gsearchdocs] to find types, traits, etc. quickly)
433 * Don't be afraid to ask! The Rust community is friendly and helpful.
435 [rustc guide]: https://rust-lang.github.io/rustc-guide/about-this-guide.html
436 [gdfrustc]: https://doc.rust-lang.org/nightly/nightly-rustc/rustc/
437 [gsearchdocs]: https://www.google.com/search?q=site:doc.rust-lang.org+your+query+here
438 [rif]: http://internals.rust-lang.org
439 [rr]: https://doc.rust-lang.org/book/README.html
440 [rustforge]: https://forge.rust-lang.org/
441 [tlgba]: http://tomlee.co/2014/04/a-more-detailed-tour-of-the-rust-compiler/
442 [ro]: http://www.rustaceans.org/
443 [rctd]: https://rust-lang.github.io/rustc-guide/tests/intro.html
444 [cheatsheet]: https://buildbot2.rust-lang.org/homu/