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 [rustc-guide]: https://rust-lang.github.io/rustc-guide/
32 [walkthrough]: https://rust-lang.github.io/rustc-guide/walkthrough.html
35 [feature-requests]: #feature-requests
37 To request a change to the way the Rust language works, please head over
38 to the [RFCs repository](https://github.com/rust-lang/rfcs) and view the
39 [README](https://github.com/rust-lang/rfcs/blob/master/README.md)
43 [bug-reports]: #bug-reports
45 While bugs are unfortunate, they're a reality in software. We can't fix what we
46 don't know about, so please report liberally. If you're not sure if something
47 is a bug or not, feel free to file a bug anyway.
49 **If you believe reporting your bug publicly represents a security risk to Rust users,
50 please follow our [instructions for reporting security vulnerabilities](https://www.rust-lang.org/policies/security)**.
52 If you have the chance, before reporting a bug, please [search existing
53 issues](https://github.com/rust-lang/rust/search?q=&type=Issues&utf8=%E2%9C%93),
54 as it's possible that someone else has already reported your error. This doesn't
55 always work, and sometimes it's hard to know what to search for, so consider this
56 extra credit. We won't mind if you accidentally file a duplicate report.
58 Similarly, to help others who encountered the bug find your issue,
59 consider filing an issue with a descriptive title, which contains information that might be unique to it.
60 This can be the language or compiler feature used, the conditions that trigger the bug,
61 or part of the error message if there is any.
62 An example could be: **"impossible case reached" on lifetime inference for impl Trait in return position**.
64 Opening an issue is as easy as following [this
65 link](https://github.com/rust-lang/rust/issues/new) and filling out the fields.
66 Here's a template that you can use to file a bug, though it's not necessary to
69 <short summary of the bug>
73 <code sample that causes the bug>
75 I expected to see this happen: <explanation>
77 Instead, this happened: <explanation>
81 `rustc --version --verbose`:
85 All three components are important: what you did, what you expected, what
86 happened instead. Please include the output of `rustc --version --verbose`,
87 which includes important information about what platform you're on, what
88 version of Rust you're using, etc.
90 Sometimes, a backtrace is helpful, and so including that is nice. To get
91 a backtrace, set the `RUST_BACKTRACE` environment variable to a value
92 other than `0`. The easiest way
93 to do this is to invoke `rustc` like this:
96 $ RUST_BACKTRACE=1 rustc ...
101 For info on how to configure and build the compiler, please see [this
102 chapter][rustcguidebuild] of the rustc-guide. This chapter contains info for
103 contributions to the compiler and the standard library. It also lists some
104 really useful commands to the build system (`./x.py`), which could save you a
107 [rustcguidebuild]: https://rust-lang.github.io/rustc-guide/how-to-build-and-run.html
110 [pull-requests]: #pull-requests
112 Pull requests are the primary mechanism we use to change Rust. GitHub itself
113 has some [great documentation][about-pull-requests] on using the Pull Request feature.
114 We use the "fork and pull" model [described here][development-models], where
115 contributors push changes to their personal fork and create pull requests to
116 bring those changes into the source repository.
118 [about-pull-requests]: https://help.github.com/articles/about-pull-requests/
119 [development-models]: https://help.github.com/articles/about-collaborative-development-models/
121 Please make pull requests against the `master` branch.
123 Please make sure your pull request is in compliance with Rust's style
124 guidelines by running
126 $ python x.py test src/tools/tidy
128 Make this check before every pull request (and every new commit in a pull
129 request); you can add [git hooks](https://git-scm.com/book/en/v2/Customizing-Git-Git-Hooks)
130 before every push to make sure you never forget to make this check.
132 All pull requests are reviewed by another person. We have a bot,
133 @rust-highfive, that will automatically assign a random person to review your
136 If you want to request that a specific person reviews your pull request,
137 you can add an `r?` to the message. For example, Steve usually reviews
138 documentation changes. So if you were to make a documentation change, add
142 to the end of the message, and @rust-highfive will assign @steveklabnik instead
143 of a random person. This is entirely optional.
145 After someone has reviewed your pull request, they will leave an annotation
146 on the pull request with an `r+`. It will look something like this:
150 This tells @bors, our lovable integration bot, that your pull request has
151 been approved. The PR then enters the [merge queue][merge-queue], where @bors
152 will run all the tests on every platform we support. If it all works out,
153 @bors will merge your code into `master` and close the pull request.
155 [merge-queue]: https://buildbot2.rust-lang.org/homu/queue/rust
157 Speaking of tests, Rust has a comprehensive test suite. More information about
158 it can be found [here][rctd].
160 ### External Dependencies
161 [external-dependencies]: #external-dependencies
163 Currently building Rust will also build the following external projects:
165 * [clippy](https://github.com/rust-lang/rust-clippy)
166 * [miri](https://github.com/rust-lang/miri)
167 * [rustfmt](https://github.com/rust-lang/rustfmt)
168 * [rls](https://github.com/rust-lang/rls/)
170 We allow breakage of these tools in the nightly channel. Maintainers of these
171 projects will be notified of the breakages and should fix them as soon as
174 After the external is fixed, one could add the changes with
177 git add path/to/submodule
180 outside the submodule.
182 In order to prepare your tool-fixing PR, you can run the build locally by doing
183 `./x.py build src/tools/TOOL`. If you will be editing the sources
184 there, you may wish to set `submodules = false` in the `config.toml`
185 to prevent `x.py` from resetting to the original branch.
187 Breakage is not allowed in the beta and stable channels, and must be addressed
188 before the PR is merged.
190 #### Breaking Tools Built With The Compiler
191 [breaking-tools-built-with-the-compiler]: #breaking-tools-built-with-the-compiler
193 Rust's build system builds a number of tools that make use of the
194 internals of the compiler. This includes
195 [Clippy](https://github.com/rust-lang/rust-clippy),
196 [RLS](https://github.com/rust-lang/rls) and
197 [rustfmt](https://github.com/rust-lang/rustfmt). If these tools
198 break because of your changes, you may run into a sort of "chicken and egg"
199 problem. These tools rely on the latest compiler to be built so you can't update
200 them to reflect your changes to the compiler until those changes are merged into
201 the compiler. At the same time, you can't get your changes merged into the compiler
202 because the rust-lang/rust build won't pass until those tools build and pass their
205 That means that, in the default state, you can't update the compiler without first
206 fixing rustfmt, rls and the other tools that the compiler builds.
208 Luckily, a feature was [added to Rust's build](https://github.com/rust-lang/rust/issues/45861)
209 to make all of this easy to handle. The idea is that we allow these tools to be "broken",
210 so that the rust-lang/rust build passes without trying to build them, then land the change
211 in the compiler, wait for a nightly, and go update the tools that you broke. Once you're done
212 and the tools are working again, you go back in the compiler and update the tools
213 so they can be distributed again.
215 This should avoid a bunch of synchronization dances and is also much easier on contributors as
216 there's no need to block on rls/rustfmt/other tools changes going upstream.
218 Here are those same steps in detail:
220 1. (optional) First, if it doesn't exist already, create a `config.toml` by copying
221 `config.toml.example` in the root directory of the Rust repository.
222 Set `submodules = false` in the `[build]` section. This will prevent `x.py`
223 from resetting to the original branch after you make your changes. If you
224 need to [update any submodules to their latest versions][updating-submodules],
225 see the section of this file about that for more information.
226 2. (optional) Run `./x.py test src/tools/rustfmt` (substituting the submodule
227 that broke for `rustfmt`). Fix any errors in the submodule (and possibly others).
228 3. (optional) Make commits for your changes and send them to upstream repositories as a PR.
229 4. (optional) Maintainers of these submodules will **not** merge the PR. The PR can't be
230 merged because CI will be broken. You'll want to write a message on the PR referencing
231 your change, and how the PR should be merged once your change makes it into a nightly.
232 5. Wait for your PR to merge.
233 6. Wait for a nightly
234 7. (optional) Help land your PR on the upstream repository now that your changes are in nightly.
235 8. (optional) Send a PR to rust-lang/rust updating the submodule.
237 #### Updating submodules
238 [updating-submodules]: #updating-submodules
240 These instructions are specific to updating `rustfmt`, however they may apply
241 to the other submodules as well. Please help by improving these instructions
242 if you find any discrepancies or special cases that need to be addressed.
244 To update the `rustfmt` submodule, start by running the appropriate
245 [`git submodule` command](https://git-scm.com/book/en/v2/Git-Tools-Submodules).
246 For example, to update to the latest commit on the remote master branch,
249 git submodule update --remote src/tools/rustfmt
251 If you run `./x.py build` now, and you are lucky, it may just work. If you see
252 an error message about patches that did not resolve to any crates, you will need
253 to complete a few more steps which are outlined with their rationale below.
255 *(This error may change in the future to include more information.)*
257 error: failed to resolve patches for `https://github.com/rust-lang/rustfmt`
260 patch for `rustfmt-nightly` in `https://github.com/rust-lang/rustfmt` did not resolve to any crates
261 failed to run: ~/rust/build/x86_64-unknown-linux-gnu/stage0/bin/cargo build --manifest-path ~/rust/src/bootstrap/Cargo.toml
264 If you haven't used the `[patch]`
265 section of `Cargo.toml` before, there is [some relevant documentation about it
266 in the cargo docs](http://doc.crates.io/manifest.html#the-patch-section). In
267 addition to that, you should read the
268 [Overriding dependencies](http://doc.crates.io/specifying-dependencies.html#overriding-dependencies)
269 section of the documentation as well.
271 Specifically, the following [section in Overriding dependencies](http://doc.crates.io/specifying-dependencies.html#testing-a-bugfix) reveals what the problem is:
273 > 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.
275 > 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!
277 This says that when we updated the submodule, the version number in our
278 `src/tools/rustfmt/Cargo.toml` changed. The new version is different from
279 the version in `Cargo.lock`, so the build can no longer continue.
281 To resolve this, we need to update `Cargo.lock`. Luckily, cargo provides a
282 command to do this easily.
285 $ cargo update -p rustfmt-nightly
288 This should change the version listed in `Cargo.lock` to the new version you updated
289 the submodule to. Running `./x.py build` should work now.
291 ## Writing Documentation
292 [writing-documentation]: #writing-documentation
294 Documentation improvements are very welcome. The source of `doc.rust-lang.org`
295 is located in `src/doc` in the tree, and standard API documentation is generated
296 from the source code itself.
298 Documentation pull requests function in the same way as other pull requests,
299 though you may see a slightly different form of `r+`:
301 @bors: r+ 38fe8d2 rollup
303 That additional `rollup` tells @bors that this change is eligible for a 'rollup'.
304 To save @bors some work, and to get small changes through more quickly, when
305 @bors attempts to merge a commit that's rollup-eligible, it will also merge
306 the other rollup-eligible patches too, and they'll get tested and merged at
309 To find documentation-related issues, sort by the [T-doc label][tdoc].
311 [tdoc]: https://github.com/rust-lang/rust/issues?q=is%3Aopen%20is%3Aissue%20label%3AT-doc
313 You can find documentation style guidelines in [RFC 1574][rfc1574].
315 [rfc1574]: https://github.com/rust-lang/rfcs/blob/master/text/1574-more-api-documentation-conventions.md#appendix-a-full-conventions-text
317 In many cases, you don't need a full `./x.py doc`. You can use `rustdoc` directly
318 to check small fixes. For example, `rustdoc src/doc/reference.md` will render
319 reference to `doc/reference.html`. The CSS might be messed up, but you can
320 verify that the HTML is right.
322 Additionally, contributions to the [rustc-guide] are always welcome. Contributions
323 can be made directly at [the
324 rust-lang/rustc-guide](https://github.com/rust-lang/rustc-guide) repo. The issue
325 tracker in that repo is also a great way to find things that need doing. There
326 are issues for beginners and advanced compiler devs alike!
329 [issue-triage]: #issue-triage
331 Sometimes, an issue will stay open, even though the bug has been fixed. And
332 sometimes, the original bug may go stale because something has changed in the
335 It can be helpful to go through older bug reports and make sure that they are
336 still valid. Load up an older issue, double check that it's still true, and
337 leave a comment letting us know if it is or is not. The [least recently
338 updated sort][lru] is good for finding issues like this.
340 Contributors with sufficient permissions on the Rust repo can help by adding
341 labels to triage issues:
343 * Yellow, **A**-prefixed labels state which **area** of the project an issue
346 * Magenta, **B**-prefixed labels identify bugs which are **blockers**.
348 * Dark blue, **beta-** labels track changes which need to be backported into
351 * Light purple, **C**-prefixed labels represent the **category** of an issue.
353 * Green, **E**-prefixed labels explain the level of **experience** necessary
356 * The dark blue **final-comment-period** label marks bugs that are using the
357 RFC signoff functionality of [rfcbot][rfcbot] and are currently in the final
360 * Red, **I**-prefixed labels indicate the **importance** of the issue. The
361 [I-nominated][inom] label indicates that an issue has been nominated for
362 prioritizing at the next triage meeting.
364 * The purple **metabug** label marks lists of bugs collected by other
367 * Purple gray, **O**-prefixed labels are the **operating system** or platform
368 that this issue is specific to.
370 * Orange, **P**-prefixed labels indicate a bug's **priority**. These labels
371 are only assigned during triage meetings, and replace the [I-nominated][inom]
374 * The gray **proposed-final-comment-period** label marks bugs that are using
375 the RFC signoff functionality of [rfcbot][rfcbot] and are currently awaiting
376 signoff of all team members in order to enter the final comment period.
378 * Pink, **regression**-prefixed labels track regressions from stable to the
381 * The light orange **relnotes** label marks issues that should be documented in
382 the release notes of the next release.
384 * Gray, **S**-prefixed labels are used for tracking the **status** of pull
387 * Blue, **T**-prefixed bugs denote which **team** the issue belongs to.
389 If you're looking for somewhere to start, check out the [E-easy][eeasy] tag.
391 [inom]: https://github.com/rust-lang/rust/issues?q=is%3Aopen+is%3Aissue+label%3AI-nominated
392 [eeasy]: https://github.com/rust-lang/rust/issues?q=is%3Aopen+is%3Aissue+label%3AE-easy
393 [lru]: https://github.com/rust-lang/rust/issues?q=is%3Aissue+is%3Aopen+sort%3Aupdated-asc
394 [rfcbot]: https://github.com/anp/rfcbot-rs/
396 ## Out-of-tree Contributions
397 [out-of-tree-contributions]: #out-of-tree-contributions
399 There are a number of other ways to contribute to Rust that don't deal with
402 Answer questions in [#rust][pound-rust], or on [users.rust-lang.org][users],
403 or on [StackOverflow][so].
405 Participate in the [RFC process](https://github.com/rust-lang/rfcs).
407 Find a [requested community library][community-library], build it, and publish
408 it to [Crates.io](http://crates.io). Easier said than done, but very, very
411 [pound-rust]: http://chat.mibbit.com/?server=irc.mozilla.org&channel=%23rust
412 [users]: https://users.rust-lang.org/
413 [so]: http://stackoverflow.com/questions/tagged/rust
414 [community-library]: https://github.com/rust-lang/rfcs/labels/A-community-library
416 ## Helpful Links and Information
417 [helpful-info]: #helpful-info
419 For people new to Rust, and just starting to contribute, or even for
420 more seasoned developers, some useful places to look for information
423 * The [rustc guide] contains information about how various parts of the compiler work and how to contribute to the compiler
424 * [Rust Forge][rustforge] contains additional documentation, including write-ups of how to achieve common tasks
425 * The [Rust Internals forum][rif], a place to ask questions and
426 discuss Rust's internals
427 * The [generated documentation for rust's compiler][gdfrustc]
428 * The [rust reference][rr], even though it doesn't specifically talk about Rust's internals, it's a great resource nonetheless
429 * Although out of date, [Tom Lee's great blog article][tlgba] is very helpful
430 * [rustaceans.org][ro] is helpful, but mostly dedicated to IRC
431 * The [Rust Compiler Testing Docs][rctd]
432 * For @bors, [this cheat sheet][cheatsheet] is helpful (Remember to replace `@homu` with `@bors` in the commands that you use.)
433 * **Google!** ([search only in Rust Documentation][gsearchdocs] to find types, traits, etc. quickly)
434 * Don't be afraid to ask! The Rust community is friendly and helpful.
436 [rustc guide]: https://rust-lang.github.io/rustc-guide/about-this-guide.html
437 [gdfrustc]: https://doc.rust-lang.org/nightly/nightly-rustc/rustc/
438 [gsearchdocs]: https://www.google.com/search?q=site:doc.rust-lang.org+your+query+here
439 [rif]: http://internals.rust-lang.org
440 [rr]: https://doc.rust-lang.org/book/README.html
441 [rustforge]: https://forge.rust-lang.org/
442 [tlgba]: http://tomlee.co/2014/04/a-more-detailed-tour-of-the-rust-compiler/
443 [ro]: http://www.rustaceans.org/
444 [rctd]: https://rust-lang.github.io/rustc-guide/tests/intro.html
445 [cheatsheet]: https://buildbot2.rust-lang.org/homu/