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-dev-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-dev-guide]: https://rustc-dev-guide.rust-lang.org/
33 [walkthrough]: https://rustc-dev-guide.rust-lang.org/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're using the nightly channel, please check if the bug exists in the
54 latest toolchain before filing your bug. It might be fixed already.
56 If you have the chance, before reporting a bug, please [search existing
57 issues](https://github.com/rust-lang/rust/search?q=&type=Issues&utf8=%E2%9C%93),
58 as it's possible that someone else has already reported your error. This doesn't
59 always work, and sometimes it's hard to know what to search for, so consider this
60 extra credit. We won't mind if you accidentally file a duplicate report.
62 Similarly, to help others who encountered the bug find your issue,
63 consider filing an issue with a descriptive title, which contains information that might be unique to it.
64 This can be the language or compiler feature used, the conditions that trigger the bug,
65 or part of the error message if there is any.
66 An example could be: **"impossible case reached" on lifetime inference for impl Trait in return position**.
68 Opening an issue is as easy as following [this
69 link](https://github.com/rust-lang/rust/issues/new) and filling out the fields.
70 Here's a template that you can use to file a bug, though it's not necessary to
73 <short summary of the bug>
77 <code sample that causes the bug>
79 I expected to see this happen: <explanation>
81 Instead, this happened: <explanation>
85 `rustc --version --verbose`:
89 All three components are important: what you did, what you expected, what
90 happened instead. Please include the output of `rustc --version --verbose`,
91 which includes important information about what platform you're on, what
92 version of Rust you're using, etc.
94 Sometimes, a backtrace is helpful, and so including that is nice. To get
95 a backtrace, set the `RUST_BACKTRACE` environment variable to a value
96 other than `0`. The easiest way
97 to do this is to invoke `rustc` like this:
100 $ RUST_BACKTRACE=1 rustc ...
105 For info on how to configure and build the compiler, please see [this
106 chapter][rustcguidebuild] of the rustc-dev-guide. This chapter contains info for
107 contributions to the compiler and the standard library. It also lists some
108 really useful commands to the build system (`./x.py`), which could save you a
111 [rustcguidebuild]: https://rustc-dev-guide.rust-lang.org/building/how-to-build-and-run.html
114 [pull-requests]: #pull-requests
116 Pull requests are the primary mechanism we use to change Rust. GitHub itself
117 has some [great documentation][about-pull-requests] on using the Pull Request feature.
118 We use the "fork and pull" model [described here][development-models], where
119 contributors push changes to their personal fork and create pull requests to
120 bring those changes into the source repository.
122 [about-pull-requests]: https://help.github.com/articles/about-pull-requests/
123 [development-models]: https://help.github.com/articles/about-collaborative-development-models/
125 Please make pull requests against the `master` branch.
127 Rust follows a no merge policy, meaning, when you encounter merge
128 conflicts you are expected to always rebase instead of merge.
129 E.g. always use rebase when bringing the latest changes from
130 the master branch to your feature branch.
131 Also, please make sure that fixup commits are squashed into other related
132 commits with meaningful commit messages.
134 GitHub allows [closing issues using keywords][closing-keywords]. This feature
135 should be used to keep the issue tracker tidy. However, it is generally preferred
136 to put the "closes #123" text in the PR description rather than the issue commit;
137 particularly during rebasing, citing the issue number in the commit can "spam"
138 the issue in question.
140 [closing-keywords]: https://help.github.com/en/articles/closing-issues-using-keywords
142 Please make sure your pull request is in compliance with Rust's style
143 guidelines by running
145 $ python x.py test tidy
147 Make this check before every pull request (and every new commit in a pull
148 request); you can add [git hooks](https://git-scm.com/book/en/v2/Customizing-Git-Git-Hooks)
149 before every push to make sure you never forget to make this check.
151 All pull requests are reviewed by another person. We have a bot,
152 [@rust-highfive][rust-highfive], that will automatically assign a random person to review your
155 If you want to request that a specific person reviews your pull request,
156 you can add an `r?` to the pull request description. For example, [Steve][steveklabnik] usually reviews
157 documentation changes. So if you were to make a documentation change, add
161 to the end of the pull request description, and [@rust-highfive][rust-highfive] will assign
162 [@steveklabnik][steveklabnik] instead of a random person. This is entirely optional.
164 After someone has reviewed your pull request, they will leave an annotation
165 on the pull request with an `r+`. It will look something like this:
169 This tells [@bors][bors], our lovable integration bot, that your pull request has
170 been approved. The PR then enters the [merge queue][merge-queue], where [@bors][bors]
171 will run all the tests on every platform we support. If it all works out,
172 [@bors][bors] will merge your code into `master` and close the pull request.
174 Depending on the scale of the change, you may see a slightly different form of `r+`:
178 The additional `rollup` tells [@bors][bors] that this change is eligible for to be
179 "rolled up". Changes that are rolled up are tested and merged at the same time, to
180 speed the process up. Typically only small changes that are expected not to conflict
181 with one another are rolled up.
183 [rust-highfive]: https://github.com/rust-highfive
184 [steveklabnik]: https://github.com/steveklabnik
185 [bors]: https://github.com/bors
186 [merge-queue]: https://buildbot2.rust-lang.org/homu/queue/rust
188 Speaking of tests, Rust has a comprehensive test suite. More information about
189 it can be found [here][rctd].
191 ### External Dependencies (subtree)
193 As a developer to this repository, you don't have to treat the following external projects
194 differently from other crates that are directly in this repo:
196 * none so far, see https://github.com/rust-lang/rust/issues/70651 for more info
198 They are just regular files and directories. This is in contrast to `submodule` dependencies
199 (see below for those).
201 #### Synchronizing a subtree
203 There are two synchronization directions: `subtree push` and `subtree pull`.
205 A `git subtree push -P src/tools/clippy`
206 takes all the changes that
207 happened to the copy in this repo and creates commits on the remote repo that match the local
208 changes (so every local commit that touched the subtree causes a commit on the remote repo).
210 A `git subtree pull -P src/tools/clippy` takes all changes since the last `subtree pull` from the clippy
211 repo and creates a single commit in the rustc repo with all the changes.
213 You always need to specifiy the `-P` prefix to the subtree directory. If you specify the wrong directory
214 you'll get very fun merges that try to push the wrong directory to the remote repository. Luckily you
215 can just abort this without any consequences.
217 #### Creating a new subtree dependency
219 If you want to create a new subtree dependency from an existing repository, call (from this
220 repository's root directory!!)
223 git subtree add -P src/tools/clippy https://github.com/rust-lang/rust-clippy.git master
226 This will create a new commit, which you may not rebase under any circumstances! Delete the commit
227 and redo the operation if you need to rebase.
229 Now you're done, the `src/tools/clippy` directory behaves as if clippy were part of the rustc
230 monorepo, so no one but you (or others that synchronize subtrees) needs actually use `git subtree`.
233 ### External Dependencies (submodules)
235 Currently building Rust will also build the following external projects:
237 * [clippy](https://github.com/rust-lang/rust-clippy)
238 * [miri](https://github.com/rust-lang/miri)
239 * [rustfmt](https://github.com/rust-lang/rustfmt)
240 * [rls](https://github.com/rust-lang/rls/)
242 We allow breakage of these tools in the nightly channel. Maintainers of these
243 projects will be notified of the breakages and should fix them as soon as
246 After the external is fixed, one could add the changes with
249 git add path/to/submodule
252 outside the submodule.
254 In order to prepare your tool-fixing PR, you can run the build locally by doing
255 `./x.py build src/tools/TOOL`. If you will be editing the sources
256 there, you may wish to set `submodules = false` in the `config.toml`
257 to prevent `x.py` from resetting to the original branch.
259 Breakage is not allowed in the beta and stable channels, and must be addressed
260 before the PR is merged.
262 #### Breaking Tools Built With The Compiler
264 Rust's build system builds a number of tools that make use of the
265 internals of the compiler. This includes
266 [RLS](https://github.com/rust-lang/rls) and
267 [rustfmt](https://github.com/rust-lang/rustfmt). If these tools
268 break because of your changes, you may run into a sort of "chicken and egg"
269 problem. These tools rely on the latest compiler to be built so you can't update
270 them to reflect your changes to the compiler until those changes are merged into
271 the compiler. At the same time, you can't get your changes merged into the compiler
272 because the rust-lang/rust build won't pass until those tools build and pass their
275 That means that, in the default state, you can't update the compiler without first
276 fixing rustfmt, rls and the other tools that the compiler builds.
278 Luckily, a feature was [added to Rust's build](https://github.com/rust-lang/rust/issues/45861)
279 to make all of this easy to handle. The idea is that we allow these tools to be "broken",
280 so that the rust-lang/rust build passes without trying to build them, then land the change
281 in the compiler, wait for a nightly, and go update the tools that you broke. Once you're done
282 and the tools are working again, you go back in the compiler and update the tools
283 so they can be distributed again.
285 This should avoid a bunch of synchronization dances and is also much easier on contributors as
286 there's no need to block on rls/rustfmt/other tools changes going upstream.
288 Here are those same steps in detail:
290 1. (optional) First, if it doesn't exist already, create a `config.toml` by copying
291 `config.toml.example` in the root directory of the Rust repository.
292 Set `submodules = false` in the `[build]` section. This will prevent `x.py`
293 from resetting to the original branch after you make your changes. If you
294 need to [update any submodules to their latest versions](#updating-submodules),
295 see the section of this file about that for more information.
296 2. (optional) Run `./x.py test src/tools/rustfmt` (substituting the submodule
297 that broke for `rustfmt`). Fix any errors in the submodule (and possibly others).
298 3. (optional) Make commits for your changes and send them to upstream repositories as a PR.
299 4. (optional) Maintainers of these submodules will **not** merge the PR. The PR can't be
300 merged because CI will be broken. You'll want to write a message on the PR referencing
301 your change, and how the PR should be merged once your change makes it into a nightly.
302 5. Wait for your PR to merge.
303 6. Wait for a nightly
304 7. (optional) Help land your PR on the upstream repository now that your changes are in nightly.
305 8. (optional) Send a PR to rust-lang/rust updating the submodule.
307 #### Updating submodules
309 These instructions are specific to updating `rustfmt`, however they may apply
310 to the other submodules as well. Please help by improving these instructions
311 if you find any discrepancies or special cases that need to be addressed.
313 To update the `rustfmt` submodule, start by running the appropriate
314 [`git submodule` command](https://git-scm.com/book/en/v2/Git-Tools-Submodules).
315 For example, to update to the latest commit on the remote master branch,
318 git submodule update --remote src/tools/rustfmt
320 If you run `./x.py build` now, and you are lucky, it may just work. If you see
321 an error message about patches that did not resolve to any crates, you will need
322 to complete a few more steps which are outlined with their rationale below.
324 *(This error may change in the future to include more information.)*
326 error: failed to resolve patches for `https://github.com/rust-lang/rustfmt`
329 patch for `rustfmt-nightly` in `https://github.com/rust-lang/rustfmt` did not resolve to any crates
330 failed to run: ~/rust/build/x86_64-unknown-linux-gnu/stage0/bin/cargo build --manifest-path ~/rust/src/bootstrap/Cargo.toml
333 If you haven't used the `[patch]`
334 section of `Cargo.toml` before, there is [some relevant documentation about it
335 in the cargo docs](http://doc.crates.io/manifest.html#the-patch-section). In
336 addition to that, you should read the
337 [Overriding dependencies](http://doc.crates.io/specifying-dependencies.html#overriding-dependencies)
338 section of the documentation as well.
340 Specifically, the following [section in Overriding dependencies](http://doc.crates.io/specifying-dependencies.html#testing-a-bugfix) reveals what the problem is:
342 > 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.
344 > 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!
346 This says that when we updated the submodule, the version number in our
347 `src/tools/rustfmt/Cargo.toml` changed. The new version is different from
348 the version in `Cargo.lock`, so the build can no longer continue.
350 To resolve this, we need to update `Cargo.lock`. Luckily, cargo provides a
351 command to do this easily.
354 $ cargo update -p rustfmt-nightly
357 This should change the version listed in `Cargo.lock` to the new version you updated
358 the submodule to. Running `./x.py build` should work now.
360 ## Writing Documentation
362 Documentation improvements are very welcome. The source of `doc.rust-lang.org`
363 is located in `src/doc` in the tree, and standard API documentation is generated
364 from the source code itself. Documentation pull requests function in the same way
365 as other pull requests.
367 To find documentation-related issues, sort by the [T-doc label][tdoc].
369 [tdoc]: https://github.com/rust-lang/rust/issues?q=is%3Aopen%20is%3Aissue%20label%3AT-doc
371 You can find documentation style guidelines in [RFC 1574][rfc1574].
373 [rfc1574]: https://github.com/rust-lang/rfcs/blob/master/text/1574-more-api-documentation-conventions.md#appendix-a-full-conventions-text
375 In many cases, you don't need a full `./x.py doc`. You can use `rustdoc` directly
376 to check small fixes. For example, `rustdoc src/doc/reference.md` will render
377 reference to `doc/reference.html`. The CSS might be messed up, but you can
378 verify that the HTML is right.
380 Additionally, contributions to the [rustc-dev-guide] are always welcome. Contributions
381 can be made directly at [the
382 rust-lang/rustc-dev-guide](https://github.com/rust-lang/rustc-dev-guide) repo. The issue
383 tracker in that repo is also a great way to find things that need doing. There
384 are issues for beginners and advanced compiler devs alike!
388 Sometimes, an issue will stay open, even though the bug has been fixed. And
389 sometimes, the original bug may go stale because something has changed in the
392 It can be helpful to go through older bug reports and make sure that they are
393 still valid. Load up an older issue, double check that it's still true, and
394 leave a comment letting us know if it is or is not. The [least recently
395 updated sort][lru] is good for finding issues like this.
397 Contributors with sufficient permissions on the Rust repo can help by adding
398 labels to triage issues:
400 * Yellow, **A**-prefixed labels state which **area** of the project an issue
403 * Magenta, **B**-prefixed labels identify bugs which are **blockers**.
405 * Dark blue, **beta-** labels track changes which need to be backported into
408 * Light purple, **C**-prefixed labels represent the **category** of an issue.
410 * Green, **E**-prefixed labels explain the level of **experience** necessary
413 * The dark blue **final-comment-period** label marks bugs that are using the
414 RFC signoff functionality of [rfcbot] and are currently in the final
417 * Red, **I**-prefixed labels indicate the **importance** of the issue. The
418 [I-nominated][inom] label indicates that an issue has been nominated for
419 prioritizing at the next triage meeting.
421 * The purple **metabug** label marks lists of bugs collected by other
424 * Purple gray, **O**-prefixed labels are the **operating system** or platform
425 that this issue is specific to.
427 * Orange, **P**-prefixed labels indicate a bug's **priority**. These labels
428 are only assigned during triage meetings, and replace the [I-nominated][inom]
431 * The gray **proposed-final-comment-period** label marks bugs that are using
432 the RFC signoff functionality of [rfcbot] and are currently awaiting
433 signoff of all team members in order to enter the final comment period.
435 * Pink, **regression**-prefixed labels track regressions from stable to the
438 * The light orange **relnotes** label marks issues that should be documented in
439 the release notes of the next release.
441 * Gray, **S**-prefixed labels are used for tracking the **status** of pull
444 * Blue, **T**-prefixed bugs denote which **team** the issue belongs to.
446 If you're looking for somewhere to start, check out the [E-easy][eeasy] tag.
448 [inom]: https://github.com/rust-lang/rust/issues?q=is%3Aopen+is%3Aissue+label%3AI-nominated
449 [eeasy]: https://github.com/rust-lang/rust/issues?q=is%3Aopen+is%3Aissue+label%3AE-easy
450 [lru]: https://github.com/rust-lang/rust/issues?q=is%3Aissue+is%3Aopen+sort%3Aupdated-asc
451 [rfcbot]: https://github.com/anp/rfcbot-rs/
453 ## Out-of-tree Contributions
455 There are a number of other ways to contribute to Rust that don't deal with
458 Answer questions in the _Get Help!_ channels from the [Rust Discord server][rust-discord], on [users.rust-lang.org][users],
459 or on [StackOverflow][so].
461 Participate in the [RFC process](https://github.com/rust-lang/rfcs).
463 Find a [requested community library][community-library], build it, and publish
464 it to [Crates.io](http://crates.io). Easier said than done, but very, very
467 [rust-discord]: https://discord.gg/rust-lang
468 [users]: https://users.rust-lang.org/
469 [so]: http://stackoverflow.com/questions/tagged/rust
470 [community-library]: https://github.com/rust-lang/rfcs/labels/A-community-library
472 ## Helpful Links and Information
474 For people new to Rust, and just starting to contribute, or even for
475 more seasoned developers, some useful places to look for information
478 * The [rustc dev guide] contains information about how various parts of the compiler work and how to contribute to the compiler
479 * [Rust Forge][rustforge] contains additional documentation, including write-ups of how to achieve common tasks
480 * The [Rust Internals forum][rif], a place to ask questions and
481 discuss Rust's internals
482 * The [generated documentation for rust's compiler][gdfrustc]
483 * The [rust reference][rr], even though it doesn't specifically talk about Rust's internals, it's a great resource nonetheless
484 * Although out of date, [Tom Lee's great blog article][tlgba] is very helpful
485 * [rustaceans.org][ro] is helpful, but mostly dedicated to IRC
486 * The [Rust Compiler Testing Docs][rctd]
487 * For [@bors][bors], [this cheat sheet][cheatsheet] is helpful
488 (though you'll need to replace `@homu` with `@bors` in any commands)
489 * **Google!** ([search only in Rust Documentation][gsearchdocs] to find types, traits, etc. quickly)
490 * Don't be afraid to ask! The Rust community is friendly and helpful.
492 [rustc dev guide]: https://rustc-dev-guide.rust-lang.org/about-this-guide.html
493 [gdfrustc]: https://doc.rust-lang.org/nightly/nightly-rustc/rustc/
494 [gsearchdocs]: https://www.google.com/search?q=site:doc.rust-lang.org+your+query+here
495 [rif]: http://internals.rust-lang.org
496 [rr]: https://doc.rust-lang.org/book/README.html
497 [rustforge]: https://forge.rust-lang.org/
498 [tlgba]: http://tomlee.co/2014/04/a-more-detailed-tour-of-the-rust-compiler/
499 [ro]: http://www.rustaceans.org/
500 [rctd]: https://rustc-dev-guide.rust-lang.org/tests/intro.html
501 [cheatsheet]: https://buildbot2.rust-lang.org/homu/