Clippy welcomes contributions from everyone. There are many ways to contribute to Clippy and the following document
explains how you can contribute and how to get started. If you have any questions about contributing or need help with
-anything, feel free to ask questions on issues or visit the `#clippy` IRC channel on `irc.mozilla.org` or meet us in
-`#clippy` on [Discord](https://discord.gg/rust-lang).
+anything, feel free to ask questions on issues or visit the `#clippy` on [Zulip].
-All contributors are expected to follow the [Rust Code of Conduct](http://www.rust-lang.org/conduct.html).
+All contributors are expected to follow the [Rust Code of Conduct].
-* [Getting started](#getting-started)
- * [Finding something to fix/improve](#finding-something-to-fiximprove)
-* [Writing code](#writing-code)
-* [How Clippy works](#how-clippy-works)
-* [Fixing nightly build failures](#fixing-build-failures-caused-by-rust)
-* [Issue and PR Triage](#issue-and-pr-triage)
-* [Bors and Homu](#bors-and-homu)
-* [Contributions](#contributions)
+- [Contributing to Clippy](#contributing-to-clippy)
+ - [The Clippy book](#the-clippy-book)
+ - [High level approach](#high-level-approach)
+ - [Finding something to fix/improve](#finding-something-to-fiximprove)
+ - [Getting code-completion for rustc internals to work](#getting-code-completion-for-rustc-internals-to-work)
+ - [IntelliJ Rust](#intellij-rust)
+ - [Rust Analyzer](#rust-analyzer)
+ - [How Clippy works](#how-clippy-works)
+ - [Issue and PR triage](#issue-and-pr-triage)
+ - [Bors and Homu](#bors-and-homu)
+ - [Contributions](#contributions)
-## Getting started
+[Zulip]: https://rust-lang.zulipchat.com/#narrow/stream/clippy
+[Rust Code of Conduct]: https://www.rust-lang.org/policies/code-of-conduct
-High level approach:
+## The Clippy book
+
+If you're new to Clippy and don't know where to start, the [Clippy book] includes
+a [developer guide] and is a good place to start your journey.
+
+[Clippy book]: https://doc.rust-lang.org/nightly/clippy/index.html
+[developer guide]: https://doc.rust-lang.org/nightly/clippy/development/index.html
+
+## High level approach
1. Find something to fix/improve
2. Change code (likely some file in `clippy_lints/src/`)
-3. Follow the instructions in the [docs for writing lints](doc/adding_lints.md) such as running the `setup-toolchain.sh` script
+3. Follow the instructions in the [Basics docs](book/src/development/basics.md)
+ to get set up
4. Run `cargo test` in the root directory and wiggle code until it passes
5. Open a PR (also can be done after 2. if you run into problems)
-### Finding something to fix/improve
+## Finding something to fix/improve
-All issues on Clippy are mentored, if you want help with a bug just ask @Manishearth, @llogiq, @mcarton or @oli-obk.
+All issues on Clippy are mentored, if you want help simply ask someone from the
+Clippy team directly by mentioning them in the issue or over on [Zulip]. All
+currently active team members can be found
+[here](https://github.com/rust-lang/highfive/blob/master/highfive/configs/rust-lang/rust-clippy.json#L3)
-Some issues are easier than others. The [`good first issue`](https://github.com/rust-lang/rust-clippy/labels/good%20first%20issue)
-label can be used to find the easy issues. If you want to work on an issue, please leave a comment
-so that we can assign it to you!
+Some issues are easier than others. The [`good-first-issue`] label can be used to find the easy
+issues. You can use `@rustbot claim` to assign the issue to yourself.
-There are also some abandoned PRs, marked with
-[`S-inactive-closed`](https://github.com/rust-lang/rust-clippy/pulls?q=is%3Aclosed+label%3AS-inactive-closed).
+There are also some abandoned PRs, marked with [`S-inactive-closed`].
Pretty often these PRs are nearly completed and just need some extra steps
(formatting, addressing review comments, ...) to be merged. If you want to
complete such a PR, please leave a comment in the PR and open a new one based
on it.
-Issues marked [`T-AST`](https://github.com/rust-lang/rust-clippy/labels/T-AST) involve simple
-matching of the syntax tree structure, and are generally easier than
-[`T-middle`](https://github.com/rust-lang/rust-clippy/labels/T-middle) issues, which involve types
+Issues marked [`T-AST`] involve simple matching of the syntax tree structure,
+and are generally easier than [`T-middle`] issues, which involve types
and resolved paths.
-[`T-AST`](https://github.com/rust-lang/rust-clippy/labels/T-AST) issues will generally need you to match against a
-predefined syntax structure. To figure out how this syntax structure is encoded in the AST, it is recommended to run
-`rustc -Z ast-json` on an example of the structure and compare with the [nodes in the AST
-docs](https://doc.rust-lang.org/nightly/nightly-rustc/syntax/ast). Usually the lint will end up to be a nested series of
-matches and ifs, [like
-so](https://github.com/rust-lang/rust-clippy/blob/de5ccdfab68a5e37689f3c950ed1532ba9d652a0/src/misc.rs#L34).
+[`T-AST`] issues will generally need you to match against a predefined syntax structure.
+To figure out how this syntax structure is encoded in the AST, it is recommended to run
+`rustc -Z unpretty=ast-tree` on an example of the structure and compare with the [nodes in the AST docs].
+Usually the lint will end up to be a nested series of matches and ifs, [like so][deep-nesting].
+But we can make it nest-less by using [let chains], [like this][nest-less].
-[`E-medium`](https://github.com/rust-lang/rust-clippy/labels/E-medium) issues are generally
-pretty easy too, though it's recommended you work on an E-easy issue first. They are mostly classified
-as `E-medium`, since they might be somewhat involved code wise, but not difficult per-se.
+[`E-medium`] issues are generally pretty easy too, though it's recommended you work on an [`good-first-issue`]
+first. Sometimes they are only somewhat involved code wise, but not difficult per-se.
+Note that [`E-medium`] issues may require some knowledge of Clippy internals or some
+debugging to find the actual problem behind the issue.
-[`T-middle`](https://github.com/rust-lang/rust-clippy/labels/T-middle) issues can
-be more involved and require verifying types. The
-[`ty`](https://doc.rust-lang.org/nightly/nightly-rustc/rustc/ty) module contains a
+[`T-middle`] issues can be more involved and require verifying types. The [`ty`] module contains a
lot of methods that are useful, though one of the most useful would be `expr_ty` (gives the type of
an AST expression). `match_def_path()` in Clippy's `utils` module can also be useful.
-## Writing code
+[`good-first-issue`]: https://github.com/rust-lang/rust-clippy/labels/good-first-issue
+[`S-inactive-closed`]: https://github.com/rust-lang/rust-clippy/pulls?q=is%3Aclosed+label%3AS-inactive-closed
+[`T-AST`]: https://github.com/rust-lang/rust-clippy/labels/T-AST
+[`T-middle`]: https://github.com/rust-lang/rust-clippy/labels/T-middle
+[`E-medium`]: https://github.com/rust-lang/rust-clippy/labels/E-medium
+[`ty`]: https://doc.rust-lang.org/nightly/nightly-rustc/rustc_middle/ty
+[nodes in the AST docs]: https://doc.rust-lang.org/nightly/nightly-rustc/rustc_ast/ast/
+[deep-nesting]: https://github.com/rust-lang/rust-clippy/blob/5e4f0922911536f80d9591180fa604229ac13939/clippy_lints/src/mem_forget.rs#L31-L45
+[let chains]: https://github.com/rust-lang/rust/pull/94927
+[nest-less]: https://github.com/rust-lang/rust-clippy/blob/5e4f0922911536f80d9591180fa604229ac13939/clippy_lints/src/bit_mask.rs#L133-L159
+
+## Getting code-completion for rustc internals to work
+
+### IntelliJ Rust
+Unfortunately, [`IntelliJ Rust`][IntelliJ_rust_homepage] does not (yet?) understand how Clippy uses compiler-internals
+using `extern crate` and it also needs to be able to read the source files of the rustc-compiler which are not
+available via a `rustup` component at the time of writing.
+To work around this, you need to have a copy of the [rustc-repo][rustc_repo] available which can be obtained via
+`git clone https://github.com/rust-lang/rust/`.
+Then you can run a `cargo dev` command to automatically make Clippy use the rustc-repo via path-dependencies
+which `IntelliJ Rust` will be able to understand.
+Run `cargo dev setup intellij --repo-path <repo-path>` where `<repo-path>` is a path to the rustc repo
+you just cloned.
+The command will add path-dependencies pointing towards rustc-crates inside the rustc repo to
+Clippy's `Cargo.toml`s and should allow `IntelliJ Rust` to understand most of the types that Clippy uses.
+Just make sure to remove the dependencies again before finally making a pull request!
+
+[rustc_repo]: https://github.com/rust-lang/rust/
+[IntelliJ_rust_homepage]: https://intellij-rust.github.io/
+
+### Rust Analyzer
+For [`rust-analyzer`][ra_homepage] to work correctly make sure that in the `rust-analyzer` configuration you set
+
+```json
+{ "rust-analyzer.rustc.source": "discover" }
+```
-Have a look at the [docs for writing lints](doc/adding_lints.md) for more details. [Llogiq's blog post on
-lints](https://llogiq.github.io/2015/06/04/workflows.html) is also a nice primer to lint-writing, though it does get
-into advanced stuff and may be a bit outdated.
+You should be able to see information on things like `Expr` or `EarlyContext` now if you hover them, also
+a lot more type hints.
-If you want to add a new lint or change existing ones apart from bugfixing, it's
-also a good idea to give the [stability guarantees][rfc_stability] and
-[lint categories][rfc_lint_cats] sections of the [Clippy 1.0 RFC][clippy_rfc] a
-quick read.
+To have `rust-analyzer` also work in the `clippy_dev` and `lintcheck` crates, add the following configuration
-## How Clippy works
+```json
+{
+ "rust-analyzer.linkedProjects": [
+ "./Cargo.toml",
+ "clippy_dev/Cargo.toml",
+ "lintcheck/Cargo.toml",
+ ]
+}
+```
+
+[ra_homepage]: https://rust-analyzer.github.io/
-Clippy is a [rustc compiler plugin][compiler_plugin]. The main entry point is at [`src/lib.rs`][main_entry]. In there,
-the lint registration is delegated to the [`clippy_lints`][lint_crate] crate.
+## How Clippy works
-[`clippy_lints/src/lib.rs`][lint_crate_entry] imports all the different lint modules and registers them with the rustc
-plugin registry. For example, the [`else_if_without_else`][else_if_without_else] lint is registered like this:
+[`clippy_lints/src/lib.rs`][lint_crate_entry] imports all the different lint modules and registers in the [`LintStore`].
+For example, the [`else_if_without_else`][else_if_without_else] lint is registered like this:
```rust
// ./clippy_lints/src/lib.rs
pub mod else_if_without_else;
// ...
-pub fn register_plugins(reg: &mut rustc_driver::plugin::Registry) {
+pub fn register_plugins(store: &mut rustc_lint::LintStore, sess: &Session, conf: &Conf) {
// ...
- reg.register_early_lint_pass(box else_if_without_else::ElseIfWithoutElse);
+ store.register_early_pass(|| box else_if_without_else::ElseIfWithoutElse);
// ...
- reg.register_lint_group("clippy::restriction", vec![
+ store.register_group(true, "clippy::restriction", Some("clippy_restriction"), vec![
// ...
- else_if_without_else::ELSE_IF_WITHOUT_ELSE,
+ LintId::of(&else_if_without_else::ELSE_IF_WITHOUT_ELSE),
// ...
]);
}
```
-The [`plugin::PluginRegistry`][plugin_registry] provides two methods to register lints:
-[register_early_lint_pass][reg_early_lint_pass] and [register_late_lint_pass][reg_late_lint_pass]. Both take an object
+The [`rustc_lint::LintStore`][`LintStore`] provides two methods to register lints:
+[register_early_pass][reg_early_pass] and [register_late_pass][reg_late_pass]. Both take an object
that implements an [`EarlyLintPass`][early_lint_pass] or [`LateLintPass`][late_lint_pass] respectively. This is done in
every single lint. It's worth noting that the majority of `clippy_lints/src/lib.rs` is autogenerated by `cargo dev
-update_lints` and you don't have to add anything by hand. When you are writing your own lint, you can use that script to
-save you some time.
+update_lints`. When you are writing your own lint, you can use that script to save you some time.
```rust
// ./clippy_lints/src/else_if_without_else.rs
AST information. The methods of the `LateLintPass` trait are executed after type checking and contain type information
via the `LateContext` parameter.
-That's why the `else_if_without_else` example uses the `register_early_lint_pass` function. Because the [actual lint
-logic][else_if_without_else] does not depend on any type information.
-
-## Fixing build failures caused by Rust
-
-Clippy will sometimes fail to build from source because building it depends on unstable internal Rust features. Most of
-the times we have to adapt to the changes and only very rarely there's an actual bug in Rust. Fixing build failures
-caused by Rust updates, can be a good way to learn about Rust internals.
+That's why the `else_if_without_else` example uses the `register_early_pass` function. Because the
+[actual lint logic][else_if_without_else] does not depend on any type information.
-In order to find out why Clippy does not work properly with a new Rust commit, you can use the [rust-toolstate commit
-history][toolstate_commit_history]. You will then have to look for the last commit that contains `test-pass ->
-build-fail` or `test-pass` -> `test-fail` for the `clippy-driver` component. [Here][toolstate_commit] is an example.
-
-The commit message contains a link to the PR. The PRs are usually small enough to discover the breaking API change and
-if they are bigger, they likely include some discussion that may help you to fix Clippy.
-
-To check if Clippy is available for a specific target platform, you can check
-the [rustup component history][rustup_component_history].
-
-If you decide to make Clippy work again with a Rust commit that breaks it,
-you probably want to install the latest Rust from master locally and run Clippy
-using that version of Rust.
-
-You can use [rustup-toolchain-install-master][rtim] to do that:
-
-```bash
-cargo install rustup-toolchain-install-master
-rustup-toolchain-install-master --force -n master -c rustc-dev
-rustup override set master
-cargo test
-```
-
-After fixing the build failure on this repository, we can submit a pull request
-to [`rust-lang/rust`] to fix the toolstate.
-
-To submit a pull request, you should follow these steps:
-
-```bash
-# Assuming you already cloned the rust-lang/rust repo and you're in the correct directory
-git submodule update --remote src/tools/clippy
-cargo update -p clippy
-git add -u
-git commit -m "Update Clippy"
-./x.py test -i --stage 1 src/tools/clippy # This is optional and should succeed anyway
-# Open a PR in rust-lang/rust
-```
+[lint_crate_entry]: https://github.com/rust-lang/rust-clippy/blob/master/clippy_lints/src/lib.rs
+[else_if_without_else]: https://github.com/rust-lang/rust-clippy/blob/4253aa7137cb7378acc96133c787e49a345c2b3c/clippy_lints/src/else_if_without_else.rs
+[`LintStore`]: https://doc.rust-lang.org/nightly/nightly-rustc/rustc_lint/struct.LintStore.html
+[reg_early_pass]: https://doc.rust-lang.org/nightly/nightly-rustc/rustc_lint/struct.LintStore.html#method.register_early_pass
+[reg_late_pass]: https://doc.rust-lang.org/nightly/nightly-rustc/rustc_lint/struct.LintStore.html#method.register_late_pass
+[early_lint_pass]: https://doc.rust-lang.org/nightly/nightly-rustc/rustc_lint/trait.EarlyLintPass.html
+[late_lint_pass]: https://doc.rust-lang.org/nightly/nightly-rustc/rustc_lint/trait.LateLintPass.html
## Issue and PR triage
responding to issues there may not always be enough time to stay on top of it
all.
-Our highest priority is fixing [crashes][l-crash] and [bugs][l-bug]. We don't
+Our highest priority is fixing [crashes][l-crash] and [bugs][l-bug], for example
+an ICE in a popular crate that many other crates depend on. We don't
want Clippy to crash on your code and we want it to be as reliable as the
suggestions from Rust compiler errors.
+We have prioritization labels and a sync-blocker label, which are described below.
+- [P-low][p-low]: Requires attention (fix/response/evaluation) by a team member but isn't urgent.
+- [P-medium][p-medium]: Should be addressed by a team member until the next sync.
+- [P-high][p-high]: Should be immediately addressed and will require an out-of-cycle sync or a backport.
+- [L-sync-blocker][l-sync-blocker]: An issue that "blocks" a sync.
+Or rather: before the sync this should be addressed,
+e.g. by removing a lint again, so it doesn't hit beta/stable.
+
## Bors and Homu
We use a bot powered by [Homu][homu] to help automate testing and landing of pull
If you have @bors permissions, you can find an overview of the available
commands [here][homu_instructions].
+[triage]: https://forge.rust-lang.org/release/triage-procedure.html
+[l-crash]: https://github.com/rust-lang/rust-clippy/labels/L-crash
+[l-bug]: https://github.com/rust-lang/rust-clippy/labels/L-bug
+[p-low]: https://github.com/rust-lang/rust-clippy/labels/P-low
+[p-medium]: https://github.com/rust-lang/rust-clippy/labels/P-medium
+[p-high]: https://github.com/rust-lang/rust-clippy/labels/P-high
+[l-sync-blocker]: https://github.com/rust-lang/rust-clippy/labels/L-sync-blocker
+[homu]: https://github.com/rust-lang/homu
+[homu_instructions]: https://bors.rust-lang.org/
+[homu_queue]: https://bors.rust-lang.org/queue/clippy
## Contributions
be reviewed by a core contributor (someone with permission to land patches) and either landed in the
main tree or given feedback for changes that would be required.
-All code in this repository is under the [Apache-2.0](http://www.apache.org/licenses/LICENSE-2.0>)
-or the [MIT](http://opensource.org/licenses/MIT) license.
+All code in this repository is under the [Apache-2.0] or the [MIT] license.
<!-- adapted from https://github.com/servo/servo/blob/master/CONTRIBUTING.md -->
-[main_entry]: https://github.com/rust-lang/rust-clippy/blob/c5b39a5917ffc0f1349b6e414fa3b874fdcf8429/src/lib.rs#L14
-[lint_crate]: https://github.com/rust-lang/rust-clippy/tree/c5b39a5917ffc0f1349b6e414fa3b874fdcf8429/clippy_lints/src
-[lint_crate_entry]: https://github.com/rust-lang/rust-clippy/blob/c5b39a5917ffc0f1349b6e414fa3b874fdcf8429/clippy_lints/src/lib.rs
-[else_if_without_else]: https://github.com/rust-lang/rust-clippy/blob/c5b39a5917ffc0f1349b6e414fa3b874fdcf8429/clippy_lints/src/else_if_without_else.rs
-[compiler_plugin]: https://doc.rust-lang.org/unstable-book/language-features/plugin.html#lint-plugins
-[plugin_registry]: https://doc.rust-lang.org/nightly/nightly-rustc/rustc_plugin_impl/registry/struct.Registry.html
-[reg_early_lint_pass]: https://doc.rust-lang.org/nightly/nightly-rustc/rustc_plugin_impl/registry/struct.Registry.html#method.register_early_lint_pass
-[reg_late_lint_pass]: https://doc.rust-lang.org/nightly/nightly-rustc/rustc_plugin_impl/registry/struct.Registry.html#method.register_late_lint_pass
-[early_lint_pass]: https://doc.rust-lang.org/nightly/nightly-rustc/rustc/lint/trait.EarlyLintPass.html
-[late_lint_pass]: https://doc.rust-lang.org/nightly/nightly-rustc/rustc/lint/trait.LateLintPass.html
-[toolstate_commit_history]: https://github.com/rust-lang-nursery/rust-toolstate/commits/master
-[toolstate_commit]: https://github.com/rust-lang-nursery/rust-toolstate/commit/6ce0459f6bfa7c528ae1886492a3e0b5ef0ee547
-[rtim]: https://github.com/kennytm/rustup-toolchain-install-master
-[rustup_component_history]: https://mexus.github.io/rustup-components-history
-[clippy_rfc]: https://github.com/rust-lang/rfcs/blob/master/text/2476-clippy-uno.md
-[rfc_stability]: https://github.com/rust-lang/rfcs/blob/master/text/2476-clippy-uno.md#stability-guarantees
-[rfc_lint_cats]: https://github.com/rust-lang/rfcs/blob/master/text/2476-clippy-uno.md#lint-audit-and-categories
-[triage]: https://forge.rust-lang.org/triage-procedure.html
-[l-crash]: https://github.com/rust-lang/rust-clippy/labels/L-crash%20%3Aboom%3A
-[l-bug]: https://github.com/rust-lang/rust-clippy/labels/L-bug%20%3Abeetle%3A
-[homu]: https://github.com/servo/homu
-[homu_instructions]: https://buildbot2.rust-lang.org/homu/
-[homu_queue]: https://buildbot2.rust-lang.org/homu/queue/clippy
-[`rust-lang/rust`]: https://github.com/rust-lang/rust
+[Apache-2.0]: https://www.apache.org/licenses/LICENSE-2.0
+[MIT]: https://opensource.org/licenses/MIT
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