3 [![Clippy Test](https://github.com/rust-lang/rust-clippy/workflows/Clippy%20Test/badge.svg?branch=auto&event=push)](https://github.com/rust-lang/rust-clippy/actions?query=workflow%3A%22Clippy+Test%22+event%3Apush+branch%3Aauto)
4 [![License: MIT OR Apache-2.0](https://img.shields.io/crates/l/clippy.svg)](#license)
6 A collection of lints to catch common mistakes and improve your [Rust](https://github.com/rust-lang/rust) code.
8 [There are over 550 lints included in this crate!](https://rust-lang.github.io/rust-clippy/master/index.html)
10 Lints are divided into categories, each with a default [lint level](https://doc.rust-lang.org/rustc/lints/levels.html).
11 You can choose how much Clippy is supposed to ~~annoy~~ help you by changing the lint level by category.
13 | Category | Description | Default level |
14 | --------------------- | ----------------------------------------------------------------------------------- | ------------- |
15 | `clippy::all` | all lints that are on by default (correctness, suspicious, style, complexity, perf) | **warn/deny** |
16 | `clippy::correctness` | code that is outright wrong or useless | **deny** |
17 | `clippy::suspicious` | code that is most likely wrong or useless | **warn** |
18 | `clippy::style` | code that should be written in a more idiomatic way | **warn** |
19 | `clippy::complexity` | code that does something simple but in a complex way | **warn** |
20 | `clippy::perf` | code that can be written to run faster | **warn** |
21 | `clippy::pedantic` | lints which are rather strict or have occasional false positives | allow |
22 | `clippy::nursery` | new lints that are still under development | allow |
23 | `clippy::cargo` | lints for the cargo manifest | allow |
25 More to come, please [file an issue](https://github.com/rust-lang/rust-clippy/issues) if you have ideas!
27 The [lint list](https://rust-lang.github.io/rust-clippy/master/index.html) also contains "restriction lints", which are
28 for things which are usually not considered "bad", but may be useful to turn on in specific cases. These should be used
29 very selectively, if at all.
33 * [Usage instructions](#usage)
34 * [Configuration](#configuration)
35 * [Contributing](#contributing)
40 Below are instructions on how to use Clippy as a cargo subcommand,
41 in projects that do not use cargo, or in Travis CI.
43 ### As a cargo subcommand (`cargo clippy`)
45 One way to use Clippy is by installing Clippy through rustup as a cargo
48 #### Step 1: Install Rustup
50 You can install [Rustup](https://rustup.rs/) on supported platforms. This will help
51 us install Clippy and its dependencies.
53 If you already have Rustup installed, update to ensure you have the latest
60 #### Step 2: Install Clippy
62 Once you have rustup and the latest stable release (at least Rust 1.29) installed, run the following command:
65 rustup component add clippy
67 If it says that it can't find the `clippy` component, please run `rustup self update`.
69 #### Step 3: Run Clippy
71 Now you can run Clippy by invoking the following command:
77 #### Automatically applying Clippy suggestions
79 Clippy can automatically apply some lint suggestions, just like the compiler.
87 All the usual workspace options should work with Clippy. For example the following command
88 will run Clippy on the `example` crate:
91 cargo clippy -p example
94 As with `cargo check`, this includes dependencies that are members of the workspace, like path dependencies.
95 If you want to run Clippy **only** on the given crate, use the `--no-deps` option like this:
98 cargo clippy -p example -- --no-deps
101 ### Using `clippy-driver`
103 Clippy can also be used in projects that do not use cargo. To do so, run `clippy-driver`
104 with the same arguments you use for `rustc`. For example:
107 clippy-driver --edition 2018 -Cpanic=abort foo.rs
110 Note that `clippy-driver` is designed for running Clippy only and should not be used as a general
111 replacement for `rustc`. `clippy-driver` may produce artifacts that are not optimized as expected,
116 You can add Clippy to Travis CI in the same way you use it locally:
124 - rustup component add clippy
127 # if you want the build job to fail when encountering warnings, use
128 - cargo clippy -- -D warnings
129 # in order to also check tests and non-default crate features, use
130 - cargo clippy --all-targets --all-features -- -D warnings
135 Note that adding `-D warnings` will cause your build to fail if **any** warnings are found in your code.
136 That includes warnings found by rustc (e.g. `dead_code`, etc.). If you want to avoid this and only cause
137 an error for Clippy warnings, use `#![deny(clippy::all)]` in your code or `-D clippy::all` on the command
138 line. (You can swap `clippy::all` with the specific lint category you are targeting.)
142 Some lints can be configured in a TOML file named `clippy.toml` or `.clippy.toml`. It contains a basic `variable =
146 avoid-breaking-exported-api = false
147 blacklisted-names = ["toto", "tata", "titi"]
148 cognitive-complexity-threshold = 30
151 See the [list of lints](https://rust-lang.github.io/rust-clippy/master/index.html) for more information about which
152 lints can be configured and the meaning of the variables.
154 Note that configuration changes will not apply for code that has already been compiled and cached under `./target/`;
155 for example, adding a new string to `doc-valid-idents` may still result in Clippy flagging that string. To be sure that
156 any configuration changes are applied, you may want to run `cargo clean` and re-compile your crate from scratch.
158 To deactivate the “for further information visit *lint-link*” message you can
159 define the `CLIPPY_DISABLE_DOCS_LINKS` environment variable.
161 ### Allowing/denying lints
163 You can add options to your code to `allow`/`warn`/`deny` Clippy lints:
165 * the whole set of `Warn` lints using the `clippy` lint group (`#![deny(clippy::all)]`).
166 Note that `rustc` has additional [lint groups](https://doc.rust-lang.org/rustc/lints/groups.html).
168 * all lints using both the `clippy` and `clippy::pedantic` lint groups (`#![deny(clippy::all)]`,
169 `#![deny(clippy::pedantic)]`). Note that `clippy::pedantic` contains some very aggressive
170 lints prone to false positives.
172 * only some lints (`#![deny(clippy::single_match, clippy::box_vec)]`, etc.)
174 * `allow`/`warn`/`deny` can be limited to a single function or module using `#[allow(...)]`, etc.
176 Note: `allow` means to suppress the lint for your code. With `warn` the lint
177 will only emit a warning, while with `deny` the lint will emit an error, when
178 triggering for your code. An error causes clippy to exit with an error code, so
179 is useful in scripts like CI/CD.
181 If you do not want to include your lint levels in your code, you can globally
182 enable/disable lints by passing extra flags to Clippy during the run:
184 To allow `lint_name`, run
187 cargo clippy -- -A clippy::lint_name
190 And to warn on `lint_name`, run
193 cargo clippy -- -W clippy::lint_name
196 This also works with lint groups. For example, you
197 can run Clippy with warnings for all lints enabled:
199 cargo clippy -- -W clippy::pedantic
202 If you care only about a single lint, you can allow all others and then explicitly warn on
203 the lint(s) you are interested in:
205 cargo clippy -- -A clippy::all -W clippy::useless_format -W clippy::...
208 ### Specifying the minimum supported Rust version
210 Projects that intend to support old versions of Rust can disable lints pertaining to newer features by
211 specifying the minimum supported Rust version (MSRV) in the clippy configuration file.
217 Alternatively, the [`rust-version` field](https://doc.rust-lang.org/cargo/reference/manifest.html#the-rust-version-field)
218 in the `Cargo.toml` can be used.
222 rust-version = "1.30"
225 The MSRV can also be specified as an inner attribute, like below.
228 #![feature(custom_inner_attributes)]
229 #![clippy::msrv = "1.30.0"]
236 You can also omit the patch version when specifying the MSRV, so `msrv = 1.30`
237 is equivalent to `msrv = 1.30.0`.
239 Note: `custom_inner_attributes` is an unstable feature, so it has to be enabled explicitly.
241 Lints that recognize this configuration option can be found [here](https://rust-lang.github.io/rust-clippy/master/index.html#msrv)
245 If you want to contribute to Clippy, you can find more information in [CONTRIBUTING.md](https://github.com/rust-lang/rust-clippy/blob/master/CONTRIBUTING.md).
249 Copyright 2014-2022 The Rust Project Developers
251 Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
252 [https://www.apache.org/licenses/LICENSE-2.0](https://www.apache.org/licenses/LICENSE-2.0)> or the MIT license
253 <LICENSE-MIT or [https://opensource.org/licenses/MIT](https://opensource.org/licenses/MIT)>, at your
254 option. Files in the project may not be
255 copied, modified, or distributed except according to those terms.