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 400 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, style, complexity, perf) | **warn/deny** |
16 | `clippy::correctness` | code that is outright wrong or very useless | **deny** |
17 | `clippy::style` | code that should be written in a more idiomatic way | **warn** |
18 | `clippy::complexity` | code that does something simple but in a complex way | **warn** |
19 | `clippy::perf` | code that can be written to run faster | **warn** |
20 | `clippy::pedantic` | lints which are rather strict or might have false positives | allow |
21 | `clippy::nursery` | new lints that are still under development | allow |
22 | `clippy::cargo` | lints for the cargo manifest | allow |
24 More to come, please [file an issue](https://github.com/rust-lang/rust-clippy/issues) if you have ideas!
26 The [lint list](https://rust-lang.github.io/rust-clippy/master/index.html) also contains "restriction lints", which are
27 for things which are usually not considered "bad", but may be useful to turn on in specific cases. These should be used
28 very selectively, if at all.
32 * [Usage instructions](#usage)
33 * [Configuration](#configuration)
34 * [Contributing](#contributing)
39 Below are instructions on how to use Clippy as a subcommand, compiled from source
42 ### As a cargo subcommand (`cargo clippy`)
44 One way to use Clippy is by installing Clippy through rustup as a cargo
47 #### Step 1: Install rustup
49 You can install [rustup](https://rustup.rs/) on supported platforms. This will help
50 us install Clippy and its dependencies.
52 If you already have rustup installed, update to ensure you have the latest
59 #### Step 2: Install Clippy
61 Once you have rustup and the latest stable release (at least Rust 1.29) installed, run the following command:
64 rustup component add clippy
66 If it says that it can't find the `clippy` component, please run `rustup self update`.
68 #### Step 3: Run Clippy
70 Now you can run Clippy by invoking the following command:
76 #### Automatically applying Clippy suggestions
78 Clippy can automatically apply some lint suggestions.
79 Note that this is still experimental and only supported on the nightly channel:
82 cargo clippy --fix -Z unstable-options
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
103 You can add Clippy to Travis CI in the same way you use it locally:
111 - rustup component add clippy
114 # if you want the build job to fail when encountering warnings, use
115 - cargo clippy -- -D warnings
116 # in order to also check tests and non-default crate features, use
117 - cargo clippy --all-targets --all-features -- -D warnings
122 Note that adding `-D warnings` will cause your build to fail if **any** warnings are found in your code.
123 That includes warnings found by rustc (e.g. `dead_code`, etc.). If you want to avoid this and only cause
124 an error for Clippy warnings, use `#![deny(clippy::all)]` in your code or `-D clippy::all` on the command
125 line. (You can swap `clippy::all` with the specific lint category you are targeting.)
129 Some lints can be configured in a TOML file named `clippy.toml` or `.clippy.toml`. It contains a basic `variable =
133 blacklisted-names = ["toto", "tata", "titi"]
134 cognitive-complexity-threshold = 30
137 See the [list of lints](https://rust-lang.github.io/rust-clippy/master/index.html) for more information about which
138 lints can be configured and the meaning of the variables.
140 To deactivate the “for further information visit *lint-link*” message you can
141 define the `CLIPPY_DISABLE_DOCS_LINKS` environment variable.
143 ### Allowing/denying lints
145 You can add options to your code to `allow`/`warn`/`deny` Clippy lints:
147 * the whole set of `Warn` lints using the `clippy` lint group (`#![deny(clippy::all)]`)
149 * all lints using both the `clippy` and `clippy::pedantic` lint groups (`#![deny(clippy::all)]`,
150 `#![deny(clippy::pedantic)]`). Note that `clippy::pedantic` contains some very aggressive
151 lints prone to false positives.
153 * only some lints (`#![deny(clippy::single_match, clippy::box_vec)]`, etc.)
155 * `allow`/`warn`/`deny` can be limited to a single function or module using `#[allow(...)]`, etc.
157 Note: `allow` means to suppress the lint for your code. With `warn` the lint
158 will only emit a warning, while with `deny` the lint will emit an error, when
159 triggering for your code. An error causes clippy to exit with an error code, so
160 is useful in scripts like CI/CD.
162 If you do not want to include your lint levels in your code, you can globally
163 enable/disable lints by passing extra flags to Clippy during the run:
165 To allow `lint_name`, run
168 cargo clippy -- -A clippy::lint_name
171 And to warn on `lint_name`, run
174 cargo clippy -- -W clippy::lint_name
177 This also works with lint groups. For example you
178 can run Clippy with warnings for all lints enabled:
180 cargo clippy -- -W clippy::pedantic
183 If you care only about a single lint, you can allow all others and then explicitly warn on
184 the lint(s) you are interested in:
186 cargo clippy -- -A clippy::all -W clippy::useless_format -W clippy::...
188 Note that if you've run clippy before, this may only take effect after you've modified a file or ran `cargo clean`.
190 ### Specifying the minimum supported Rust version
192 Projects that intend to support old versions of Rust can disable lints pertaining to newer features by
193 specifying the minimum supported Rust version (MSRV) in the clippy configuration file.
199 The MSRV can also be specified as an inner attribute, like below.
202 #![feature(custom_inner_attributes)]
203 #![clippy::msrv = "1.30.0"]
210 You can also omit the patch version when specifying the MSRV, so `msrv = 1.30`
211 is equivalent to `msrv = 1.30.0`.
213 Note: `custom_inner_attributes` is an unstable feature so it has to be enabled explicitly.
215 Lints that recognize this configuration option can be found [here](https://rust-lang.github.io/rust-clippy/master/index.html#msrv)
219 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).
223 Copyright 2014-2020 The Rust Project Developers
225 Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
226 [https://www.apache.org/licenses/LICENSE-2.0](https://www.apache.org/licenses/LICENSE-2.0)> or the MIT license
227 <LICENSE-MIT or [https://opensource.org/licenses/MIT](https://opensource.org/licenses/MIT)>, at your
228 option. Files in the project may not be
229 copied, modified, or distributed except according to those terms.