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 361 lints included in this crate!](https://rust-lang.github.io/rust-clippy/master/index.html)
10 We have a bunch of lint categories to allow you to choose how much Clippy is supposed to ~~annoy~~ help you:
12 * `clippy::all` (everything that is on by default: all the categories below except for `nursery`, `pedantic`, and `cargo`)
13 * `clippy::correctness` (code that is just **outright wrong** or **very very useless**, causes hard errors by default)
14 * `clippy::style` (code that should be written in a more idiomatic way)
15 * `clippy::complexity` (code that does something simple but in a complex way)
16 * `clippy::perf` (code that can be written in a faster way)
17 * `clippy::pedantic` (lints which are rather strict, off by default)
18 * `clippy::nursery` (new lints that aren't quite ready yet, off by default)
19 * `clippy::cargo` (checks against the cargo manifest, off by default)
21 More to come, please [file an issue](https://github.com/rust-lang/rust-clippy/issues) if you have ideas!
23 Only the following of those categories are enabled by default:
26 * `clippy::correctness`
27 * `clippy::complexity`
30 Other categories need to be enabled in order for their lints to be executed.
32 The [lint list](https://rust-lang.github.io/rust-clippy/master/index.html) also contains "restriction lints", which are
33 for things which are usually not considered "bad", but may be useful to turn on in specific cases. These should be used
34 very selectively, if at all.
38 * [Usage instructions](#usage)
39 * [Configuration](#configuration)
40 * [Contributing](#contributing)
45 Since this is a tool for helping the developer of a library or application
46 write better code, it is recommended not to include Clippy as a hard dependency.
47 Options include using it as an optional dependency, as a cargo subcommand, or
48 as an included feature during build. These options are detailed below.
50 ### As a cargo subcommand (`cargo clippy`)
52 One way to use Clippy is by installing Clippy through rustup as a cargo
55 #### Step 1: Install rustup
57 You can install [rustup](https://rustup.rs/) on supported platforms. This will help
58 us install Clippy and its dependencies.
60 If you already have rustup installed, update to ensure you have the latest
67 #### Step 2: Install Clippy
69 Once you have rustup and the latest stable release (at least Rust 1.29) installed, run the following command:
72 rustup component add clippy
74 If it says that it can't find the `clippy` component, please run `rustup self update`.
76 #### Step 3: Run Clippy
78 Now you can run Clippy by invoking the following command:
84 #### Automatically applying Clippy suggestions
86 Some Clippy lint suggestions can be automatically applied by `cargo fix`.
87 Note that this is still experimental and only supported on the nightly channel:
90 cargo fix -Z unstable-options --clippy
93 #### Running only a single lint
95 If you care only about the warnings of a single lint and want to ignore everything else, you
96 can first deny all the clippy lints and then explicitly enable the lint(s) you care about:
98 cargo clippy -- -Aclippy::all -Wclippy::useless_format
101 ### Running Clippy from the command line without installing it
103 To have cargo compile your crate with Clippy without Clippy installation
104 in your code, you can use:
107 cargo run --bin cargo-clippy --manifest-path=path_to_clippys_Cargo.toml
110 *Note:* Be sure that Clippy was compiled with the same version of rustc that cargo invokes here!
114 You can add Clippy to Travis CI in the same way you use it locally:
122 - rustup component add clippy
125 # if you want the build job to fail when encountering warnings, use
126 - cargo clippy -- -D warnings
127 # in order to also check tests and non-default crate features, use
128 - cargo clippy --all-targets --all-features -- -D warnings
133 If you are on nightly, It might happen that Clippy is not available for a certain nightly release.
134 In this case you can try to conditionally install Clippy from the Git repo.
141 - rustup component add clippy --toolchain=nightly || cargo install --git https://github.com/rust-lang/rust-clippy/ --force clippy
145 Note that adding `-D warnings` will cause your build to fail if **any** warnings are found in your code.
146 That includes warnings found by rustc (e.g. `dead_code`, etc.). If you want to avoid this and only cause
147 an error for Clippy warnings, use `#![deny(clippy::all)]` in your code or `-D clippy::all` on the command
148 line. (You can swap `clippy::all` with the specific lint category you are targeting.)
152 Some lints can be configured in a TOML file named `clippy.toml` or `.clippy.toml`. It contains a basic `variable =
156 blacklisted-names = ["toto", "tata", "titi"]
157 cognitive-complexity-threshold = 30
160 See the [list of lints](https://rust-lang.github.io/rust-clippy/master/index.html) for more information about which
161 lints can be configured and the meaning of the variables.
163 To deactivate the “for further information visit *lint-link*” message you can
164 define the `CLIPPY_DISABLE_DOCS_LINKS` environment variable.
166 ### Allowing/denying lints
168 You can add options to your code to `allow`/`warn`/`deny` Clippy lints:
170 * the whole set of `Warn` lints using the `clippy` lint group (`#![deny(clippy::all)]`)
172 * all lints using both the `clippy` and `clippy::pedantic` lint groups (`#![deny(clippy::all)]`,
173 `#![deny(clippy::pedantic)]`). Note that `clippy::pedantic` contains some very aggressive
174 lints prone to false positives.
176 * only some lints (`#![deny(clippy::single_match, clippy::box_vec)]`, etc.)
178 * `allow`/`warn`/`deny` can be limited to a single function or module using `#[allow(...)]`, etc.
180 Note: `deny` produces errors instead of warnings.
182 If you do not want to include your lint levels in your code, you can globally enable/disable lints by passing extra
183 flags to Clippy during the run: `cargo clippy -- -A clippy::lint_name` will run Clippy with `lint_name` disabled and
184 `cargo clippy -- -W clippy::lint_name` will run it with that enabled. This also works with lint groups. For example you
185 can run Clippy with warnings for all lints enabled: `cargo clippy -- -W clippy::pedantic`
189 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).
193 Copyright 2014-2020 The Rust Project Developers
195 Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
196 [https://www.apache.org/licenses/LICENSE-2.0](https://www.apache.org/licenses/LICENSE-2.0)> or the MIT license
197 <LICENSE-MIT or [https://opensource.org/licenses/MIT](https://opensource.org/licenses/MIT)>, at your
198 option. Files in the project may not be
199 copied, modified, or distributed except according to those terms.