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 362 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 Clippy can automatically apply some lint suggestions.
87 Note that this is still experimental and only supported on the nightly channel:
90 cargo clippy --fix -Z unstable-options
93 ### Running Clippy from the command line without installing it
95 To have cargo compile your crate with Clippy without Clippy installation
96 in your code, you can use:
99 cargo run --bin cargo-clippy --manifest-path=path_to_clippys_Cargo.toml
102 *Note:* Be sure that Clippy was compiled with the same version of rustc that cargo invokes here!
106 You can add Clippy to Travis CI in the same way you use it locally:
114 - rustup component add clippy
117 # if you want the build job to fail when encountering warnings, use
118 - cargo clippy -- -D warnings
119 # in order to also check tests and non-default crate features, use
120 - cargo clippy --all-targets --all-features -- -D warnings
125 If you are on nightly, It might happen that Clippy is not available for a certain nightly release.
126 In this case you can try to conditionally install Clippy from the Git repo.
133 - rustup component add clippy --toolchain=nightly || cargo install --git https://github.com/rust-lang/rust-clippy/ --force clippy
137 Note that adding `-D warnings` will cause your build to fail if **any** warnings are found in your code.
138 That includes warnings found by rustc (e.g. `dead_code`, etc.). If you want to avoid this and only cause
139 an error for Clippy warnings, use `#![deny(clippy::all)]` in your code or `-D clippy::all` on the command
140 line. (You can swap `clippy::all` with the specific lint category you are targeting.)
144 Some lints can be configured in a TOML file named `clippy.toml` or `.clippy.toml`. It contains a basic `variable =
148 blacklisted-names = ["toto", "tata", "titi"]
149 cognitive-complexity-threshold = 30
152 See the [list of lints](https://rust-lang.github.io/rust-clippy/master/index.html) for more information about which
153 lints can be configured and the meaning of the variables.
155 To deactivate the “for further information visit *lint-link*” message you can
156 define the `CLIPPY_DISABLE_DOCS_LINKS` environment variable.
158 ### Allowing/denying lints
160 You can add options to your code to `allow`/`warn`/`deny` Clippy lints:
162 * the whole set of `Warn` lints using the `clippy` lint group (`#![deny(clippy::all)]`)
164 * all lints using both the `clippy` and `clippy::pedantic` lint groups (`#![deny(clippy::all)]`,
165 `#![deny(clippy::pedantic)]`). Note that `clippy::pedantic` contains some very aggressive
166 lints prone to false positives.
168 * only some lints (`#![deny(clippy::single_match, clippy::box_vec)]`, etc.)
170 * `allow`/`warn`/`deny` can be limited to a single function or module using `#[allow(...)]`, etc.
172 Note: `deny` produces errors instead of warnings.
174 If you do not want to include your lint levels in your code, you can globally enable/disable lints by passing extra
175 flags to Clippy during the run: `cargo clippy -- -A clippy::lint_name` will run Clippy with `lint_name` disabled and
176 `cargo clippy -- -W clippy::lint_name` will run it with that enabled. This also works with lint groups. For example you
177 can run Clippy with warnings for all lints enabled: `cargo clippy -- -W clippy::pedantic`
178 If you care only about a single lint, you can allow all others and then explicitly reenable
179 the lint(s) you are interested in: `cargo clippy -- -Aclippy::all -Wclippy::useless_format -Wclippy::...`
183 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).
187 Copyright 2014-2020 The Rust Project Developers
189 Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
190 [https://www.apache.org/licenses/LICENSE-2.0](https://www.apache.org/licenses/LICENSE-2.0)> or the MIT license
191 <LICENSE-MIT or [https://opensource.org/licenses/MIT](https://opensource.org/licenses/MIT)>, at your
192 option. Files in the project may not be
193 copied, modified, or distributed except according to those terms.