3 [![Build Status](https://travis-ci.com/rust-lang/rust-clippy.svg?branch=master)](https://travis-ci.com/rust-lang/rust-clippy)
4 [![Windows Build status](https://ci.appveyor.com/api/projects/status/id677xpw1dguo7iw?svg=true)](https://ci.appveyor.com/project/rust-lang-libs/rust-clippy)
5 [![License: MIT/Apache-2.0](https://img.shields.io/crates/l/clippy.svg)](#license)
7 A collection of lints to catch common mistakes and improve your [Rust](https://github.com/rust-lang/rust) code.
9 [There are 306 lints included in this crate!](https://rust-lang.github.io/rust-clippy/master/index.html)
11 We have a bunch of lint categories to allow you to choose how much Clippy is supposed to ~~annoy~~ help you:
13 * `clippy::all` (everything that is on by default: all the categories below except for `nursery`, `pedantic`, and `cargo`)
14 * `clippy::correctness` (code that is just **outright wrong** or **very very useless**, causes hard errors by default)
15 * `clippy::style` (code that should be written in a more idiomatic way)
16 * `clippy::complexity` (code that does something simple but in a complex way)
17 * `clippy::perf` (code that can be written in a faster way)
18 * `clippy::pedantic` (lints which are rather strict, off by default)
19 * `clippy::nursery` (new lints that aren't quite ready yet, off by default)
20 * `clippy::cargo` (checks against the cargo manifest, off by default)
22 More to come, please [file an issue](https://github.com/rust-lang/rust-clippy/issues) if you have ideas!
24 Only the following of those categories are enabled by default:
27 * `clippy::correctness`
28 * `clippy::complexity`
31 Other categories need to be enabled in order for their lints to be executed.
33 The [lint list](https://rust-lang.github.io/rust-clippy/master/index.html) also contains "restriction lints", which are for things which are usually not considered "bad", but may be useful to turn on in specific cases. These should be used very selectively, if at all.
37 * [Usage instructions](#usage)
38 * [Configuration](#configuration)
43 Since this is a tool for helping the developer of a library or application
44 write better code, it is recommended not to include Clippy as a hard dependency.
45 Options include using it as an optional dependency, as a cargo subcommand, or
46 as an included feature during build. These options are detailed below.
48 ### As a cargo subcommand (`cargo clippy`)
50 One way to use Clippy is by installing Clippy through rustup as a cargo
53 #### Step 1: Install rustup
55 You can install [rustup](http://rustup.rs/) on supported platforms. This will help
56 us install Clippy and its dependencies.
58 If you already have rustup installed, update to ensure you have the latest
65 #### Step 2: Install Clippy
67 Once you have rustup and the latest stable release (at least Rust 1.29) installed, run the following command:
70 rustup component add clippy
72 If it says that it can't find the `clippy` component, please run `rustup self update`.
74 #### Step 3: Run Clippy
76 Now you can run Clippy by invoking the following command:
82 ### Running Clippy from the command line without installing it
84 To have cargo compile your crate with Clippy without Clippy installation
85 in your code, you can use:
88 cargo run --bin cargo-clippy --manifest-path=path_to_clippys_Cargo.toml
91 *[Note](https://github.com/rust-lang/rust-clippy/wiki#a-word-of-warning):*
92 Be sure that Clippy was compiled with the same version of rustc that cargo invokes here!
96 You can add Clippy to Travis CI in the same way you use it locally:
104 - rustup component add clippy
107 # if you want the build job to fail when encountering warnings, use
108 - cargo clippy -- -D warnings
109 # in order to also check tests and non-default crate features, use
110 - cargo clippy --all-targets --all-features -- -D warnings
115 If you are on nightly, It might happen that Clippy is not available for a certain nightly release.
116 In this case you can try to conditionally install Clippy from the git repo.
123 - rustup component add clippy --toolchain=nightly || cargo install --git https://github.com/rust-lang/rust-clippy/ --force clippy
127 Note that adding `-D warnings` will cause your build to fail if **any** warnings are found in your code.
128 That includes warnings found by rustc (e.g. `dead_code`, etc.). If you want to avoid this and only cause
129 an error for clippy warnings, use `#![deny(clippy::all)]` in your code or `-D clippy::all` on the command
130 line. (You can swap `clippy::all` with the specific lint category you are targeting.)
134 Some lints can be configured in a TOML file named `clippy.toml` or `.clippy.toml`. It contains a basic `variable = value` mapping eg.
137 blacklisted-names = ["toto", "tata", "titi"]
138 cognitive-complexity-threshold = 30
141 See the [list of lints](https://rust-lang.github.io/rust-clippy/master/index.html) for more information about which lints can be configured and the
142 meaning of the variables.
144 To deactivate the “for further information visit *lint-link*” message you can
145 define the `CLIPPY_DISABLE_DOCS_LINKS` environment variable.
147 ### Allowing/denying lints
149 You can add options to your code to `allow`/`warn`/`deny` Clippy lints:
151 * the whole set of `Warn` lints using the `clippy` lint group (`#![deny(clippy::all)]`)
153 * all lints using both the `clippy` and `clippy::pedantic` lint groups (`#![deny(clippy::all)]`,
154 `#![deny(clippy::pedantic)]`). Note that `clippy::pedantic` contains some very aggressive
155 lints prone to false positives.
157 * only some lints (`#![deny(clippy::single_match, clippy::box_vec)]`, etc)
159 * `allow`/`warn`/`deny` can be limited to a single function or module using `#[allow(...)]`, etc
161 Note: `deny` produces errors instead of warnings.
163 If you do not want to include your lint levels in your code, you can globally enable/disable lints by passing extra flags to Clippy during the run: `cargo clippy -- -A clippy::lint_name` will run Clippy with `lint_name` disabled and `cargo clippy -- -W clippy::lint_name` will run it with that enabled. This also works with lint groups. For example you can run Clippy with warnings for all lints enabled: `cargo clippy -- -W clippy::pedantic`
167 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).
171 Copyright 2014-2019 The Rust Project Developers
173 Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
174 [http://www.apache.org/licenses/LICENSE-2.0](http://www.apache.org/licenses/LICENSE-2.0)> or the MIT license
175 <LICENSE-MIT or [http://opensource.org/licenses/MIT](http://opensource.org/licenses/MIT)>, at your
176 option. All files in the project carrying such notice may not be
177 copied, modified, or distributed except according to those terms.