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
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
85 ### Running Clippy from the command line without installing it
87 To have cargo compile your crate with Clippy without Clippy installation
88 in your code, you can use:
91 cargo run --bin cargo-clippy --manifest-path=path_to_clippys_Cargo.toml
94 *Note:* Be sure that Clippy was compiled with the same version of rustc that cargo invokes here!
98 You can add Clippy to Travis CI in the same way you use it locally:
106 - rustup component add clippy
109 # if you want the build job to fail when encountering warnings, use
110 - cargo clippy -- -D warnings
111 # in order to also check tests and non-default crate features, use
112 - cargo clippy --all-targets --all-features -- -D warnings
117 If you are on nightly, It might happen that Clippy is not available for a certain nightly release.
118 In this case you can try to conditionally install Clippy from the Git repo.
125 - rustup component add clippy --toolchain=nightly || cargo install --git https://github.com/rust-lang/rust-clippy/ --force clippy
129 Note that adding `-D warnings` will cause your build to fail if **any** warnings are found in your code.
130 That includes warnings found by rustc (e.g. `dead_code`, etc.). If you want to avoid this and only cause
131 an error for Clippy warnings, use `#![deny(clippy::all)]` in your code or `-D clippy::all` on the command
132 line. (You can swap `clippy::all` with the specific lint category you are targeting.)
136 Some lints can be configured in a TOML file named `clippy.toml` or `.clippy.toml`. It contains a basic `variable =
140 blacklisted-names = ["toto", "tata", "titi"]
141 cognitive-complexity-threshold = 30
144 See the [list of lints](https://rust-lang.github.io/rust-clippy/master/index.html) for more information about which
145 lints can be configured and the meaning of the variables.
147 To deactivate the “for further information visit *lint-link*” message you can
148 define the `CLIPPY_DISABLE_DOCS_LINKS` environment variable.
150 ### Allowing/denying lints
152 You can add options to your code to `allow`/`warn`/`deny` Clippy lints:
154 * the whole set of `Warn` lints using the `clippy` lint group (`#![deny(clippy::all)]`)
156 * all lints using both the `clippy` and `clippy::pedantic` lint groups (`#![deny(clippy::all)]`,
157 `#![deny(clippy::pedantic)]`). Note that `clippy::pedantic` contains some very aggressive
158 lints prone to false positives.
160 * only some lints (`#![deny(clippy::single_match, clippy::box_vec)]`, etc.)
162 * `allow`/`warn`/`deny` can be limited to a single function or module using `#[allow(...)]`, etc.
164 Note: `allow` means to suppress the lint for your code. With `warn` the lint
165 will only emit a warning, while with `deny` the lint will emit an error, when
166 triggering for your code. An error causes clippy to exit with an error code, so
167 is useful in scripts like CI/CD.
169 If you do not want to include your lint levels in your code, you can globally
170 enable/disable lints by passing extra flags to Clippy during the run:
172 To allow `lint_name`, run
175 cargo clippy -- -A clippy::lint_name
178 And to warn on `lint_name`, run
181 cargo clippy -- -W clippy::lint_name
184 This also works with lint groups. For example you
185 can run Clippy with warnings for all lints enabled:
187 cargo clippy -- -W clippy::pedantic
190 If you care only about a single lint, you can allow all others and then explicitly warn on
191 the lint(s) you are interested in:
193 cargo clippy -- -A clippy::all -W clippy::useless_format -W clippy::...
195 Note that if you've run clippy before, this may only take effect after you've modified a file or ran `cargo clean`.
199 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).
203 Copyright 2014-2020 The Rust Project Developers
205 Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
206 [https://www.apache.org/licenses/LICENSE-2.0](https://www.apache.org/licenses/LICENSE-2.0)> or the MIT license
207 <LICENSE-MIT or [https://opensource.org/licenses/MIT](https://opensource.org/licenses/MIT)>, at your
208 option. Files in the project may not be
209 copied, modified, or distributed except according to those terms.