3 [![Build Status](https://travis-ci.org/rust-lang-nursery/rust-clippy.svg?branch=master)](https://travis-ci.org/rust-lang-nursery/rust-clippy)
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5 [![Current Version](http://meritbadge.herokuapp.com/clippy)](https://crates.io/crates/clippy)
6 [![License: MPL-2.0](https://img.shields.io/crates/l/clippy.svg)](#license)
8 A collection of lints to catch common mistakes and improve your [Rust](https://github.com/rust-lang/rust) code.
10 [There are 249 lints included in this crate!](https://rust-lang-nursery.github.io/rust-clippy/master/index.html)
12 We have a bunch of lint categories to allow you to choose how much clippy is supposed to ~~annoy~~ help you:
14 * `clippy` (everything that has no false positives)
15 * `clippy_pedantic` (everything)
16 * `clippy_style` (code that should be written in a more idiomatic way)
17 * `clippy_complexity` (code that does something simple but in a complex way)
18 * `clippy_perf` (code that can be written in a faster way)
19 * **`clippy_correctness`** (code that is just outright wrong or very very useless)
21 More to come, please [file an issue](https://github.com/rust-lang-nursery/rust-clippy/issues) if you have ideas!
25 * [Usage instructions](#usage)
26 * [Configuration](#configuration)
31 Since this is a tool for helping the developer of a library or application
32 write better code, it is recommended not to include clippy as a hard dependency.
33 Options include using it as an optional dependency, as a cargo subcommand, or
34 as an included feature during build. All of these options are detailed below.
36 As a general rule clippy will only work with the *latest* Rust nightly for now.
38 To install Rust nightly, the recommended way is to use [rustup](https://rustup.rs/):
41 rustup install nightly
44 ### As a cargo subcommand (`cargo clippy`)
46 One way to use clippy is by installing clippy through cargo as a cargo
50 cargo +nightly install clippy
53 (The `+nightly` is not necessary if your default `rustup` install is nightly)
55 Now you can run clippy by invoking `cargo +nightly clippy`.
57 To update the subcommand together with the latest nightly use the [rust-update](rust-update) script or run:
61 cargo +nightly install --force clippy
64 In case you are not using rustup, you need to set the environment flag
65 `SYSROOT` during installation so clippy knows where to find `librustc` and
69 SYSROOT=/path/to/rustc/sysroot cargo install clippy
72 ### Optional dependency
74 In some cases you might want to include clippy in your project directly, as an
75 optional dependency. To do this, just modify `Cargo.toml`:
79 clippy = { version = "*", optional = true }
82 And, in your `main.rs` or `lib.rs`, add these lines:
85 #![cfg_attr(feature="clippy", feature(plugin))]
86 #![cfg_attr(feature="clippy", plugin(clippy))]
89 Then build by enabling the feature: `cargo +nightly build --features "clippy"`.
91 Instead of adding the `cfg_attr` attributes you can also run clippy on demand:
92 `cargo rustc --features clippy -- -Z no-trans -Z extra-plugins=clippy`
93 (the `-Z no trans`, while not necessary, will stop the compilation process after
94 typechecking (and lints) have completed, which can significantly reduce the runtime).
96 Alternatively, to only run clippy when testing:
100 clippy = { version = "*" }
103 and add to `main.rs` or `lib.rs`:
106 #![cfg_attr(test, feature(plugin))]
107 #![cfg_attr(test, plugin(clippy))]
110 ### Running clippy from the command line without installing it
112 To have cargo compile your crate with clippy without clippy installation and without needing `#![plugin(clippy)]`
113 in your code, you can use:
116 cargo run --bin cargo-clippy --manifest-path=path_to_clippys_Cargo.toml
119 *[Note](https://github.com/rust-lang-nursery/rust-clippy/wiki#a-word-of-warning):*
120 Be sure that clippy was compiled with the same version of rustc that cargo invokes here!
122 ### As a Compiler Plugin
124 *Note:* This is not a recommended installation method.
126 Since stable Rust is backwards compatible, you should be able to
127 compile your stable programs with nightly Rust with clippy plugged in to
130 Add in your `Cargo.toml`:
137 You then need to add `#![feature(plugin)]` and `#![plugin(clippy)]` to the top
138 of your crate entry point (`main.rs` or `lib.rs`).
151 Some(y) => println!("{:?}", y),
157 Produces this warning:
160 src/main.rs:8:5: 11:6 warning: you seem to be trying to use match for destructuring a single type. Consider using `if let`, #[warn(single_match)] on by default
161 src/main.rs:8 match x {
162 src/main.rs:9 Some(y) => println!("{:?}", y),
163 src/main.rs:10 _ => ()
165 src/main.rs:8:5: 11:6 help: Try
166 if let Some(y) = x { println!("{:?}", y) }
171 Some lints can be configured in a TOML file named with `clippy.toml` or `.clippy.toml`. It contains basic `variable = value` mapping eg.
174 blacklisted-names = ["toto", "tata", "titi"]
175 cyclomatic-complexity-threshold = 30
178 See the [list of lints](https://rust-lang-nursery.github.io/rust-clippy/master/index.html) for more information about which lints can be configured and the
179 meaning of the variables.
181 You can also specify the path to the configuration file with:
184 #![plugin(clippy(conf_file="path/to/clippy's/configuration"))]
187 To deactivate the “for further information visit *lint-link*” message you can
188 define the `CLIPPY_DISABLE_DOCS_LINKS` environment variable.
190 ### Allowing/denying lints
192 You can add options to `allow`/`warn`/`deny`:
194 * the whole set of `Warn` lints using the `clippy` lint group (`#![deny(clippy)]`)
196 * all lints using both the `clippy` and `clippy_pedantic` lint groups (`#![deny(clippy)]`,
197 `#![deny(clippy_pedantic)]`). Note that `clippy_pedantic` contains some very aggressive
198 lints prone to false positives.
200 * only some lints (`#![deny(single_match, box_vec)]`, etc)
202 * `allow`/`warn`/`deny` can be limited to a single function or module using `#[allow(...)]`, etc
204 Note: `deny` produces errors instead of warnings.
206 For convenience, `cargo clippy` automatically defines a `cargo-clippy`
207 feature. This lets you set lint levels and compile with or without clippy
211 #[cfg_attr(feature = "cargo-clippy", allow(needless_lifetimes))]
216 Sometimes, rustc moves forward without clippy catching up. Therefore updating
217 rustc may leave clippy a non-functional state until we fix the resulting
220 You can use the [rust-update](rust-update) script to update rustc only if
221 clippy would also update correctly.
225 Licensed under [MPL](https://www.mozilla.org/MPL/2.0/).
226 If you're having issues with the license, let me know and I'll try to change it to something more permissive.