3 [![Build Status](https://travis-ci.org/rust-lang-nursery/rust-clippy.svg?branch=master)](https://travis-ci.org/rust-lang-nursery/rust-clippy)
4 [![Windows build status](https://ci.appveyor.com/api/projects/status/github/rust-lang-nursery/rust-clippy?svg=true)](https://ci.appveyor.com/project/rust-lang-nursery/rust-clippy)
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 257 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_nursery` (new lints that aren't quite ready yet)
17 * `clippy_style` (code that should be written in a more idiomatic way)
18 * `clippy_complexity` (code that does something simple but in a complex way)
19 * `clippy_perf` (code that can be written in a faster way)
20 * **`clippy_correctness`** (code that is just outright wrong or very very useless)
22 More to come, please [file an issue](https://github.com/rust-lang-nursery/rust-clippy/issues) if you have ideas!
26 * [Usage instructions](#usage)
27 * [Configuration](#configuration)
32 Since this is a tool for helping the developer of a library or application
33 write better code, it is recommended not to include clippy as a hard dependency.
34 Options include using it as an optional dependency, as a cargo subcommand, or
35 as an included feature during build. All of these options are detailed below.
37 As a general rule clippy will only work with the *latest* Rust nightly for now.
39 To install Rust nightly, the recommended way is to use [rustup](https://rustup.rs/):
42 rustup install nightly
45 ### As a cargo subcommand (`cargo clippy`)
47 One way to use clippy is by installing clippy through cargo as a cargo
51 cargo +nightly install clippy
54 (The `+nightly` is not necessary if your default `rustup` install is nightly)
56 Now you can run clippy by invoking `cargo +nightly clippy`.
58 To update the subcommand together with the latest nightly use the [rust-update](rust-update) script or run:
62 cargo +nightly install --force clippy
65 In case you are not using rustup, you need to set the environment flag
66 `SYSROOT` during installation so clippy knows where to find `librustc` and
70 SYSROOT=/path/to/rustc/sysroot cargo install clippy
73 ### Optional dependency
75 In some cases you might want to include clippy in your project directly, as an
76 optional dependency. To do this, just modify `Cargo.toml`:
80 clippy = { version = "*", optional = true }
83 And, in your `main.rs` or `lib.rs`, add these lines:
86 #![cfg_attr(feature="clippy", feature(plugin))]
87 #![cfg_attr(feature="clippy", plugin(clippy))]
90 Then build by enabling the feature: `cargo +nightly build --features "clippy"`.
92 Instead of adding the `cfg_attr` attributes you can also run clippy on demand:
93 `cargo rustc --features clippy -- -Z no-trans -Z extra-plugins=clippy`
94 (the `-Z no trans`, while not necessary, will stop the compilation process after
95 typechecking (and lints) have completed, which can significantly reduce the runtime).
97 Alternatively, to only run clippy when testing:
101 clippy = { version = "*" }
104 and add to `main.rs` or `lib.rs`:
107 #![cfg_attr(test, feature(plugin))]
108 #![cfg_attr(test, plugin(clippy))]
111 ### Running clippy from the command line without installing it
113 To have cargo compile your crate with clippy without clippy installation and without needing `#![plugin(clippy)]`
114 in your code, you can use:
117 cargo run --bin cargo-clippy --manifest-path=path_to_clippys_Cargo.toml
120 *[Note](https://github.com/rust-lang-nursery/rust-clippy/wiki#a-word-of-warning):*
121 Be sure that clippy was compiled with the same version of rustc that cargo invokes here!
123 ### As a Compiler Plugin
125 *Note:* This is not a recommended installation method.
127 Since stable Rust is backwards compatible, you should be able to
128 compile your stable programs with nightly Rust with clippy plugged in to
131 Add in your `Cargo.toml`:
138 You then need to add `#![feature(plugin)]` and `#![plugin(clippy)]` to the top
139 of your crate entry point (`main.rs` or `lib.rs`).
152 Some(y) => println!("{:?}", y),
158 Produces this warning:
161 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
162 src/main.rs:8 match x {
163 src/main.rs:9 Some(y) => println!("{:?}", y),
164 src/main.rs:10 _ => ()
166 src/main.rs:8:5: 11:6 help: Try
167 if let Some(y) = x { println!("{:?}", y) }
172 Some lints can be configured in a TOML file named with `clippy.toml` or `.clippy.toml`. It contains basic `variable = value` mapping eg.
175 blacklisted-names = ["toto", "tata", "titi"]
176 cyclomatic-complexity-threshold = 30
179 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
180 meaning of the variables.
182 You can also specify the path to the configuration file with:
185 #![plugin(clippy(conf_file="path/to/clippy's/configuration"))]
188 To deactivate the “for further information visit *lint-link*” message you can
189 define the `CLIPPY_DISABLE_DOCS_LINKS` environment variable.
191 ### Allowing/denying lints
193 You can add options to `allow`/`warn`/`deny`:
195 * the whole set of `Warn` lints using the `clippy` lint group (`#![deny(clippy)]`)
197 * all lints using both the `clippy` and `clippy_pedantic` lint groups (`#![deny(clippy)]`,
198 `#![deny(clippy_pedantic)]`). Note that `clippy_pedantic` contains some very aggressive
199 lints prone to false positives.
201 * only some lints (`#![deny(single_match, box_vec)]`, etc)
203 * `allow`/`warn`/`deny` can be limited to a single function or module using `#[allow(...)]`, etc
205 Note: `deny` produces errors instead of warnings.
207 For convenience, `cargo clippy` automatically defines a `cargo-clippy`
208 feature. This lets you set lint levels and compile with or without clippy
212 #[cfg_attr(feature = "cargo-clippy", allow(needless_lifetimes))]
217 Sometimes, rustc moves forward without clippy catching up. Therefore updating
218 rustc may leave clippy a non-functional state until we fix the resulting
221 You can use the [rust-update](rust-update) script to update rustc only if
222 clippy would also update correctly.
226 Licensed under [MPL](https://www.mozilla.org/MPL/2.0/).
227 If you're having issues with the license, let me know and I'll try to change it to something more permissive.