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 248 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 * `complexity` (code that does something simple but in a complex way)
18 * `perf` (code that can be written in a faster way)
19 * **`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 ### As a cargo subcommand (`cargo clippy`)
40 One way to use clippy is by installing clippy through cargo as a cargo
44 cargo +nightly install clippy
47 (The `+nightly` is not necessary if your default `rustup` install is nightly)
49 Now you can run clippy by invoking `cargo +nightly clippy`.
51 In case you are not using rustup, you need to set the environment flag
52 `SYSROOT` during installation so clippy knows where to find `librustc` and
56 SYSROOT=/path/to/rustc/sysroot cargo install clippy
59 ### Optional dependency
61 In some cases you might want to include clippy in your project directly, as an
62 optional dependency. To do this, just modify `Cargo.toml`:
66 clippy = { version = "*", optional = true }
69 And, in your `main.rs` or `lib.rs`, add these lines:
72 #![cfg_attr(feature="clippy", feature(plugin))]
73 #![cfg_attr(feature="clippy", plugin(clippy))]
76 Then build by enabling the feature: `cargo +nightly build --features "clippy"`.
78 Instead of adding the `cfg_attr` attributes you can also run clippy on demand:
79 `cargo rustc --features clippy -- -Z no-trans -Z extra-plugins=clippy`
80 (the `-Z no trans`, while not necessary, will stop the compilation process after
81 typechecking (and lints) have completed, which can significantly reduce the runtime).
83 Alternatively, to only run clippy when testing:
87 clippy = { version = "*" }
90 and add to `main.rs` or `lib.rs`:
93 #![cfg_attr(test, feature(plugin))]
94 #![cfg_attr(test, plugin(clippy))]
97 ### Running clippy from the command line without installing it
99 To have cargo compile your crate with clippy without clippy installation and without needing `#![plugin(clippy)]`
100 in your code, you can use:
103 cargo run --bin cargo-clippy --manifest-path=path_to_clippys_Cargo.toml
106 *[Note](https://github.com/rust-lang-nursery/rust-clippy/wiki#a-word-of-warning):*
107 Be sure that clippy was compiled with the same version of rustc that cargo invokes here!
109 ### As a Compiler Plugin
111 *Note:* This is not a recommended installation method.
113 Since stable Rust is backwards compatible, you should be able to
114 compile your stable programs with nightly Rust with clippy plugged in to
117 Add in your `Cargo.toml`:
124 You then need to add `#![feature(plugin)]` and `#![plugin(clippy)]` to the top
125 of your crate entry point (`main.rs` or `lib.rs`).
138 Some(y) => println!("{:?}", y),
144 Produces this warning:
147 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
148 src/main.rs:8 match x {
149 src/main.rs:9 Some(y) => println!("{:?}", y),
150 src/main.rs:10 _ => ()
152 src/main.rs:8:5: 11:6 help: Try
153 if let Some(y) = x { println!("{:?}", y) }
158 Some lints can be configured in a TOML file named with `clippy.toml` or `.clippy.toml`. It contains basic `variable = value` mapping eg.
161 blacklisted-names = ["toto", "tata", "titi"]
162 cyclomatic-complexity-threshold = 30
165 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
166 meaning of the variables.
168 You can also specify the path to the configuration file with:
171 #![plugin(clippy(conf_file="path/to/clippy's/configuration"))]
174 To deactivate the “for further information visit *lint-link*” message you can
175 define the `CLIPPY_DISABLE_DOCS_LINKS` environment variable.
177 ### Allowing/denying lints
179 You can add options to `allow`/`warn`/`deny`:
181 * the whole set of `Warn` lints using the `clippy` lint group (`#![deny(clippy)]`)
183 * all lints using both the `clippy` and `clippy_pedantic` lint groups (`#![deny(clippy)]`,
184 `#![deny(clippy_pedantic)]`). Note that `clippy_pedantic` contains some very aggressive
185 lints prone to false positives.
187 * only some lints (`#![deny(single_match, box_vec)]`, etc)
189 * `allow`/`warn`/`deny` can be limited to a single function or module using `#[allow(...)]`, etc
191 Note: `deny` produces errors instead of warnings.
193 For convenience, `cargo clippy` automatically defines a `cargo-clippy`
194 features. This lets you set lints level and compile with or without clippy
198 #[cfg_attr(feature = "cargo-clippy", allow(needless_lifetimes))]
203 Sometimes, rustc moves forward without clippy catching up. Therefore updating
204 rustc may leave clippy a non-functional state until we fix the resulting
207 You can use the [rust-update](rust-update) script to update rustc only if
208 clippy would also update correctly.
212 Licensed under [MPL](https://www.mozilla.org/MPL/2.0/).
213 If you're having issues with the license, let me know and I'll try to change it to something more permissive.