# Clippy [![Build Status](https://travis-ci.com/rust-lang/rust-clippy.svg?branch=master)](https://travis-ci.com/rust-lang/rust-clippy) [![Windows Build status](https://ci.appveyor.com/api/projects/status/id677xpw1dguo7iw?svg=true)](https://ci.appveyor.com/project/rust-lang-libs/rust-clippy) [![Current Version](https://meritbadge.herokuapp.com/clippy)](https://crates.io/crates/clippy) [![License: MIT/Apache-2.0](https://img.shields.io/crates/l/clippy.svg)](#license) A collection of lints to catch common mistakes and improve your [Rust](https://github.com/rust-lang/rust) code. [There are 293 lints included in this crate!](https://rust-lang.github.io/rust-clippy/master/index.html) We have a bunch of lint categories to allow you to choose how much Clippy is supposed to ~~annoy~~ help you: * `clippy::all` (everything that has no false positives) * `clippy::pedantic` (everything) * `clippy::nursery` (new lints that aren't quite ready yet) * `clippy::style` (code that should be written in a more idiomatic way) * `clippy::complexity` (code that does something simple but in a complex way) * `clippy::perf` (code that can be written in a faster way) * `clippy::cargo` (checks against the cargo manifest) * **`clippy::correctness`** (code that is just outright wrong or very very useless) More to come, please [file an issue](https://github.com/rust-lang/rust-clippy/issues) if you have ideas! Only the following of those categories are enabled by default: * `clippy::style` * `clippy::correctness` * `clippy::complexity` * `clippy::perf` Other categories need to be enabled in order for their lints to be executed. Table of contents: * [Usage instructions](#usage) * [Configuration](#configuration) * [License](#license) ## Usage Since this is a tool for helping the developer of a library or application write better code, it is recommended not to include Clippy as a hard dependency. Options include using it as an optional dependency, as a cargo subcommand, or as an included feature during build. These options are detailed below. ### As a cargo subcommand (`cargo clippy`) One way to use Clippy is by installing Clippy through rustup as a cargo subcommand. #### Step 1: Install rustup You can install [rustup](http://rustup.rs/) on supported platforms. This will help us install Clippy and its dependencies. If you already have rustup installed, update to ensure you have the latest rustup and compiler: ```terminal rustup update ``` #### Step 2: Install Clippy Once you have rustup and the latest stable release (at least Rust 1.29) installed, run the following command: ```terminal rustup component add clippy ``` If it says that it can't find the `clippy` component, please run `rustup self update`. #### Step 3: Run Clippy Now you can run Clippy by invoking the following command: ```terminal cargo clippy ``` ### Running Clippy from the command line without installing it To have cargo compile your crate with Clippy without Clippy installation in your code, you can use: ```terminal cargo run --bin cargo-clippy --manifest-path=path_to_clippys_Cargo.toml ``` *[Note](https://github.com/rust-lang/rust-clippy/wiki#a-word-of-warning):* Be sure that Clippy was compiled with the same version of rustc that cargo invokes here! ### Travis CI You can add Clippy to Travis CI in the same way you use it locally: ```yml language: rust rust: - stable - beta before_script: - rustup component add clippy script: - cargo clippy # if you want the build job to fail when encountering warnings, use - cargo clippy -- -D warnings # in order to also check tests and none-default crate features, use - cargo clippy --all-targets --all-features -- -D warnings - cargo test # etc. ``` It might happen that Clippy is not available for a certain nightly release. In this case you can try to conditionally install Clippy from the git repo. ```yaml language: rust rust: - nightly before_script: - rustup component add clippy --toolchain=nightly || cargo install --git https://github.com/rust-lang/rust-clippy/ --force clippy # etc ``` ## Configuration Some lints can be configured in a TOML file named `clippy.toml` or `.clippy.toml`. It contains a basic `variable = value` mapping eg. ```toml blacklisted-names = ["toto", "tata", "titi"] cyclomatic-complexity-threshold = 30 ``` 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 meaning of the variables. To deactivate the “for further information visit *lint-link*” message you can define the `CLIPPY_DISABLE_DOCS_LINKS` environment variable. ### Allowing/denying lints You can add options to your code to `allow`/`warn`/`deny` Clippy lints: * the whole set of `Warn` lints using the `clippy` lint group (`#![deny(clippy::all)]`) * all lints using both the `clippy` and `clippy::pedantic` lint groups (`#![deny(clippy::all)]`, `#![deny(clippy::pedantic)]`). Note that `clippy::pedantic` contains some very aggressive lints prone to false positives. * only some lints (`#![deny(clippy::single_match, clippy::box_vec)]`, etc) * `allow`/`warn`/`deny` can be limited to a single function or module using `#[allow(...)]`, etc Note: `deny` produces errors instead of warnings. 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` ## Contributing 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). ## License Copyright 2014-2019 The Rust Project Developers Licensed under the Apache License, Version 2.0 or the MIT license , at your option. All files in the project carrying such notice may not be copied, modified, or distributed except according to those terms.