| # Clippy |
| |
| [![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) |
| [![License: MIT OR 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 over 500 lints included in this crate!](https://rust-lang.github.io/rust-clippy/master/index.html) |
| |
| Lints are divided into categories, each with a default [lint level](https://doc.rust-lang.org/rustc/lints/levels.html). |
| You can choose how much Clippy is supposed to ~~annoy~~ help you by changing the lint level by category. |
| |
| | Category | Description | Default level | |
| | --------------------- | ----------------------------------------------------------------------------------- | ------------- | |
| | `clippy::all` | all lints that are on by default (correctness, suspicious, style, complexity, perf) | **warn/deny** | |
| | `clippy::correctness` | code that is outright wrong or useless | **deny** | |
| | `clippy::suspicious` | code that is most likely wrong or useless | **warn** | |
| | `clippy::style` | code that should be written in a more idiomatic way | **warn** | |
| | `clippy::complexity` | code that does something simple but in a complex way | **warn** | |
| | `clippy::perf` | code that can be written to run faster | **warn** | |
| | `clippy::pedantic` | lints which are rather strict or have occasional false positives | allow | |
| | `clippy::nursery` | new lints that are still under development | allow | |
| | `clippy::cargo` | lints for the cargo manifest | allow | |
| |
| More to come, please [file an issue](https://github.com/rust-lang/rust-clippy/issues) if you have ideas! |
| |
| The [lint list](https://rust-lang.github.io/rust-clippy/master/index.html) also contains "restriction lints", which are |
| for things which are usually not considered "bad", but may be useful to turn on in specific cases. These should be used |
| very selectively, if at all. |
| |
| Table of contents: |
| |
| * [Usage instructions](#usage) |
| * [Configuration](#configuration) |
| * [Contributing](#contributing) |
| * [License](#license) |
| |
| ## Usage |
| |
| Below are instructions on how to use Clippy as a cargo subcommand, |
| in projects that do not use cargo, or in Travis CI. |
| |
| ### 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](https://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 |
| ``` |
| |
| #### Automatically applying Clippy suggestions |
| |
| Clippy can automatically apply some lint suggestions, just like the compiler. |
| |
| ```terminal |
| cargo clippy --fix |
| ``` |
| |
| #### Workspaces |
| |
| All the usual workspace options should work with Clippy. For example the following command |
| will run Clippy on the `example` crate: |
| |
| ```terminal |
| cargo clippy -p example |
| ``` |
| |
| As with `cargo check`, this includes dependencies that are members of the workspace, like path dependencies. |
| If you want to run Clippy **only** on the given crate, use the `--no-deps` option like this: |
| |
| ```terminal |
| cargo clippy -p example -- --no-deps |
| ``` |
| |
| ### Using `clippy-driver` |
| |
| Clippy can also be used in projects that do not use cargo. To do so, run `clippy-driver` |
| with the same arguments you use for `rustc`. For example: |
| |
| ```terminal |
| clippy-driver --edition 2018 -Cpanic=abort foo.rs |
| ``` |
| |
| Note that `clippy-driver` is designed for running Clippy only and should not be used as a general |
| replacement for `rustc`. `clippy-driver` may produce artifacts that are not optimized as expected, |
| for example. |
| |
| ### 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 non-default crate features, use |
| - cargo clippy --all-targets --all-features -- -D warnings |
| - cargo test |
| # etc. |
| ``` |
| |
| Note that adding `-D warnings` will cause your build to fail if **any** warnings are found in your code. |
| That includes warnings found by rustc (e.g. `dead_code`, etc.). If you want to avoid this and only cause |
| an error for Clippy warnings, use `#![deny(clippy::all)]` in your code or `-D clippy::all` on the command |
| line. (You can swap `clippy::all` with the specific lint category you are targeting.) |
| |
| ## Configuration |
| |
| Some lints can be configured in a TOML file named `clippy.toml` or `.clippy.toml`. It contains a basic `variable = |
| value` mapping e.g. |
| |
| ```toml |
| avoid-breaking-exported-api = false |
| blacklisted-names = ["toto", "tata", "titi"] |
| cognitive-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. |
| |
| Note that configuration changes will not apply for code that has already been compiled and cached under `./target/`; |
| for example, adding a new string to `doc-valid-idents` may still result in Clippy flagging that string. To be sure that |
| any configuration changes are applied, you may want to run `cargo clean` and re-compile your crate from scratch. |
| |
| 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)]`). |
| Note that `rustc` has additional [lint groups](https://doc.rust-lang.org/rustc/lints/groups.html). |
| |
| * 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: `allow` means to suppress the lint for your code. With `warn` the lint |
| will only emit a warning, while with `deny` the lint will emit an error, when |
| triggering for your code. An error causes clippy to exit with an error code, so |
| is useful in scripts like CI/CD. |
| |
| 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: |
| |
| To allow `lint_name`, run |
| |
| ```terminal |
| cargo clippy -- -A clippy::lint_name |
| ``` |
| |
| And to warn on `lint_name`, run |
| |
| ```terminal |
| cargo clippy -- -W clippy::lint_name |
| ``` |
| |
| This also works with lint groups. For example, you |
| can run Clippy with warnings for all lints enabled: |
| ```terminal |
| cargo clippy -- -W clippy::pedantic |
| ``` |
| |
| If you care only about a single lint, you can allow all others and then explicitly warn on |
| the lint(s) you are interested in: |
| ```terminal |
| cargo clippy -- -A clippy::all -W clippy::useless_format -W clippy::... |
| ``` |
| |
| ### Specifying the minimum supported Rust version |
| |
| Projects that intend to support old versions of Rust can disable lints pertaining to newer features by |
| specifying the minimum supported Rust version (MSRV) in the clippy configuration file. |
| |
| ```toml |
| msrv = "1.30.0" |
| ``` |
| |
| The MSRV can also be specified as an inner attribute, like below. |
| |
| ```rust |
| #![feature(custom_inner_attributes)] |
| #![clippy::msrv = "1.30.0"] |
| |
| fn main() { |
| ... |
| } |
| ``` |
| |
| You can also omit the patch version when specifying the MSRV, so `msrv = 1.30` |
| is equivalent to `msrv = 1.30.0`. |
| |
| Note: `custom_inner_attributes` is an unstable feature, so it has to be enabled explicitly. |
| |
| Lints that recognize this configuration option can be found [here](https://rust-lang.github.io/rust-clippy/master/index.html#msrv) |
| |
| ## 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 2014-2022 The Rust Project Developers |
| |
| Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or |
| [https://www.apache.org/licenses/LICENSE-2.0](https://www.apache.org/licenses/LICENSE-2.0)> or the MIT license |
| <LICENSE-MIT or [https://opensource.org/licenses/MIT](https://opensource.org/licenses/MIT)>, at your |
| option. Files in the project may not be |
| copied, modified, or distributed except according to those terms. |