187 lines
7.2 KiB
Markdown
187 lines
7.2 KiB
Markdown
# Clippy
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[](https://travis-ci.com/rust-lang/rust-clippy)
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[](https://ci.appveyor.com/project/rust-lang-libs/rust-clippy)
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[](#license)
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A collection of lints to catch common mistakes and improve your [Rust](https://github.com/rust-lang/rust) code.
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[There are 346 lints included in this crate!](https://rust-lang.github.io/rust-clippy/master/index.html)
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We have a bunch of lint categories to allow you to choose how much Clippy is supposed to ~~annoy~~ help you:
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* `clippy::all` (everything that is on by default: all the categories below except for `nursery`, `pedantic`, and `cargo`)
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* `clippy::correctness` (code that is just **outright wrong** or **very very useless**, causes hard errors by default)
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* `clippy::style` (code that should be written in a more idiomatic way)
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* `clippy::complexity` (code that does something simple but in a complex way)
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* `clippy::perf` (code that can be written in a faster way)
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* `clippy::pedantic` (lints which are rather strict, off by default)
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* `clippy::nursery` (new lints that aren't quite ready yet, off by default)
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* `clippy::cargo` (checks against the cargo manifest, off by default)
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More to come, please [file an issue](https://github.com/rust-lang/rust-clippy/issues) if you have ideas!
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Only the following of those categories are enabled by default:
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* `clippy::style`
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* `clippy::correctness`
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* `clippy::complexity`
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* `clippy::perf`
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Other categories need to be enabled in order for their lints to be executed.
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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.
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Table of contents:
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* [Usage instructions](#usage)
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* [Configuration](#configuration)
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* [Contributing](#contributing)
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* [License](#license)
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## Usage
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Since this is a tool for helping the developer of a library or application
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write better code, it is recommended not to include Clippy as a hard dependency.
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Options include using it as an optional dependency, as a cargo subcommand, or
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as an included feature during build. These options are detailed below.
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### As a cargo subcommand (`cargo clippy`)
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One way to use Clippy is by installing Clippy through rustup as a cargo
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subcommand.
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#### Step 1: Install rustup
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You can install [rustup](https://rustup.rs/) on supported platforms. This will help
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us install Clippy and its dependencies.
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If you already have rustup installed, update to ensure you have the latest
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rustup and compiler:
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```terminal
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rustup update
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```
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#### Step 2: Install Clippy
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Once you have rustup and the latest stable release (at least Rust 1.29) installed, run the following command:
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```terminal
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rustup component add clippy
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```
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If it says that it can't find the `clippy` component, please run `rustup self update`.
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#### Step 3: Run Clippy
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Now you can run Clippy by invoking the following command:
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```terminal
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cargo clippy
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```
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#### Automatically applying Clippy suggestions
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Some Clippy lint suggestions can be automatically applied by `cargo fix`.
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Note that this is still experimental and only supported on the nightly channel:
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```terminal
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cargo fix -Z unstable-options --clippy
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```
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### Running Clippy from the command line without installing it
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To have cargo compile your crate with Clippy without Clippy installation
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in your code, you can use:
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```terminal
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cargo run --bin cargo-clippy --manifest-path=path_to_clippys_Cargo.toml
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```
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*Note:* Be sure that Clippy was compiled with the same version of rustc that cargo invokes here!
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### Travis CI
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You can add Clippy to Travis CI in the same way you use it locally:
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```yml
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language: rust
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rust:
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- stable
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- beta
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before_script:
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- rustup component add clippy
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script:
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- cargo clippy
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# if you want the build job to fail when encountering warnings, use
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- cargo clippy -- -D warnings
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# in order to also check tests and non-default crate features, use
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- cargo clippy --all-targets --all-features -- -D warnings
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- cargo test
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# etc.
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```
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If you are on nightly, It might happen that Clippy is not available for a certain nightly release.
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In this case you can try to conditionally install Clippy from the Git repo.
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```yaml
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language: rust
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rust:
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- nightly
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before_script:
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- rustup component add clippy --toolchain=nightly || cargo install --git https://github.com/rust-lang/rust-clippy/ --force clippy
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# etc.
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```
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Note that adding `-D warnings` will cause your build to fail if **any** warnings are found in your code.
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That includes warnings found by rustc (e.g. `dead_code`, etc.). If you want to avoid this and only cause
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an error for Clippy warnings, use `#![deny(clippy::all)]` in your code or `-D clippy::all` on the command
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line. (You can swap `clippy::all` with the specific lint category you are targeting.)
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## Configuration
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Some lints can be configured in a TOML file named `clippy.toml` or `.clippy.toml`. It contains a basic `variable = value` mapping eg.
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```toml
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blacklisted-names = ["toto", "tata", "titi"]
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cognitive-complexity-threshold = 30
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```
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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
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meaning of the variables.
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To deactivate the “for further information visit *lint-link*” message you can
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define the `CLIPPY_DISABLE_DOCS_LINKS` environment variable.
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### Allowing/denying lints
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You can add options to your code to `allow`/`warn`/`deny` Clippy lints:
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* the whole set of `Warn` lints using the `clippy` lint group (`#![deny(clippy::all)]`)
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* all lints using both the `clippy` and `clippy::pedantic` lint groups (`#![deny(clippy::all)]`,
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`#![deny(clippy::pedantic)]`). Note that `clippy::pedantic` contains some very aggressive
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lints prone to false positives.
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* only some lints (`#![deny(clippy::single_match, clippy::box_vec)]`, etc.)
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* `allow`/`warn`/`deny` can be limited to a single function or module using `#[allow(...)]`, etc.
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Note: `deny` produces errors instead of warnings.
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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`
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## Contributing
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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).
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## License
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Copyright 2014-2019 The Rust Project Developers
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Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
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[https://www.apache.org/licenses/LICENSE-2.0](https://www.apache.org/licenses/LICENSE-2.0)> or the MIT license
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<LICENSE-MIT or [https://opensource.org/licenses/MIT](https://opensource.org/licenses/MIT)>, at your
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option. Files in the project may not be
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copied, modified, or distributed except according to those terms.
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