194 lines
7.3 KiB
Markdown
194 lines
7.3 KiB
Markdown
# Clippy
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[](https://github.com/rust-lang/rust-clippy/actions?query=workflow%3A%22Clippy+Test%22+event%3Apush+branch%3Aauto)
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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 362 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
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for things which are usually not considered "bad", but may be useful to turn on in specific cases. These should be used
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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 =
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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
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lints can be configured and the 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
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flags to Clippy during the run: `cargo clippy -- -A clippy::lint_name` will run Clippy with `lint_name` disabled and
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`cargo clippy -- -W clippy::lint_name` will run it with that enabled. This also works with lint groups. For example you
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can run Clippy with warnings for all lints enabled: `cargo clippy -- -W clippy::pedantic`
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If you care only about a single lint, you can allow all others and then explicitly reenable
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the lint(s) you are interested in: `cargo clippy -- -Aclippy::all -Wclippy::useless_format -Wclippy::...`
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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 2014-2020 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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