mirror of
https://github.com/rust-lang/rust-clippy
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204 lines
6.2 KiB
Markdown
204 lines
6.2 KiB
Markdown
# rust-clippy
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[](https://travis-ci.org/rust-lang-nursery/rust-clippy)
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[](https://ci.appveyor.com/project/rust-lang-nursery/rust-clippy)
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[](https://crates.io/crates/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 208 lints included in this crate!](https://rust-lang-nursery.github.io/rust-clippy/master/index.html)
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More to come, please [file an issue](https://github.com/rust-lang-nursery/rust-clippy/issues) if you have ideas!
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Table of contents:
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* [Usage instructions](#usage)
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* [Configuration](#configuration)
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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. All of these options are detailed below.
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As a general rule clippy will only work with the *latest* Rust nightly for now.
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### As a cargo subcommand (`cargo clippy`)
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One way to use clippy is by installing clippy through cargo as a cargo
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subcommand.
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```terminal
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cargo +nightly install clippy
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```
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(The `+nightly` is not necessary if your default `rustup` install is nightly)
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Now you can run clippy by invoking `cargo +nightly clippy`.
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In case you are not using rustup, you need to set the environment flag
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`SYSROOT` during installation so clippy knows where to find `librustc` and
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similar crates.
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```terminal
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SYSROOT=/path/to/rustc/sysroot cargo install clippy
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```
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### Optional dependency
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In some cases you might want to include clippy in your project directly, as an
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optional dependency. To do this, just modify `Cargo.toml`:
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```toml
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[dependencies]
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clippy = { version = "*", optional = true }
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```
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And, in your `main.rs` or `lib.rs`, add these lines:
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```rust
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#![cfg_attr(feature="clippy", feature(plugin))]
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#![cfg_attr(feature="clippy", plugin(clippy))]
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```
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Then build by enabling the feature: `cargo +nightly build --features "clippy"`.
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Instead of adding the `cfg_attr` attributes you can also run clippy on demand:
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`cargo rustc --features clippy -- -Z no-trans -Z extra-plugins=clippy`
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(the `-Z no trans`, while not necessary, will stop the compilation process after
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typechecking (and lints) have completed, which can significantly reduce the runtime).
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Alternatively, to only run clippy when testing:
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```toml
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[dev-dependencies]
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clippy = { version = "*" }
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```
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and add to `main.rs` or `lib.rs`:
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```
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#![cfg_attr(test, feature(plugin))]
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#![cfg_attr(test, plugin(clippy))]
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```
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### Running clippy from the command line without installing
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To have cargo compile your crate with clippy without needing `#![plugin(clippy)]`
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in your code, you can use:
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```terminal
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cargo rustc -- -L /path/to/clippy_so/dir/ -Z extra-plugins=clippy
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```
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*[Note](https://github.com/rust-lang-nursery/rust-clippy/wiki#a-word-of-warning):*
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Be sure that clippy was compiled with the same version of rustc that cargo invokes here!
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### As a Compiler Plugin
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*Note:* This is not a recommended installation method.
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Since stable Rust is backwards compatible, you should be able to
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compile your stable programs with nightly Rust with clippy plugged in to
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circumvent this.
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Add in your `Cargo.toml`:
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```toml
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[dependencies]
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clippy = "*"
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```
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You then need to add `#![feature(plugin)]` and `#![plugin(clippy)]` to the top
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of your crate entry point (`main.rs` or `lib.rs`).
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Sample `main.rs`:
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```rust
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#![feature(plugin)]
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#![plugin(clippy)]
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fn main(){
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let x = Some(1u8);
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match x {
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Some(y) => println!("{:?}", y),
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_ => ()
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}
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}
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```
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Produces this warning:
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```terminal
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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
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src/main.rs:8 match x {
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src/main.rs:9 Some(y) => println!("{:?}", y),
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src/main.rs:10 _ => ()
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src/main.rs:11 }
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src/main.rs:8:5: 11:6 help: Try
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if let Some(y) = x { println!("{:?}", y) }
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```
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## Configuration
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Some lints can be configured in a `clippy.toml` file. It contains basic `variable = value` mapping eg.
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```toml
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blacklisted-names = ["toto", "tata", "titi"]
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cyclomatic-complexity-threshold = 30
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```
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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
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meaning of the variables.
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You can also specify the path to the configuration file with:
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```rust
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#![plugin(clippy(conf_file="path/to/clippy's/configuration"))]
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```
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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 `allow`/`warn`/`deny`:
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* the whole set of `Warn` lints using the `clippy` lint group (`#![deny(clippy)]`)
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* all lints using both the `clippy` and `clippy_pedantic` lint groups (`#![deny(clippy)]`,
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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(single_match, 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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For convenience, `cargo clippy` automatically defines a `cargo-clippy`
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features. This lets you set lints level and compile with or without clippy
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transparently:
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```rust
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#[cfg_attr(feature = "cargo-clippy", allow(needless_lifetimes))]
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```
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## Updating rustc
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Sometimes, rustc moves forward without clippy catching up. Therefore updating
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rustc may leave clippy a non-functional state until we fix the resulting
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breakage.
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You can use the [rust-update](rust-update) script to update rustc only if
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clippy would also update correctly.
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## License
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Licensed under [MPL](https://www.mozilla.org/MPL/2.0/).
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If you're having issues with the license, let me know and I'll try to change it to something more permissive.
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