A collection of lints to catch common mistakes and improve your Rust code.
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 is on by default: all the categories below except for
clippy::correctness(code that is just outright wrong or very very useless, causes hard errors by default)
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::pedantic(lints which are rather strict, off by default)
clippy::nursery(new lints that aren't quite ready yet, off by default)
clippy::cargo(checks against the cargo manifest, off by default)
More to come, please file an issue if you have ideas!
Only the following of those categories are enabled by default:
Other categories need to be enabled in order for their lints to be executed.
The lint list 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:
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 (
One way to use Clippy is by installing Clippy through rustup as a cargo subcommand.
Step 1: Install rustup
You can install rustup 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:
Step 2: Install Clippy
Once you have rustup and the latest stable release (at least Rust 1.29) installed, run the following command:
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:
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:
cargo run --bin cargo-clippy --manifest-path=path_to_clippys_Cargo.toml
Note: Be sure that Clippy was compiled with the same version of rustc that cargo invokes here!
You can add Clippy to Travis CI in the same way you use it locally:
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.
If you are on nightly, 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.
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
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.)
Some lints can be configured in a TOML file named
.clippy.toml. It contains a basic
variable = value mapping eg.
blacklisted-names = ["toto", "tata", "titi"] cognitive-complexity-threshold = 30
See the list of lints 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
CLIPPY_DISABLE_DOCS_LINKS environment variable.
You can add options to your code to
deny Clippy lints:
the whole set of
Warnlints using the
clippylint group (
all lints using both the
clippy::pedanticlint groups (
#![deny(clippy::pedantic)]). Note that
clippy::pedanticcontains some very aggressive lints prone to false positives.
only some lints (
#![deny(clippy::single_match, clippy::box_vec)], etc)
denycan be limited to a single function or module using
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
If you want to contribute to Clippy, you can find more information in CONTRIBUTING.md.
Copyright 2014-2019 The Rust Project Developers
Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or http://www.apache.org/licenses/LICENSE-2.0> or the MIT license <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your option. All files in the project carrying such notice may not be copied, modified, or distributed except according to those terms.