rust/README.md

We are currently in the process of discussing Clippy 1.0 via the RFC process in https://github.com/rust-lang/rfcs/pull/2476 . The RFC's goal is to clarify policies around lint categorizations and the policy around which lints should be in the compiler and which lints should be in Clippy. Please leave your thoughts on the RFC PR.

Clippy

A collection of lints to catch common mistakes and improve your Rust code.

There are 281 lints included in this crate!

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 has no false positives)
• clippy::pedantic (everything)
• clippy::nursery (new lints that aren't quite ready yet)
• 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::cargo (checks against the cargo manifest)
• clippy::correctness (code that is just outright wrong or very very useless)

More to come, please file an issue if you have ideas!

Only the following of those categories are enabled by default:

• clippy::style
• clippy::correctness
• clippy::complexity
• clippy::perf

Other categories need to be enabled in order for their lints to be executed.

Table of contents:

• Usage instructions
• Configuration
• License

Usage

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 (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 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:

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:

rustup component add clippy-preview

Now you can run Clippy by invoking cargo clippy.

If it says that it can't find the clippy subcommand, please run rustup self update

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!

Travis CI

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-preview
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 none-default crate features, use
  - cargo clippy --all-targets --all-features -- -D warnings
  - cargo test
  # etc.

Configuration

Some lints can be configured in a TOML file named clippy.toml or .clippy.toml. It contains a basic variable = value mapping eg.

blacklisted-names = ["toto", "tata", "titi"]
cyclomatic-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 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)])

• 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: deny produces errors instead of warnings.

Note: To use the new clippy::lint_name syntax, a recent compiler has to be used currently. If you want to compile your code with the stable toolchain you can use a cfg_attr to activate the tool_lints feature:

#![cfg_attr(feature = "cargo-clippy", allow(clippy::lint_name))]

For this to work you have to use Clippy on the nightly toolchain: cargo +nightly clippy. If you want to use Clippy with the stable toolchain, you can stick to the old unscoped method to enable/disable Clippy lints until tool_lints are stable:

#![cfg_attr(feature = "cargo-clippy", allow(clippy_lint))]

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 lint_name will run clippy with lint_name disabled and cargo clippy -- -W lint_name will run it with that enabled. On newer compilers you may need to use clippy::lint_name instead.

License

Copyright 2014-2018 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.