rustfmt

A tool for formatting Rust code according to style guidelines.

If you'd like to help out (and you should, it's a fun project!), see Contributing.md.

Quick start

To install:

cargo install rustfmt

to run on a cargo project in the current working directory:

cargo fmt

Installation

Note: this method currently requires you to be running cargo 0.6.0 or newer.

cargo install rustfmt

or if you're using multirust

multirust run nightly cargo install rustfmt

Usually cargo-fmt, which enables usage of Cargo subcommand cargo fmt, is installed alongside rustfmt. To only install rustfmt run

cargo install --no-default-features rustfmt

Running

You can run Rustfmt by just typing rustfmt filename if you used cargo install. This runs rustfmt on the given file, if the file includes out of line modules, then we reformat those too. So to run on a whole module or crate, you just need to run on the root file (usually mod.rs or lib.rs). Rustfmt can also read data from stdin. Alternatively, you can use cargo fmt to format all binary and library targets of your crate.

You'll probably want to specify the write mode. Currently, there are modes for replace, overwrite, display, and coverage. The replace mode is the default and overwrites the original files after renaming them. In overwrite mode, rustfmt does not backup the source files. To print the output to stdout, use the display mode. The write mode can be set by passing the --write-mode flag on the command line.

rustfmt filename --write-mode=display prints the output of rustfmt to the screen, for example.

You can run rustfmt --help for more information.

cargo fmt uses --write-mode=replace by default.

Running Rustfmt from your editor

• Vim
• Emacs
• Sublime Text 3
• Atom

How to build and test

First make sure you've got Rust 1.4.0 or greater available, then:

cargo build to build.

cargo test to run all tests.

To run rustfmt after this, use cargo run --bin rustfmt -- filename. See the notes above on running rustfmt.

What style does Rustfmt use?

Rustfmt is designed to be very configurable. You can create a TOML file called rustfmt.toml, place it in the project directory and it will apply the options in that file. See cargo run -- --config-help for the options which are available, or if you prefer to see source code, [src/config.rs].

By default, Rustfmt uses a style which (mostly) conforms to the Rust style guidelines. There are many details which the style guidelines do not cover, and in these cases we try to adhere to a style similar to that used in the Rust repo. Once Rustfmt is more complete, and able to re-format large repositories like Rust, we intend to go through the Rust RFC process to nail down the default style in detail.

If there are styling choices you don't agree with, we are usually happy to add options covering different styles. File an issue, or even better, submit a PR.

Gotchas

• For things you do not want rustfmt to mangle, use one of

  #[rustfmt_skip]
  #[cfg_attr(rustfmt, rustfmt_skip)]
  

• When you run rustfmt, place a file named rustfmt.toml in target file directory or its parents to override the default settings of rustfmt.

• After successful compilation, a rustfmt executable can be found in the target directory.