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 and our Code of Conduct.
You can use rustfmt in Travis CI builds. We provide a minimal Travis CI configuration (see here) and verify its status using another repository. The status of that repository's build is reported by the "travis example" badge above.
Quick start
You can run rustfmt
with Rust 1.24 and above.
On the Stable toolchain
To install:
To run on a cargo project in the current working directory:
On the Nightly toolchain
For the latest and greatest rustfmt
, nightly is required.
To install:
To run on a cargo project in the current working directory:
Limitations
Rustfmt tries to work on as much Rust code as possible, sometimes, the code doesn't even need to compile! As we approach a 1.0 release we are also looking to limit areas of instability; in particular, post-1.0, the formatting of most code should not change as Rustfmt improves. However, there are some things that Rustfmt can't do or can't do well (and thus where formatting might change significantly, even post-1.0). We would like to reduce the list of limitations over time.
The following list enumerates areas where Rustfmt does not work or where the stability guarantees do not apply (we don't make a distinction between the two because in the future Rustfmt might work on code where it currently does not):
- a program where any part of the program does not parse (parsing is an early stage of compilation and in Rust includes macro expansion).
- Macro declarations and uses (current status: some macro declarations and uses are formatted).
- Comments, including any AST node with a comment 'inside' (Rustfmt does not currently attempt to format comments, it does format code with comments inside, but that formatting may change in the future).
- Rust code in code blocks in comments.
- Any fragment of a program (i.e., stability guarantees only apply to whole programs, even where fragments of a program can be formatted today).
- Code containing non-ascii unicode characters (we believe Rustfmt mostly works here, but do not have the test coverage or experience to be 100% sure).
- Bugs in Rustfmt (like any software, Rustfmt has bugs, we do not consider bug fixes to break our stability guarantees).
Installation
Installing from source
To install from source (nightly required), first checkout to the tag or branch you want to install, then issue
This will install rustfmt
in your ~/.cargo/bin
. Make sure to add ~/.cargo/bin
directory to
your PATH variable.
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 can run rustfmt --help
for information about available arguments.
When running with --check
, Rustfmt will exit with 0
if Rustfmt would not
make any formatting changes to the input, and 1
if Rustfmt would make changes.
In other modes, Rustfmt will exit with 1
if there was some error during
formatting (for example a parsing or internal error) and 0
if formatting
completed without error (whether or not changes were made).
Running Rustfmt from your editor
- Vim
- Emacs
- Sublime Text 3
- Atom
- Visual Studio Code using vscode-rust, vsc-rustfmt or rls_vscode through RLS.
- IntelliJ or CLion
Checking style on a CI server
To keep your code base consistently formatted, it can be helpful to fail the CI build
when a pull request contains unformatted code. Using --check
instructs
rustfmt to exit with an error code if the input is not formatted correctly.
It will also print any found differences. (Older versions of Rustfmt don't
support --check
, use --write-mode diff
).
A minimal Travis setup could look like this (requires Rust 1.24.0 or greater):
language: rust
before_script:
- rustup component add rustfmt
script:
- cargo build
- cargo test
- cargo fmt --all -- --check
See this blog post for more info.
How to build and test
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.
Configuring Rustfmt
Rustfmt is designed to be very configurable. You can create a TOML file called
rustfmt.toml
or .rustfmt.toml
, place it in the project or any other parent
directory and it will apply the options in that file. See rustfmt --help=config
for the options which are available, or if you prefer to see
visual style previews, GitHub page.
By default, Rustfmt uses a style which conforms to the Rust style guide that has been formalized through the style RFC process.
Configuration options are either stable or unstable. Stable options can always be used, while unstable ones are only available on a nightly toolchain, and opt-in. See GitHub page for details.
Rust's Editions
Rustfmt is able to pick up the edition used by reading the Cargo.toml
file if
executed through the Cargo's formatting tool cargo fmt
. Otherwise, the edition
needs to be specified in rustfmt.toml
, e.g., with edition = "2018"
.
Tips
-
For things you do not want rustfmt to mangle, use
#[rustfmt::skip]
-
To prevent rustfmt from formatting a macro or an attribute, use
#[rustfmt::skip::macros(target_macro_name)]
or#[rustfmt::skip::attributes(target_attribute_name)]
Example:
-
When you run rustfmt, place a file named
rustfmt.toml
or.rustfmt.toml
in target file directory or its parents to override the default settings of rustfmt. You can generate a file containing the default configuration withrustfmt --print-config default rustfmt.toml
and customize as needed. -
After successful compilation, a
rustfmt
executable can be found in the target directory. -
If you're having issues compiling Rustfmt (or compile errors when trying to install), make sure you have the most recent version of Rust installed.
-
You can change the way rustfmt emits the changes with the --emit flag:
Example:
Options:
Flag Description Nightly Only files overwrites output to files No stdout writes output to stdout No coverage displays how much of the input file was processed Yes checkstyle emits in a checkstyle format Yes json emits diffs in a json format Yes
License
Rustfmt is distributed under the terms of both the MIT license and the Apache License (Version 2.0).
See LICENSE-APACHE and LICENSE-MIT for details.