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.
We are changing the default style used by rustfmt. There is an ongoing RFC process. The last version using the old style was 0.8.6. From 0.9 onwards, the RFC style is the default. If you want the old style back, you can use legacy-rustfmt.toml as your rustfmt.toml.
The current master branch uses libsyntax (part of the compiler). It is
published as rustfmt-nightly. The syntex branch uses Syntex instead of
libsyntax, it is published (for now) as rustfmt. Most development happens on
the master branch, however, this only supports nightly toolchains. If you use
stable or beta Rust toolchains, you must use the Syntex version (which is likely
to be a bit out of date). Version 0.1 of rustfmt-nightly is forked from version
0.9 of the syntex branch.
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.
You can use rustfmt on Rust 1.24 and above.
To install:
rustup component add rustfmt-preview
to run on a cargo project in the current working directory:
cargo fmt
For the latest and greatest rustfmt (nightly required):
rustup component add rustfmt-preview --toolchain nightly
To run:
cargo +nightly fmt
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):
rustup component add rustfmt-preview
To install from source (nightly required), first checkout to the tag or branch you want to install, then issue
cargo install --path .
This will install rustfmt in your ~/.cargo/bin. Make sure to add ~/.cargo/bin directory to
your PATH variable.
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
check, diff, replace, overwrite, display, coverage, checkstyle, and plain.
overwrite Is the default and overwrites the original files without creating backups.replace Overwrites the original files after creating backups of the files.display Will print the formatted files to stdout.plain Also writes to stdout, but with no metadata.diff Will print a diff between the original files and formatted files to stdout.
Will also exit with an error code if there are any differences.check Checks if the program's formatting matches what rustfmt would do. Silently exits
with code 0 if so, emits a diff and exits with code 1 if not. This option is
designed to be run in CI-like where a non-zero exit signifies incorrect formatting.checkstyle Will output the lines that need to be corrected as a checkstyle XML file,
that can be used by tools like Jenkins.The write mode can be set by passing the --write-mode flag on
the command line. For example rustfmt --write-mode=display src/filename.rs
cargo fmt uses --write-mode=overwrite by default.
If you want to restrict reformatting to specific sets of lines, you can
use the --file-lines option. Its argument is a JSON array of objects
with file and range properties, where file is a file name, and
range is an array representing a range of lines like [7,13]. Ranges
are 1-based and inclusive of both end points. Specifying an empty array
will result in no files being formatted. For example,
rustfmt --file-lines '[
{"file":"src/lib.rs","range":[7,13]},
{"file":"src/lib.rs","range":[21,29]},
{"file":"src/foo.rs","range":[10,11]},
{"file":"src/foo.rs","range":[15,15]}]'
would format lines 7-13 and 21-29 of src/lib.rs, and lines 10-11,
and 15 of src/foo.rs. No other files would be formatted, even if they
are included as out of line modules from src/lib.rs.
If rustfmt successfully reformatted the code it will exit with 0 exit
status. Exit status 1 signals some unexpected error, like an unknown option or
a failure to read a file. Exit status 2 is returned if there are syntax errors
in the input files. rustfmt can't format syntactically invalid code. Finally,
exit status 3 is returned if there are some issues which can't be resolved
automatically. For example, if you have a very long comment line rustfmt
doesn't split it. Instead it prints a warning and exits with 3.
You can run rustfmt --help for more information.
To keep your code base consistently formatted, it can be helpful to fail the CI build
when a pull request contains unformatted code. Using --write-mode=diff instructs
rustfmt to exit with an error code if the input is not formatted correctly.
It will also print any found differences.
A minimal Travis setup could look like this (requires Rust 1.24.0 or greater):
yaml
language: rust
before_script:
- rustup component add rustfmt-preview
script:
- cargo fmt --all -- --write-mode=diff
- cargo build
- cargo 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.
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
--config-help for the options which are available, or if you prefer to see
visual style previews, Configurations.md.
By default, Rustfmt uses a style which conforms to the [Rust style guide][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 Configurations.md for details.
For things you do not want rustfmt to mangle, use one of
```rust
```
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 with
rustfmt --dump-default-config rustfmt.toml and customize as needed.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.
If you get an error like error while loading shared libraries while starting
up rustfmt you should try the following:
On Linux:
export LD_LIBRARY_PATH=$(rustc --print sysroot)/lib:$LD_LIBRARY_PATH
On MacOS:
export DYLD_LIBRARY_PATH=$(rustc --print sysroot)/lib:$DYLD_LIBRARY_PATH
On Windows (Git Bash/Mingw):
export PATH=$(rustc --print sysroot)/lib/rustlib/x86_64-pc-windows-gnu/lib/:$PATH
(Substitute x86_64 by i686 and gnu by msvc depending on which version of rustc was used to install rustfmt).
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.