A tool for formatting Rust code according to style guidelines.
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.
master branch uses libsyntax (part of the compiler). It is
syntex branch uses Syntex instead of
libsyntax, it is published (for now) as
rustfmt. Most development happens on
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to be a bit out of date).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.
rustup component add rustfmt-preview
to run on a cargo project in the current working directory:
For the latest and greatest
rustfmt (nightly required):
rustup component add rustfmt-preview --toolchain nightly
cargo +nightly fmt
To format code that requires edition 2018, create a
rustfmt.toml configuration file containing:
edition = "Edition2018"
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).
rustup component add rustfmt-preview
Installing from source
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 can run
rustfmt --help for information about argument.
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
- Sublime Text 3
- Visual Studio Code using vscode-rust, vsc-rustfmt or rls_vscode through RLS.
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
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
A minimal Travis setup could look like this (requires Rust 1.24.0 or greater):
language: rust rust: - nightly before_script: - rustup component add rustfmt-preview script: - cargo fmt --all -- --check - cargo build - cargo test
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.
Rustfmt is designed to be very configurable. You can create a TOML file called
.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.
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
#[rustfmt::skip] // requires nightly Rust and #![feature(tool_attributes)] in crate root #[cfg_attr(rustfmt, rustfmt_skip)] // works in stable
When you run rustfmt, place a file named
.rustfmt.tomlin target file directory or its parents to override the default settings of rustfmt. You can generate a file containing the default configuration with
rustfmt --print-config default rustfmt.tomland customize as needed.
After successful compilation, a
rustfmtexecutable 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 librarieswhile starting up rustfmt you should try the following:
export LD_LIBRARY_PATH=$(rustc --print sysroot)/lib:$LD_LIBRARY_PATH
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
msvcdepending on which version of rustc was used to install rustfmt).
You can change the way rustfmt emits the changes with the --emit flag:
cargo fmt --emit files
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
Rustfmt is distributed under the terms of both the MIT license and the Apache License (Version 2.0).