| # rustfmt [](https://github.com/rust-lang/rustfmt/actions/workflows/linux.yml) [](https://github.com/rust-lang/rustfmt/actions/workflows/mac.yml) [](https://github.com/rust-lang/rustfmt/actions/workflows/windows.yml) [](https://crates.io/crates/rustfmt-nightly) | |
| 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](Contributing.md) and our [Code of | |
| Conduct](CODE_OF_CONDUCT.md). | |
| You can use rustfmt in Travis CI builds. We provide a minimal Travis CI | |
| configuration (see [here](#checking-style-on-a-ci-server)). | |
| ## Quick start | |
| You can run `rustfmt` with Rust 1.24 and above. | |
| ### On the Stable toolchain | |
| To install: | |
| ```sh | |
| rustup component add rustfmt | |
| ``` | |
| To run on a cargo project in the current working directory: | |
| ```sh | |
| cargo fmt | |
| ``` | |
| ### On the Nightly toolchain | |
| For the latest and greatest `rustfmt`, nightly is required. | |
| To install: | |
| ```sh | |
| rustup component add rustfmt --toolchain nightly | |
| ``` | |
| To run on a cargo project in the current working directory: | |
| ```sh | |
| cargo +nightly fmt | |
| ``` | |
| ## Limitations | |
| Rustfmt tries to work on as much Rust code as possible. Sometimes, the code | |
| doesn't even need to compile! In general, we are 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). | |
| ## 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. | |
| The easiest way to run rustfmt against a project is with `cargo fmt`. `cargo fmt` works on both | |
| single-crate projects and [cargo workspaces](https://doc.rust-lang.org/book/ch14-03-cargo-workspaces.html). | |
| Please see `cargo fmt --help` for usage information. | |
| You can specify the path to your own `rustfmt` binary for cargo to use by setting the`RUSTFMT` | |
| environment variable. This was added in v1.4.22, so you must have this version or newer to leverage this feature (`cargo fmt --version`) | |
| ### Running `rustfmt` directly | |
| To format individual files or arbitrary codes from stdin, the `rustfmt` binary should be used. Some | |
| examples follow: | |
| - `rustfmt lib.rs main.rs` will format "lib.rs" and "main.rs" in place | |
| - `rustfmt` will read a code from stdin and write formatting to stdout | |
| - `echo "fn main() {}" | rustfmt` would emit "fn main() {}". | |
| For more information, including arguments and emit options, see `rustfmt --help`. | |
| ### Verifying code is formatted | |
| 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](https://github.com/rust-lang/rust.vim#formatting-with-rustfmt) | |
| * [Emacs](https://github.com/rust-lang/rust-mode) | |
| * [Sublime Text 3](https://packagecontrol.io/packages/RustFmt) | |
| * [Atom](atom.md) | |
| * [Visual Studio Code](https://marketplace.visualstudio.com/items?itemName=rust-lang.rust-analyzer) | |
| * [IntelliJ or CLion](intellij.md) | |
| ## 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 1.31.0 or greater): | |
| ```yaml | |
| language: rust | |
| before_script: | |
| - rustup component add rustfmt | |
| script: | |
| - cargo build | |
| - cargo test | |
| - cargo fmt --all -- --check | |
| ``` | |
| See [this blog post](https://medium.com/@ag_dubs/enforcing-style-in-ci-for-rust-projects-18f6b09ec69d) | |
| 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](https://rust-lang.github.io/rustfmt/). | |
| By default, Rustfmt uses a style which conforms to the [Rust style guide][style | |
| guide] that has been formalized through the [style RFC | |
| process][fmt rfcs]. | |
| 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](https://rust-lang.github.io/rustfmt/) for details. | |
| ### Rust's Editions | |
| The `edition` option determines the Rust language edition used for parsing the code. This is important for syntax compatibility but does not directly control formatting behavior (see [Style Editions](#style-editions)). | |
| When running `cargo fmt`, the `edition` is automatically read from the `Cargo.toml` file. However, when running `rustfmt` directly, the `edition` defaults to 2015. For consistent parsing between rustfmt and `cargo fmt`, you should configure the `edition` in your `rustfmt.toml` file: | |
| ```toml | |
| edition = "2018" | |
| ``` | |
| ### Style Editions | |
| This option is inferred from the [`edition`](#rusts-editions) if not specified. | |
| See [Rust Style Editions] for details on formatting differences between style editions. | |
| rustfmt has a default style edition of `2015` while `cargo fmt` infers the style edition from the `edition` set in `Cargo.toml`. This can lead to inconsistencies between `rustfmt` and `cargo fmt` if the style edition is not explicitly configured. | |
| To ensure consistent formatting, it is recommended to specify the `style_edition` in a `rustfmt.toml` configuration file. For example: | |
| ```toml | |
| style_edition = "2024" | |
| ``` | |
| [Rust Style Editions]: https://doc.rust-lang.org/nightly/style-guide/editions.html?highlight=editions#rust-style-editions | |
| [Rust Style Guide]: https://doc.rust-lang.org/nightly/style-guide/ | |
| [RFC 3338]: https://rust-lang.github.io/rfcs/3338-style-evolution.html | |
| ## Tips | |
| * To ensure consistent parsing between `cargo fmt` and `rustfmt`, you should configure the [`edition`](#rusts-editions) in your `rustfmt.toml` file. | |
| * To ensure consistent formatting between `cargo fmt` and `rustfmt`, you should configure the [`style_edition`](#style-editions) in your `rustfmt.toml` file. | |
| * 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: | |
| ```rust | |
| #![rustfmt::skip::attributes(custom_attribute)] | |
| #[custom_attribute(formatting , here , should , be , Skipped)] | |
| #[rustfmt::skip::macros(html)] | |
| fn main() { | |
| let macro_result1 = html! { <div> | |
| Hello</div> | |
| }.to_string(); | |
| ``` | |
| * 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 with | |
| `rustfmt --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: | |
| ```sh | |
| cargo fmt -- --emit files | |
| ``` | |
| 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](LICENSE-APACHE) and [LICENSE-MIT](LICENSE-MIT) for details. | |
| [rust]: https://github.com/rust-lang/rust | |
| [fmt rfcs]: https://github.com/rust-dev-tools/fmt-rfcs | |
| [style guide]: https://doc.rust-lang.org/nightly/style-guide/ |