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https://github.com/rust-lang/rustfmt

Format Rust code
https://github.com/rust-lang/rustfmt

codeformatter formatter rust rustfmt

Last synced: 3 days ago
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Format Rust code

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# rustfmt [![linux](https://github.com/rust-lang/rustfmt/actions/workflows/linux.yml/badge.svg?event=push)](https://github.com/rust-lang/rustfmt/actions/workflows/linux.yml) [![mac](https://github.com/rust-lang/rustfmt/actions/workflows/mac.yml/badge.svg?event=push)](https://github.com/rust-lang/rustfmt/actions/workflows/mac.yml) [![windows](https://github.com/rust-lang/rustfmt/actions/workflows/windows.yml/badge.svg?event=push)](https://github.com/rust-lang/rustfmt/actions/workflows/windows.yml) [![crates.io](https://img.shields.io/crates/v/rustfmt-nightly.svg)](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



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:



    ```rust

    #![rustfmt::skip::attributes(custom_attribute)]



    #[custom_attribute(formatting , here , should , be , Skipped)]

    #[rustfmt::skip::macros(html)]

    fn main() {

        let macro_result1 = html! { 


    Hello


        }.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/