253 lines
9.4 KiB
Markdown
253 lines
9.4 KiB
Markdown
# rustfmt [](https://travis-ci.com/rust-lang/rustfmt) [](https://ci.appveyor.com/project/rust-lang-libs/rustfmt) [](https://crates.io/crates/rustfmt-nightly) [](https://travis-ci.org/davidalber/rustfmt-travis)
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A tool for formatting Rust code according to style guidelines.
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If you'd like to help out (and you should, it's a fun project!), see
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[Contributing.md](Contributing.md) and our [Code of
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Conduct](CODE_OF_CONDUCT.md).
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You can use rustfmt in Travis CI builds. We provide a minimal Travis CI
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configuration (see [here](#checking-style-on-a-ci-server)) and verify its status
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using another repository. The status of that repository's build is reported by
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the "travis example" badge above.
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## Quick start
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You can run `rustfmt` with Rust 1.24 and above.
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### On the Stable toolchain
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To install:
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```sh
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rustup component add rustfmt
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```
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To run on a cargo project in the current working directory:
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```sh
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cargo fmt
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```
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### On the Nightly toolchain
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For the latest and greatest `rustfmt`, nightly is required.
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To install:
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```sh
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rustup component add rustfmt --toolchain nightly
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```
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To run on a cargo project in the current working directory:
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```sh
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cargo +nightly fmt
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```
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## Limitations
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Rustfmt tries to work on as much Rust code as possible. Sometimes, the code
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doesn't even need to compile! In general, we are looking to limit areas of
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instability; in particular, post-1.0, the formatting of most code should not
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change as Rustfmt improves. However, there are some things that Rustfmt can't
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do or can't do well (and thus where formatting might change significantly,
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even post-1.0). We would like to reduce the list of limitations over time.
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The following list enumerates areas where Rustfmt does not work or where the
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stability guarantees do not apply (we don't make a distinction between the two
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because in the future Rustfmt might work on code where it currently does not):
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* a program where any part of the program does not parse (parsing is an early
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stage of compilation and in Rust includes macro expansion).
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* Macro declarations and uses (current status: some macro declarations and uses
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are formatted).
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* Comments, including any AST node with a comment 'inside' (Rustfmt does not
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currently attempt to format comments, it does format code with comments inside, but that formatting may change in the future).
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* Rust code in code blocks in comments.
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* Any fragment of a program (i.e., stability guarantees only apply to whole
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programs, even where fragments of a program can be formatted today).
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* Code containing non-ascii unicode characters (we believe Rustfmt mostly works
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here, but do not have the test coverage or experience to be 100% sure).
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* Bugs in Rustfmt (like any software, Rustfmt has bugs, we do not consider bug
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fixes to break our stability guarantees).
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## Installation
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```sh
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rustup component add rustfmt
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```
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## Installing from source
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To install from source (nightly required), first checkout to the tag or branch you want to install, then issue
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```sh
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cargo install --path .
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```
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This will install `rustfmt` in your `~/.cargo/bin`. Make sure to add `~/.cargo/bin` directory to
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your PATH variable.
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## Running
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You can run Rustfmt by just typing `rustfmt filename` if you used `cargo
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install`. This runs rustfmt on the given file, if the file includes out of line
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modules, then we reformat those too. So to run on a whole module or crate, you
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just need to run on the root file (usually mod.rs or lib.rs). Rustfmt can also
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read data from stdin. Alternatively, you can use `cargo fmt` to format all
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binary and library targets of your crate.
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You can run `rustfmt --help` for information about available arguments.
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The easiest way to run rustfmt against a project is with `cargo fmt`. `cargo fmt` works on both
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single-crate projects and [cargo workspaces](https://doc.rust-lang.org/book/ch14-03-cargo-workspaces.html).
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Please see `cargo fmt --help` for usage information.
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You can specify the path to your own `rustfmt` binary for cargo to use by setting the`RUSTFMT`
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environment variable. This was added in v1.4.22, so you must have this version or newer to leverage this feature (`cargo fmt --version`)
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### Running `rustfmt` directly
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To format individual files or arbitrary codes from stdin, the `rustfmt` binary should be used. Some
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examples follow:
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- `rustfmt lib.rs main.rs` will format "lib.rs" and "main.rs" in place
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- `rustfmt` will read a code from stdin and write formatting to stdout
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- `echo "fn main() {}" | rustfmt` would emit "fn main() {}".
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For more information, including arguments and emit options, see `rustfmt --help`.
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### Verifying code is formatted
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When running with `--check`, Rustfmt will exit with `0` if Rustfmt would not
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make any formatting changes to the input, and `1` if Rustfmt would make changes.
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In other modes, Rustfmt will exit with `1` if there was some error during
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formatting (for example a parsing or internal error) and `0` if formatting
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completed without error (whether or not changes were made).
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## Running Rustfmt from your editor
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* [Vim](https://github.com/rust-lang/rust.vim#formatting-with-rustfmt)
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* [Emacs](https://github.com/rust-lang/rust-mode)
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* [Sublime Text 3](https://packagecontrol.io/packages/RustFmt)
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* [Atom](atom.md)
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* [Visual Studio Code](https://marketplace.visualstudio.com/items?itemName=rust-lang.rust-analyzer)
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* [IntelliJ or CLion](intellij.md)
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## Checking style on a CI server
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To keep your code base consistently formatted, it can be helpful to fail the CI build
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when a pull request contains unformatted code. Using `--check` instructs
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rustfmt to exit with an error code if the input is not formatted correctly.
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It will also print any found differences. (Older versions of Rustfmt don't
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support `--check`, use `--write-mode diff`).
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A minimal Travis setup could look like this (requires Rust 1.31.0 or greater):
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```yaml
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language: rust
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before_script:
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- rustup component add rustfmt
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script:
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- cargo build
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- cargo test
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- cargo fmt --all -- --check
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```
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See [this blog post](https://medium.com/@ag_dubs/enforcing-style-in-ci-for-rust-projects-18f6b09ec69d)
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for more info.
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## How to build and test
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`cargo build` to build.
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`cargo test` to run all tests.
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To run rustfmt after this, use `cargo run --bin rustfmt -- filename`. See the
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notes above on running rustfmt.
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## Configuring Rustfmt
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Rustfmt is designed to be very configurable. You can create a TOML file called
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`rustfmt.toml` or `.rustfmt.toml`, place it in the project or any other parent
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directory and it will apply the options in that file. See `rustfmt
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--help=config` for the options which are available, or if you prefer to see
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visual style previews, [GitHub page](https://rust-lang.github.io/rustfmt/).
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By default, Rustfmt uses a style which conforms to the [Rust style guide][style
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guide] that has been formalized through the [style RFC
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process][fmt rfcs].
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Configuration options are either stable or unstable. Stable options can always
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be used, while unstable ones are only available on a nightly toolchain, and opt-in.
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See [GitHub page](https://rust-lang.github.io/rustfmt/) for details.
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### Rust's Editions
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Rustfmt is able to pick up the edition used by reading the `Cargo.toml` file if
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executed through the Cargo's formatting tool `cargo fmt`. Otherwise, the edition
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needs to be specified in `rustfmt.toml`, e.g., with `edition = "2018"`.
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## Tips
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* For things you do not want rustfmt to mangle, use `#[rustfmt::skip]`
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* To prevent rustfmt from formatting a macro or an attribute,
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use `#[rustfmt::skip::macros(target_macro_name)]` or
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`#[rustfmt::skip::attributes(target_attribute_name)]`
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Example:
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```rust
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#![rustfmt::skip::attributes(custom_attribute)]
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#[custom_attribute(formatting , here , should , be , Skipped)]
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#[rustfmt::skip::macros(html)]
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fn main() {
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let macro_result1 = html! { <div>
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Hello</div>
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}.to_string();
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```
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* When you run rustfmt, place a file named `rustfmt.toml` or `.rustfmt.toml` in
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target file directory or its parents to override the default settings of
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rustfmt. You can generate a file containing the default configuration with
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`rustfmt --print-config default rustfmt.toml` and customize as needed.
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* After successful compilation, a `rustfmt` executable can be found in the
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target directory.
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* If you're having issues compiling Rustfmt (or compile errors when trying to
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install), make sure you have the most recent version of Rust installed.
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* You can change the way rustfmt emits the changes with the --emit flag:
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Example:
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```sh
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cargo fmt -- --emit files
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```
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Options:
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| Flag |Description| Nightly Only |
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|:---:|:---:|:---:|
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| files | overwrites output to files | No |
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| stdout | writes output to stdout | No |
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| coverage | displays how much of the input file was processed | Yes |
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| checkstyle | emits in a checkstyle format | Yes |
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| json | emits diffs in a json format | Yes |
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## License
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Rustfmt is distributed under the terms of both the MIT license and the
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Apache License (Version 2.0).
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See [LICENSE-APACHE](LICENSE-APACHE) and [LICENSE-MIT](LICENSE-MIT) for details.
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[rust]: https://github.com/rust-lang/rust
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[fmt rfcs]: https://github.com/rust-dev-tools/fmt-rfcs
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[style guide]: https://github.com/rust-dev-tools/fmt-rfcs/blob/master/guide/guide.md
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