259 lines
10 KiB
Markdown
259 lines
10 KiB
Markdown
# rustfmt [](https://travis-ci.org/rust-lang-nursery/rustfmt) [](https://ci.appveyor.com/project/nrc/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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We are changing the default style used by rustfmt. There is an ongoing [RFC
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process][fmt rfcs]. The last version using the old style was 0.8.6. From 0.9
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onwards, the RFC style is the default. If you want the old style back, you can
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use [legacy-rustfmt.toml](legacy-rustfmt.toml) as your rustfmt.toml.
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The current `master` branch uses libsyntax (part of the compiler). It is
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published as `rustfmt-nightly`. The `syntex` branch uses Syntex instead of
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libsyntax, it is published (for now) as `rustfmt`. Most development happens on
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the `master` branch, however, this only supports nightly toolchains. If you use
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stable or beta Rust toolchains, you must use the Syntex version (which is likely
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to be a bit out of date). Version 0.1 of rustfmt-nightly is forked from version
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0.9 of the syntex branch.
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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 use `rustfmt` on Rust 1.24 and above.
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To install:
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```
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rustup component add rustfmt-preview
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```
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to run on a cargo project in the current working directory:
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```
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cargo fmt
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```
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For the latest and greatest `rustfmt` (nightly required):
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```
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rustup component add rustfmt-preview --toolchain nightly
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```
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To run:
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```
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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! As we approach a 1.0 release we are also looking
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to limit areas of instability; in particular, post-1.0, the formatting of most
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code should not change as Rustfmt improves. However, there are some things that
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Rustfmt can't do or can't do well (and thus where formatting might change
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significantly, even post-1.0). We would like to reduce the list of limitations
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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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```
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rustup component add rustfmt-preview
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```
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## Installing from source
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To install from source, first checkout to the tag or branch you want to install, then issue
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```
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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'll probably want to specify the write mode. Currently, there are modes for
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`diff`, `replace`, `overwrite`, `display`, `coverage`, `checkstyle`, and `plain`.
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* `overwrite` Is the default and overwrites the original files _without_ creating backups.
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* `replace` Overwrites the original files after creating backups of the files.
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* `display` Will print the formatted files to stdout.
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* `plain` Also writes to stdout, but with no metadata.
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* `diff` Will print a diff between the original files and formatted files to stdout.
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Will also exit with an error code if there are any differences.
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* `checkstyle` Will output the lines that need to be corrected as a checkstyle XML file,
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that can be used by tools like Jenkins.
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The write mode can be set by passing the `--write-mode` flag on
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the command line. For example `rustfmt --write-mode=display src/filename.rs`
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`cargo fmt` uses `--write-mode=overwrite` by default.
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If you want to restrict reformatting to specific sets of lines, you can
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use the `--file-lines` option. Its argument is a JSON array of objects
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with `file` and `range` properties, where `file` is a file name, and
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`range` is an array representing a range of lines like `[7,13]`. Ranges
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are 1-based and inclusive of both end points. Specifying an empty array
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will result in no files being formatted. For example,
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```
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rustfmt --file-lines '[
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{"file":"src/lib.rs","range":[7,13]},
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{"file":"src/lib.rs","range":[21,29]},
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{"file":"src/foo.rs","range":[10,11]},
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{"file":"src/foo.rs","range":[15,15]}]'
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```
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would format lines `7-13` and `21-29` of `src/lib.rs`, and lines `10-11`,
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and `15` of `src/foo.rs`. No other files would be formatted, even if they
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are included as out of line modules from `src/lib.rs`.
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If `rustfmt` successfully reformatted the code it will exit with `0` exit
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status. Exit status `1` signals some unexpected error, like an unknown option or
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a failure to read a file. Exit status `2` is returned if there are syntax errors
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in the input files. `rustfmt` can't format syntactically invalid code. Finally,
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exit status `3` is returned if there are some issues which can't be resolved
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automatically. For example, if you have a very long comment line `rustfmt`
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doesn't split it. Instead it prints a warning and exits with `3`.
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You can run `rustfmt --help` for more information.
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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 using [vscode-rust](https://github.com/editor-rs/vscode-rust), [vsc-rustfmt](https://github.com/Connorcpu/vsc-rustfmt) or [rls_vscode](https://github.com/jonathandturner/rls_vscode) through RLS.
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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 `--write-mode=diff` 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.
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A minimal Travis setup could look like this (requires Rust 1.24.0 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-preview
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script:
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- cargo fmt --all -- --write-mode=diff
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- cargo build
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- cargo test
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```
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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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--config-help` for the options which are available, or if you prefer to see
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visual style previews, [Configurations.md](Configurations.md).
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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 [Configurations.md](Configurations.md) for details.
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## Tips
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* For things you do not want rustfmt to mangle, use one of
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```rust
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#[rustfmt_skip] // requires nightly and #![feature(custom_attribute)] in crate root
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#[cfg_attr(rustfmt, rustfmt_skip)] // works in stable
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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 --dump-default-config 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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* If you get an error like `error while loading shared libraries` while starting
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up rustfmt you should try the following:
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On Linux:
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```
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export LD_LIBRARY_PATH=$(rustc --print sysroot)/lib:$LD_LIBRARY_PATH
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```
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On MacOS:
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```
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export DYLD_LIBRARY_PATH=$(rustc --print sysroot)/lib:$DYLD_LIBRARY_PATH
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```
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On Windows (Git Bash/Mingw):
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```
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export PATH=$(rustc --print sysroot)/lib/rustlib/x86_64-pc-windows-gnu/lib/:$PATH
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```
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(Substitute `x86_64` by `i686` and `gnu` by `msvc` depending on which version of rustc was used to install rustfmt).
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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-lang-nursery/fmt-rfcs
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[style guide]: https://github.com/rust-lang-nursery/fmt-rfcs/blob/master/guide/guide.md
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