README.md - rustfmt - Git at Google

 # rustfmt [![Build Status](https://travis-ci.org/rust-lang-nursery/rustfmt.svg)](https://travis-ci.org/rust-lang-nursery/rustfmt) [![Build Status](https://ci.appveyor.com/api/projects/status/github/rust-lang-nursery/rustfmt?svg=true)](https://ci.appveyor.com/project/nrc/rustfmt) [![crates.io](https://img.shields.io/crates/v/rustfmt-nightly.svg)](https://crates.io/crates/rustfmt-nightly) [![Travis Configuration Status](https://img.shields.io/travis/davidalber/rustfmt-travis.svg?label=travis%20example)](https://travis-ci.org/davidalber/rustfmt-travis)

 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).

 We are changing the default style used by rustfmt. There is an ongoing [RFC
 process][fmt rfcs]. 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](legacy-rustfmt.toml) as your rustfmt.toml.

 The current `master` branch uses libsyntax (part of the compiler). It is
 published as `rustfmt-nightly`. The `syntex` branch uses Syntex instead of
 libsyntax, it is published (for now) as `rustfmt`. Most development happens on
 the `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 to be a bit out of date).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](#checking-style-on-a-ci-server)) and verify its status
 using another repository. The status of that repository's build is reported by
 the "travis example" badge above.


 ## Quick start

 You can use `rustfmt` on Rust 1.24 and above.

 To install:

 ```
 rustup component add rustfmt-preview
 ```

 to run on a cargo project in the current working directory:

 ```
 cargo fmt
 ```


 ## Limitations

 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).


 ## Installation

 ```
 rustup component add rustfmt-preview
 ```

 ## Installing from source

 To install from source, 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.


 ## 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'll probably want to specify the write mode. Currently, there are modes for
 `diff`, `replace`, `overwrite`, `display`, `coverage`, `checkstyle`, and `plain`.

 * `overwrite` Is the default and overwrites the original files _without_ creating backups.
 * `replace` Overwrites the original files after creating backups of the files.
 * `display` Will print the formatted files to stdout.
 * `plain` Also writes to stdout, but with no metadata.
 * `diff` Will print a diff between the original files and formatted files to stdout.
          Will also exit with an error code if there are any differences.
 * `checkstyle` Will output the lines that need to be corrected as a checkstyle XML file,
   that can be used by tools like Jenkins.

 The write mode can be set by passing the `--write-mode` flag on
 the command line. For example `rustfmt --write-mode=display src/filename.rs`

 `cargo fmt` uses `--write-mode=overwrite` by default.

 If you want to restrict reformatting to specific sets of lines, you can
 use the `--file-lines` option. Its argument is a JSON array of objects
 with `file` and `range` properties, where `file` is a file name, and
 `range` is an array representing a range of lines like `[7,13]`. Ranges
 are 1-based and inclusive of both end points. Specifying an empty array
 will result in no files being formatted. For example,

 ```
 rustfmt --file-lines '[
     {"file":"src/lib.rs","range":[7,13]},
     {"file":"src/lib.rs","range":[21,29]},
     {"file":"src/foo.rs","range":[10,11]},
     {"file":"src/foo.rs","range":[15,15]}]'
 ```

 would format lines `7-13` and `21-29` of `src/lib.rs`, and lines `10-11`,
 and `15` of `src/foo.rs`. No other files would be formatted, even if they
 are included as out of line modules from `src/lib.rs`.

 If `rustfmt` successfully reformatted the code it will exit with `0` exit
 status. Exit status `1` signals some unexpected error, like an unknown option or
 a failure to read a file. Exit status `2` is returned if there are syntax errors
 in the input files. `rustfmt` can't format syntactically invalid code. Finally,
 exit status `3` is returned if there are some issues which can't be resolved
 automatically. For example, if you have a very long comment line `rustfmt`
 doesn't split it. Instead it prints a warning and exits with `3`.

 You can run `rustfmt --help` for more information.


 ## 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 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.

 ## 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 `--write-mode=diff` instructs
 rustfmt to exit with an error code if the input is not formatted correctly.
 It will also print any found differences.

 A minimal Travis setup could look like this (requires Rust 1.24.0 or greater):

 ```yaml
 language: rust
 before_script:
 - rustup component add rustfmt-preview
 script:
 - cargo fmt --all -- --write-mode=diff
 - cargo build
 - cargo test
 ```

 ## 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
 --config-help` for the options which are available, or if you prefer to see
 visual style previews, [Configurations.md](Configurations.md).

 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 [Configurations.md](Configurations.md) for details.


 ## Tips

 * For things you do not want rustfmt to mangle, use one of

     ```rust
     #[rustfmt_skip]  // requires nightly and #![feature(custom_attribute)] in crate root
     #[cfg_attr(rustfmt, rustfmt_skip)]  // works in stable
     ```
 * 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 --dump-default-config 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.

 * If you get an error like `error while loading shared libraries` while starting
   up rustfmt you should try the following:

   On Linux:

   ```
   export LD_LIBRARY_PATH=$(rustc --print sysroot)/lib:$LD_LIBRARY_PATH
   ```

   On MacOS:

   ```
   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
   ```

   (Substitute `x86_64` by `i686` and `gnu` by `msvc` depending on which version of rustc was used to install rustfmt).

 ## 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-lang-nursery/fmt-rfcs
 [style guide]: https://github.com/rust-lang-nursery/fmt-rfcs/blob/master/guide/guide.md
	# rustfmt [![Build Status](https://travis-ci.org/rust-lang-nursery/rustfmt.svg)](https://travis-ci.org/rust-lang-nursery/rustfmt) [![Build Status](https://ci.appveyor.com/api/projects/status/github/rust-lang-nursery/rustfmt?svg=true)](https://ci.appveyor.com/project/nrc/rustfmt) [![crates.io](https://img.shields.io/crates/v/rustfmt-nightly.svg)](https://crates.io/crates/rustfmt-nightly) [![Travis Configuration Status](https://img.shields.io/travis/davidalber/rustfmt-travis.svg?label=travis%20example)](https://travis-ci.org/davidalber/rustfmt-travis)

	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).

	We are changing the default style used by rustfmt. There is an ongoing [RFC
	process][fmt rfcs]. 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](legacy-rustfmt.toml) as your rustfmt.toml.

	The current `master` branch uses libsyntax (part of the compiler). It is
	published as `rustfmt-nightly`. The `syntex` branch uses Syntex instead of
	libsyntax, it is published (for now) as `rustfmt`. Most development happens on
	the `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](#checking-style-on-a-ci-server)) and verify its status
	using another repository. The status of that repository's build is reported by
	the "travis example" badge above.


	## Quick start

	You can use `rustfmt` on Rust 1.24 and above.

	To install:

	```
	rustup component add rustfmt-preview
	```

	to run on a cargo project in the current working directory:

	```
	cargo fmt
	```


	## Limitations

	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).


	## Installation

	```
	rustup component add rustfmt-preview
	```

	## Installing from source

	To install from source, 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.


	## 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'll probably want to specify the write mode. Currently, there are modes for
	`diff`, `replace`, `overwrite`, `display`, `coverage`, `checkstyle`, and `plain`.

	* `overwrite` Is the default and overwrites the original files _without_ creating backups.
	* `replace` Overwrites the original files after creating backups of the files.
	* `display` Will print the formatted files to stdout.
	* `plain` Also writes to stdout, but with no metadata.
	* `diff` Will print a diff between the original files and formatted files to stdout.
	Will also exit with an error code if there are any differences.
	* `checkstyle` Will output the lines that need to be corrected as a checkstyle XML file,
	that can be used by tools like Jenkins.

	The write mode can be set by passing the `--write-mode` flag on
	the command line. For example `rustfmt --write-mode=display src/filename.rs`

	`cargo fmt` uses `--write-mode=overwrite` by default.

	If you want to restrict reformatting to specific sets of lines, you can
	use the `--file-lines` option. Its argument is a JSON array of objects
	with `file` and `range` properties, where `file` is a file name, and
	`range` is an array representing a range of lines like `[7,13]`. Ranges
	are 1-based and inclusive of both end points. Specifying an empty array
	will result in no files being formatted. For example,

	```
	rustfmt --file-lines '[
	{"file":"src/lib.rs","range":[7,13]},
	{"file":"src/lib.rs","range":[21,29]},
	{"file":"src/foo.rs","range":[10,11]},
	{"file":"src/foo.rs","range":[15,15]}]'
	```

	would format lines `7-13` and `21-29` of `src/lib.rs`, and lines `10-11`,
	and `15` of `src/foo.rs`. No other files would be formatted, even if they
	are included as out of line modules from `src/lib.rs`.

	If `rustfmt` successfully reformatted the code it will exit with `0` exit
	status. Exit status `1` signals some unexpected error, like an unknown option or
	a failure to read a file. Exit status `2` is returned if there are syntax errors
	in the input files. `rustfmt` can't format syntactically invalid code. Finally,
	exit status `3` is returned if there are some issues which can't be resolved
	automatically. For example, if you have a very long comment line `rustfmt`
	doesn't split it. Instead it prints a warning and exits with `3`.

	You can run `rustfmt --help` for more information.


	## 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 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.

	## 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 `--write-mode=diff` instructs
	rustfmt to exit with an error code if the input is not formatted correctly.
	It will also print any found differences.

	A minimal Travis setup could look like this (requires Rust 1.24.0 or greater):

	```yaml
	language: rust
	before_script:
	- rustup component add rustfmt-preview
	script:
	- cargo fmt --all -- --write-mode=diff
	- cargo build
	- cargo test
	```

	## 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
	--config-help` for the options which are available, or if you prefer to see
	visual style previews, [Configurations.md](Configurations.md).

	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 [Configurations.md](Configurations.md) for details.


	## Tips

	* For things you do not want rustfmt to mangle, use one of

	```rust
	#[rustfmt_skip] // requires nightly and #![feature(custom_attribute)] in crate root
	#[cfg_attr(rustfmt, rustfmt_skip)] // works in stable
	```
	* 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 --dump-default-config 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.

	* If you get an error like `error while loading shared libraries` while starting
	up rustfmt you should try the following:

	On Linux:

	```
	export LD_LIBRARY_PATH=$(rustc --print sysroot)/lib:$LD_LIBRARY_PATH
	```

	On MacOS:

	```
	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
	```

	(Substitute `x86_64` by `i686` and `gnu` by `msvc` depending on which version of rustc was used to install rustfmt).

	## 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-lang-nursery/fmt-rfcs
	[style guide]: https://github.com/rust-lang-nursery/fmt-rfcs/blob/master/guide/guide.md