1 # 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)
3 A tool for formatting Rust code according to style guidelines.
5 If you'd like to help out (and you should, it's a fun project!), see
6 [Contributing.md](Contributing.md) and our [Code of
7 Conduct](CODE_OF_CONDUCT.md).
9 We are changing the default style used by rustfmt. There is an ongoing [RFC
10 process][fmt rfcs]. The last version using the old style was 0.8.6. From 0.9
11 onwards, the RFC style is the default. If you want the old style back, you can
12 use [legacy-rustfmt.toml](legacy-rustfmt.toml) as your rustfmt.toml.
14 The current `master` branch uses libsyntax (part of the compiler). It is
15 published as `rustfmt-nightly`. The `syntex` branch uses Syntex instead of
16 libsyntax, it is published (for now) as `rustfmt`. Most development happens on
17 the `master` branch, however, this only supports nightly toolchains. If you use
18 stable or beta Rust toolchains, you must use the Syntex version (which is likely
19 to be a bit out of date). Version 0.1 of rustfmt-nightly is forked from version
20 0.9 of the syntex branch.
22 You can use rustfmt in Travis CI builds. We provide a minimal Travis CI
23 configuration (see [here](#checking-style-on-a-ci-server)) and verify its status
24 using another repository. The status of that repository's build is reported by
25 the "travis example" badge above.
30 You can use `rustfmt` on Rust 1.24 and above.
35 rustup component add rustfmt-preview
38 to run on a cargo project in the current working directory:
47 Rustfmt tries to work on as much Rust code as possible, sometimes, the code
48 doesn't even need to compile! As we approach a 1.0 release we are also looking
49 to limit areas of instability; in particular, post-1.0, the formatting of most
50 code should not change as Rustfmt improves. However, there are some things that
51 Rustfmt can't do or can't do well (and thus where formatting might change
52 significantly, even post-1.0). We would like to reduce the list of limitations
55 The following list enumerates areas where Rustfmt does not work or where the
56 stability guarantees do not apply (we don't make a distinction between the two
57 because in the future Rustfmt might work on code where it currently does not):
59 * a program where any part of the program does not parse (parsing is an early
60 stage of compilation and in Rust includes macro expansion).
61 * Macro declarations and uses (current status: some macro declarations and uses
63 * Comments, including any AST node with a comment 'inside' (Rustfmt does not
64 currently attempt to format comments, it does format code with comments inside, but that formatting may change in the future).
65 * Rust code in code blocks in comments.
66 * Any fragment of a program (i.e., stability guarantees only apply to whole
67 programs, even where fragments of a program can be formatted today).
68 * Code containing non-ascii unicode characters (we believe Rustfmt mostly works
69 here, but do not have the test coverage or experience to be 100% sure).
70 * Bugs in Rustfmt (like any software, Rustfmt has bugs, we do not consider bug
71 fixes to break our stability guarantees).
77 rustup component add rustfmt-preview
80 ## Installing from source
82 To install from source, first checkout to the tag or branch you want to install, then issue
84 cargo install --path .
87 This will install `rustfmt` in your `~/.cargo/bin`. Make sure to add `~/.cargo/bin` directory to
93 You can run Rustfmt by just typing `rustfmt filename` if you used `cargo
94 install`. This runs rustfmt on the given file, if the file includes out of line
95 modules, then we reformat those too. So to run on a whole module or crate, you
96 just need to run on the root file (usually mod.rs or lib.rs). Rustfmt can also
97 read data from stdin. Alternatively, you can use `cargo fmt` to format all
98 binary and library targets of your crate.
100 You'll probably want to specify the write mode. Currently, there are modes for
101 `diff`, `replace`, `overwrite`, `display`, `coverage`, `checkstyle`, and `plain`.
103 * `overwrite` Is the default and overwrites the original files _without_ creating backups.
104 * `replace` Overwrites the original files after creating backups of the files.
105 * `display` Will print the formatted files to stdout.
106 * `plain` Also writes to stdout, but with no metadata.
107 * `diff` Will print a diff between the original files and formatted files to stdout.
108 Will also exit with an error code if there are any differences.
109 * `checkstyle` Will output the lines that need to be corrected as a checkstyle XML file,
110 that can be used by tools like Jenkins.
112 The write mode can be set by passing the `--write-mode` flag on
113 the command line. For example `rustfmt --write-mode=display src/filename.rs`
115 `cargo fmt` uses `--write-mode=overwrite` by default.
117 If you want to restrict reformatting to specific sets of lines, you can
118 use the `--file-lines` option. Its argument is a JSON array of objects
119 with `file` and `range` properties, where `file` is a file name, and
120 `range` is an array representing a range of lines like `[7,13]`. Ranges
121 are 1-based and inclusive of both end points. Specifying an empty array
122 will result in no files being formatted. For example,
125 rustfmt --file-lines '[
126 {"file":"src/lib.rs","range":[7,13]},
127 {"file":"src/lib.rs","range":[21,29]},
128 {"file":"src/foo.rs","range":[10,11]},
129 {"file":"src/foo.rs","range":[15,15]}]'
132 would format lines `7-13` and `21-29` of `src/lib.rs`, and lines `10-11`,
133 and `15` of `src/foo.rs`. No other files would be formatted, even if they
134 are included as out of line modules from `src/lib.rs`.
136 If `rustfmt` successfully reformatted the code it will exit with `0` exit
137 status. Exit status `1` signals some unexpected error, like an unknown option or
138 a failure to read a file. Exit status `2` is returned if there are syntax errors
139 in the input files. `rustfmt` can't format syntactically invalid code. Finally,
140 exit status `3` is returned if there are some issues which can't be resolved
141 automatically. For example, if you have a very long comment line `rustfmt`
142 doesn't split it. Instead it prints a warning and exits with `3`.
144 You can run `rustfmt --help` for more information.
147 ## Running Rustfmt from your editor
149 * [Vim](https://github.com/rust-lang/rust.vim#formatting-with-rustfmt)
150 * [Emacs](https://github.com/rust-lang/rust-mode)
151 * [Sublime Text 3](https://packagecontrol.io/packages/RustFmt)
153 * 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.
155 ## Checking style on a CI server
157 To keep your code base consistently formatted, it can be helpful to fail the CI build
158 when a pull request contains unformatted code. Using `--write-mode=diff` instructs
159 rustfmt to exit with an error code if the input is not formatted correctly.
160 It will also print any found differences.
162 A minimal Travis setup could look like this (requires Rust 1.24.0 or greater):
167 - rustup component add rustfmt-preview
169 - cargo fmt --all -- --write-mode=diff
174 ## How to build and test
176 `cargo build` to build.
178 `cargo test` to run all tests.
180 To run rustfmt after this, use `cargo run --bin rustfmt -- filename`. See the
181 notes above on running rustfmt.
184 ## Configuring Rustfmt
186 Rustfmt is designed to be very configurable. You can create a TOML file called
187 `rustfmt.toml` or `.rustfmt.toml`, place it in the project or any other parent
188 directory and it will apply the options in that file. See `rustfmt
189 --config-help` for the options which are available, or if you prefer to see
190 visual style previews, [Configurations.md](Configurations.md).
192 By default, Rustfmt uses a style which conforms to the [Rust style guide][style
193 guide] that has been formalized through the [style RFC
196 Configuration options are either stable or unstable. Stable options can always
197 be used, while unstable ones are only available on a nightly toolchain, and opt-in.
198 See [Configurations.md](Configurations.md) for details.
203 * For things you do not want rustfmt to mangle, use one of
206 #[rustfmt_skip] // requires nightly and #![feature(custom_attribute)] in crate root
207 #[cfg_attr(rustfmt, rustfmt_skip)] // works in stable
209 * When you run rustfmt, place a file named `rustfmt.toml` or `.rustfmt.toml` in
210 target file directory or its parents to override the default settings of
211 rustfmt. You can generate a file containing the default configuration with
212 `rustfmt --dump-default-config rustfmt.toml` and customize as needed.
213 * After successful compilation, a `rustfmt` executable can be found in the
215 * If you're having issues compiling Rustfmt (or compile errors when trying to
216 install), make sure you have the most recent version of Rust installed.
218 * If you get an error like `error while loading shared libraries` while starting
219 up rustfmt you should try the following:
224 export LD_LIBRARY_PATH=$(rustc --print sysroot)/lib:$LD_LIBRARY_PATH
230 export DYLD_LIBRARY_PATH=$(rustc --print sysroot)/lib:$DYLD_LIBRARY_PATH
233 On Windows (Git Bash/Mingw):
236 export PATH=$(rustc --print sysroot)/lib/rustlib/x86_64-pc-windows-gnu/lib/:$PATH
239 (Substitute `x86_64` by `i686` and `gnu` by `msvc` depending on which version of rustc was used to install rustfmt).
243 Rustfmt is distributed under the terms of both the MIT license and the
244 Apache License (Version 2.0).
246 See [LICENSE-APACHE](LICENSE-APACHE) and [LICENSE-MIT](LICENSE-MIT) for details.
248 [rust]: https://github.com/rust-lang/rust
249 [fmt rfcs]: https://github.com/rust-lang-nursery/fmt-rfcs
250 [style guide]: https://github.com/rust-lang-nursery/fmt-rfcs/blob/master/guide/guide.md