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19 to be a bit out of date).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:
44 For the latest and greatest `rustfmt` (nightly required):
46 rustup component add rustfmt-preview --toolchain nightly
55 Rustfmt tries to work on as much Rust code as possible, sometimes, the code
56 doesn't even need to compile! As we approach a 1.0 release we are also looking
57 to limit areas of instability; in particular, post-1.0, the formatting of most
58 code should not change as Rustfmt improves. However, there are some things that
59 Rustfmt can't do or can't do well (and thus where formatting might change
60 significantly, even post-1.0). We would like to reduce the list of limitations
63 The following list enumerates areas where Rustfmt does not work or where the
64 stability guarantees do not apply (we don't make a distinction between the two
65 because in the future Rustfmt might work on code where it currently does not):
67 * a program where any part of the program does not parse (parsing is an early
68 stage of compilation and in Rust includes macro expansion).
69 * Macro declarations and uses (current status: some macro declarations and uses
71 * Comments, including any AST node with a comment 'inside' (Rustfmt does not
72 currently attempt to format comments, it does format code with comments inside, but that formatting may change in the future).
73 * Rust code in code blocks in comments.
74 * Any fragment of a program (i.e., stability guarantees only apply to whole
75 programs, even where fragments of a program can be formatted today).
76 * Code containing non-ascii unicode characters (we believe Rustfmt mostly works
77 here, but do not have the test coverage or experience to be 100% sure).
78 * Bugs in Rustfmt (like any software, Rustfmt has bugs, we do not consider bug
79 fixes to break our stability guarantees).
85 rustup component add rustfmt-preview
88 ## Installing from source
90 To install from source (nightly required), first checkout to the tag or branch you want to install, then issue
92 cargo install --path .
95 This will install `rustfmt` in your `~/.cargo/bin`. Make sure to add `~/.cargo/bin` directory to
101 You can run Rustfmt by just typing `rustfmt filename` if you used `cargo
102 install`. This runs rustfmt on the given file, if the file includes out of line
103 modules, then we reformat those too. So to run on a whole module or crate, you
104 just need to run on the root file (usually mod.rs or lib.rs). Rustfmt can also
105 read data from stdin. Alternatively, you can use `cargo fmt` to format all
106 binary and library targets of your crate.
108 You'll probably want to specify the write mode. Currently, there are modes for
109 `diff`, `replace`, `overwrite`, `display`, `coverage`, `checkstyle`, and `plain`.
111 * `overwrite` Is the default and overwrites the original files _without_ creating backups.
112 * `replace` Overwrites the original files after creating backups of the files.
113 * `display` Will print the formatted files to stdout.
114 * `plain` Also writes to stdout, but with no metadata.
115 * `diff` Will print a diff between the original files and formatted files to stdout.
116 Will also exit with an error code if there are any differences.
117 * `checkstyle` Will output the lines that need to be corrected as a checkstyle XML file,
118 that can be used by tools like Jenkins.
120 The write mode can be set by passing the `--write-mode` flag on
121 the command line. For example `rustfmt --write-mode=display src/filename.rs`
123 `cargo fmt` uses `--write-mode=overwrite` by default.
125 If you want to restrict reformatting to specific sets of lines, you can
126 use the `--file-lines` option. Its argument is a JSON array of objects
127 with `file` and `range` properties, where `file` is a file name, and
128 `range` is an array representing a range of lines like `[7,13]`. Ranges
129 are 1-based and inclusive of both end points. Specifying an empty array
130 will result in no files being formatted. For example,
133 rustfmt --file-lines '[
134 {"file":"src/lib.rs","range":[7,13]},
135 {"file":"src/lib.rs","range":[21,29]},
136 {"file":"src/foo.rs","range":[10,11]},
137 {"file":"src/foo.rs","range":[15,15]}]'
140 would format lines `7-13` and `21-29` of `src/lib.rs`, and lines `10-11`,
141 and `15` of `src/foo.rs`. No other files would be formatted, even if they
142 are included as out of line modules from `src/lib.rs`.
144 If `rustfmt` successfully reformatted the code it will exit with `0` exit
145 status. Exit status `1` signals some unexpected error, like an unknown option or
146 a failure to read a file. Exit status `2` is returned if there are syntax errors
147 in the input files. `rustfmt` can't format syntactically invalid code. Finally,
148 exit status `3` is returned if there are some issues which can't be resolved
149 automatically. For example, if you have a very long comment line `rustfmt`
150 doesn't split it. Instead it prints a warning and exits with `3`.
152 You can run `rustfmt --help` for more information.
155 ## Running Rustfmt from your editor
157 * [Vim](https://github.com/rust-lang/rust.vim#formatting-with-rustfmt)
158 * [Emacs](https://github.com/rust-lang/rust-mode)
159 * [Sublime Text 3](https://packagecontrol.io/packages/RustFmt)
161 * 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.
163 ## Checking style on a CI server
165 To keep your code base consistently formatted, it can be helpful to fail the CI build
166 when a pull request contains unformatted code. Using `--write-mode=diff` instructs
167 rustfmt to exit with an error code if the input is not formatted correctly.
168 It will also print any found differences.
170 A minimal Travis setup could look like this (requires Rust 1.24.0 or greater):
175 - rustup component add rustfmt-preview
177 - cargo fmt --all -- --write-mode=diff
182 ## How to build and test
184 `cargo build` to build.
186 `cargo test` to run all tests.
188 To run rustfmt after this, use `cargo run --bin rustfmt -- filename`. See the
189 notes above on running rustfmt.
192 ## Configuring Rustfmt
194 Rustfmt is designed to be very configurable. You can create a TOML file called
195 `rustfmt.toml` or `.rustfmt.toml`, place it in the project or any other parent
196 directory and it will apply the options in that file. See `rustfmt
197 --config-help` for the options which are available, or if you prefer to see
198 visual style previews, [Configurations.md](Configurations.md).
200 By default, Rustfmt uses a style which conforms to the [Rust style guide][style
201 guide] that has been formalized through the [style RFC
204 Configuration options are either stable or unstable. Stable options can always
205 be used, while unstable ones are only available on a nightly toolchain, and opt-in.
206 See [Configurations.md](Configurations.md) for details.
211 * For things you do not want rustfmt to mangle, use one of
214 #[rustfmt_skip] // requires nightly and #![feature(custom_attribute)] in crate root
215 #[cfg_attr(rustfmt, rustfmt_skip)] // works in stable
217 * When you run rustfmt, place a file named `rustfmt.toml` or `.rustfmt.toml` in
218 target file directory or its parents to override the default settings of
219 rustfmt. You can generate a file containing the default configuration with
220 `rustfmt --dump-default-config rustfmt.toml` and customize as needed.
221 * After successful compilation, a `rustfmt` executable can be found in the
223 * If you're having issues compiling Rustfmt (or compile errors when trying to
224 install), make sure you have the most recent version of Rust installed.
226 * If you get an error like `error while loading shared libraries` while starting
227 up rustfmt you should try the following:
232 export LD_LIBRARY_PATH=$(rustc --print sysroot)/lib:$LD_LIBRARY_PATH
238 export DYLD_LIBRARY_PATH=$(rustc --print sysroot)/lib:$DYLD_LIBRARY_PATH
241 On Windows (Git Bash/Mingw):
244 export PATH=$(rustc --print sysroot)/lib/rustlib/x86_64-pc-windows-gnu/lib/:$PATH
247 (Substitute `x86_64` by `i686` and `gnu` by `msvc` depending on which version of rustc was used to install rustfmt).
251 Rustfmt is distributed under the terms of both the MIT license and the
252 Apache License (Version 2.0).
254 See [LICENSE-APACHE](LICENSE-APACHE) and [LICENSE-MIT](LICENSE-MIT) for details.
256 [rust]: https://github.com/rust-lang/rust
257 [fmt rfcs]: https://github.com/rust-lang-nursery/fmt-rfcs
258 [style guide]: https://github.com/rust-lang-nursery/fmt-rfcs/blob/master/guide/guide.md