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).
+[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
## Quick start
-Currently, you can use `rustfmt` on nightly and beta. Rust 1.24 stable will work,
-but we're not quite there yet!
+You can use `rustfmt` on Rust 1.24 and above.
To install:
```
-rustup component add rustfmt-preview --toolchain=nightly
+rustup component add rustfmt-preview
```
-If `nightly` is your default toolchain, you can leave the `--toolchain` off.
-
to run on a cargo project in the current working directory:
```
-cargo +nightly fmt
+cargo fmt
```
-If `nightly` is your default toolchain, you can leave off the `+nightly`.
-
-## Installation
-
+For the latest and greatest `rustfmt` (nightly required):
```
-rustup component add rustfmt-preview --toolchain=nightly
+rustup component add rustfmt-preview --toolchain nightly
```
-
-If you don't have a nightly toolchain, you can add it using rustup:
-
+To run:
```
-rustup install nightly
+cargo +nightly fmt
```
-You can make the nightly toolchain the default by running:
+## 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 default nightly
+rustup component add rustfmt-preview
```
-If you choose not to do that you'll have to run rustfmt using `rustup run ...`
-or by adding `+nightly` to the cargo invocation.
-
## Installing from source
-To install from source, first checkout to the tag or branch you want to install, then issue
+To install from source (nightly required), first checkout to the tag or branch you want to install, then issue
```
-cargo install --path .
+cargo install --path .
```
This will install `rustfmt` in your `~/.cargo/bin`. Make sure to add `~/.cargo/bin` directory to
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`.
+You can run `rustfmt --help` for information about argument.
-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`.
+When running with `--check`, Rustfmt will exit with `0` if Rustfmt would not
+make any formatting changes to the input, and `1` if Rustfmt would make changes.
+In other modes, Rustfmt will exit with `1` if there was some error during
+formatting (for example a parsing or internal error) and `0` if formatting
+completed without error (whether or not changes were made).
-You can run `rustfmt --help` for more information.
## Running Rustfmt from your editor
## 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
+when a pull request contains unformatted code. Using `--check` 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:
+A minimal Travis setup could look like this (requires Rust 1.24.0 or greater):
```yaml
language: rust
+rust:
+- nightly
before_script:
-- rustup toolchain install nightly
-- rustup component add --toolchain nightly rustfmt-preview
-- which rustfmt || cargo install --force rustfmt-nightly
+- rustup component add rustfmt-preview
script:
-- cargo +nightly fmt --all -- --write-mode=diff
+- cargo fmt --all -- --check
- cargo build
- cargo test
```
* For things you do not want rustfmt to mangle, use one of
```rust
- #[rustfmt_skip] // requires nightly and #![feature(custom_attribute)] in crate root
+ #[rustfmt::skip] // requires nightly Rust and #![feature(tool_attributes)] 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
projects / rust.git / blobdiff