Use correct span for UseTree

[rust.git] / README.md

diff --git a/README.md b/README.md
index 69f4d800dfc841a77d3cf8e95e70ff0fdb3280e1..020d6bf3b20813ae26c4fd7cf7f3b309c09fc382 100644 (file)
--- a/README.md
+++ b/README.md
@@ -3,7 +3,8 @@
 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
@@ -40,6 +41,44 @@ to run on a cargo project in the current working directory:
 cargo fmt
 ```
 
+For the latest and greatest `rustfmt` (nightly required):
+```
+rustup component add rustfmt-preview --toolchain nightly
+```
+To run:
+```
+cargo +nightly 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
 
 ```
@@ -48,9 +87,9 @@ 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
+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
@@ -67,7 +106,7 @@ 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`.
+`check`, `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.
@@ -75,6 +114,9 @@ You'll probably want to specify the write mode. Currently, there are modes for
 * `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.
+* `check` Checks if the program's formatting matches what rustfmt would do. Silently exits
+          with code 0 if so, emits a diff and exits with code 1 if not. This option is
+          designed to be run in CI-like where a non-zero exit signifies incorrect formatting.
 * `checkstyle` Will output the lines that need to be corrected as a checkstyle XML file,
   that can be used by tools like Jenkins.
 
@@ -128,16 +170,14 @@ when a pull request contains unformatted code. Using `--write-mode=diff` instruc
 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
 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 -- --write-mode=diff
 - cargo build
 - cargo test
 ```