grin/doc/style.md
Simon B 765996a630 rustfmt install instruction gotcha (#663)
* rustfmt install instruction gotcha

rustfmt stopped working for me. It turns out people started having trouble with this last year already https://github.com/rust-lang-nursery/rustfmt/issues/2304

* rustfmt on a single file now works! Secrets inside

After `rustup component add rustfmt-preview` I get rustfmt as a command in my terminal.

`rustfmt --help` reveals --write-mode [replace|overwrite|display|plain|diff|coverage|checkstyle] and we've been using the default which is either `overwrite` or `replace` (depending on rustfmt version) and this was changing a bunch of files and a messed up workflow.

* Newcomer-friendly explanation how to use `rustfmt`
2018-01-30 08:36:18 -05:00

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# Grin Style Guide
Grin uses [rustfmt](https://github.com/rust-lang-nursery/rustfmt) to maintain consistent formatting.
## Install rustfmt (nightly)
Note: we assume Rust has been installed via [Rustup](https://www.rustup.rs/).
See [build docs](./build.md) for more info.
rustfmt itself requires the nightly toolchain -
```
rustup update
rustup install nightly
rustup run nightly cargo install rustfmt-nightly
```
If you still get problems with running `cargo +nightly fmt`, you might need to also do `rustup component add rustfmt-preview` (see [more info](https://github.com/rust-lang-nursery/rustfmt/issues/2304))
## Install git pre-commit hook
There is a basic git [pre-commit](../.hooks/pre-commit) hook in the repo.
The pre-commit hook will not prevent commits if style issues are present but it will
indicate any files that need formatting.
To enable this, create a symlink in `.git/hooks` (note the relative path) -
```
cd .git/hooks
ln -s -f ../../.hooks/pre-commit
```
## Running rustfmt
To run rustfmt against a single file, this __new__ command works with latest rust and after having done `rustup component add rustfmt-preview` and by setting --write-mode it doesn't overwrite files.
First maybe try a dry-run to see what changes would be made:
`rustfmt --write-mode diff -- client.rs`
Then if you don't want to do any other cleanups manually, make rustfmt make the changes
`rustfmt -- client.rs`
and add that as a separate commit at the end of your Pull Request.
The old method would typically change formatting in _nearly every file_ in the grin repo. If you feel adventurous, try this:
`cargo +nightly fmt -- ./core/src/lib.rs`
(and please take care, since the ending `-- file/names.rs` actually doesn't have any effect)