Hassle-free rustfmt setup

[matklad]

It would be cool to have all the code formatted with rustfmt. The problem is that setting up rustfmt is not-trivial (mainly because you need to know the precise version). I think a (probably slightly over-engineered) solution to this is to add format command to tools which should

• install rustfmt for a specific version of rust (command can assume rustup is used)
• run rustfmt on all code

The end goal is that git clone ... && cd rust-analyzer && cargo format always works.

As a bonus, add cargo format --instal-hook, which installs pre-commit hook for reformatting changed files.

As an extra bonus, package that as a reusable crate.

[kjeremy]

We should probably have stuff in our rustfmt.toml as well

[mominul]

As I have worked on the tools crate earlier, I'd like to take this issue!

[alanhdu]

For installing the right version of rustfmt, if we're assuming that rustup is installed can we just used rust-toolchain to specify the right version or Rust and Rustfmt to use? Or is the tool supposed to do something like:

1. Push nightly-2018-10-xx onto override stack
2. rustup component add rustfmt-preview (if necessary)
3. Run cargo fmt
4. Pop nightly-2018-10-xx off of the override stack to use whatever version dev had before

?

[CAD97]

rustup install nightly-2018-xx-xx
rustup component add rustfmt-preview --toolchain nightly-2018-xx-xx
cargo +nightly-2018-xx-xx fmt

Should be sufficient. Both rustup install and rustup component add return a success code without doing work when the said toolchain/component is already installed.

[matklad]

@alanhdu more like the second approach, though, instead of overrides, you can directly call rustup run toolchain-version -- cargo fmt.

I don't want to pick a particular blessed rust version, I think it is OK if you, for example, just use the current nightly. For formatting though, it is important to pin the version.

[matklad]

Status update: we now have cargo format which reformats everything. The only thing we need is a one-time cargo format --install-commit-hook which adds cargo format as a pre-commit hook.

Unfortunatelly, we cant' just commit hooks to the repository.

[mominul]

Unfortunatelly, we cant' just commit hooks to the repository.

I know we haven't implemented it yet, are there any restrictions you talking about?

[DJMcNab]

I think he means that we can't create a commit containing a .git/hooks/pre-commit file, as git doesn't support that.

The precommit hook must be manually installed