Provide a GitHub Action that translates spotless apply diff into GitHub pull request code suggestion comments

[timtebeek]

Hi! Couldn't find anything related through search; please correct me if this is not the right place to suggest such a new feature.

Background
Lately I've been contributing to Apache Maven, which uses Spotless to enforce formatting; as they've implemented it, the build pipeline breaks and it's up to the developer to apply spotless manually and push a new commit.

Idea
Instead I'd hope to see a Spotless GitHub Action developed & applied which takes the diff as created through spotless:apply and uses for instance googleapis/code-suggester to create code suggestion comments on the pull request.
This way the developer or reviewer is able to quickly apply all formatting directly from the pull request view, instead of having to checkout a local copy, run spotless again, and commit the resulting changes.

Technically it seems the components are already mostly there, especially when leveraging code-suggester. Having this available as an official GitHub Action could take away some of the friction experienced when using Spotless, especially for incidental contributors.

[nedtwigg]

This would be a great idea, it is tracked at

• spotlessCheck could add comments and suggested fix to GitHub PR #655

Implementing it is blocked by

• Internal-only breaking changes #1096
• Add support for linters #1097

If someone is eager to build it, the API's in #1096 are stable, you can make a PR against that and it will get merged eventually.

[timtebeek]

Ah that's a slightly different approach; would still work but from what I understand it still has some dependencies. I could see the violations format being more broadly applicable, so I understand why you'd nudge towards that existing effort.

With code-suggester you'd run spotless:apply as it is right now, and it'll create the code suggestion comments based on the diff. Could be a quicker way to achieve the same, but understandable if it does not get priority.

[nedtwigg]

Interesting, I had not seen code-suggester before. That's a great approach, it doesn't have the dependencies on #1096 and #1097, so I'd be happy to merge something like that now. I'll open an issue referencing this discussion.

[blacelle]

This relates with https://github.com/solven-eu/cleanthat#github-app-freepaid which is GitHub App, applying automatically Spotless to unprotected branches, and opening PR for protected branches.

[nedtwigg]

Wow, I didn't realize how far along you had already gotten @blacelle! This is great!

If I understand correctly, cleanthat currently provides feedback by opening new PRs. Does it also offer feedback by adding suggested-change diffs to already open PRs?

[blacelle]

@nedtwigg this feature was already available in Cleanthat before Spotless integration :).

cleanthat currently provides feedback by opening new PRs. Does it also offer feedback by adding suggested-change diffs to already open PRs?

There is essentially 2 way of proceeding for now:

1. Either the commit affect a protected branch: then, Cleanthat will suggests changes through a PR. (e.g. https://github.com/solven-eu/cleanthat/pull/493/files)
2. Or the commit affects a not protected branch, used as head of a PR to a protected branch: then Cleanthat will apply the changes directly to the branch. (e.g. solven-eu/cleanthat@7161270)
3. Other cases are currently discarded (e.g. commit to a PR-less branch)

[nedtwigg]

Is a "suggest changes on PRs" option on the roadmap?

[blacelle]

Not not yet on the roadmap, but I open solven-eu/cleanthat#552 for the purpose.