Add an `--exit-non-zero-on-fix` equivalent to the formatter.

[TheReverend403]

Title says it all really. --exit-non-zero-on-change? I think this would be useful when using tools like pre-commit with CI in the same way as the checker's --exit-non-zero-on-fix.

[MichaReiser]

How does your setup look like? Do you use --diff or --check? The formatter already exits with 0 when not using --check or --diff.

How do you detect changes when using ruff in CI when using --diff or --check when it exists with 0?

[TheReverend403]

How does your setup look like?

https://github.com/TheReverend403/cappuccino/blob/main/.pre-commit-config.yaml#L34-L44

Do you use --diff or --check? The formatter already exits with 0 when not using --check or --diff.

I already use --check and I know the formatter exits 0 without it. What I'm suggesting is a way to make it format and exit non-zero if anything changed in the same way as check --fix --exit-non-zero-on-fix. The problem with using --check alone is that if you run pre-commit locally, you first have to run pre-commit to see that things need formatting, then run ruff format separately without --check. I can't just remove --check because then when the CI runs pre-commit, it won't fail if somebody committed code without first formatting it, it will just quietly make the changes which is not useful on CI where those changes won't persist.

[MichaReiser]

I already use --check and I know the formatter exits 0 without it. What I'm suggesting is a way to make it format and exit non-zero if anything changed in the same way as check --fix --exit-non-zero-on-fix.

ruff format --check has different semantics than ruff check --fix. It only checks if files would be reformatted but it doesn't change the files on disk. You want to use ruff format (without check) if you want to format AND persist the files.

[TheReverend403]

Updated my previous comment.

[MichaReiser]

Oh sorry. I misunderstood you. If I understand you correctly, you're asking that ruff format --check exits with a non-zero exit code if it would reformat any files but it would also write the changes back to disk so that running ruff format isn't necessary locally.

I'm a bit torn where to integrate this functionality best. We could either to ruff format --exit-non-zero-on-fix (undecided on the name of the flag) without using check. However, the option would be incompatible when using with --check or --diff.

Did you use black before? If so, how did your setup look like?

[zanieb]

We could either to ruff format --exit-non-zero-on-fix (undecided on the name of the flag) without using check. However, the option would be incompatible when using with --check or --diff.

This seems like a reasonable approach if we do implement it. It isn't incompatible with --check though, it just has no effect. With --diff I don't know our exit code behavior.

[TheReverend403]

If I understand you correctly, you're asking that ruff format --check exits with a non-zero exit code if it would reformat any files but it would also write the changes back to disk so that running ruff format isn't necessary locally.

Exactly, but as an additional flag rather than changing --check so as to avoid breaking everyone's current CI workflows. 😏

Did you use black before? If so, how did your setup look like?

I used black, just not with this behaviour. It was actually ruff's own --exit-non-zero-on-fix that gave me this idea for the formatter.

[henryiii]

FYI, --exit-non-zero-on-fix in the checker isn't required in pre-commit; pre-commit checks for changed files.

[zanieb]

Hm so ruff format is all you should need in pre-commit? Having pre-commit tooling check for differences makes a lot more sense than adding more exit code flags to Ruff.

[henryiii]

Yes, a non-zero exit code has always only been required if there were no file changes.

[TheReverend403]

Oh shit you're right. How did I overlook the fact that pre-commit has its own exit code? Idiot. 😔