IIRC running, e.g., isort as a check-only linter now runs it as a formatter under the covers and then discards the edits in the sandbox? What happens with linters that have useful output in check-only mode but not in change-the-file mode? (isort is such an example) We now lose that output, I think?

Yes

I think the

ruff

backend has separate behaviour for fix vs. lint?

so... is this a problem? I forget if we discussed this when making that otherwise-nice change.

I'm not sure I understand the question... but in my brief experiments with ruff, I was getting useful output from

lint

, not just "this file would be changed" (or similar)

I'm seeing this specifically for isort, which outputs the diff in check mode, and just quietly applies the diff in modify mode

That not surprising. Are you suggesting something or just reporting something?

Wondering if this is a problem - we decided to re-implement checks as "format and discard", which generally seems more streamlined, but I don't remember if we considered this angle.

Yes, it's likely in the original proposal