I can see the case for leaving the .flake8 file around for a while to not break people's editor workflows.

I can see the case for leaving the .flake8 file around for a while to not break people's editor workflows.

Fair. We should then add a comment to the file that we don't use it anymore.

Ruff implements

• all pydocstyle rules (apart from the deprecated D302 rule)
• all pyflakes rules
• all pycodestyle rules, apaprt from E121 to E133, E704, E901, W503, W504.

Of the pycodestyle rules not implemented in ruff, we use (ie don't ignore, and they are in the default pycodestyle ruleset):

• E122: continuation line missing indentation or outdented
• E124: closing bracket does not match visual indentation
• E125: continuation line with same indent as next logical line
• E128: continuation line under-indented for visual indent
• E129: visually indented line with same indent as next logical line
• E901: SyntaxError or IndentationError

I'm not sure what E901 means, but I understand it's a Python syntax error that I'm 90% sure would be caught just by importing a file.

For the rest, I'm not sure how much we care about keeping strictly to these visual indentation rules, since we do not enforce a code formatter (e.g., black) at the moment anyway). My two cents is that it's worth sacrificing these rules for switching to ruff and providing the benefits of being able to autofix issues. Also worth noting that pydocstyle was last updated two years ago, and is now expclitly deprecated in favour of ruff.

On keeping .flake8, I'm 👍 to just 'tearing the plaster off' and removing it - if we put a release notes entry in, hopefully developers can adapt to use ruff fine? But also happy to leave a comment at the top of .flake8 saying it's deprecated and will be removed in 6(?) months, if that's what folks prefer?

It seems we should just remove flake8 if we don't use it? Developers who still need it for something could still copy one into their directory. Given that there is no way to deprecate its use, it seems the easiest way to let people know is to remove it.

The only two rules I saw as "missing" when I last checked was E122 and E302, which is why they are listed as the "external rules" (which prevents warnings for e.g. ignore comments on those rules)

Looking into it, looks like E302 is now implemented, so it really is just E122, which has to do with indentation on continuation lines, which is relatively niche to begin with.

Personally, I'd be good with swapping to ruff only at this point. I had been hoping for 100% parity, but we are so close it's probably good enough.

Consensus seems to be this is ready to go then. The last open question seems to be keeping the .flake8 file or not. I'm +1 just removing it to signal to developers that we're not actively using flake8 any more, but if there are enough voices in the other direction I'm happy to keep it for a bit.

Ok, let's go.