Generalise `skip_ruff` to support skipping linting only, or formatting only

[huonw]

Is your feature request related to a problem? Please describe.

Currently the skip_ruff field, e.g. python_sources(skip_ruff=True), on a target seems to skip both linting and formatting, but a user might want to only skip one. This is the skip-field version of #20545.

Describe the solution you'd like

Two separate skip fields, for the separate pants.backend.experimental.python.lint.ruff.check and pants.backend.experimental.python.lint.ruff.format backends/functionality:

python_sources(
  skip_ruff_format=True,
  skip_ruff_check=True,
)

Describe alternatives you've considered

N/A
Additional context

It might be nice to ship this in 2.20 if we can get to it soon, but probably not critical.

[krishnan-chandra]

I can definitely ship this; the question becomes, what happens for folks who are already using the existing skip_ruff field? I think a sane default might be to have skip_ruff be equivalent to skip_ruff_check in the new world.

[huonw]

Yeah, that sounds sensible. Just to convince myself some more, drawing an analogy to the backend changes, pants.backend.experimental.python.lint.ruff was deprecated in favour of pants.backend.experimental.python.lint.ruff.check and thus it'd make sense that its associated skip_ruff field is deprecated in favour of skip_ruff_check. Good thinking!

[kaos]

why not have skip_ruff be the equiv. of having skip_ruff_check and skip_ruff_format?

To me, it feels like the shorter name could be the parent of both of them, that is skip_ruff as a parent skip field to skip all ruff stuff.. current and future features that may be added to it.

[krishnan-chandra]

why not have skip_ruff be the equiv. of having skip_ruff_check and skip_ruff_format?

That's basically what it does now 😄

I had a go at this last night and I think it's probably going to be more complicated than expected because of the way that the skip fields work. I'll still try to get it in before 2.20 releases but we may have to push it out to the next release instead.