Group plain imports

[DanielNoord]

Closes #2455

Code is still to be improved. I'm also unsure about some of the changes to expected test output...

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 99.33%. Comparing base (8d8d49d) to head (a114126).
⚠️ Report is 22 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #2614      +/-   ##
==========================================
- Coverage   99.39%   99.33%   -0.07%     
==========================================
  Files          41       41              
  Lines        3163     3172       +9     
  Branches      682      686       +4     
==========================================
+ Hits         3144     3151       +7     
- Misses         11       12       +1     
- Partials        8        9       +1     

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[staticdev]

@DanielNoord on a first look I see:

• Still it does not address --fss may lead to incorrect import separation for mixed multi-line and alias imports #2455’s exact long multiline --fss reproducer
• It broadens comment behavior by merging comments with semicolons and moving noqa comments, beyond the issue’s scope.
• It skips unrelated Django and Habitat integration tests.

If you want I can try to do commits to help this PR as well.

[DanielNoord]

@staticdev

Doesn't this address it? I thought it did but might need to double check. I think the original error is just attributing an underlying problem (not merging/grouping plain from imports) to unrelated configuration options.
By grouping plain imports we necessarily need to handle comments on the import statements we are grouping.
The tests fail because this is a breaking change and both django and habitat don't conform to this style. Note that this is the style that ruff enforces by default.

[staticdev]

@DanielNoord sorry, I double-checked and the core behavior looks correct: the original multiline reproducer groups all plain imports into one statement, keeps the aliased import separate, and is idempotent with and without --fss.

I would propose to close this:

• Add the exact long multiline #2455 reproducer as a regression test.
• Add the reverse alias-before-plain case and assert idempotency.
• Keep the Django and Habitat skips, but clarify that they reflect incompatibility with the intentional breaking style.