[Prateek99-s]

Summary

Fixes #4026
Fixes #3713

Problem

When a bracketed construct (such as a list literal or function call) contains a standalone comment
before a short expression with operators (binary math, comparisons, comprehensions, etc.), Black
unnecessarily breaks the expression across multiple lines even when it easily fits well within
--line-length:

# Before
foobar = [
    # comment
    pathlib.Path("foo")
    / "bar"
    / "baz",
]

fizzbuzz = [
    # comment
    23
    / 7
]

func(
    # comment
    a
    * b
)

Solution

Avoid splitting on delimiters when a preceding standalone comment pushed the line onto its own line
and the expression comfortably fits on a single line.

# After (with --preview)
foobar = [
    # comment
    pathlib.Path("foo") / "bar" / "baz",
]

fizzbuzz = [
    # comment
    23 / 7
]

func(
    # comment
    a * b
)

Test Plan

• Added regression tests in tests/data/cases/.
• Ran full test suite and pre-commit checks.

[github-actions]

diff-shades results comparing this PR (bd80859) to main (e74a324):

--preview style (View full diff):

╭─────────────────────── Summary ────────────────────────╮
│ 9 projects & 45 files changed / 278 changes [+94/-184] │
│                                                        │
│ ... out of 3 108 161 lines, 14 187 files & 22 projects │
╰────────────────────────────────────────────────────────╯
Differences found.

--stable style: no changes

---

What is this? | Workflow run | diff-shades documentation

[cobaltt7]

Your PR descriptions are often oddly formatted, with unnecessary indentation and line breaks. In this case, it causes the "Fixes" statements not to be picked up, and the example seems to cut off early. Please fix this PR's description as well as paying attention to these issues for any future PRs. Thanks

[Prateek99-s]

Thanks for the review!

- Fixed the PR description formatting and links.                                         
- Expanded the fix to cover all delimiters(like comprehensions and `==`) and added tests.
- Renamed the feature to `keep_commented_expressions_together`.         
- Rebased on latest main, and all CI checks are green now.  

[cobaltt7]

Thanks!