[beduldul]

Closes #2756.

A bare # parses to an empty comment string, and the checks used truthiness, so "" was treated as "no comment". The comment was dropped and the whitespace that content.split("#", 1) left behind stayed on the line:

>>> isort.code("from sys import super_long_name  #\n", force_grid_wrap=3, line_length=30)
'from sys import \\\n    super_long_name  \n'

The second line ends with two spaces, and the next run strips them, so the output is not a fixpoint. A non-empty comment on the same input was already handled correctly.

_with_star_comments() had the same check, which dropped the # from star imports even when nothing needed wrapping:

>>> isort.code("from sys import *  #\n")
'from sys import *\n'

Test for None instead, which is what an absent comment actually is, in wrap.line() and _with_star_comments(). comment_suffix and _comma had the same if comment / not comment shape and are fixed alongside so a bare # behaves like any other comment there.

>>> isort.code("from sys import super_long_name  #\n", force_grid_wrap=3, line_length=30)
'from sys import \\\n    super_long_name  #\n'
>>> isort.code("from sys import *  #\n")
'from sys import *  #\n'

Two regression tests in test_regressions.py cover the wrapped line and the star import, and both assert the output is a fixpoint. They fail without the change. tests/unit is 718 passed, 1 skipped, and flake8 is clean.

[Copilot]

🟢 Approved

No active review issues are recorded for the change preserving bare # comments during import formatting.

No open issues 🎉

What changed in this PR

Fixes #2756 by preserving bare # comments during import formatting, distinguishing empty comments from absent comments.

Changes:

• Updates wrapping and comma handling to check for None rather than comment truthiness.
• Preserves empty comments on star imports.
• Adds regression coverage for wrapped imports, star imports, and wrapped-import idempotence.

File	Description
tests/​unit/​test_regressions.py	Adds regression tests for preserving bare # comments.
isort/​wrap.py	Treats empty comments as present when wrapping imports.
isort/​output.py	Retains empty comments attached to star imports.

_{Review effort: Balanced}

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 99.38%. Comparing base (1d60803) to head (b451e8c).
⚠️ Report is 1 commits behind head on main.

Additional details and impacted files

@@           Coverage Diff           @@
##             main    #2757   +/-   ##
=======================================
  Coverage   99.38%   99.38%           
=======================================
  Files          40       40           
  Lines        3275     3275           
  Branches      707      707           
=======================================
  Hits         3255     3255           
  Misses         12       12           
  Partials        8        8           

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