Preserve trailing comments for aliased imports

[SemTiOne]

• Fixes Trailing comment removed from as imports with combine_as_imports = true and force_single_line = true #2094

Trailing comment removed from as imports with combine_as_imports = true and force_single_line = true.

[Manny7717]

Verified locally on head 3a04399 (Py3.14, repo venv) against base 131f4ad.

Bug confirmed on base — brute-force across 112 shapes (combine_as_imports × force_single_line / remove_redundant_aliases / multi_line_output / include_trailing_comma / force_grid_wrap × single/multi-alias, plain-import aliases, submodules, mixed alias+plain): 87 shapes drop the trailing comment on base, including the exact issue #2094 scenario (all three comment types lost on the aliased lines).

Head behavior: comments preserved in 109/112 shapes. The 3 remaining "losses" are duplicate-comment collapse when two IDENTICAL comments (# C + # C) merge onto one combined line — identical on base, not a regression. Two DIFFERENT comments merge correctly (# C1; C2), a single comment on either alias survives the combine, and force_single_line keeps one comment per alias line.

Regression test is revert-proven: copied the PR's test into the base worktree → fails (assertion 2: from some_module import the_function as some_function loses # type: ignore); passes on head. Second-pass idempotency asserted by the test and verified manually on all probe shapes.

No regressions: full unit suite head 624 passed / 2 failed vs base 623 passed / 2 failed — identical failure set (pre-existing FileNotFoundError env noise issue_909/938), +1 = the new test.

Mechanism review: parse.py now keys alias comments per-base in straight["<module>.<base>"] (previously a single from["<module>"].__combined_as__ bucket); output.py pops per-base in both the force_single_line and combined paths, and the removed nested_module = None line had no remaining readers (grep-verified). The # C1; C2 join is the existing with_comments separator behavior, not new logic. Non-alias comments (straight imports, non-aliased from-imports) and import m as x # C plain-import aliases are byte-identical to base.

Clean minimal fix; APPROVE.

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 99.44%. Comparing base (f292a60) to head (1ad379e).
⚠️ Report is 3 commits behind head on main.

Additional details and impacted files

@@           Coverage Diff           @@
##             main    #2648   +/-   ##
=======================================
  Coverage   99.44%   99.44%           
=======================================
  Files          41       41           
  Lines        3217     3233   +16     
  Branches      691      695    +4     
=======================================
+ Hits         3199     3215   +16     
  Misses         11       11           
  Partials        7        7           

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[Copilot]

Copilot review overview

🟡 Changes recommended

Alias comments share a non-unique key, causing comments to merge or disappear for multiple aliases of the same import.

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Review effort: Balanced
Findings: 1

Open (1)

• Prevent comment collisions between aliased and regular imports · New

What changed in this PR

Preserves trailing comments on aliased imports when combining aliases into single-line imports.

Changes:

• Stores and retrieves comments for combined aliases.
• Adds regression and idempotence coverage for issue #2094.

File	Description
isort/​parse.py	Changes alias-comment categorization.
isort/​output.py	Restores comments when rendering aliases.
tests/​unit/​test_regressions.py	Adds regression tests.

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[Copilot]

Copilot review overview

🟡 Changes recommended

Two comment-routing paths can misassign or duplicate comments between imports.

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Review effort: Balanced
Findings: 1

Open (1)

• Separate comment keys for straight and from imports · New

Resolved since last review (1)

• Prevent comment collisions between aliased and regular imports

[Copilot]

Copilot review overview

🟡 Changes recommended

Opening-line comments can move onto an attribute when the same symbol has multiple aliases.

Get a fresh assessment by requesting another Copilot review.

Review effort: Balanced
Findings: 1

Open (1)

• Preserve opening comments for multi-alias parenthesized imports · New

Resolved since last review (1)

• Separate comment keys for straight and from imports

[DanielNoord]

Closing due to inactivity of the AI bot.

[SemTiOne]

Wait I’m still interested in working on this. I was away for a while, but I’d like to pick this back up.