multi_line_output=10 emits unparsable code when an import has a trailing comment

Summary

With multi_line_output=10 (HANGING_INDENT_WITH_PARENTHESES), isort can rewrite a valid file into one that no longer parses when an import carries a trailing comment. Both shapes below start as valid Python.

Closing parenthesis captured by the comment

$ echo 'from a import b, c  # trailing
from a import d' | isort --multi-line 10 --line-length 40 --force-grid-wrap 2 -
from a import (b, c, d  # trailing)

) is inside the comment, so the statement is never closed.

Comma lost at a wrap point

$ echo 'from mypkg.submodule import alpha, beta, gamma, delta, epsilon, zeta, eta  # noqa: F401' | isort --multi-line 10 -
from mypkg.submodule import (alpha, beta, delta, epsilon, eta  # noqa: F401
    gamma, zeta)

The comma after eta is gone, so the names read as eta gamma.

Both outputs raise SyntaxError under ast.parse, and isort itself then refuses them with ExistingSyntaxErrors: Parenthesis is not closed.

How much of the option space this affects

Sweeping 7 sources x 12 wrap modes x 3 line lengths x 6 option combinations (1512 runs), 17 produce output that Python cannot parse, and all 17 are multi_line_output=10. The other 11 modes are clean. It reproduces at the default line length and at 88, with # noqa: and # type: ignore — the comments most likely to sit on an import.

Why only this mode

The sibling grouped modes hoist the comment onto the ( line, so their last line never ends in a comment and appending , or ) is always safe. hanging_indent_with_parentheses keeps the comment on the import line and then appends punctuation to it unconditionally:

• the final return appends ) after the comment, and
• at a wrap point, interface["statement"] + "," puts the comma after the comment, where comments.add_to_line strips it off with the old comment before re-adding it — so the comma is dropped rather than commented out.

Version

main at 131f4adc, isort 9.0.1, CPython 3.12.13.

I have a fix and a regression test ready and will open a PR referencing this issue.

Reproduce the examples with isort --multi-line 10 and confirm the output fails under ast.parse. Start with the hanging_indent_with_parentheses path and comments.add_to_line behavior described in the issue; done means preserving valid punctuation around trailing comments and adding a regression test for both failure shapes.