fix(parametrize): handle trailing comma in string argnames #14125
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…v#719) Make "arg," behave like ("arg",) by not wrapping tuple values. Co-authored-by: Cursor AI <ai@cursor.sh> Co-authored-by: Claude Opus 4 <claude@anthropic.com>
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Pull request overview
This PR fixes a bug in pytest.mark.parametrize where string argnames with trailing commas (e.g., "arg,") were not behaving like their tuple equivalents (e.g., ("arg",)). The fix ensures that when a single-argument string has a trailing comma, argvalues are treated as tuples to unpack rather than values to wrap.
Changes:
- Modified the
_parse_parametrize_argsmethod to detect trailing commas in string argnames and adjust theforce_tupleflag accordingly - Added comprehensive unit and functional tests to verify the behavior
- Added a changelog entry documenting the fix
Reviewed changes
Copilot reviewed 3 out of 3 changed files in this pull request and generated no comments.
| File | Description |
|---|---|
| src/_pytest/mark/structures.py | Added trailing comma detection logic to make "arg," behave like ("arg",) by adjusting the force_tuple flag |
| testing/python/metafunc.py | Added unit test verifying that tuple form, string with trailing comma, and string without comma all behave correctly; added functional test verifying the behavior in actual test execution |
| changelog/719.bugfix.rst | Added changelog entry documenting the bugfix for issue #719 |
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Change :func: to :ref: with proper target label to fix ReadTheDocs build. Co-authored-by: Cursor AI <ai@cursor.sh> Co-authored-by: Anthropic Claude Opus 4.5 <claude@anthropic.com>
nicoddemus
approved these changes
Jan 24, 2026
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Make
"arg,"behave like("arg",)by detecting trailing comma and not wrapping tuple values.Fixes #719