fix(parametrize): handle trailing comma in string argnames #14125
+83
−1
Conversation
This file contains hidden or bidirectional Unicode text that may be interpreted or compiled differently than what appears below. To review, open the file in an editor that reveals hidden Unicode characters.
Learn more about bidirectional Unicode characters
RonnyPfannschmidt
added
type: bug
psf-chronographer
bot
added
bot:chronographer:provided
RonnyPfannschmidt
added
the
backport 9.0.x
There was a problem hiding this comment.
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 |
💡 Add Copilot custom instructions for smarter, more guided reviews. Learn how to get started.
nicoddemus
approved these changes
Jan 24, 2026
RonnyPfannschmidt
force-pushed
the
fix-719-parametrize-trailing-comma
branch
from
8e09ae7 to
c5aefb5
Compare
RonnyPfannschmidt
force-pushed
the
fix-719-parametrize-trailing-comma
branch
from
c5aefb5 to
5e7ea97
Compare
…v#719) Make `"arg,"` behave like `("arg",)` by detecting trailing comma and not wrapping tuple values. This allows users to use trailing comma syntax in string argnames for single-parameter parametrize. Fixes pytest-dev#719 Co-authored-by: Cursor AI <[email protected]> Co-authored-by: Anthropic Claude Opus 4.5 <[email protected]>
RonnyPfannschmidt
force-pushed
the
fix-719-parametrize-trailing-comma
branch
from
5e7ea97 to
3fc824a
Compare
Backport to 9.0.x: 💚 backport PR created✅ Backport PR branch: Backported as #14149 🤖 @patchback |
patchback bot
pushed a commit
that referenced
this pull request
Jan 29, 2026
…trailing-comma fix(parametrize): handle trailing comma in string argnames (cherry picked from commit 5f59a74)
Sign up for free
to join this conversation on GitHub.
Already have an account?
Sign in to comment
2 participants
Add this suggestion to a batch that can be applied as a single commit.
This suggestion is invalid because no changes were made to the code.
Suggestions cannot be applied while the pull request is closed.
Suggestions cannot be applied while viewing a subset of changes.
Only one suggestion per line can be applied in a batch.
Add this suggestion to a batch that can be applied as a single commit.
Applying suggestions on deleted lines is not supported.
You must change the existing code in this line in order to create a valid suggestion.
Outdated suggestions cannot be applied.
This suggestion has been applied or marked resolved.
Suggestions cannot be applied from pending reviews.
Suggestions cannot be applied on multi-line comments.
Suggestions cannot be applied while the pull request is queued to merge.
Suggestion cannot be applied right now. Please check back later.
Make
"arg,"behave like("arg",)by detecting trailing comma and not wrapping tuple values.Fixes #719