fix #13564 - warn when fixtures get wrapped with a decorator #13745
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RonnyPfannschmidt
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Sep 22, 2025
RonnyPfannschmidt
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- closes Fixture definition check in parsefactories is too strict #13564
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Refactor the wrapped fixture detection logic to safely handle: - Mock objects (which have _mock_name attribute) - Proxy objects with problematic __class__ properties - Wrapper loops (like in mock.call) - Objects that raise exceptions during isinstance checks The new _find_wrapped_fixture_def() method walks the wrapper chain more safely and avoids infinite loops and errors from special objects. 🤖 Generated with [Claude Code](https://claude.com/claude-code) Co-Authored-By: Claude <[email protected]>
Prevent OOM crash when encountering objects with self-referential __wrapped__ attributes. The loop detection logic now checks object IDs at the start of each iteration and includes a maximum depth limit as an additional safeguard. The original code had a timing issue where it checked id(wrapped) against seen after fetching __wrapped__ but before updating current, which failed to detect self-referential objects properly. 🤖 Generated with [Claude Code](https://claude.com/claude-code) Co-Authored-By: Claude <[email protected]>
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Pull Request Overview
This PR adds a warning mechanism to detect when pytest fixtures are wrapped with custom decorators, which prevents pytest from discovering them during collection. The warning helps developers understand why their fixtures might not be working as expected.
Key Changes:
- Added a warning system that detects fixtures wrapped in decorators using
functools.wraps - Implemented safe wrapper chain traversal with loop detection and special object handling
- Added comprehensive test coverage for the new warning functionality
Reviewed Changes
Copilot reviewed 3 out of 4 changed files in this pull request and generated 2 comments.
| File | Description |
|---|---|
src/_pytest/fixtures.py |
Implements the core detection logic for wrapped fixtures and issues warnings when found |
testing/python/fixtures.py |
Adds test case to verify the warning is correctly issued for decorated fixtures |
changelog/13564.improvement.rst |
Documents the new warning feature for wrapped fixtures |
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| """ | ||
| from _pytest.compat import safe_getattr | ||
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| # Skip mock objects (they have _mock_name attribute) |
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[nitpick] The comment should clarify why mock objects need to be skipped. Consider: 'Skip mock objects (they have _mock_name attribute) to avoid false positives when traversing their wrapper chains.'
Suggested change
| # Skip mock objects (they have _mock_name attribute) | |
| # Skip mock objects (they have _mock_name attribute) to avoid false positives when traversing their wrapper chains. |
| return None | ||
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| # Try to get the next wrapped object using safe_getattr to handle | ||
| # "evil objects" that raise on attribute access (see issue #214) |
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[nitpick] The reference to 'issue #214' is unclear without context. Consider specifying the full issue reference (e.g., 'pytest issue #214') or linking to the relevant documentation.
Suggested change
| # "evil objects" that raise on attribute access (see issue #214) | |
| # "evil objects" that raise on attribute access (see pytest issue #214: https://github.com/pytest-dev/pytest/issues/214) |
Zac-HD
approved these changes
Oct 24, 2025
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| wrapped = safe_getattr(current, "__wrapped__", None) | ||
| if wrapped is None: | ||
| break | ||
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| current = wrapped |
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Suggested change
| wrapped = safe_getattr(current, "__wrapped__", None) | |
| if wrapped is None: | |
| break | |
| current = wrapped | |
| current = safe_getattr(current, "__wrapped__", None) |
redundant with start-of-loop logic
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