--doctest-modules uses GBs of memory on modules importing unittest.mock.call when the recursion limit is raised #15333

🤖 Written by Claude Opus 5.5 via Claude Code for the pytest maintainers; I prompted it, it did the work, I read it.

Found while working on #15281 / #15283. This is a separate problem that already exists in 9.1.1, not the 9.2.0 regression.

Reproducer

conftest.py:

import sys

sys.setrecursionlimit(30_000)

mod_c.py:

"""
>>> 1
1
"""
from unittest.mock import call

pytest -q -p no:cacheprovider --doctest-modules

Measured on Python 3.13, Linux:

At a limit of 100 000 the process is OOM-killed.

Cause

On Python 3.10+, the stdlib DocTestFinder._is_routine calls inspect.unwrap(obj) on every module attribute and only catches ValueError. mock.call.__wrapped__ keeps returning a new _Call with a longer name, so unwrapping runs until sys.getrecursionlimit(). Memory grows roughly quadratically with the limit.

pytest used to guard against this. MockAwareDocTestFinder._find skipped _is_mocked objects and ran the stdlib _find under _patch_unwrap_mock_aware() (#3456, python/cpython#69718). That override was limited to Python < 3.10 and was removed along with 3.9 support in bb712f1. _patch_unwrap_mock_aware itself is now only used by its own test.

Possible fix

Restore the _find override for all Python versions (about 14 lines in src/_pytest/doctest.py). I prototyped it locally: the reproducer drops to 0.09 s / 33 MB and the full test suite passes. A regression test is still needed.