Summary

PR #15321 (pre-commit.ci autoupdate) has widespread CI failures across the test_extra, oldest-deps, 3.14t and 3.15-dev jobs that look unrelated to the version bumps it contains, but they're actually a direct side effect of the autoupdate.

The failure is:

ValueError: line 7 of the docstring for tests.test_ipunittest.Foo.ipdt_method lacks blank after    : '   ....:'

Root cause: tests/test_ipunittest.py contains @ipdoctest/@ipdocstring fixtures whose continuation-prompt lines ( ....: ) intentionally end in trailing whitespace — IPython's ipdoctest parser (_check_prompt_blank in IPython/testing/plugin/ipdoctest.py) requires that whitespace to recognize a blank continuation line. The file has a # fmt: off comment to protect it from black/darker reformatting, but that comment has no effect on the pre-commit-hooks trailing-whitespace hook.

When pre-commit.ci ran its autofix as part of #15321's autoupdate, trailing-whitespace stripped that intentional trailing whitespace, which breaks doctest collection for Foo.ipdt_method on every job except the one Python/OS combo that happens not to hit that autofixed line count difference... in practice it broke it everywhere except the two test (ubuntu-latest, 3.13) / test (macos-14, 3.13) jobs that apparently ran before pre-commit.ci pushed its autofix commit onto the PR branch.

Fix

Add an exclude for tests/test_ipunittest.py on the trailing-whitespace hook in .pre-commit-config.yaml, so future pre-commit run --all-files invocations (including pre-commit.ci's) leave this fixture's meaningful trailing whitespace alone.

Verified locally:

• pre-commit run trailing-whitespace --files tests/test_ipunittest.py now reports "no files to check / Skipped".
• pytest tests/test_ipunittest.py passes (5 passed).

Test plan

• pytest tests/test_ipunittest.py passes locally
• pre-commit run trailing-whitespace --files tests/test_ipunittest.py skips the excluded file
• CI green on this PR

Generated by Claude Code