Fix rootdir detection when setup.py exists in temp directory

[jayalath-jknr]

Fixes #13822

This PR addresses a bug where pytest incorrectly identifies the system temp directory as the project rootdir when a setup.py file exists in /tmp (or the system temp directory).

Problem

When a setup.py file exists in the temp directory (e.g., /tmp/setup.py), pytest's rootdir detection logic would walk up the directory tree and find this file, incorrectly setting /tmp as the rootdir. This caused test nodeids to include the full temporary path instead of just the filename, breaking the test_warning_recorded_hook test and potentially affecting other functionality.

Solution

The fix modifies the determine_setup function in src/_pytest/config/findpaths.py to skip setup.py files specifically located in the directory returned by tempfile.gettempdir(). This prevents the temp directory from being mistakenly identified as a project root while preserving normal setup.py detection for legitimate project directories.

Changes

• src/_pytest/config/findpaths.py: Added logic to skip setup.py files in the temp directory when determining rootdir
• testing/test_findpaths.py: Added comprehensive tests to ensure the fix works and normal setup.py detection still functions

Testing

The fix has been validated with:

1. Reproduction of the original issue with /tmp/setup.py present
2. Verification that the fix resolves the failing test_warning_recorded_hook test
3. New unit tests ensuring temp directory setup.py files are ignored
4. Regression tests confirming normal setup.py detection still works
5. Full test suite validation for rootdir-related functionality

This is a targeted fix that specifically addresses the temp directory edge case without affecting other pytest functionality.