Fix ValueError when tracing across Windows drives#83
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KaykCaputo merged 1 commit intoJul 8, 2026
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os.path.commonpath raises ValueError when its arguments sit on different Windows drives. _is_user_code hit this in three places (project root, stdlib, site-packages), and because it runs inside the profile callback, one interpreter-on-C:/project-on-F: setup killed tracing for every single call event. A different drive can never be inside the project root, nor be the stdlib or site-packages, so each comparison now treats ValueError as 'not a match'. Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>
KaykCaputo
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Jul 8, 2026
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Follow-up from #82, as discussed.
Symptom: on Windows, when the interpreter and the traced project live on different drives (e.g. Python on
C:, project onF:), every call event printsand the run ends with
No calls traced.Nothing can be traced at all in that setup — 10 of the existing tests also fail on such a machine.Cause:
os.path.commonpathraisesValueErrorfor paths on different drives._is_user_codecalls it in three places (project root, stdlib, site-packages), inside thesys.setprofilecallback, so the first cross-drive comparison poisons every event.Fix: treat
ValueErroras 'not a match' at each comparison — a different drive can never be inside the project root, and can never be the stdlib or site-packages.Tests: two regression tests that simulate the cross-drive
ValueErrorportably (so they exercise the guards on Linux CI too). Both fail on master, pass with the fix. On my multi-drive Windows machine the full suite goes from 10 failures to green with this patch.🤖 Generated with Claude Code