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fix: set fixed paths_list in TreeMatcher init#2130

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nedbat merged 1 commit intocoveragepy:mainfrom
colorlace:set-paths
Feb 7, 2026
Merged

fix: set fixed paths_list in TreeMatcher init#2130
nedbat merged 1 commit intocoveragepy:mainfrom
colorlace:set-paths

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@colorlace
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@colorlace colorlace commented Feb 7, 2026

This lil fix simply ensures we don't get hit with RuntimeError: Set changed size during iteration if there's any concurrent update to sys.paths while TreeMatcher.__init__ runs.

My CI pipeline has encountered this error:

.venv/lib/python3.11/site-packages/coverage/inorout.py:354: in should_trace
    self.set_matchers_depending_on_syspath()
.venv/lib/python3.11/site-packages/coverage/inorout.py:308: in set_matchers_depending_on_syspath 
    self.third_match = TreeMatcher(self.third_paths, "third", "Third-party lib", self._debug)
                                    ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
.venv/lib/python3.11/site-packages/coverage/files.py:266: in __init_
    for p in paths: 
E     RuntimeError: Set changed size during iteration

This seems like a very similar situation to #1733
which was fixed by something similar: 08fc997.

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nedbat commented Feb 7, 2026

Thanks for this. Can you share the project that caused the error? I'd like to understand better where the concurrent access is coming from.

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colorlace commented Feb 7, 2026 •
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Thanks for this. Can you share the project that caused the error? I'd like to understand better where the concurrent access is coming from.

Unfortunately it's a closed-source company project. But I believe it occurs because, during testing, we run

from pyspark.sql import SparkSession

which updates the sys.path. I suppose this happens concurrently while coveragepy is doin its thang.

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nedbat commented Feb 7, 2026

It looks like a good fix, thanks.

@nedbat nedbat merged commit 371fcc5 into coveragepy:main Feb 7, 2026
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colorlace commented Feb 7, 2026

Thanks Ned you're a legend! (Unicode sandwich saved me ten years ago when I started coding)

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nedbat commented Feb 7, 2026

Wow, Unicode sandwich, a historical deep cut! :D

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colorlace commented Feb 7, 2026

Haha I did a double take when I saw your name on the contributors list. Definitely uncovered some old memories of string processing pain (and retribution) XD

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nedbat commented Feb 9, 2026

This is now released as part of coverage 7.13.4.

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@colorlace @nedbat