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[mypyc] Add test for incremental builtin_base class construction across groups#21524

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p-sawicki merged 2 commits into
python:masterfrom
VaggelisD:fix-load-type-map-builtin-base
May 22, 2026
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[mypyc] Add test for incremental builtin_base class construction across groups#21524
p-sawicki merged 2 commits into
python:masterfrom
VaggelisD:fix-load-type-map-builtin-base

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@georgesittas georgesittas commented May 20, 2026 •
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The fix for this was included in #21369, but no dedicated test was added.

This adds testIncrementalBuiltinBaseClassConstruction to run-multimodule.test: three modules compiled with separate=True, where step 2 changes a helper module's signature to force the caller to be recompiled while the exception module is only loaded from cache.

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p-sawicki commented May 21, 2026

can i get instructions how to reproduce the original issue? i checked out the parent of the merge commit of #21369 and cherry-picked this test but pytest mypyc/test/test_run.py::TestRunSeparate::run-multimodule.test::testIncrementalBuiltinBaseClassConstruction_separate passed. i've also patched fudge_dir_mtimes in case it forced recompilation without it but it still passed.

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georgesittas commented May 21, 2026

Ah, it seems like the test framework only treats files matching other*.py as additional compiled sources (source, comment), anything else is written to disk as plain Python, not added to the build.

I missed this and named the helper files myerrors.py and myutil.py, so MyError would not be in a compiled group. Which is why the bug, which needs cross-group emit, is not triggered.

Sorry for the confusion. Feel free to give it another shot; I also verified that the test fails in the parent commit and should pass in this PR.

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p-sawicki approved these changes May 22, 2026
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great, now it reproduces. thanks!

@p-sawicki p-sawicki merged commit e61adea into python:master May 22, 2026
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@georgesittas georgesittas deleted the fix-load-type-map-builtin-base branch May 22, 2026 15:22
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