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__lazy_import__ crashes with user-defined filters #144851
Description
Crash report
Bug description:
This crashes from an assertion error, only when __lazy_import__ is called directly:
import sys
def li_filter(importing_module: str, imported_module: str, fromlist: tuple[str, ...]) -> bool:
return False
sys.set_lazy_imports_filter(li_filter)
__lazy_import__('wave')Moved from LazyImportsCabal#45 (couldn't have transferred it).
The compiler would always put a LOAD_CONST (None) before any IMPORT_NAME for imports without from, which is why this crash never happens in a regular lazy import.
CPython versions tested on:
CPython main branch
Operating systems tested on:
No response
Activity
johnslavik commentedon Mar 1, 2026
This hard crashes (segfaults) in the release build, so I'm marking this as a release blocker.
johnslavik commentedon Mar 1, 2026
cc @pablogsal @DinoV @Yhg1s @brittanyrey
gh-144851: Fix `__lazy_import__` crash with user-defined filters (#14…
johnslavik commentedon Mar 2, 2026
Thanks @Yhg1s for the quick review!
pythongh-144851: Fix `__lazy_import__` crash with user-defined filters (