Fix crash with # type: ignore in incremental mode #1906
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Previously, the semantic analyzer seemed to always mark import symbols as being of kind MODULE_REF during the third pass and did not preserve whether the module was previously marked with the `# type: ignore` comment or not. This caused a contradiction in some cases when mypy was run in incremental mode: suppose file a.py imported file b.py, and marked that import with the ignore annotation. Since the import is being ignored, mypy would not register that import as a dependency, but since the import (during the previous run) was marked as a MODULE_REF, mypy would attempt to load that module anyways in some cases. This commit fixes python#1904.
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I'm holding off reviewing this pending a fix for #1911. |
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This commit fixes the bug described in #1904.
More precisely, the bug manifests when...
# type: ignorecomment#type: ignorecomment after the regular import.The bug appears to stem from how the semantic analyzer seemed to always mark import symbols as being of kind
MODULE_REFand did not preserve whether the module was previously marked with the# type: ignorecomment or not.This caused a contradiction since how mypy decides to order dependencies differs whether you're starting with a cold cache or a warm cache.
When you start with a cold cache, mypy determines what each module's dependencies are based roughly on the order mypy encounters each file while parsing and whether the import is marked as ignorable or not.
However, when you start with a warm cache, mypy will use the previously computed list of dependencies, but will also attempt to typecheck each symbol marked as being of kind
MODULE_REF. This presents a problem, since if the module was marked as being ignorable, it wouldn't be in the list of dependencies, but since it was marked asMODULE_REF, mypy assumes it is...This pull request fixes this problem by modifying the semantic analyzer so that it determines whether it needs to mark import symbols of being kind
MODULE_REForUNBOUND_IMPORTEDto keep the behavior consistent during both runs.