Document what to do if a class is not generic at runtime #5833
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docs/source/common_issues.rst
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| In some cases a class may be declared as generic in stubs, while | ||
| it is not generic at runtime. For example this is the case for some |
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Suggested rewording: "Some classes are declared as generic in stubs, but not at runtime. Examples in the standard library include os.PathLike and queue.Queue. Subscripting such a class will result in a runtime error:"
docs/source/common_issues.rst
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| results: Queue[int] = Queue() # TypeError: 'type' object is not subscriptable | ||
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| To avoid these errors while still having precise types one can either use | ||
| string literals or ``typing.TYPE_CHECKING``: |
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"string literals" is a bit vague. Maybe reword as "string literal types".
docs/source/common_issues.rst
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| results: Queue[int] = Queue() # TypeError: 'type' object is not subscriptable | ||
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| To avoid these errors while still having precise types one can either use |
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Style nit: use "you" instead of "one" for consistency.
docs/source/common_issues.rst
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| from typing import TYPE_CHECKING | ||
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| if TYPE_CHECKING: | ||
| BaseQueue = Queue[str] |
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Maybe add descriptive comment here -- this is only processed by mypy.
docs/source/common_issues.rst
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| if TYPE_CHECKING: | ||
| BaseQueue = Queue[str] | ||
| else: | ||
| BaseQueue = Queue |
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Another descriptive comment could be helpful here -- this is not seen by mypy but will be executed at runtime.
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@JelleZijlstra @JukkaL thanks for review! I pushed an update. |
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As I understand there are no more comments, so I am going to merge this soon. |
Fixes #5667