[typing] Add missing _from_iterable classmethod to Set ABCs#15331
[typing] Add missing _from_iterable classmethod to Set ABCs#15331emmanuel-ferdman wants to merge 3 commits intopython:mainfrom
_from_iterable classmethod to Set ABCs#15331Conversation
Signed-off-by: Emmanuel Ferdman <emmanuelferdman@gmail.com>
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Hey @srittau could you please review this small PR when you get the chance? thank you! |
stdlib/typing.pyi
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| class ItemsView(MappingView, AbstractSet[tuple[_KT_co, _VT_co]], Generic[_KT_co, _VT_co]): | ||
| def __init__(self, mapping: SupportsGetItemViewable[_KT_co, _VT_co]) -> None: ... # undocumented | ||
| @classmethod | ||
| def _from_iterable(cls, it: Iterable[Any]) -> set[Any]: ... |
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Why not def [S](cls, it: Iterable[S]) -> set[S] ?
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Good call, updated to use Iterable[_S] -> set[_S]. Used the existing _S TypeVar since PEP 695 syntax isn't used elsewhere in typeshed.
stdlib/typing.pyi
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| def _hash(self) -> int: ... | ||
| # Mixin methods | ||
| @classmethod | ||
| def _from_iterable(cls, it: Iterable[Any]) -> AbstractSet[Any]: ... |
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This should return Self, not any AbstractSet, since the implementation is return cls(it) and other methods on MutableSet that rely on this are annotated to return Self.
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Updated to AbstractSet[_S] for type preservation, but can't use Self here - KeysView and ItemsView override this to return set, not Self. Using Self on the base would make those overrides invalid. Also MutableSet.__ior__/__iand__ etc. don't actually call _from_iterable, they mutate in-place directly.
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Actually, the type we want here is more like def [S](cls, Iterable[S]) -> Self & AbstractSet[S], which is not expressible at the moment.
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So -> AbstractSet[S] seems like the best approximation atm.
Signed-off-by: Emmanuel Ferdman <emmanuelferdman@gmail.com>
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The failing test is unrelated to this PR - Python 3.9 support is EOLd I guess. |
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Diff from mypy_primer, showing the effect of this PR on open source code: discord.py (https://github.com/Rapptz/discord.py)
- ...typeshed_to_test/stdlib/typing.pyi:1049: note: "update" of "TypedDict" defined here
+ ...typeshed_to_test/stdlib/typing.pyi:1055: note: "update" of "TypedDict" defined here
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Btw. in the original issue I posted a comment that this is probably a bad idea at the moment -- sorry I didn't mention it here earlier, I didn't realize this was a different account than the OP of #15298 |
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PR Summary
This PR adds
_from_iterabletoAbstractSet(returningAbstractSet[_S]to preserve element types while allowing subclasses that return set), and toKeysView/ItemsViewwhich override it to returnset[_S].MutableSetinherits fromAbstractSetso no separate definition is needed.Fixes #15298.