Fix MutableMapping.update to require string keys #14099
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Currently with most type checkers you can do:
```python
d: dict[int, int] = {}
d.update(a=2)
```
The reason for that is that `update` merely requires `MutableMapping[_KT, _VT]`, whereas as soon as you are passing kwargs, you must have a str key type.
AlexWaygood
reviewed
May 19, 2025
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Could you also update the other methods that need to be kept in line with this method, as per this comment?
Lines 790 to 800 in ec8b6ec
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Oh no scratch that, none of those other methods take keyword arguments |
AlexWaygood
approved these changes
May 19, 2025
|
Diff from mypy_primer, showing the effect of this PR on open source code: aioredis (https://github.com/aio-libs/aioredis)
+ aioredis/client.py:146: note: def update(self, SupportsKeysAndGetItem[Any, Any], /) -> None
+ aioredis/client.py:146: note: @overload
+ aioredis/client.py:146: note: @overload
+ aioredis/client.py:146: note: def update(self, Iterable[tuple[Any, Any]], /) -> None
operator (https://github.com/canonical/operator)
+ ops/model.py:1960: note: def update(self, SupportsKeysAndGetItem[str, str], /) -> None
+ ops/model.py:1960: note: @overload
+ ops/model.py:1960: note: @overload
+ ops/model.py:1960: note: def update(self, Iterable[tuple[str, str]], /) -> None
ibis (https://github.com/ibis-project/ibis)
+ ibis/common/annotations.py:450: note: def update(self, SupportsKeysAndGetItem[Any, Any], /) -> None
+ ibis/common/annotations.py:450: note: def update(self, Iterable[tuple[Any, Any]], /) -> None
mongo-python-driver (https://github.com/mongodb/mongo-python-driver)
+ bson/son.py:146: error: Unused "type: ignore" comment [unused-ignore]
werkzeug (https://github.com/pallets/werkzeug)
+ src/werkzeug/datastructures/mixins.py:309: error: No overload variant of "update" of "MutableMapping" matches argument type "dict[str, V]" [call-overload]
+ src/werkzeug/datastructures/mixins.py:309: note: Possible overload variants:
+ src/werkzeug/datastructures/mixins.py:309: note: def update(self, SupportsKeysAndGetItem[K, V], /) -> None
+ src/werkzeug/datastructures/mixins.py:309: note: def update(self, Iterable[tuple[K, V]], /) -> None
discord.py (https://github.com/Rapptz/discord.py)
+ discord/client.py:733: note: def update(self, SupportsKeysAndGetItem[str, int | None], /) -> None
+ discord/client.py:733: note: def update(self, Iterable[tuple[str, int | None]], /) -> None
+ discord/client.py:759: note: def update(self, SupportsKeysAndGetItem[str, int | None], /) -> None
+ discord/client.py:759: note: def update(self, Iterable[tuple[str, int | None]], /) -> None
meson (https://github.com/mesonbuild/meson)
+ mesonbuild/options.py:1149:9: error: No overload variant of "update" of "MutableMapping" matches argument type "dict[str, UserBooleanOption | UserComboOption | UserFeatureOption | UserIntegerOption | UserStdOption | UserStringArrayOption | UserStringOption | UserUmaskOption]" [call-overload]
+ mesonbuild/options.py:1149:9: note: Possible overload variants:
+ mesonbuild/options.py:1149:9: note: def update(self, SupportsKeysAndGetItem[OptionKey, UserBooleanOption | UserComboOption | UserFeatureOption | UserIntegerOption | UserStdOption | UserStringArrayOption | UserStringOption | UserUmaskOption], /) -> None
+ mesonbuild/options.py:1149:9: note: def update(self, Iterable[tuple[OptionKey, UserBooleanOption | UserComboOption | UserFeatureOption | UserIntegerOption | UserStdOption | UserStringArrayOption | UserStringOption | UserUmaskOption]], /) -> None
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The only two new errors here are in |
srittau
reviewed
May 19, 2025
| @overload | ||
| def update(self, m: Iterable[tuple[_KT, _VT]], /, **kwargs: _VT) -> None: ... | ||
| def update(self: Mapping[str, _VT], m: SupportsKeysAndGetItem[_KT, _VT], /, **kwargs: _VT) -> None: ... |
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Should this be:
def update(self: Mapping[str, _VT], m: SupportsKeysAndGetItem[str, _VT], /, **kwargs: _VT) -> None: ...It's possible that _KT is constrained to str anyway via the self mapping, but I still think being explicit would be better (and easier on the type checkers).
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I think SupportsKeysAndGetItem is invariant in the first arg so that might cause trouble?
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#14100 for these cleanups.
| def update(self, **kwargs: _VT) -> None: ... | ||
| def update(self, m: Iterable[tuple[_KT, _VT]], /) -> None: ... | ||
| @overload | ||
| def update(self: Mapping[str, _VT], m: Iterable[tuple[_KT, _VT]], /, **kwargs: _VT) -> None: ... |
ndmitchell
added a commit
to ndmitchell/typeshed
that referenced
this pull request
May 19, 2025
We are confining `_KT` to `str`, so use that everywhere. Equivalent, but simpler.
srittau
pushed a commit
that referenced
this pull request
May 19, 2025
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Hello, The new annotation will not allow the following, I think. Shouldn't it be: ? |
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We should probably add more test cases for these basic collection types, especially for more complex cases like |
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That said, the following test case passes: def check_update_method() -> None:
d: dict[int, int] = {}
d.update({1:2}, a=3)
d.update([(1, 2)], a=3)But we need the explicit annotation for the dict. |
srittau
added a commit
to srittau/typeshed
that referenced
this pull request
May 20, 2025
|
In fact, while the mypy tests pass, the pyright tests don't: #14104 |
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Currently with most type checkers you can do:
The reason for that is that
updatemerely requiresMutableMapping[_KT, _VT], whereas as soon as you are passing kwargs, you must have a str key type.