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sobolevn opened this issue Nov 6, 2021 · 2 comments · Fixed by #11483
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dataclasses plugins does not respect slots=True argument #11482

sobolevn opened this issue Nov 6, 2021 · 2 comments · Fixed by #11483
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bug mypy got something wrong

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sobolevn commented Nov 6, 2021

Since 3.10 now has slots=True argument for @dataclass decorator, we need to support it, since #10864 is merged.

Failing case right now:

from dataclasses import dataclass

@dataclass(slots=True)
class Some:
    x: int

    def __init__(self, x: int) -> None:
        self.x = x  # ok
        self.y = 1  # should be an error, but `mypy` is ok
        # Traceback (most recent call last):
        #   ...
        # AttributeError: 'Some' object has no attribute 'y'

Compare it with regular class, which works fine:

class Some:
    __slots__ = ('x',)

    def __init__(self, x: int) -> None:
        self.x = x  # ok
        self.y = 1  # E: Trying to assign name "y" that is not in "__slots__" of type "ex.Some"

Docs: https://docs.python.org/3/library/dataclasses.html#dataclasses.dataclass

Refs #11463
@sobolevn sobolevn added the bug mypy got something wrong label Nov 6, 2021
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sobolevn commented Nov 6, 2021

I cannot assign myself, but consider me assigned 🙂

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sobolevn commented Nov 6, 2021

We also need to check for slots confict:

from dataclasses import dataclass

@dataclass(slots=True)
class Some:
    __slots__ = ('x',)
    x: int
# Traceback (most recent call last):
#   ...
# TypeError: Some already specifies __slots__

@sobolevn sobolevn mentioned this issue Nov 6, 2021
Merged
hauntsaninja pushed a commit that referenced this issue Nov 7, 2021
@sobolevn
Adds slots=True support for @dataclass (#11483)
5bba0f3 
Closes #11482
@sobolevn sobolevn mentioned this issue Nov 8, 2021
Merged
JukkaL pushed a commit that referenced this issue Nov 9, 2021
@sobolevn
Adds slots=True support for @attr.s, refs #11487 (#11489)
b1c438d 
Closes #11487
Refs #11482
Refs #10801
@parafoxia parafoxia mentioned this issue Dec 3, 2021
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tushar-deepsource pushed a commit to DeepSourceCorp/mypy that referenced this issue Jan 20, 2022
@sobolevn @tushar-deepsource
Adds slots=True support for @dataclass (python#11483)
61ecaf8 
Closes python#11482
tushar-deepsource pushed a commit to DeepSourceCorp/mypy that referenced this issue Jan 20, 2022
@sobolevn @tushar-deepsource
Adds slots=True support for @attr.s, refs python#11487 (python#11489
2a1fdb7 
)

Closes python#11487
Refs python#11482
Refs python#10801
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Adds slots=True support for @dataclass
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