Description

jbaudisch

opened on Feb 20, 2023

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We recently discovered the following error in our project:
TypeError: descriptor '__weakref__' for 'XYZ' objects doesn't apply to a 'XYZ' object

XYZ in our case is a dataclass which uses slots (added v3.10) and weakref_slot (added v3.11) parameters.

We further investigated the error and have come to the following example to reproduce it:

import dataclasses
import weakref


@dataclasses.dataclass(slots=True, weakref_slot=True)
class EntityAsDataclass:
    x: int = 10


class Entity:
    __slots__ = ("x", "__weakref__")

    def __init__(self, x: int = 10) -> None:
        self.x = x


e1 = Entity()
e1_ref = weakref.ref(e1)

e2 = EntityAsDataclass()
e2_ref = weakref.ref(e2)


assert e1.__weakref__ is e1_ref  # works
assert e2.__weakref__ is e2_ref  # fails with "TypeError: descriptor '__weakref__' for 'EntityAsDataclass' objects doesn't apply to a 'EntityAsDataclass' object"

I don't know if this is intended, but we expect EntityAsDataclass and Entity to have the same behavior here.

Thanks!

Linked PRs

• gh-102069: Fix __weakref__ descriptor generation for custom dataclasses #102075
• [3.11] gh-102069: Fix __weakref__ descriptor generation for custom dataclasses (GH-102075) #102662

Activity

1. AlexWaygood

   added

   stdlibStandard Library Python modules in the Lib/ directoryStandard Library Python modules in the Lib/ directory

   3.11only security fixesonly security fixes

   on Feb 20, 2023
2. sobolevn

   self-assigned this

   on Feb 20, 2023
3. sobolevn commented on Feb 20, 2023

   

   sobolevn

   on Feb 20, 2023

   Member

   More actions

   I know how to fix it! Thanks for the report! PR is on its way.

   Reacted by Justin Baudisch and Carl Meyer
4. sobolevn

   added a commit that references this issue on Feb 20, 2023

   pythongh-102069: Fix `__weakref__` descriptor generation for custom d…

   a388296
5. sobolevn

   added

   type-bugAn unexpected behavior, bug, or errorAn unexpected behavior, bug, or error

   on Feb 21, 2023
6. carljm

   added a commit that references this issue on Mar 13, 2023

   gh-102069: Fix `__weakref__` descriptor generation for custom datacla…

   d97757f
7. miss-islington

   added a commit that references this issue on Mar 13, 2023

   pythongh-102069: Fix `__weakref__` descriptor generation for custom d…

   ad32998
8. carljm

   added a commit that references this issue on Mar 13, 2023

   [3.11] gh-102069: Fix `__weakref__` descriptor generation for custom …

   b0e221c
9. carljm

   closed this as completedon Mar 13, 2023
10. carljm

    added a commit that references this issue on Mar 14, 2023

    Merge branch 'main' into inlinecomp2

    6c5f269
11. Fidget-Spinner

    added a commit that references this issue on Mar 27, 2023

    pythongh-102069: Fix `__weakref__` descriptor generation for custom d…

    98b34ba
12. warsaw

    added a commit that references this issue on Apr 11, 2023

    pythongh-102069: Fix `__weakref__` descriptor generation for custom d…

    29f35a9

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