dataclasses: implicitly defined __dict__ and __weakref__ slots of inherited classes are ignored.

[avboag]

Bug report

The weakref slot is redefined when inherited from a class which didn't specify slots at all (and thus has a dict and weakref slots).

from dataclasses import dataclass

class A:
    pass

@dataclass(slots=True, weakref_slot=True)
class B(A):
    pass

gives the following error:

TypeError: __weakref__ slot disallowed: either we already got one, or __itemsize__ != 0

Linked PRs

• Fixed _get_slots bug, according to issue gh-105866 #105870
• [3.12] gh-105866: fix dataclass with slots=True, weakref_slot=True (GH-105870) #116978
• [3.11] gh-105866: fix dataclass with slots=True, weakref_slot=True (GH-105870) #116979

[avboag]

The fix seems to be simple, _get_slots should yield from ('dict', 'weakref') when no slots are defined.

[avboag]

ping

[ambv]

All maint branches merged. Thanks!