dataclass tries to generate `__init__()` even though the class already defines one

Bug report

Bug description:

When running this code:

from dataclasses import dataclass

@dataclass
class A:
    a: int = 1

@dataclass
class B(A):
    b: int
    def __init__(self, *args, **kwargs): ...

I got TypeError: non-default argument 'b' follows default argument

However, if I set init=False for the second dataclass, like this:

from dataclasses import dataclass

@dataclass
class A:
    a: int = 1

@dataclass(init=False)
class B(A):
    b: int
    def __init__(self, *args, **kwargs): ...

There error disappeared.

I think the error comes from the process where dataclass tries to generate the default __init__() and checks the fields. But, if I understand correctly, this should not happen when the class already defines its own __init__().

Although I'm not sure whether the behavior should be defined as a bug, I do find the results inconsistant with the docs, which says

If the class already defines __init__(), this parameter (init) is ignored.

so, intuitively, adding init=False shouldn't have changed the result.

CPython versions tested on:

3.12, 3.13, 3.14

Operating systems tested on:

Windows

Linked PRs

• gh-151184
• gh-153601

Reproduisez les deux exemples avec dataclasses.dataclass, puis examinez le travail associé dans gh-151184 et gh-153601 avant de décider si le comportement ou la documentation est incohérent. Le travail est terminé lorsque la gestion prévue d’un init existant est établie et couverte par des éléments de régression appropriés.