[issue43764] Turning off generation of __match_args__ for dataclasses

[Brandt Bucher]

Brandt Bucher <brandtbucher at gmail.com> added the comment:

> init=False is used to make sure there's no __init__ defined, because there's a difference between a class with an __init__ and one without. If there was a difference between __match_args__ being not present and __match_args__=(), then I'd support a matchargs=False argument.

Ah, I see now how this might possibly be useful.

If you want to inherit a parent's __match_args__ in a dataclass, it currently must be as spelled something like:

@dataclass
class Child(Parent):
    __match_args__ = Parent.__match_args__
    ...

It's even uglier when you're unsure if Parent defines __match_args__ at all, or if multiple-inheritance is involved:

@dataclass
class Child(Parent, Mixin):
    __match_args__ = ()
    ...

del Child.__match_args__

I'm not sure how likely it is that code out in the wild may need to look like this. As I understand it, though, the fact that dataclasses allow for "normal" inheritance is one of their big selling-points. So it could be a valid reason to include this option.

If it seems like the above code might become reasonably common, I agree that the proposed solution is much cleaner:

@dataclass(match_args=False)
class Child(Parent):
    ...

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<https://bugs.python.org/issue43764>
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