TypeError when calling super() in decorated method

[kdebrab]

Following code:

import attrs


def decorated(method):
    def wrapped(self, *args, **kwargs):
        return method(self, *args, **kwargs)

    return wrapped


@attrs.define()
class A:
    def f(self):
        pass


@attrs.define()
class B(A):
    @decorated
    def f(self):
        super().f()


B().f()

raises following error

TypeError: super(type, obj): obj must be an instance or subtype of type

If I use super(B, self), everything works just fine.

[hynek]

This problem is related to cell rewriting for slotted classes. Put simply we have to cheat a bit to make them work by rewriting method contents.

You get the same behavior with dataclasses:

@dataclasses.dataclass(slots=True)
@attrs.define
class C:
    @decorated
    def f(self):
        super().f()

TypeError: super(type, obj): obj must be an instance or subtype of type

Short fixes:

• don't use super that way
• disable slots (@attrs.define(slots=False))

Long-term fixes:

• open a bug on CPython for the dataclasses case and we'll steal it from them
• convince @Tinche to fix it for attrs right away ;)

I'm a bit dubious if it's actually possible to fix tho. :-/ Maybe, if functools.wraps is used and we follow the __wrapped__ attributes?

[kdebrab]

Thanks for the quick response! I'll use super(B, self) for now.