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super(cls, self) seemingly has no attribute it actually has #13497
Description
Bug Report
I wanted to have a quick way of concatenating results of several mixin-like implementations of similar algorithms. Below is a MWE of what I wanted to implement
To Reproduce
MWE:
from abc import abstractmethod
from typing import List
class A:
@abstractmethod
def foo(self, arg: str) -> str:
raise NotImplementedError
def bar(self, arg: str) -> List[str]:
ret: List[str] = []
for c in self.__class__.mro():
c_super = super(c, self)
if hasattr(c_super, 'foo'):
try:
ret.append(c_super.foo(arg))
except NotImplementedError:
pass
try:
ret.append(self.foo(arg))
except NotImplementedError:
pass
return ret
class B(A):
def foo(self, arg: str) -> str:
return f'B.foo[{arg}]'
class C(B):
def foo(self, arg: str) -> str:
return f'C.foo[{arg}]'
hello = 'hello'
c = C()
print(f'foo: {c.foo(hello)}')
print(f'bar: {c.bar(hello)}')
Expected Behavior
No warning
Actual Behavior
mypy recognizes
mwe.py:15: error: "super" has no attribute "foo"
even though it is executed after if hasattr(...)
What's even more strange, if you construct a similar pattern but with the method foo with no arguments, then the same example just passes mypy checks.
Your Environment
- Mypy version used: 0.812, 0.900, 0.971
- Python version used: 3.8
- Operating system and version: Ubuntu 22.04
Activity
AlexWaygood commentedon Aug 24, 2022
Mypy has to implement quite a lot of special-casing in order to support
super()at all. I think it's pretty unlikely that mypy is going to add the necessary complexity in order to support highly dynamic (and quite unusual) uses ofsuper()like this, unfortunately.n1ngu commentedon Sep 23, 2022
This
already fails.
erictraut commentedon Aug 13, 2023
This appears to have been fixed in mypy 0.990. It does not repro since that release.
AlexWaygood commentedon Aug 13, 2023
Wow, I never expected to see this one fixed
hauntsaninja commentedon Aug 13, 2023
Fixed by #13544. mypy will now get out of your way because of the hasattr