false positive: abstract-method for typing.Protocol inheritance with abc.abstractmethod

[huwcbjones]

Bug description

It appears that if:

1. you have two protocols that have abstract methods
2. create a third protocol that inherits from both of them and does not implement the abstractmethods (because a protocol is not a concrete implementation)

pylint thinks that the abstract methods from the parent classes are not implemented.
From reading PEP 544 I believe this is acceptable and therefore shouldn't be a false positive.

"""FooBar Protocol"""
# pylint: disable=too-few-public-methods,disallowed-name
from abc import abstractmethod
from typing import Protocol, Literal


class FooProtocol(Protocol):
    """Foo Protocol"""

    @abstractmethod
    def foo(self) -> Literal["foo"]:  # pylint: disable=invalid-name
        """foo method"""


class BarProtocol(Protocol):
    """Bar Protocol"""
    @abstractmethod
    def bar(self) -> Literal["bar"]:
        """bar method"""


class FooBarProtocol(FooProtocol, BarProtocol, Protocol):
    """FooBar Protocol"""


class FooBar(FooBarProtocol):
    """FooBar object"""

    def bar(self) -> Literal["bar"]:
        return "bar"

    def foo(self) -> Literal["foo"]:
        return "foo"

Configuration

No response

Command used

pylint mwe.py

Pylint output

************* Module mwe
mwe.py:22:0: W0223: Method 'bar' is abstract in class 'BarProtocol' but is not overridden (abstract-method)
mwe.py:22:0: W0223: Method 'foo' is abstract in class 'FooProtocol' but is not overridden (abstract-method)

Expected behavior

No warnings

Pylint version

pylint 2.13.9
astroid 2.11.7
Python 3.9.1 (default, Mar 15 2021, 18:22:18)
[Clang 12.0.0 (clang-1200.0.32.27)]

pylint3 2.2.2
astroid 2.1.0
Python 3.7.3 (default, Jun  2 2021, 09:53:27)
[GCC 8.3.0]

OS / Environment

macOS 11.6.1

~Debian Buster

Additional dependencies

No response

[clavedeluna]

Trying to triage this but reading PEP544 I'm more confused than ever. @huwcbjones could you maybe specify which part of the PEP suggests to you this is a FP? In reading it I'm getting the opposite in some examples.

[DanielNoord]

We should simply never raise abstract-method if it comes from a Protocol. That should be the fix here 😄

[huwcbjones]

@clavedeluna see the section about Merging and extending protocols

I agree with @DanielNoord