False positive arguments-differ when converting @staticmethod to/from bound method

[tl24]

Bug description

When changing a base class static method with the @staticmethod decorator to a bound method using self, the arguments-differ warning is being generated. I don't believe this should be the case as calling the child class method using self works correctly.

# pylint: disable=too-few-public-methods
class BaseClass:
    @staticmethod
    def handlers():
        return {}


class ChildClass(BaseClass):
    def handlers(self):
        return {"foo": self.foo_handler}

    def foo_handler(self):
        pass

Command used

pylint tests/args_differ.py

Pylint output

************* Module tests.args_differ
tests/args_differ.py:9:4: W0221: Number of parameters was 0 in 'BaseClass.handlers' and is now 1 in overridden 'ChildClass.handlers' method (arguments-differ)

Expected behavior

No warnings generated

Pylint version

pylint 2.13.2
astroid 2.11.2
Python 3.9.9 (main, Nov 15 2021, 18:05:17) 
[GCC 5.4.0 20160609]

OS / Environment

Ubuntu 20.04

[cdce8p]

I don't believe this should be the case as calling the child class method using self works correctly.

True, but the other way doesn't work. You can't replace a call to Base.handlers() with Child.handlers(). If you know that you'll be calling the method with self.xxx anyway, it probably shouldn't be a static one.

Btw. both pyright and mypy also emits an error here.

# pyright
Method "handlers" overrides class "BaseClass" in an incompatible manner
  Positional parameter count mismatch; base method has 0, but override has 1

# mypy
error: Signature of "handlers" incompatible with supertype "BaseClass"  [override]
note:      Superclass:
note:          @staticmethod
note:          def handlers() -> Dict[Any, Any]
note:      Subclass:
note:          def handlers(self) -> Dict[Any, Any]

[tl24]

Ok, so is the guidance here just to disable the "no-self-use" warning in the base class if the intent is for it to be overridden in the child class and possibly needing the self reference?

[cdce8p]

Ok, so is the guidance here just to disable the "no-self-use" warning in the base class if the intent is for it to be overridden in the child class and possibly needing the self reference?

Exactly! IMO the no-self-use checker encourages the wrong behavior here. Just because the base implementation of a method doesn't use self, doesn't mean it should be a static method. I opened an issue for that a while ago

• Move no-self-use to optional checker #5502