[stubtest] Check __slots__ better #13906
Description
Right now __slots__ has limited support in stubtest. For example, if we have a case like this:
# ex.py
class A: ...
class B:
__slots__ = ('a', 'b')
class C:
__slots__ = ('a',)
# ex.pyi
class A:
__slots__ = ()
class B:
__slots__ = ('a', 'c')
class C: ...stubtest will only report:
» stubtest ex
error: ex.B.a is not present in stub
Stub: in file /Users/sobolev/Desktop/mypy/ex.pyi
MISSING
Runtime:
<member 'a' of 'B' objects>
error: ex.B.b is not present in stub
Stub: in file /Users/sobolev/Desktop/mypy/ex.pyi
MISSING
Runtime:
<member 'b' of 'B' objects>
error: ex.C.a is not present in stub
Stub: in file /Users/sobolev/Desktop/mypy/ex.pyi
MISSING
Runtime:
<member 'a' of 'C' objects>
Which is not correct.
I propose to check __slots__ to be exact on runtime and stub objects.
This is useful for cases like:
class SomeStub: ... # defined in typeshed without actual `__slots__`
class A(SomeStub): # user's code
__slots__ = ("b",)
def __init__(self) -> None:
# All three will pass, because `SomeStub` parent has `__dict__`:
self.a = 1
self.b = 2
self._one = 1Compare it to the next case, where we have __slots__ defined:
class SomeStubWithSlots: # defined in typeshed
__slots__ = ("a",)
class A(SomeStubWithSlots): # user's code
__slots__ = ("b",)
def __init__(self) -> None:
self.a = 1
self.b = 2
self._one = 1 # E: Trying to assign name "_one" that is not in "__slots__" of type "ex.A"Refs python/typeshed#8832