fix tests by fixing the protocol member listing

tests/test_protocols.py

@@ -1,3 +1,5 @@
+import functools
+import inspect
 from types import ModuleType
 from typing import Protocol, cast
 
@@ -23,6 +25,7 @@ def _is_runtime_protocol(cls: type) -> bool:
     return _is_protocol(cls) and getattr(cls, '_is_runtime_protocol', False)
 
 
+@functools.cache
 def _get_protocol_members(cls: type) -> frozenset[str]:
     """
     A variant of `typing_extensions.get_protocol_members()` that doesn't
@@ -33,7 +36,9 @@ def _get_protocol_members(cls: type) -> frozenset[str]:
     assert _is_protocol(cls)
 
     module = cls.__module__
-    members = cls.__annotations__.keys() | {
+    annotations = cls.__annotations__
+
+    members = annotations.keys() | {
         name for name, v in vars(cls).items()
         if (
             callable(v) and (
@@ -63,19 +68,29 @@ def _get_protocol_members(cls: type) -> frozenset[str]:
             and v.fget.__module__ == module
         )
     }
-    if not members:
-        # no idea why this happens, probably something to do with inheritance..
-        # ... investigating this can of worms any further will physically harm
-        # my very soul, or at least, what's left of it at this point.
-        # ...
-        # anyway, this hack here is plagiarized from the (often incorrect)
-        # `typing_extensions.get_protocol_members`.
-        # Maybe the `typing.get_protocol_members` that's coming in 3.13 will
-        # won't be as broken. I have little hope though...
-        members = cast(
-            set[str],
-            getattr(cls, '__protocol_attrs__', None) or set(),
-        )
+
+    # this hack here is plagiarized from the (often incorrect)
+    # `typing_extensions.get_protocol_members`.
+    # Maybe the `typing.get_protocol_member`s` that's coming in 3.13 will
+    # won't be as broken. I have little hope though...
+    members |= cast(
+        set[str],
+        getattr(cls, '__protocol_attrs__', None) or set(),
+    )
+
+    # sometimes __protocol_attrs__ hallicunates some non-existing dunders.
+    # the `getattr_static` avoids potential descriptor magic
+    members = {
+        member for member in members
+        if member in annotations
+        or inspect.getattr_static(cls, member) is not None
+        # or getattr(cls, member) is not None
+    }
+
+    # also include any of the parents
+    for supercls in cls.mro()[1:]:
+        if _is_protocol(supercls):
+            members |= _get_protocol_members(supercls)
 
     return frozenset(members)