gh-74690: typing._ProtocolMeta.__instancecheck__: Exit early for prot…

…ocols that only have callable members
python · AlexWaygood · Apr 6, 2023 · Apr 6, 2023 · 8cc20e60e14e1d5f634e20b692a0064776bd232a
commit 8cc20e60e14e1d5f634e20b692a0064776bd232a
@@ -2577,6 +2577,18 @@ def meth(x): ...
        class PG(Protocol[T]):
            def meth(x): ...

+        @runtime_checkable
+        class WeirdProto(Protocol):
+            meth = str.maketrans
+
+        class CustomCallable:
+            def __call__(self, *args, **kwargs):
+                pass
+
+        @runtime_checkable
+        class WeirderProto(Protocol):
+            meth = CustomCallable()
+
        class BadP(Protocol):
            def meth(x): ...

@@ -2588,6 +2600,8 @@ def meth(x): ...

        self.assertIsInstance(C(), P)
        self.assertIsInstance(C(), PG)
+        self.assertIsInstance(C(), WeirdProto)
+        self.assertIsInstance(C(), WeirderProto)
        with self.assertRaises(TypeError):
            isinstance(C(), PG[T])
        with self.assertRaises(TypeError):

@@ -2032,7 +2032,11 @@ def __instancecheck__(cls, instance):
        if super().__instancecheck__(instance):
            return True

-        if is_protocol_cls:
+        # Skip the below loop for protocols where `cls.__callable_proto_members_only__ == True`.
+        # For these protocols, this just duplicates checks that have already been done
+        # in the `_proto_hook` function,
+        # which is called as part of the super().__instancecheck__ method above.
+        if is_protocol_cls and not cls.__callable_proto_members_only__:
            getattr_static = _lazy_load_getattr_static()
            for attr in cls.__protocol_attrs__:
                try: