Support validate call decorator for methods in classes with __slots__

pydantic/_internal/_validate_call.py

@@ -108,6 +108,11 @@ def __get__(self, obj: Any, objtype: type[Any] | None = None) -> ValidateCallWra
 
         bound_function = self.raw_function.__get__(obj, objtype)
         result = self.__class__(bound_function, self._config, self._validate_return)
+
+        # skip binding to instance when obj or objtype has __slots__ attribute
+        if hasattr(obj, '__slots__') or hasattr(objtype, '__slots__'):
+            return result
+
         if self._name is not None:
             if obj is not None:
                 object.__setattr__(obj, self._name, result)
@@ -120,3 +125,6 @@ def __set_name__(self, owner: Any, name: str) -> None:
 
     def __repr__(self) -> str:
         return f'ValidateCallWrapper({self.raw_function})'
+
+    def __eq__(self, other):
+        return self.raw_function == other.raw_function

tests/test_validate_call.py

@@ -725,3 +725,32 @@ async def foo(a: Any) -> int:
             'input': 'x',
         }
     ]
+
+
+def test_validate_call_with_slots() -> None:
+    class ClassWithSlots:
+        __slots__ = {}
+
+        @validate_call(validate_return=True)
+        def some_instance_method(self, x: str) -> str:
+            return x
+
+        @classmethod
+        @validate_call(validate_return=True)
+        def some_class_method(cls, x: str) -> str:
+            return x
+
+        @staticmethod
+        @validate_call(validate_return=True)
+        def some_static_method(x: str) -> str:
+            return x
+
+    c = ClassWithSlots()
+    assert c.some_instance_method(x='potato') == 'potato'
+    assert c.some_class_method(x='pepper') == 'pepper'
+    assert c.some_static_method(x='onion') == 'onion'
+
+    # verify that equality still holds for instance methods
+    assert c.some_instance_method == c.some_instance_method
+    assert c.some_class_method == c.some_class_method
+    assert c.some_static_method == c.some_static_method