Fix issue not allowing validate_call decorator to be dynamically assigned to a class method.

pydantic/_internal/_validate_call.py

@@ -118,6 +118,11 @@ def __call__(self, *args: Any, **kwargs: Any) -> Any:
     def __get__(self, obj: Any, objtype: type[Any] | None = None) -> ValidateCallWrapper:
         """Bind the raw function and return another ValidateCallWrapper wrapping that."""
         if obj is None:
+            # It's possible this wrapper is dynamically applied to a class attribute not allowing
+            # name to be populated by __set_name__. In this case, we'll manually acquire the name
+            # from the function reference.
+            if self._name is None:
+                self._name = self.raw_function.__name__
             try:
                 # Handle the case where a method is accessed as a class attribute
                 return objtype.__getattribute__(objtype, self._name)  # type: ignore

tests/test_validate_call.py

@@ -684,6 +684,18 @@ def test(self, x: int):
     assert bar.test('1') == (bar, 1)
 
 
+def test_dynamic_method_decoration():
+    class Foo:
+        def bar(self, value: str) -> str:
+            return f'bar-{value}'
+
+    Foo.bar = validate_call(Foo.bar)
+    assert Foo.bar
+
+    foo = Foo()
+    assert foo.bar('test') == 'bar-test'
+
+
 @pytest.mark.parametrize('decorator', [staticmethod, classmethod])
 def test_classmethod_order_error(decorator):
     name = decorator.__name__