Allow register_kernel() to take dispatcher name as input (#7796)

test/test_transforms_v2_refactored.py

@@ -2181,3 +2181,36 @@ class TestShapeGetters:
 
         with pytest.raises(TypeError, match=re.escape(str(type(input)))):
             dispatcher(input)
+
+
+class TestRegisterKernel:
+    @pytest.mark.parametrize("dispatcher", (F.resize, "resize"))
+    def test_register_kernel(self, dispatcher):
+        class CustomDatapoint(datapoints.Datapoint):
+            pass
+
+        kernel_was_called = False
+
+        @F.register_kernel(dispatcher, CustomDatapoint)
+        def new_resize(dp, *args, **kwargs):
+            nonlocal kernel_was_called
+            kernel_was_called = True
+            return dp
+
+        t = transforms.Resize(size=(224, 224), antialias=True)
+
+        my_dp = CustomDatapoint(torch.rand(3, 10, 10))
+        out = t(my_dp)
+        assert out is my_dp
+        assert kernel_was_called
+
+        # Sanity check to make sure we didn't override the kernel of other types
+        t(torch.rand(3, 10, 10)).shape == (3, 224, 224)
+        t(datapoints.Image(torch.rand(3, 10, 10))).shape == (3, 224, 224)
+
+    def test_bad_disaptcher_name(self):
+        class CustomDatapoint(datapoints.Datapoint):
+            pass
+
+        with pytest.raises(ValueError, match="Could not find dispatcher with name"):
+            F.register_kernel("bad_name", CustomDatapoint)

torchvision/transforms/v2/functional/_utils.py

@@ -37,7 +37,18 @@ def _register_kernel_internal(dispatcher, datapoint_cls, *, datapoint_wrapper=Tr
     return decorator
 
 
+def _name_to_dispatcher(name):
+    import torchvision.transforms.v2.functional  # noqa
+
+    try:
+        return getattr(torchvision.transforms.v2.functional, name)
+    except AttributeError:
+        raise ValueError(f"Could not find dispatcher with name '{name}'.") from None
+
+
 def register_kernel(dispatcher, datapoint_cls):
+    if isinstance(dispatcher, str):
+        dispatcher = _name_to_dispatcher(name=dispatcher)
     return _register_kernel_internal(dispatcher, datapoint_cls, datapoint_wrapper=False)