make convert_format_bounding_box a hybrid kernel dispatcher

test/prototype_common_utils.py

@@ -237,6 +237,13 @@ class TensorLoader:
     def load(self, device):
         return self.fn(self.shape, self.dtype, device)
 
+    def unwrap(self):
+        return TensorLoader(
+            fn=lambda shape, dtype, device: self.fn(shape, dtype, device).as_subclass(torch.Tensor),
+            shape=self.shape,
+            dtype=self.dtype,
+        )
+
 
 @dataclasses.dataclass
 class ImageLoader(TensorLoader):

test/prototype_transforms_kernel_infos.py

@@ -26,7 +26,6 @@
     make_video_loader,
     make_video_loaders,
     mark_framework_limitation,
-    TensorLoader,
     TestMark,
 )
 from torch.utils._pytree import tree_map
@@ -660,7 +659,8 @@ def sample_inputs_affine_video():
 def sample_inputs_convert_format_bounding_box():
     formats = list(datapoints.BoundingBoxFormat)
     for bounding_box_loader, new_format in itertools.product(make_bounding_box_loaders(formats=formats), formats):
-        yield ArgsKwargs(bounding_box_loader, old_format=bounding_box_loader.format, new_format=new_format)
+        yield ArgsKwargs(bounding_box_loader, new_format=new_format)
+        yield ArgsKwargs(bounding_box_loader.unwrap(), old_format=bounding_box_loader.format, new_format=new_format)
 
 
 def reference_convert_format_bounding_box(bounding_box, old_format, new_format):
@@ -671,8 +671,14 @@ def reference_convert_format_bounding_box(bounding_box, old_format, new_format):
 
 def reference_inputs_convert_format_bounding_box():
     for args_kwargs in sample_inputs_convert_format_bounding_box():
-        if len(args_kwargs.args[0].shape) == 2:
-            yield args_kwargs
+        if len(args_kwargs.args[0].shape) != 2:
+            continue
+
+        (loader, *other_args), kwargs = args_kwargs
+        if isinstance(loader, BoundingBoxLoader):
+            kwargs["old_format"] = loader.format
+            loader = loader.unwrap()
+        yield ArgsKwargs(loader, *other_args, **kwargs)
 
 
 KERNEL_INFOS.append(
@@ -682,6 +688,18 @@ def reference_inputs_convert_format_bounding_box():
         reference_fn=reference_convert_format_bounding_box,
         reference_inputs_fn=reference_inputs_convert_format_bounding_box,
         logs_usage=True,
+        test_marks=[
+            mark_framework_limitation(
+                ("TestKernels", "test_scripted_vs_eager"),
+                reason=(
+                    "The function is hybrid kernel / dispatcher. JIT unwraps a `datapoints.BoundingBox` into a "
+                    "`torch.Tensor`, but then the kernel (rightfully) complains that neither `format` nor "
+                    "`spatial_size` was passed"
+                ),
+                condition=lambda arg_kwargs: isinstance(arg_kwargs.args[0], BoundingBoxLoader)
+                and arg_kwargs.kwargs.get("old_format") is None,
+            )
+        ],
     ),
 )
 
@@ -2014,13 +2032,10 @@ def sample_inputs_clamp_bounding_box():
     for bounding_box_loader in make_bounding_box_loaders():
         yield ArgsKwargs(bounding_box_loader)
 
-        simple_tensor_loader = TensorLoader(
-            fn=lambda shape, dtype, device: bounding_box_loader.fn(shape, dtype, device).as_subclass(torch.Tensor),
-            shape=bounding_box_loader.shape,
-            dtype=bounding_box_loader.dtype,
-        )
         yield ArgsKwargs(
-            simple_tensor_loader, format=bounding_box_loader.format, spatial_size=bounding_box_loader.spatial_size
+            bounding_box_loader.unwrap(),
+            format=bounding_box_loader.format,
+            spatial_size=bounding_box_loader.spatial_size,
         )
 
 

test/test_prototype_transforms_functional.py

@@ -572,7 +572,7 @@ class TestClampBoundingBox:
     def test_simple_tensor_insufficient_metadata(self, metadata):
         simple_tensor = next(make_bounding_boxes()).as_subclass(torch.Tensor)
 
-        with pytest.raises(ValueError, match="simple tensor"):
+        with pytest.raises(ValueError, match=re.escape("`format` and `spatial_size` has to be passed")):
             F.clamp_bounding_box(simple_tensor, **metadata)
 
     @pytest.mark.parametrize(
@@ -586,10 +586,37 @@ def test_simple_tensor_insufficient_metadata(self, metadata):
     def test_datapoint_explicit_metadata(self, metadata):
         datapoint = next(make_bounding_boxes())
 
-        with pytest.raises(ValueError, match="bounding box datapoint"):
+        with pytest.raises(ValueError, match=re.escape("`format` and `spatial_size` must not be passed")):
             F.clamp_bounding_box(datapoint, **metadata)
 
 
+class TestConvertFormatBoundingBox:
+    @pytest.mark.parametrize(
+        ("inpt", "old_format"),
+        [
+            (next(make_bounding_boxes()), None),
+            (next(make_bounding_boxes()).as_subclass(torch.Tensor), datapoints.BoundingBoxFormat.XYXY),
+        ],
+    )
+    def test_missing_new_format(self, inpt, old_format):
+        with pytest.raises(TypeError, match=re.escape("missing 1 required argument: 'new_format'")):
+            F.convert_format_bounding_box(inpt, old_format)
+
+    def test_simple_tensor_insufficient_metadata(self):
+        simple_tensor = next(make_bounding_boxes()).as_subclass(torch.Tensor)
+
+        with pytest.raises(ValueError, match=re.escape("`old_format` has to be passed")):
+            F.convert_format_bounding_box(simple_tensor, new_format=datapoints.BoundingBoxFormat.CXCYWH)
+
+    def test_datapoint_explicit_metadata(self):
+        datapoint = next(make_bounding_boxes())
+
+        with pytest.raises(ValueError, match=re.escape("`old_format` must not be passed")):
+            F.convert_format_bounding_box(
+                datapoint, old_format=datapoint.format, new_format=datapoints.BoundingBoxFormat.CXCYWH
+            )
+
+
 # TODO: All correctness checks below this line should be ported to be references on a `KernelInfo` in
 #  `prototype_transforms_kernel_infos.py`
 

torchvision/prototype/transforms/_meta.py

@@ -19,12 +19,7 @@ def __init__(self, format: Union[str, datapoints.BoundingBoxFormat]) -> None:
         self.format = format
 
     def _transform(self, inpt: datapoints.BoundingBox, params: Dict[str, Any]) -> datapoints.BoundingBox:
-        # We need to unwrap here to avoid unnecessary `__torch_function__` calls,
-        # since `convert_format_bounding_box` does not have a dispatcher function that would do that for us
-        output = F.convert_format_bounding_box(
-            inpt.as_subclass(torch.Tensor), old_format=inpt.format, new_format=params["format"]
-        )
-        return datapoints.BoundingBox.wrap_like(inpt, output, format=params["format"])
+        return F.convert_format_bounding_box(inpt, new_format=self.format)  # type: ignore[return-value]
 
 
 class ConvertDtype(Transform):

torchvision/prototype/transforms/functional/_meta.py

@@ -186,11 +186,9 @@ def _xyxy_to_cxcywh(xyxy: torch.Tensor, inplace: bool) -> torch.Tensor:
     return xyxy
 
 
-def convert_format_bounding_box(
+def _convert_format_bounding_box(
     bounding_box: torch.Tensor, old_format: BoundingBoxFormat, new_format: BoundingBoxFormat, inplace: bool = False
 ) -> torch.Tensor:
-    if not torch.jit.is_scripting():
-        _log_api_usage_once(convert_format_bounding_box)
 
     if new_format == old_format:
         return bounding_box
@@ -209,6 +207,37 @@ def convert_format_bounding_box(
     return bounding_box
 
 
+def convert_format_bounding_box(
+    inpt: datapoints.InputTypeJIT,
+    old_format: Optional[BoundingBoxFormat] = None,
+    new_format: Optional[BoundingBoxFormat] = None,
+    inplace: bool = False,
+) -> datapoints.InputTypeJIT:
+    # This being a kernel / dispatcher hybrid, we need an option to pass `old_format` explicitly for simple tensor
+    # inputs as well as extract it from `datapoints.BoundingBox` inputs. However, putting a default value on
+    # `old_format` means we also need to put one on `new_format` to have syntactically correct Python. Here we mimic the
+    # default error that would be thrown if `new_format` had no default value.
+    if new_format is None:
+        raise TypeError("convert_format_bounding_box() missing 1 required argument: 'new_format'")
+
+    if not torch.jit.is_scripting():
+        _log_api_usage_once(convert_format_bounding_box)
+
+    if torch.jit.is_scripting() or is_simple_tensor(inpt):
+        if old_format is None:
+            raise ValueError("For simple tensor inputs, `old_format` has to be passed.")
+        return _convert_format_bounding_box(inpt, old_format=old_format, new_format=new_format, inplace=inplace)
+    elif isinstance(inpt, datapoints.BoundingBox):
+        if old_format is not None:
+            raise ValueError("For bounding box datapoint inputs, `old_format` must not be passed.")
+        output = _convert_format_bounding_box(inpt, old_format=inpt.format, new_format=new_format, inplace=inplace)
+        return datapoints.BoundingBox.wrap_like(inpt, output)
+    else:
+        raise TypeError(
+            f"Input can either be a plain tensor or a bounding box datapoint, but got {type(inpt)} instead."
+        )
+
+
 def _clamp_bounding_box(
     bounding_box: torch.Tensor, format: BoundingBoxFormat, spatial_size: Tuple[int, int]
 ) -> torch.Tensor: