DM-45536: address edge cases in task mocking system

doc/changes/DM-45536.bugfix.md

@@ -0,0 +1 @@
+Fix support for task metadata as inputs in the `PipelineTask` mocking system.

python/lsst/pipe/base/connections.py

@@ -493,15 +493,8 @@
 
     datasetRef: DatasetRef
 
-    @property
-    def datasetType(self) -> DatasetType:
-        """The dataset type for this dataset."""
-        return self.datasetRef.datasetType
-
-    @property
-    def dataId(self) -> DataCoordinate:
-        """The data ID for this dataset."""
-        return self.datasetRef.dataId
+    def __getattr__(self, name: str) -> Any:
+        return getattr(self.datasetRef, name)
 
 
 class PipelineTaskConnections(metaclass=PipelineTaskConnectionsMetaclass):

python/lsst/pipe/base/tests/mocks/_pipeline_task.py

@@ -425,6 +425,11 @@
                 raise ValueError(
                     f"Unmocked dataset type {connection.name!r} cannot be used as an init-output."
                 )
+            elif connection.name.endswith("_metadata") and connection.storageClass == "TaskMetadata":
+                # Task metadata does not use a mock storage class, because it's
+                # written by the system, but it does end up with the _mock_*
+                # prefix because the task label does.
+                connection = dataclasses.replace(connection, name=get_mock_name(connection.name))
             setattr(self, name, connection)
 
     def getSpatialBoundsConnections(self) -> Iterable[str]: