Make extent not required for VerticalSpatialDimension

pystac/extensions/datacube.py

@@ -142,15 +142,18 @@ def from_dict(d: dict[str, Any]) -> Dimension:
 
 class SpatialDimension(Dimension):
     @property
-    def extent(self) -> list[float]:
+    def extent(self) -> list[float] | None:
         """Extent (lower and upper bounds) of the dimension as two-dimensional array.
         Open intervals with ``None`` are not allowed."""
-        return get_required(
-            self.properties.get(DIM_EXTENT_PROP), "cube:dimension", DIM_EXTENT_PROP
+        return cast(
+            list[float],
+            get_required(
+                self.properties.get(DIM_EXTENT_PROP), "cube:dimension", DIM_EXTENT_PROP
+            ),
         )
 
     @extent.setter
-    def extent(self, v: list[float]) -> None:
+    def extent(self, v: list[float] | None) -> None:
         self.properties[DIM_EXTENT_PROP] = v
 
     @property
@@ -228,6 +231,19 @@ def axis(self) -> VerticalSpatialDimensionAxis:
     def axis(self, v: VerticalSpatialDimensionAxis) -> None:
         self.properties[DIM_AXIS_PROP] = v
 
+    @property
+    def extent(self) -> list[float] | None:
+        """Extent (lower and upper bounds) of the dimension as two-dimensional array.
+        Open intervals with ``None`` are not allowed."""
+        return self.properties.get(DIM_EXTENT_PROP)
+
+    @extent.setter
+    def extent(self, v: list[float] | None) -> None:
+        if v is None:
+            self.properties.pop(DIM_EXTENT_PROP, None)
+        else:
+            self.properties[DIM_EXTENT_PROP] = v
+
     @property
     def unit(self) -> str | None:
         """The unit of measurement for the data, preferably compliant to `UDUNITS-2

tests/extensions/test_datacube.py

@@ -110,6 +110,20 @@ def test_temporal_dimension_description(
     assert "description" not in temporal_dimension.properties
 
 
+def test_vertical_dimension_extent_not_required() -> None:
+    props: dict[str, list[float]] = {}
+    dim = dc.VerticalSpatialDimension(props)
+    assert dim.extent is None
+
+
+def test_vertical_dimension_setting_extent_to_none_pops_it() -> None:
+    props: dict[str, list[float]] = {"extent": [10, 100]}
+    dim = dc.VerticalSpatialDimension(props)
+    assert dim.extent == [10, 100]
+    dim.extent = None
+    assert props == {}
+
+
 def test_stac_extensions(ext_item: Item) -> None:
     assert dc.DatacubeExtension.has_extension(ext_item)