Generic 'cube_dims' function for all _DimensionMetadata objects.

lib/iris/coords.py

@@ -173,6 +173,22 @@ def copy(self, values=None):
 
         return new_metadata
 
+    @abstractmethod
+    def cube_dims(self, cube):
+        """
+        Identify the cube dims of any _DimensionalMetadata object.
+
+        Return the dimensions in the cube of a matching _DimensionalMetadata
+        object, if any.
+
+        Equivalent to cube.coord_dims(self) for a Coord,
+        or cube.cell_measure_dims for a CellMeasure, and so on.
+        Simplifies generic code to handle any _DimensionalMetadata objects.
+
+        """
+        # Only makes sense for specific subclasses.
+        raise NotImplementedError()
+
     def _sanitise_array(self, src, ndmin):
         if _lazy.is_lazy_data(src):
             # Lazy data : just ensure ndmin requirement.
@@ -744,6 +760,15 @@ def has_lazy_data(self):
         """
         return super()._has_lazy_values()
 
+    def cube_dims(self, cube):
+        """
+        Return the cube dimensions of this AncillaryVariable.
+
+        Equivalent to "cube.ancillary_variable_dims(self)".
+
+        """
+        return cube.ancillary_variable_dims(self)
+
 
 class CellMeasure(AncillaryVariable):
     """
@@ -846,6 +871,15 @@ def _as_defn(self):
         )
         return defn
 
+    def cube_dims(self, cube):
+        """
+        Return the cube dimensions of this CellMeasure.
+
+        Equivalent to "cube.cell_measure_dims(self)".
+
+        """
+        return cube.cell_measure_dims(self)
+
 
 class CoordDefn(
     namedtuple(
@@ -1596,6 +1630,15 @@ def _as_defn(self):
     def __hash__(self):
         return hash(id(self))
 
+    def cube_dims(self, cube):
+        """
+        Return the cube dimensions of this Coord.
+
+        Equivalent to "cube.coord_dims(self)".
+
+        """
+        return cube.coord_dims(self)
+
     def convert_units(self, unit):
         r"""
         Change the coordinate's units, converting the values in its points

lib/iris/tests/unit/coords/test_AncillaryVariable.py

@@ -9,6 +9,8 @@
 # importing anything else.
 import iris.tests as tests
 
+from unittest import mock
+
 import dask.array as da
 import numpy as np
 import numpy.ma as ma
@@ -17,6 +19,7 @@
 
 from cf_units import Unit
 from iris.coords import AncillaryVariable
+from iris.cube import Cube
 from iris._lazy_data import as_lazy_data
 
 
@@ -683,5 +686,18 @@ def test_nanpoints_eq_copy(self):
         self.assertEqual(av1, av2)
 
 
+class Test_cube_dims(tests.IrisTest):
+    def test(self):
+        # Check that "coord.cube_dims(cube)" calls "cube.coord_dims(coord)".
+        mock_dims_result = mock.sentinel.AV_DIMS
+        mock_dims_call = mock.Mock(return_value=mock_dims_result)
+        mock_cube = mock.Mock(Cube, ancillary_variable_dims=mock_dims_call)
+        test_var = AncillaryVariable([1], long_name="test_name")
+
+        result = test_var.cube_dims(mock_cube)
+        self.assertEqual(result, mock_dims_result)
+        self.assertEqual(mock_dims_call.call_args_list, [mock.call(test_var)])
+
+
 if __name__ == "__main__":
     tests.main()

lib/iris/tests/unit/coords/test_CellMeasure.py

@@ -9,9 +9,12 @@
 # importing anything else.
 import iris.tests as tests
 
+from unittest import mock
+
 import numpy as np
 
 from iris.coords import CellMeasure
+from iris.cube import Cube
 from iris._lazy_data import as_lazy_data
 
 
@@ -119,5 +122,18 @@ def test__eq__(self):
         self.assertEqual(self.measure, self.measure)
 
 
+class Test_cube_dims(tests.IrisTest):
+    def test(self):
+        # Check that "coord.cube_dims(cube)" calls "cube.coord_dims(coord)".
+        mock_dims_result = mock.sentinel.CM_DIMS
+        mock_dims_call = mock.Mock(return_value=mock_dims_result)
+        mock_cube = mock.Mock(Cube, cell_measure_dims=mock_dims_call)
+        test_cm = CellMeasure([1], long_name="test_name")
+
+        result = test_cm.cube_dims(mock_cube)
+        self.assertEqual(result, mock_dims_result)
+        self.assertEqual(mock_dims_call.call_args_list, [mock.call(test_cm)])
+
+
 if __name__ == "__main__":
     tests.main()

lib/iris/tests/unit/coords/test_Coord.py

@@ -17,6 +17,7 @@
 import numpy as np
 
 import iris
+from iris.cube import Cube
 from iris.coords import DimCoord, AuxCoord, Coord
 from iris.exceptions import UnitConversionError
 from iris.tests.unit.coords import CoordTestMixin
@@ -1020,5 +1021,20 @@ def test(self):
             _ = Coord(points=[0, 1])
 
 
+class Test_cube_dims(tests.IrisTest):
+    def test(self):
+        # Check that "coord.cube_dims(cube)" calls "cube.coord_dims(coord)".
+        mock_dims_result = mock.sentinel.COORD_DIMS
+        mock_dims_call = mock.Mock(return_value=mock_dims_result)
+        mock_cube = mock.Mock(Cube, coord_dims=mock_dims_call)
+        test_coord = AuxCoord([1], long_name="test_name")
+
+        result = test_coord.cube_dims(mock_cube)
+        self.assertEqual(result, mock_dims_result)
+        self.assertEqual(
+            mock_dims_call.call_args_list, [mock.call(test_coord)]
+        )
+
+
 if __name__ == "__main__":
     tests.main()