For DSGs, don't attempt to aggregate non-feature axes

cf/aggregate.py

@@ -2977,11 +2977,19 @@ def aggregate(
         # ------------------------------------------------------------
         if axes is None:
             # Aggregation will be over as many axes as possible
-            aggregating_axes = meta[0].axis_ids
+            m0 = meta[0]
+            aggregating_axes = m0.axis_ids[:]
+
+            # For DSG feature types, only consider aggregating the
+            # feature dimension(s).
+            if m0.featureType:
+                for axis in aggregating_axes[:]:
+                    if not dsg_feature_type_axis(m0, axis):
+                        aggregating_axes.remove(axis)
+
             _create_hash_and_first_values(
-                meta, None, False, hfl_cache, rtol, atol
+                meta, aggregating_axes, False, hfl_cache, rtol, atol
             )
-
         else:
             # Specific aggregation axes have been selected
             aggregating_axes = []
@@ -3492,7 +3500,8 @@ def _create_hash_and_first_values(
 
         meta: `list` of `_Meta`
 
-        axes: `None` or `list`
+        axes: `list`
+            The identities of the possible aggregating axes.
 
         donotchecknonaggregatingaxes: `bool`
 
@@ -3505,10 +3514,15 @@ def _create_hash_and_first_values(
     # identity.
     canonical_direction = {}
 
+    aggregating_axes = list(axes)
+
     for m in meta:
         field = m.field
         constructs = field.constructs.todict()
 
+        # Store the aggregating axis identities
+        m.aggregating_axes = aggregating_axes
+
         m_sort_keys = m.sort_keys
         m_sort_indices = m.sort_indices
 
@@ -4131,7 +4145,7 @@ def _group_fields(meta, axis, info=False):
             group is represented by a `list` of `_Meta` objects.
 
     """
-    axes = meta[0].axis_ids
+    axes = meta[0].aggregating_axes
 
     if axes:
         if axis in axes: