Fix get_nside() and CRS coordinate in tests

easygems/healpix/__init__.py

@@ -25,7 +25,8 @@ def get_nest(dx):
 def get_nside(dx):
     try:
         grid_mapping = dx.cf["grid_mapping"]
-    except AttributeError:
+    except (KeyError, AttributeError):
+        # Catch no CF (KeyError) and no grid mapping (AttributeError)
         if dx.squeeze().ndim > 1:
             raise ValueError(
                 "Cannot infer the HEALPix resolution from a multidimensional dataset.\n"

tests/test_healpix_coords.py

@@ -25,10 +25,9 @@ def raw_ds(request):
 
     return xr.Dataset(
         coords={
-            crs_name: (
-                ("crs",),
-                [0],
-                {
+            crs_name: xr.DataArray(
+                name=crs_name,
+                attrs={
                     "grid_mapping_name": "healpix",
                     **map_parameters,
                 },
@@ -37,6 +36,16 @@ def raw_ds(request):
     )
 
 
+@pytest.fixture
+def ds(raw_ds):
+    ds = raw_ds.assign_coords(
+        cell=(("cell",), np.arange(12), {"standard_name": "healpix_index"})
+    )
+    ds = ds.assign(variable=(("cell",), np.ones(12), {"grid_mapping": "healpix"}))
+
+    return ds
+
+
 def test_attach_coords_fixes_crs(raw_ds):
     ds = attach_coords(raw_ds)
 
@@ -76,6 +85,16 @@ def test_get_nside(raw_ds):
     assert get_nside(np.arange(12)) == 1
 
 
+def test_get_nside_dataarray(ds):
+    da = ds["variable"]
+
+    # Should work with...
+    assert get_nside(da) == 1
+
+    # .. and without CRS on data arrays
+    assert get_nside(da.drop_vars(da.cf["grid_mapping"].name)) == 1
+
+
 def test_get_nest(raw_ds):
     assert get_nest(raw_ds)