Changed behaviour to catch 'no valid dimension coordinates' error and…

… return first dataset if so - necessary to indexing static files

Appears to be potential intermittent issue with Read the Docs build -
unable to reproduce reliably locally.

intake_esm/source.py

@@ -1,4 +1,5 @@
 import typing
+import warnings
 
 import dask
 import fsspec
@@ -11,6 +12,10 @@
 from .utils import OPTIONS
 
 
+class ConcatenationWarning(UserWarning):
+    pass
+
+
 class ESMDataSourceError(Exception):
     pass
 
@@ -87,10 +92,11 @@ def _open_dataset(
 
         variable_intersection = set(requested_variables).intersection(set(varname))
 
-        data_vars = [variable for variable in variable_intersection if variable in ds.data_vars]
-        coord_vars = [variable for variable in variable_intersection if variable in ds.coords]
+        data_vars = variable_intersection & set(ds.data_vars)
+        coord_vars = variable_intersection & set(ds.coords)
+
+        variables = list(data_vars | coord_vars)
 
-        variables = [*data_vars, *coord_vars]
         scalar_variables = [v for v in ds.data_vars if len(ds[v].dims) == 0]
 
         ds = ds.set_coords(scalar_variables)
@@ -262,7 +268,23 @@ def _open_dataset(self):
                     ds.set_coords(set(ds.variables) - set(ds.attrs[OPTIONS['vars_key']]))
                     for ds in datasets
                 ]
-                self._ds = xr.combine_by_coords(datasets, **self.xarray_combine_by_coords_kwargs)
+                try:
+                    self._ds = xr.combine_by_coords(
+                        datasets, **self.xarray_combine_by_coords_kwargs
+                    )
+                except ValueError as exc:
+                    if (
+                        str(exc)
+                        == 'Could not find any dimension coordinates to use to order the datasets for concatenation'
+                    ):
+                        warnings.warn(
+                            'Attempting to concatenate datasets without valid dimension coordinates: retaining only first dataset.'
+                            ' Request valid dimension coordinate to silence this warning.',
+                            category=ConcatenationWarning,
+                        )
+                        self._ds = datasets[0]
+                    else:
+                        raise exc
 
             self._ds.attrs[OPTIONS['dataset_key']] = self.key
 

tests/test_source.py

@@ -107,41 +107,38 @@ def test_update_attrs(tmp_path, data_format, attrs):
 @pytest.mark.parametrize(
     'fpath,dvars,cvars,expected',
     [
-        (f1, ['time_bnds'], [''], ['time_bnds', 'time', 'height']),
-        (f1, ['tasmax'], [''], ['time', 'tasmax', 'height', 'lat', 'lon']),
-        (f1, [], ['height'], ['height']),
+        (
+            f1,
+            ['time_bnds'],
+            [''],
+            ['time_bnds', 'height', 'time'],
+        ),
+        (f1, ['tasmax'], [''], ['tasmax', 'height', 'time', 'lat', 'lon']),
+        (
+            f1,
+            [],
+            ['height'],
+            ['height'],
+        ),
         (
             f1,
             [],
             [],
-            [
-                'time',
-                'lat',
-                'lon',
-                'height',
-                'time_bnds',
-                'lon_bnds',
-                'lat_bnds',
-                'tasmax',
-            ],
+            ['height', 'time_bnds', 'lon_bnds', 'lat_bnds', 'tasmax', 'time', 'lat', 'lon'],
+        ),
+        (multi_path, ['time_bnds'], [''], ['time_bnds', 'height', 'time']),
+        (
+            multi_path,
+            ['tasmax'],
+            [''],
+            ['tasmax', 'time', 'height', 'lat', 'lon'],
         ),
-        (multi_path, ['time_bnds'], [''], ['time_bnds', 'time', 'height']),
-        (multi_path, ['tasmax'], [''], ['time', 'tasmax', 'height', 'lat', 'lon']),
         (multi_path, [], ['height'], ['height']),
         (
             multi_path,
             [],
             [],
-            [
-                'time',
-                'lat',
-                'lon',
-                'height',
-                'time_bnds',
-                'lon_bnds',
-                'lat_bnds',
-                'tasmax',
-            ],
+            ['time_bnds', 'lon_bnds', 'lat_bnds', 'tasmax', 'time', 'height', 'lat', 'lon'],
         ),
     ],
 )