Changed behaviour of source._open_dataset to:

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
 
@@ -84,9 +89,16 @@ def _open_dataset(
  if requested_variables:
  if isinstance(requested_variables, str):
  requested_variables = [requested_variables]
+
  variable_intersection = set(requested_variables).intersection(set(varname))
- variables = [variable for variable in variable_intersection if variable in ds.data_vars]
+
+ data_vars = variable_intersection & set(ds.data_vars)
+ coord_vars = variable_intersection & set(ds.coords)
+
+ variables = list(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)
  ds = ds[variables]
  ds.attrs[OPTIONS['vars_key']] = variables
@@ -242,7 +254,7 @@ def _open_dataset(self):
  ]
 
  datasets = dask.compute(*datasets)
- if len(datasets) == 1:
+ if len(datasets) == 1 or not datasets[0].data_vars:
  self._ds = datasets[0]
  else:
  datasets = sorted(
@@ -256,7 +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

@@ -102,3 +102,62 @@ def test_update_attrs(tmp_path, data_format, attrs):
  _xarray_open_kwargs = _get_xarray_open_kwargs(data_format=data_format)
  ds_new = _open_dataset(fpath, 'tasmax', xarray_open_kwargs=_xarray_open_kwargs).compute()
  assert ds_new.attrs == ds.attrs
+
+
+@pytest.mark.parametrize(
+ 'fpath,dvars,cvars,expected',
+ [
+ (
+ f1,
+ ['time_bnds'],
+ [''],
+ ['time_bnds', 'height', 'time'],
+ ),
+ (f1, ['tasmax'], [''], ['tasmax', 'height', 'time', 'lat', 'lon']),
+ (
+ f1,
+ [],
+ ['height'],
+ ['height'],
+ ),
+ (
+ f1,
+ [],
+ [],
+ ['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, [], ['height'], ['height']),
+ (
+ multi_path,
+ [],
+ [],
+ ['time_bnds', 'lon_bnds', 'lat_bnds', 'tasmax', 'time', 'height', 'lat', 'lon'],
+ ),
+ ],
+)
+def test_request_coord_vars(fpath, dvars, cvars, expected):
+ """
+ Test requesting a combination of data & coordinate variables.
+ """
+ requested_vars = [*dvars, *cvars]
+ xarray_open_kwargs = _get_xarray_open_kwargs('netcdf')
+ ds = _open_dataset(
+ urlpath=fpath,
+ varname=['height', 'lat', 'lat_bnds', 'lon', 'lon_bnds', 'tasmax', 'time', 'time_bnds'],
+ xarray_open_kwargs=xarray_open_kwargs,
+ requested_variables=requested_vars,
+ ).compute()
+
+ ds_dvars = ds.data_vars or set()
+ ds_cvars = ds.coords or set()
+
+ found_vars = set(ds_dvars) | set(ds_cvars)
+
+ assert found_vars == set(expected)