Move dimensionless coords to attrs

tests/test_20_open_dataset.py

@@ -63,7 +63,6 @@ def test_open_dataset(tmp_path: Path, index_node: str, download: bool) -> None:
     assert set(ds.coords) == {
         "areacella",
         "experiment_id",
-        "height",
         "lat",
         "lat_bnds",
         "lon",
@@ -77,15 +76,19 @@ def test_open_dataset(tmp_path: Path, index_node: str, download: bool) -> None:
         if name != "experiment_id"
     )
 
+    # Dimensionless coords
+    assert "height" not in ds["pr"].attrs
+    assert ds["tas"].attrs["height"] == 2.0
+
     # Data vars
     assert set(ds.data_vars) == {"pr", "tas"}
-    assert ds["pr"].coordinates == "areacella experiment_id height lat lon time"
-    assert ds["tas"].coordinates == "areacella experiment_id height lat lon time"
+    assert ds["pr"].coordinates == "areacella experiment_id lat lon time"
+    assert ds["tas"].coordinates == "areacella experiment_id lat lon time"
 
     # Attributes
     assert (
         ds.coordinates
-        == "areacella experiment_id height lat lat_bnds lon lon_bnds time time_bnds"
+        == "areacella experiment_id lat lat_bnds lon lon_bnds time time_bnds"
     )
     assert ds.dataset_ids == [
         "CMIP6.ScenarioMIP.EC-Earth-Consortium.EC-Earth3-CC.ssp245.r1i1p1f1.Amon.pr.gr.v20210113",

xarray_esgf/client.py

@@ -61,6 +61,17 @@ def add_coordinates_attr_inplace(obj: Dataset | DataArray) -> None:
             add_coordinates_attr_inplace(da)
 
 
+def move_dimensionless_coords_to_attrs(ds: Dataset) -> Dataset:
+    attrs = {}
+    for var, da in ds.coords.items():
+        if not da.dims:
+            attrs[var] = da.item()
+    ds = ds.drop_vars(list(attrs))
+    for da in ds.data_vars.values():
+        da.attrs.update(attrs)
+    return ds
+
+
 @dataclasses.dataclass
 class Client:
     selection: dict[str, str | list[str]]
@@ -183,11 +194,15 @@ def _open_datasets(
                 (ds,) = datasets
             else:
                 ds = combine_datasets(datasets)
+
             ds = ds.set_coords([
                 name
                 for name, da in ds.variables.items()
                 if BOUNDS_DIMS.intersection(da.dims) or "time" not in da.dims
             ])
+
+            ds = move_dimensionless_coords_to_attrs(ds)
+
             ds = ds.expand_dims({dim: [dataset_id_dict[dim]] for dim in concat_dims})
             combined_datasets[dataset_id] = ds
             LOGGER.debug(f"{dataset_id}: {dict(ds.sizes)}")