add coordinates attribute (#37)

Author: malmans2

tests/test_20_open_dataset.py

@@ -74,9 +74,15 @@ def test_open_dataset(tmp_path: Path, index_node: str, download: bool) -> None:
     )
 
     # Data vars
-    assert set(ds.data_vars) == {"tas", "pr"}
+    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"
 
     # Attributes
+    assert (
+        ds.coordinates
+        == "areacella experiment_id height 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",
         "CMIP6.ScenarioMIP.EC-Earth-Consortium.EC-Earth3-CC.ssp245.r1i1p1f1.Amon.tas.gr.v20210113",

xarray_esgf/client.py

@@ -54,6 +54,13 @@ def combine_datasets(datasets: list[Dataset]) -> Dataset:
     return obj
 
 
+def add_coordinates_attr_inplace(obj: Dataset | DataArray) -> None:
+    obj.attrs["coordinates"] = " ".join(sorted(str(coord) for coord in obj.coords))
+    if isinstance(obj, Dataset):
+        for da in obj.data_vars.values():
+            add_coordinates_attr_inplace(da)
+
+
 @dataclasses.dataclass
 class Client:
     selection: dict[str, str | list[str]]
@@ -205,6 +212,6 @@ def open_dataset(
             if name not in obj.dims:
                 var.encoding["preferred_chunks"] = dict(var.chunksizes)
 
+        add_coordinates_attr_inplace(obj)
         obj.attrs["dataset_ids"] = sorted(combined_datasets)
-
         return obj