Merge pull request #2364 from Parcels-code/error_when_dims_have_no_axis

Raise error when creating Field with dimensions without axis

Author: erikvansebille

src/parcels/_core/field.py

@@ -21,7 +21,7 @@
 from parcels._core.utils.string import _assert_str_and_python_varname
 from parcels._core.utils.time import TimeInterval
 from parcels._core.uxgrid import UxGrid
-from parcels._core.xgrid import XGrid, _transpose_xfield_data_to_tzyx
+from parcels._core.xgrid import XGrid, _transpose_xfield_data_to_tzyx, assert_all_field_dims_have_axis
 from parcels._python import assert_same_function_signature
 from parcels._reprs import default_repr
 from parcels._typing import VectorType
@@ -103,6 +103,7 @@ def __init__(
         _assert_compatible_combination(data, grid)
 
         if isinstance(grid, XGrid):
+            assert_all_field_dims_have_axis(data, grid.xgcm_grid)
             data = _transpose_xfield_data_to_tzyx(data, grid.xgcm_grid)
 
         self.name = name

src/parcels/_core/xgrid.py

@@ -48,6 +48,16 @@ def _drop_field_data(ds: xr.Dataset) -> xr.Dataset:
     return ds.drop_vars(ds.data_vars)
 
 
+def assert_all_field_dims_have_axis(da: xr.DataArray, xgcm_grid: xgcm.Grid) -> None:
+    ax_dims = [(get_axis_from_dim_name(xgcm_grid.axes, dim), dim) for dim in da.dims]
+    for dim in ax_dims:
+        if dim[0] is None:
+            raise ValueError(
+                f'Dimension "{dim[1]}" has no axis attribute. '
+                f'HINT: You may want to add an {{"axis": A}} to your DataSet["{dim[1]}"], where A is one of "X", "Y", "Z" or "T"'
+            )
+
+
 def _transpose_xfield_data_to_tzyx(da: xr.DataArray, xgcm_grid: xgcm.Grid) -> xr.DataArray:
     """
     Transpose a DataArray of any shape into a 4D array of order TZYX. Uses xgcm to determine

tests/test_xgrid.py

@@ -136,6 +136,13 @@ def test_invalid_depth():
         XGrid.from_dataset(ds)
 
 
+def test_dim_without_axis():
+    ds = xr.Dataset({"z1d": (["depth"], [0])}, coords={"depth": [0]})
+    grid = XGrid.from_dataset(ds)
+    with pytest.raises(ValueError, match='Dimension "depth" has no axis attribute*'):
+        Field("z1d", ds["z1d"], grid, XLinear)
+
+
 def test_vertical1D_field():
     nz = 11
     ds = xr.Dataset(