Adding unit test to show combining fields with and without time doesn't currently work

Author: erikvansebille

tests/test_fieldset.py

@@ -6,6 +6,7 @@
 import numpy as np
 import pandas as pd
 import pytest
+import xarray as xr
 
 from parcels import Field, ParticleFile, ParticleSet, XGrid, convert
 from parcels._core.fieldset import FieldSet, _datetime_to_msg
@@ -359,6 +360,17 @@ def test_fieldset_add():
     assert set(fields_before) == set(fset.fields.keys())
 
 
+def test_vectorfields_without_time():
+    """Test that vector fields without a time dimension can be evaluated."""
+    ds1 = datasets_structured["ds_2d_left"][["U_A_grid", "V_A_grid", "grid"]].rename({"U_A_grid": "U", "V_A_grid": "V"})
+    ds2 = ds1.isel(time=0).drop_vars("time").rename({"U": "U_const", "V": "V_const"})
+    ds = xr.merge([ds1, ds2])
+
+    fset = FieldSet.from_sgrid_conventions(ds, mesh="flat", vector_fields={"UV_const": ("U_const", "V_const")})
+    fset.UV_const.eval(t=0, z=0, y=0, x=0)
+    fset.U_const.eval(t=0, z=0, y=0, x=0)
+
+
 def test_fieldset_add_error_on_duplicate_context_values():
     """Test that adding FieldSets with overlapping context value names raises a ValueError."""
     ds1 = datasets_structured["ds_2d_left"][["U_A_grid", "grid"]].rename({"U_A_grid": "U1"})