Remove None as option for vector_fields

Author: VeckoTheGecko

src/parcels/_core/fieldset.py

@@ -211,7 +211,7 @@ def from_ugrid_conventions(
         cls,
         ds: ux.UxDataset,
         mesh: str = "spherical",
-        vector_fields: ptyping.VectorFields | None | NotSetType = NOTSET,
+        vector_fields: ptyping.VectorFields | NotSetType = NOTSET,
     ):
         """Create a FieldSet from a Parcels compliant uxarray.UxDataset.
 
@@ -229,8 +229,7 @@ def from_ugrid_conventions(
         vector_fields : Mapping[str, tuple[str, ...]] or None, optional
             Mapping of vector field names to tuples of component variable names in the dataset.
             For example, ``{"UV": ("U", "V"), "UVW": ("U", "V", "W")}``.
-            If ``None``, no vector fields are constructed. If omitted (default), vector fields
-            are auto-discovered from standard variable names (``U``/``V``/``W``).
+            If omitted (default), vector fields are auto-discovered from standard variable names (``U``/``V``/``W``).
 
         Returns
         -------
@@ -249,7 +248,7 @@ def from_sgrid_conventions(
         cls,
         ds: xr.Dataset,
         mesh: ptyping.Mesh | None = None,
-        vector_fields: ptyping.VectorFields | None | NotSetType = NOTSET,
+        vector_fields: ptyping.VectorFields | NotSetType = NOTSET,
     ):  # TODO: Update mesh to be discovered from the dataset metadata
         """Create a FieldSet from a dataset using SGRID convention metadata.
 
@@ -267,8 +266,7 @@ def from_sgrid_conventions(
         vector_fields : Mapping[str, tuple[str, ...]] or None, optional
             Mapping of vector field names to tuples of component variable names in the dataset.
             For example, ``{"UV": ("U", "V"), "UVW": ("U", "V", "W")}``.
-            If ``None``, no vector fields are constructed. If omitted (default), vector fields
-            are auto-discovered from standard variable names (``U``/``V``/``W``).
+            If omitted (default), vector fields are auto-discovered from standard variable names (``U``/``V``/``W``).
 
         Returns
         -------

src/parcels/_core/model.py

@@ -132,7 +132,7 @@ def construct_fields(self) -> list[Field | VectorField]:
 
     @classmethod
     def from_sgrid_conventions(
-        cls, ds: xr.Dataset, mesh: Mesh | None, vector_fields: ptyping.VectorFields | None | NotSetType
+        cls, ds: xr.Dataset, mesh: Mesh | None, vector_fields: ptyping.VectorFields | NotSetType
     ) -> Self:
         ds = ds.copy()
         if mesh is None:
@@ -171,19 +171,15 @@ def from_sgrid_conventions(
         return model
 
 
-def resolve_vector_fields(
-    ds: xr.Dataset, vector_fields: ptyping.VectorFields | None | NotSetType
-) -> ptyping.VectorFields:
-    if vector_fields is None:
-        return {}
+def resolve_vector_fields(ds: xr.Dataset, vector_fields: ptyping.VectorFields | NotSetType) -> ptyping.VectorFields:
     if vector_fields is NOTSET:  # i.e., the default vectorfield discovery behaviour
         return _default_vector_field_components(list(ds.data_vars))
     return vector_fields
 
 
 def assert_valid_vector_fields(ds: xr.Dataset, vector_fields: ptyping.VectorFields) -> None:
-    # if not isinstance(vector_fields, dict):
-    #     raise ValueError(f"vector_fields must be a dictionary. Got {type(vector_fields)=!r}.")
+    if not isinstance(vector_fields, dict):
+        raise ValueError(f"vector_fields must be a dictionary. Got {type(vector_fields)=!r}.")
 
     for vfield_name, components in vector_fields.items():
         if not isinstance(vfield_name, str):
@@ -237,7 +233,7 @@ def assert_vector_field_components_in_dataset(ds: xr.Dataset, vector_fields: pty
             ),
         ),
         mesh=mesh,  # type:ignore
-        vector_fields=None,
+        vector_fields={},
     )
     for mesh in ["flat", "spherical"]
 }
@@ -283,9 +279,7 @@ def scalar_field_names(self) -> list[str]:
         return list(self.data.data_vars)
 
     @classmethod
-    def from_ugrid_conventions(
-        cls, ds: ux.UxDataset, mesh: Mesh, vector_fields: ptyping.VectorFields | None | NotSetType
-    ):
+    def from_ugrid_conventions(cls, ds: ux.UxDataset, mesh: Mesh, vector_fields: ptyping.VectorFields | NotSetType):
         ds_dims = list(ds.dims)
         if not all(dim in ds_dims for dim in ["time", "zf", "zc"]):
             raise ValueError(

tests/test_fieldset.py

@@ -1,4 +1,3 @@
-from contextlib import nullcontext
 from datetime import timedelta
 
 import cf_xarray  # noqa: F401
@@ -116,7 +115,11 @@ def test_fieldset_from_structured_generic_datasets(ds):
             pytest.raises(ValueError, match="must have either 2 or 3 components"),
             id="too-many-components",
         ),
-        pytest.param(None, nullcontext(), id="None"),
+        pytest.param(
+            None,
+            pytest.raises(ValueError, match="vector_fields must be a dictionary"),
+            id="None",
+        ),
     ],
 )
 def test_fieldset_invalid_vector_fields(vector_fields, ctx):
@@ -147,10 +150,10 @@ def test_fieldset_structured_vectorfield_custom():
     assert "UV_wind" in fset.fields
 
 
-def test_fieldset_structured_vectorfield_none():
+def test_fieldset_structured_vectorfield_empty():
     ds = datasets_structured["ds_2d_left"][["U_A_grid", "V_A_grid", "grid"]].rename({"U_A_grid": "U", "V_A_grid": "V"})
 
-    fset = FieldSet.from_sgrid_conventions(ds, mesh="flat", vector_fields=None)
+    fset = FieldSet.from_sgrid_conventions(ds, mesh="flat", vector_fields={})
 
     assert "U" in fset.fields
     assert "V" in fset.fields
@@ -177,10 +180,10 @@ def test_fieldset_unstructured_vectorfield_custom():
     assert "UV_wind" in fset.fields
 
 
-def test_fieldset_unstructured_vectorfield_none():
+def test_fieldset_unstructured_vectorfield_empty():
     ds = datasets_unstructured["stommel_gyre_delaunay"]
 
-    fset = FieldSet.from_ugrid_conventions(ds, mesh="spherical", vector_fields=None)
+    fset = FieldSet.from_ugrid_conventions(ds, mesh="spherical", vector_fields={})
 
     assert "U" in fset.fields
     assert "V" in fset.fields