Add SGRID metadata support for node_coordinates attribute

src/parcels/_core/utils/sgrid.py

@@ -54,6 +54,7 @@ def __init__(
         topology_dimension: Literal[2],
         node_dimensions: tuple[Dim, Dim],
         face_dimensions: tuple[DimDimPadding, DimDimPadding],
+        node_coordinates: None | tuple[Dim, Dim] = None,
         vertical_dimensions: None | tuple[DimDimPadding] = None,
     ):
         if cf_role != "grid_topology":
@@ -76,6 +77,14 @@ def __init__(
         ):
             raise ValueError("face_dimensions must be a tuple of 2 DimDimPadding for a 2D grid")
 
+        if node_coordinates is not None:
+            if not (
+                isinstance(node_coordinates, tuple)
+                and len(node_coordinates) == 2
+                and all(isinstance(nd, str) for nd in node_coordinates)
+            ):
+                raise ValueError("node_coordinates must be a tuple of 2 dimensions for a 2D grid")
+
         if vertical_dimensions is not None:
             if not (
                 isinstance(vertical_dimensions, tuple)
@@ -90,21 +99,21 @@ def __init__(
         self.node_dimensions = node_dimensions
         self.face_dimensions = face_dimensions
 
-        #! Optional attributes aren't really important to Parcels, can be added later if needed
+        # Optional attributes
+        self.node_coordinates = node_coordinates
+        self.vertical_dimensions = vertical_dimensions
+
+        #! Some optional attributes aren't really important to Parcels, can be added later if needed
         # Optional attributes
         # # With defaults (set in init)
         # edge1_dimensions: tuple[Dim, DimDimPadding]
         # edge2_dimensions: tuple[DimDimPadding, Dim]
 
         # # Without defaults
-        # node_coordinates: None | Any = None
         # edge1_coordinates: None | Any = None
         # edge2_coordinates: None | Any = None
         # face_coordinate: None | Any = None
 
-        #! Important optional attribute for 2D grids with vertical layering
-        self.vertical_dimensions = vertical_dimensions
-
     def __repr__(self) -> str:
         return repr_from_dunder_dict(self)
 
@@ -121,6 +130,7 @@ def from_attrs(cls, attrs):
                 topology_dimension=attrs["topology_dimension"],
                 node_dimensions=load_mappings(attrs["node_dimensions"]),
                 face_dimensions=load_mappings(attrs["face_dimensions"]),
+                node_coordinates=maybe_load_mappings(attrs.get("node_coordinates")),
                 vertical_dimensions=maybe_load_mappings(attrs.get("vertical_dimensions")),
             )
         except Exception as e:
@@ -133,6 +143,8 @@ def to_attrs(self) -> dict[str, str | int]:
             node_dimensions=dump_mappings(self.node_dimensions),
             face_dimensions=dump_mappings(self.face_dimensions),
         )
+        if self.node_coordinates is not None:
+            d["node_coordinates"] = dump_mappings(self.node_coordinates)
         if self.vertical_dimensions is not None:
             d["vertical_dimensions"] = dump_mappings(self.vertical_dimensions)
         return d
@@ -148,6 +160,7 @@ def __init__(
         topology_dimension: Literal[3],
         node_dimensions: tuple[Dim, Dim, Dim],
         volume_dimensions: tuple[DimDimPadding, DimDimPadding, DimDimPadding],
+        node_coordinates: None | tuple[Dim, Dim, Dim] = None,
     ):
         if cf_role != "grid_topology":
             raise ValueError(f"cf_role must be 'grid_topology', got {cf_role!r}")
@@ -169,13 +182,24 @@ def __init__(
         ):
             raise ValueError("face_dimensions must be a tuple of 2 DimDimPadding for a 2D grid")
 
+        if node_coordinates is not None:
+            if not (
+                isinstance(node_coordinates, tuple)
+                and len(node_coordinates) == 3
+                and all(isinstance(nd, str) for nd in node_coordinates)
+            ):
+                raise ValueError("node_coordinates must be a tuple of 3 dimensions for a 3D grid")
+
         # Required attributes
         self.cf_role = cf_role
         self.topology_dimension = topology_dimension
         self.node_dimensions = node_dimensions
         self.volume_dimensions = volume_dimensions
 
-        # ! Optional attributes aren't really important to Parcels, can be added later if needed
+        # Optional attributes
+        self.node_coordinates = node_coordinates
+
+        # ! Some optional attributes aren't really important to Parcels, can be added later if needed
         # Optional attributes
         # # With defaults (set in init)
         # edge1_dimensions: tuple[DimDimPadding, Dim, Dim]
@@ -186,7 +210,6 @@ def __init__(
         # face3_dimensions: tuple[DimDimPadding, DimDimPadding, Dim]
 
         # # Without defaults
-        # node_coordinates
         # edge *i_coordinates*
         # face *i_coordinates*
         # volume_coordinates
@@ -207,17 +230,21 @@ def from_attrs(cls, attrs):
                 topology_dimension=attrs["topology_dimension"],
                 node_dimensions=load_mappings(attrs["node_dimensions"]),
                 volume_dimensions=load_mappings(attrs["volume_dimensions"]),
+                node_coordinates=maybe_load_mappings(attrs.get("node_coordinates")),
             )
         except Exception as e:
             raise SGridParsingException(f"Failed to parse Grid3DMetadata from {attrs=!r}") from e
 
     def to_attrs(self) -> dict[str, str | int]:
-        return dict(
+        d = dict(
             cf_role=self.cf_role,
             topology_dimension=self.topology_dimension,
             node_dimensions=dump_mappings(self.node_dimensions),
             volume_dimensions=dump_mappings(self.volume_dimensions),
         )
+        if self.node_coordinates is not None:
+            d["node_coordinates"] = dump_mappings(self.node_coordinates)
+        return d
 
     def rename_dims(self, dims_dict: dict[str, str]) -> Self:
         return _metadata_rename_dims(self, dims_dict)

tests/strategies/sgrid.py

@@ -28,7 +28,7 @@
 
 @st.composite
 def grid2Dmetadata(draw) -> sgrid.Grid2DMetadata:
-    N = 6
+    N = 8
     names = draw(st.lists(dimension_name, min_size=N, max_size=N, unique=True))
     node_dimension1 = names[0]
     node_dimension2 = names[1]
@@ -37,11 +37,20 @@ def grid2Dmetadata(draw) -> sgrid.Grid2DMetadata:
     padding_type1 = draw(padding)
     padding_type2 = draw(padding)
 
-    vertical_dimensions_dim1 = names[4]
-    vertical_dimensions_dim2 = names[5]
+    node_coordinates_var1 = names[4]
+    node_coordinates_var2 = names[5]
+    has_node_coordinates = draw(st.booleans())
+
+    vertical_dimensions_dim1 = names[6]
+    vertical_dimensions_dim2 = names[7]
     vertical_dimensions_padding = draw(padding)
     has_vertical_dimensions = draw(st.booleans())
 
+    if has_node_coordinates:
+        node_coordinates = (node_coordinates_var1, node_coordinates_var2)
+    else:
+        node_coordinates = None
+
     if has_vertical_dimensions:
         vertical_dimensions = (
             sgrid.DimDimPadding(vertical_dimensions_dim1, vertical_dimensions_dim2, vertical_dimensions_padding),
@@ -57,13 +66,14 @@ def grid2Dmetadata(draw) -> sgrid.Grid2DMetadata:
             sgrid.DimDimPadding(face_dimension1, node_dimension1, padding_type1),
             sgrid.DimDimPadding(face_dimension2, node_dimension2, padding_type2),
         ),
+        node_coordinates=node_coordinates,
         vertical_dimensions=vertical_dimensions,
     )
 
 
 @st.composite
 def grid3Dmetadata(draw) -> sgrid.Grid3DMetadata:
-    N = 6
+    N = 9
     names = draw(st.lists(dimension_name, min_size=N, max_size=N, unique=True))
     node_dimension1 = names[0]
     node_dimension2 = names[1]
@@ -75,6 +85,16 @@ def grid3Dmetadata(draw) -> sgrid.Grid3DMetadata:
     padding_type2 = draw(padding)
     padding_type3 = draw(padding)
 
+    node_coordinates_var1 = names[6]
+    node_coordinates_var2 = names[7]
+    node_coordinates_dim3 = names[8]
+    has_node_coordinates = draw(st.booleans())
+
+    if has_node_coordinates:
+        node_coordinates = (node_coordinates_var1, node_coordinates_var2, node_coordinates_dim3)
+    else:
+        node_coordinates = None
+
     return sgrid.Grid3DMetadata(
         cf_role="grid_topology",
         topology_dimension=3,
@@ -84,6 +104,7 @@ def grid3Dmetadata(draw) -> sgrid.Grid3DMetadata:
             sgrid.DimDimPadding(face_dimension2, node_dimension2, padding_type2),
             sgrid.DimDimPadding(face_dimension3, node_dimension3, padding_type3),
         ),
+        node_coordinates=node_coordinates,
     )
 
 

tests/utils/test_sgrid.py

@@ -1,3 +1,5 @@
+import itertools
+
 import numpy as np
 import pytest
 import xarray as xr
@@ -7,29 +9,47 @@
 from parcels._core.utils import sgrid
 from tests.strategies import sgrid as sgrid_strategies
 
-grid2dmetadata = sgrid.Grid2DMetadata(
-    cf_role="grid_topology",
-    topology_dimension=2,
-    node_dimensions=("node_dimension1", "node_dimension2"),
-    face_dimensions=(
-        sgrid.DimDimPadding("face_dimension1", "node_dimension1", sgrid.Padding.LOW),
-        sgrid.DimDimPadding("face_dimension2", "node_dimension2", sgrid.Padding.LOW),
-    ),
-    vertical_dimensions=(
-        sgrid.DimDimPadding("vertical_dimensions_dim1", "vertical_dimensions_dim2", sgrid.Padding.LOW),
-    ),
-)
 
-grid3dmetadata = sgrid.Grid3DMetadata(
-    cf_role="grid_topology",
-    topology_dimension=3,
-    node_dimensions=("node_dimension1", "node_dimension2", "node_dimension3"),
-    volume_dimensions=(
-        sgrid.DimDimPadding("face_dimension1", "node_dimension1", sgrid.Padding.LOW),
-        sgrid.DimDimPadding("face_dimension2", "node_dimension2", sgrid.Padding.LOW),
-        sgrid.DimDimPadding("face_dimension3", "node_dimension3", sgrid.Padding.LOW),
-    ),
-)
+def create_example_grid2dmetadata(with_vertical_dimensions: bool, with_node_coordinates: bool):
+    vertical_dimensions = (
+        (sgrid.DimDimPadding("vertical_dimensions_dim1", "vertical_dimensions_dim2", sgrid.Padding.LOW),)
+        if with_vertical_dimensions
+        else None
+    )
+    node_coordinates = ("node_coordinates_var1", "node_coordinates_var2") if with_node_coordinates else None
+
+    return sgrid.Grid2DMetadata(
+        cf_role="grid_topology",
+        topology_dimension=2,
+        node_dimensions=("node_dimension1", "node_dimension2"),
+        face_dimensions=(
+            sgrid.DimDimPadding("face_dimension1", "node_dimension1", sgrid.Padding.LOW),
+            sgrid.DimDimPadding("face_dimension2", "node_dimension2", sgrid.Padding.LOW),
+        ),
+        node_coordinates=node_coordinates,
+        vertical_dimensions=vertical_dimensions,
+    )
+
+
+def create_example_grid3dmetadata(with_node_coordinates: bool):
+    node_coordinates = (
+        ("node_coordinates_var1", "node_coordinates_var2", "node_coordinates_dim3") if with_node_coordinates else None
+    )
+    return sgrid.Grid3DMetadata(
+        cf_role="grid_topology",
+        topology_dimension=3,
+        node_dimensions=("node_dimension1", "node_dimension2", "node_dimension3"),
+        volume_dimensions=(
+            sgrid.DimDimPadding("face_dimension1", "node_dimension1", sgrid.Padding.LOW),
+            sgrid.DimDimPadding("face_dimension2", "node_dimension2", sgrid.Padding.LOW),
+            sgrid.DimDimPadding("face_dimension3", "node_dimension3", sgrid.Padding.LOW),
+        ),
+        node_coordinates=node_coordinates,
+    )
+
+
+grid2dmetadata = create_example_grid2dmetadata(with_vertical_dimensions=True, with_node_coordinates=True)
+grid3dmetadata = create_example_grid3dmetadata(with_node_coordinates=True)
 
 
 def dummy_sgrid_ds(grid: sgrid.Grid2DMetadata | sgrid.Grid3DMetadata) -> xr.Dataset:
@@ -225,45 +245,10 @@ def test_parse_sgrid_3d(grid_metadata: sgrid.Grid3DMetadata):
 @pytest.mark.parametrize(
     "grid",
     [
-        (
-            sgrid.Grid2DMetadata(
-                cf_role="grid_topology",
-                topology_dimension=2,
-                node_dimensions=("node_dimension1", "node_dimension2"),
-                face_dimensions=(
-                    sgrid.DimDimPadding("face_dimension1", "node_dimension1", sgrid.Padding.LOW),
-                    sgrid.DimDimPadding("face_dimension2", "node_dimension2", sgrid.Padding.LOW),
-                ),
-                vertical_dimensions=(
-                    sgrid.DimDimPadding("vertical_dimensions_dim1", "vertical_dimensions_dim2", sgrid.Padding.LOW),
-                ),
-            )
-        ),
-        (
-            sgrid.Grid2DMetadata(
-                cf_role="grid_topology",
-                topology_dimension=2,
-                node_dimensions=("node_dimension1", "node_dimension2"),
-                face_dimensions=(
-                    sgrid.DimDimPadding("face_dimension1", "node_dimension1", sgrid.Padding.LOW),
-                    sgrid.DimDimPadding("face_dimension2", "node_dimension2", sgrid.Padding.LOW),
-                ),
-                vertical_dimensions=None,
-            )
-        ),
-        (
-            sgrid.Grid3DMetadata(
-                cf_role="grid_topology",
-                topology_dimension=3,
-                node_dimensions=("node_dimension1", "node_dimension2", "node_dimension3"),
-                volume_dimensions=(
-                    sgrid.DimDimPadding("face_dimension1", "node_dimension1", sgrid.Padding.LOW),
-                    sgrid.DimDimPadding("face_dimension2", "node_dimension2", sgrid.Padding.LOW),
-                    sgrid.DimDimPadding("face_dimension3", "node_dimension3", sgrid.Padding.LOW),
-                ),
-            )
-        ),
-    ],
+        create_example_grid2dmetadata(with_node_coordinates=i, with_vertical_dimensions=j)
+        for i, j in itertools.product([False, True], [False, True])
+    ]
+    + [create_example_grid3dmetadata(with_node_coordinates=i) for i in [False, True]],
 )
 def test_rename_dims(grid):
     dims = sgrid.get_unique_dim_names(grid)