Remove connectivity dimensions from attributes as well. Fixes #132.

This also adds a check on the dimensions sizes of connectivity variables, and some unit tests for triggering the errors.

docs/changelog.rst

@@ -36,7 +36,10 @@ Fixed
 - :class:`xugrid.CentroidLocatorRegridder`, :class:`xugrid.OverlapRegridder`,
   and :class:`xugrid.BarycentricInterpolator` will now also regrid structured
   to unstructured grid topologies.
-
+- :meth:`xugrid.Ugrid1d.to_dataset` and :meth:`xugrid.Ugrid2d.to_dataset` no
+  longer write unused connectivity variables into the attributes of the UGRID
+  dummy variable.
+
 Changed
 ~~~~~~~
 

tests/test_conventions.py

@@ -294,3 +294,40 @@ def test_dimensions(self):
 
     def test_connectivity(self):
         assert self.ds.ugrid_roles.connectivity == self.connectivity
+
+    def test_dimension_name_mismatch_error(self):
+        ds = self.ds.copy()
+
+        ds["mesh2d_edge_nodes"] = xr.DataArray(
+            data=[
+                [0, 1],
+                [1, 2],
+                [2, 3],
+                [3, 0],
+            ],
+            dims=["nEdges", "Two"],
+            attrs={"_FillValue": -1, "start_index": 0},
+        )
+
+        with pytest.raises(
+            cv.UgridDimensionError,
+            match="edge_dimension: nEdges not in edge_face_connectivity",
+        ):
+            ds.ugrid_roles.dimensions
+
+    def test_dimension_size_error(self):
+        ds = self.ds.copy()
+
+        ds["mesh2d_edge_nodes"] = xr.DataArray(
+            data=[
+                [0, 1, -1],
+                [1, 2, -1],
+                [2, 3, -1],
+                [3, 0, -1],
+            ],
+            dims=["mesh2d_nEdges", "Three"],
+            attrs={"_FillValue": -1, "start_index": 0},
+        )
+
+        with pytest.raises(cv.UgridDimensionError, match="Expected size 2"):
+            ds.ugrid_roles.dimensions

tests/test_ugrid1d.py

@@ -157,6 +157,17 @@ def test_to_crs():
 
 
 def test_to_dataset():
+    def check_attrs(ds):
+        attrs = ds[NAME].attrs.copy()
+        attrs.pop("cf_role")
+        attrs.pop("long_name")
+        attrs.pop("topology_dimension")
+        ds_contents = tuple(ds.dims) + tuple(ds.coords) + tuple(ds.data_vars)
+        for values in attrs.values():
+            # e.g node_coordinates are joined by a whitespace.
+            for value in values.split(" "):
+                assert value in ds_contents
+
     grid = grid1d()
     ds = grid.to_dataset()
     assert isinstance(ds, xr.Dataset)
@@ -166,10 +177,12 @@ def test_to_dataset():
     assert f"{NAME}_node_x" in ds.coords
     assert f"{NAME}_node_y" in ds.coords
     assert f"{NAME}_edge_nodes" in ds
+    check_attrs(ds)
 
     ds = grid.to_dataset(optional_attributes=True)
     assert f"{NAME}_edge_x" in ds.coords
     assert f"{NAME}_edge_y" in ds.coords
+    check_attrs(ds)
 
 
 def test_ugrid1d_dataset_roundtrip():

tests/test_ugrid2d.py

@@ -215,6 +215,17 @@ def test_to_crs():
 
 
 def test_to_dataset():
+    def check_attrs(ds):
+        attrs = ds[NAME].attrs.copy()
+        attrs.pop("cf_role")
+        attrs.pop("long_name")
+        attrs.pop("topology_dimension")
+        ds_contents = tuple(ds.dims) + tuple(ds.coords) + tuple(ds.data_vars)
+        for values in attrs.values():
+            # e.g node_coordinates are joined by a whitespace.
+            for value in values.split(" "):
+                assert value in ds_contents
+
     grid = grid2d()
     ds = grid.to_dataset()
     assert isinstance(ds, xr.Dataset)
@@ -224,6 +235,7 @@ def test_to_dataset():
     assert f"{NAME}_node_x" in ds.coords
     assert f"{NAME}_node_y" in ds.coords
     assert f"{NAME}_face_nodes" in ds
+    check_attrs(ds)
 
     ds = grid.to_dataset(optional_attributes=True)
     assert f"{NAME}_edge_nodes" in ds
@@ -236,6 +248,7 @@ def test_to_dataset():
     assert f"{NAME}_face_y" in ds
     assert f"{NAME}_edge_x" in ds
     assert f"{NAME}_edge_y" in ds
+    check_attrs(ds)
 
 
 def test_ugrid2d_set_node_coords():

xugrid/ugrid/conventions.py

@@ -40,19 +40,19 @@ class UgridCoordinateError(Exception):
         "face_node_connectivity",
         "edge_node_connectivity",
         "face_edge_connectivity",
-        # "face_face_connectivity",
+        "face_face_connectivity",
         "edge_face_connectivity",
-        #        "boundary_node_connectivity",
+        "boundary_node_connectivity",
     ),
 }
 
 _CONNECTIVITY_DIMS = {
     "face_node_connectivity": ("face_dimension", None),
     "edge_node_connectivity": ("edge_dimension", 2),
     "face_edge_connectivity": ("face_dimension", None),
-    # "face_face_connectivity": ("face_dimension", None),
+    "face_face_connectivity": ("face_dimension", None),
     "edge_face_connectivity": ("edge_dimension", 2),
-    # "boundary_node_connectivity": ("???","???"),
+    "boundary_node_connectivity": ("boundary_edge_dimension", 2),
 }
 
 X_STANDARD_NAMES = ("projection_x_coordinate", "longitude")
@@ -261,7 +261,7 @@ def _infer_dims(
         expected_dims = _CONNECTIVITY_DIMS[role]
         var_dims = ds[varname].dims
         for key, dim in zip(expected_dims, var_dims):
-            if isinstance(key, str):  # skip None or integer
+            if isinstance(key, str):
                 prev_dim = inferred.get(key)
                 # Not specified: default order can be used to infer dimensions.
                 if prev_dim is None:
@@ -272,6 +272,16 @@ def _infer_dims(
                             f"{key}: {prev_dim} not in {role}: {varname}"
                             f" with dimensions: {var_dims}"
                         )
+            elif isinstance(key, int):
+                dim_size = ds.dims[dim]
+                if not dim_size == key:
+                    raise UgridDimensionError(
+                        f"Expected size {key} for dimension {dim} in variable "
+                        f"{varname} with role {role}, found instead: "
+                        f"{dim_size}"
+                    )
+
+            # If key is None, we don't do any checking.
 
     for role, varnames in coordinates.items():
         key = _COORD_DIMS[role]

xugrid/ugrid/ugridbase.py

@@ -227,15 +227,16 @@ def _filtered_attrs(self, dataset: xr.Dataset):
         topodim = self.topology_dimension
         attrs = self._attrs.copy()
 
-        for key in conventions._DIM_NAMES[topodim]:
-            if key in attrs:
-                if attrs[key] not in dataset.dims:
-                    attrs.pop(key)
+        ugrid_dims = conventions._DIM_NAMES[topodim] + tuple(
+            [dims[0] for dims in conventions._CONNECTIVITY_DIMS.values()]
+        )
+        for key in ugrid_dims:
+            if key in attrs and attrs[key] not in dataset.dims:
+                attrs.pop(key)
 
         for key in conventions._CONNECTIVITY_NAMES[topodim]:
-            if key in attrs:
-                if attrs[key] not in dataset:
-                    attrs.pop(key)
+            if key in attrs and attrs[key] not in dataset:
+                attrs.pop(key)
 
         for coord in conventions._COORD_NAMES[topodim]:
             if coord in attrs: