Fix to_dataset for components with uninitialized variables

konrad/component.py

@@ -152,7 +152,16 @@ def to_dataset(self):
             self.coords["time"] = [0]
             return xr.Dataset(
                 coords=self.coords,
-                data_vars=self.data_vars,
+                # Convert `None` to ndarrays filled with np.nan
+                data_vars={
+                    k: (
+                        dim,
+                        np.full([len(self.coords[d]) for d in dim], fill_value=np.nan),
+                    )
+                    if val is None
+                    else (dim, val)
+                    for k, (dim, val) in self.data_vars.items()
+                },
                 attrs=self.attrs,
             )
 

konrad/test/test_component.py

@@ -0,0 +1,29 @@
+import numpy as np
+
+from konrad.component import Component
+
+
+class TestComponent:
+    def test_to_dataset(self):
+        """Test conversion to Xarray dataset."""
+        c = Component()
+
+        c.coords = {"dim": np.arange(10)}
+        c._data_vars = {"var": (("dim",), np.arange(10))}
+        c._attrs = {"title": "Dummy component"}
+
+        ds = c.to_dataset()
+
+        assert ds.title == "Dummy component"
+        assert ds["var"][5] == 5
+
+    def test_to_dataset_uninitialized(self):
+        """Test conversion to Xarray dataset with uninitialized data."""
+        c = Component()
+
+        c.coords = {"dim": np.arange(10)}
+        c._data_vars = {"var": (("dim",), None)}
+
+        ds = c.to_dataset()
+
+        assert np.all(np.isnan(ds["var"]))