fix: treat null CBS metadata fields as empty strings

src/cbspy/client.py

@@ -76,12 +76,13 @@ def get_metadata(self, table_id: str) -> TableMetadata:
         prop_rows = self._odata.get_json(table_id, "DataProperties")
         columns = [self._parse_column(p) for p in prop_rows]
 
+        # CBS sends explicit nulls for missing fields, so `or` rather than a .get() default.
         return TableMetadata(
-            id=info.get("Identifier", table_id),
-            title=info.get("Title", ""),
-            description=info.get("ShortDescription", ""),
-            period=info.get("Period", ""),
-            frequency=info.get("Frequency", ""),
+            id=info.get("Identifier") or table_id,
+            title=info.get("Title") or "",
+            description=info.get("ShortDescription") or "",
+            period=info.get("Period") or "",
+            frequency=info.get("Frequency") or "",
             properties=columns,
         )
 
@@ -173,9 +174,9 @@ def _build_filter(
     def _parse_column(prop: dict[str, Any]) -> Column:
         """Convert a raw DataProperties entry to a Column model."""
         return Column(
-            id=prop.get("Key", ""),
-            name=prop.get("Title", ""),
-            unit=prop.get("Unit", ""),
-            datatype=prop.get("Datatype", prop.get("Type", "")),
-            description=prop.get("Description", ""),
+            id=prop.get("Key") or "",
+            name=prop.get("Title") or "",
+            unit=prop.get("Unit") or "",
+            datatype=prop.get("Datatype") or prop.get("Type") or "",
+            description=prop.get("Description") or "",
         )

tests/test_client.py

@@ -139,6 +139,59 @@ def test_not_found_raises(self):
         with pytest.raises(TableNotFoundError):
             client.get_metadata("FAKE")
 
+    @respx.mock
+    def test_null_fields_become_empty_strings(self):
+        # CBS sends explicit nulls, e.g. 86103NED has properties with "Description": null.
+        respx.get(f"{BASE}/ODataFeed/OData/86103NED/TableInfos").mock(
+            return_value=httpx.Response(
+                200,
+                json={
+                    "value": [
+                        {
+                            "Title": "Aardgasbalans; aanbod en verbruik",
+                            "ShortDescription": None,
+                            "Identifier": "86103NED",
+                            "Period": "2015 - augustus 2026",
+                            "Frequency": None,
+                        }
+                    ]
+                },
+            )
+        )
+        respx.get(f"{BASE}/ODataFeed/OData/86103NED/DataProperties").mock(
+            return_value=httpx.Response(
+                200,
+                json={
+                    "value": [
+                        {
+                            "ID": 0,
+                            "Key": "Perioden",
+                            "Title": "Perioden",
+                            "Description": None,
+                            "Type": "TimeDimension",
+                            "Unit": None,
+                        },
+                        {
+                            "ID": 1,
+                            "Key": "TotaalVerbruik_25",
+                            "Title": "Totaal verbruik",
+                            "Description": None,
+                            "Type": "Topic",
+                            "Datatype": "Long",
+                            "Unit": "mln m3",
+                        },
+                    ]
+                },
+            )
+        )
+        client = Client()
+        meta = client.get_metadata("86103NED")
+        assert meta.description == ""
+        assert meta.frequency == ""
+        assert meta.properties[0].unit == ""
+        assert meta.properties[1].description == ""
+        assert meta.properties[1].unit == "mln m3"
+
 
 class TestGetData:
     @respx.mock