Treat missing as optional in UpdateNamespacePropertiesResponse

The REST spec marks the missing field of UpdateNamespacePropertiesResponse
as optional and nullable, and servers such as Lakekeeper omit it when no
requested removal was missing. pyiceberg required it, so
update_namespace_properties raised a ValidationError after the server had
applied the change. Default it to an empty list and map null to [].

Closes #4066

Author: mayuriphad

pyiceberg/catalog/rest/__init__.py

@@ -447,7 +447,12 @@ def replace_none_with_dict(cls, v: Any) -> Properties:
 class UpdateNamespacePropertiesResponse(IcebergBaseModel):
     removed: list[str] = Field()
     updated: list[str] = Field()
-    missing: list[str] = Field()
+    # optional and nullable in the REST spec; servers may omit it when nothing is missing
+    missing: list[str] = Field(default_factory=list)
+
+    @field_validator("missing", mode="before")
+    def missing_null_to_empty(cls, missing: list[str] | None) -> list[str]:
+        return missing if missing is not None else []
 
 
 class ListTableResponseEntry(IcebergBaseModel):

tests/catalog/test_rest.py

@@ -1342,6 +1342,25 @@ def test_update_namespace_properties_200(rest_mock: Mocker) -> None:
     assert response == PropertiesUpdateSummary(removed=[], updated=["prop"], missing=["abc"])
 
 
+@pytest.mark.parametrize(
+    "response_json",
+    [
+        {"removed": ["a", "b"], "updated": []},
+        {"removed": ["a", "b"], "updated": [], "missing": None},
+    ],
+)
+def test_update_namespace_properties_200_without_missing(rest_mock: Mocker, response_json: dict[str, Any]) -> None:
+    rest_mock.post(
+        f"{TEST_URI}v1/namespaces/fokko/properties",
+        json=response_json,
+        status_code=200,
+        request_headers=TEST_HEADERS,
+    )
+    response = RestCatalog("rest", uri=TEST_URI, token=TEST_TOKEN).update_namespace_properties(("fokko",), {"a", "b"})
+
+    assert response == PropertiesUpdateSummary(removed=["a", "b"], updated=[], missing=[])
+
+
 def test_namespace_exists_200(rest_mock: Mocker) -> None:
     rest_mock.head(
         f"{TEST_URI}v1/namespaces/fokko",