REST: Require metadata-location in view responses (#4152)

Require metadata-location in REST view responses

The REST spec marks metadata-location as required in LoadViewResult, and
Java's LoadViewResponseParser rejects responses without it. Make
ViewResponse.metadata_location required to match.

Behavior change: create_view, load_view, and register_view now raise a
pydantic ValidationError for non-compliant servers that omit
metadata-location, instead of silently accepting the response.

Co-authored-by: Copilot App <223556219+Copilot@users.noreply.github.com>

Author: kevinjqliu

pyiceberg/catalog/rest/__init__.py

@@ -361,7 +361,7 @@ class LoadCredentialsResponse(IcebergBaseModel):
 
 
 class ViewResponse(IcebergBaseModel):
-    metadata_location: str | None = Field(alias="metadata-location", default=None)
+    metadata_location: str = Field(..., alias="metadata-location")
     metadata: ViewMetadata
     config: Properties = Field(default_factory=dict)
 

tests/catalog/test_rest.py

@@ -26,6 +26,7 @@
 from urllib.parse import parse_qs, urlsplit
 
 import pytest
+from pydantic import ValidationError
 from requests import Request
 from requests.adapters import HTTPAdapter
 from requests.exceptions import HTTPError
@@ -1856,6 +1857,19 @@ def test_load_view_200(rest_mock: Mocker, example_view_metadata_rest_json: dict[
     assert actual.config == example_view_metadata_rest_json["config"]
 
 
+def test_load_view_missing_metadata_location(rest_mock: Mocker, example_view_metadata_rest_json: dict[str, Any]) -> None:
+    response = {k: v for k, v in example_view_metadata_rest_json.items() if k != "metadata-location"}
+    rest_mock.get(
+        f"{TEST_URI}v1/namespaces/fokko/views/view",
+        json=response,
+        status_code=200,
+        request_headers=TEST_HEADERS,
+    )
+    catalog = RestCatalog("rest", uri=TEST_URI, token=TEST_TOKEN)
+    with pytest.raises(ValidationError, match="metadata-location"):
+        catalog.load_view(("fokko", "view"))
+
+
 def test_load_view_404(rest_mock: Mocker) -> None:
     rest_mock.get(
         f"{TEST_URI}v1/namespaces/fokko/views/non_existent_view",