Fix Galaxy paging review findings

clients/python/src/mxgateway/galaxy.py

@@ -18,7 +18,7 @@ import grpc
 from google.protobuf.timestamp_pb2 import Timestamp
 
 from .auth import merge_metadata
-from .errors import map_rpc_error
+from .errors import MxGatewayError, map_rpc_error
 from .generated import galaxy_repository_pb2 as galaxy_pb
 from .generated import galaxy_repository_pb2_grpc as galaxy_pb_grpc
 from .options import ClientOptions, create_channel
@@ -115,6 +115,7 @@ class GalaxyRepositoryClient:
         """Return the deployed Galaxy object hierarchy as raw proto messages."""
 
         objects: list[galaxy_pb.GalaxyObject] = []
+        seen_page_tokens: set[str] = set()
         page_token = ""
         while True:
             reply = await self._unary(
@@ -129,6 +130,11 @@ class GalaxyRepositoryClient:
             page_token = reply.next_page_token
             if not page_token:
                 return objects
+            if page_token in seen_page_tokens:
+                raise MxGatewayError(
+                    f"galaxy discover hierarchy returned repeated page token {page_token!r}"
+                )
+            seen_page_tokens.add(page_token)
 
     def watch_deploy_events(
         self,

clients/python/tests/test_galaxy.py

@@ -148,6 +148,22 @@ async def test_discover_hierarchy_returns_proto_objects() -> None:
     assert objects[1].attributes[0].full_tag_reference == "DelmiaReceiver_001.DownloadPath"
 
 
+@pytest.mark.asyncio
+async def test_discover_hierarchy_rejects_repeated_page_token() -> None:
+    stub = FakeGalaxyStub()
+    stub.discover_hierarchy.replies = [
+        galaxy_pb.DiscoverHierarchyReply(next_page_token="7:1"),
+        galaxy_pb.DiscoverHierarchyReply(next_page_token="7:1"),
+    ]
+    client = await GalaxyRepositoryClient.connect(
+        ClientOptions(endpoint="fake", plaintext=True),
+        stub=stub,
+    )
+
+    with pytest.raises(Exception, match="repeated page token"):
+        await client.discover_hierarchy()
+
+
 @pytest.mark.asyncio
 async def test_watch_deploy_events_yields_events_in_order() -> None:
     ts1 = Timestamp()