address review comments and resolve test failures

Signed-off-by: Stephanie <yangcao@redhat.com>

Author: yangcao77

src/app/endpoints/conversations.py

@@ -254,7 +254,7 @@ async def get_conversation_endpoint_handler(
                 status_code=status.HTTP_404_NOT_FOUND,
                 detail={
                     "response": "Conversation not found",
-                    "cause": f"Conversation {conversation_id} could not be deleted: no sessions found",
+                    "cause": f"Conversation {conversation_id} could not be retrieved.",
                 },
             )
         session_id = str(agent_sessions[0].get("session_id"))
@@ -354,13 +354,12 @@ async def delete_conversation_endpoint_handler(
         agent_sessions = (await client.agents.session.list(agent_id=agent_id)).data
 
         if not agent_sessions:
-            logger.error("No sessions found for conversation %s", conversation_id)
-            raise HTTPException(
-                status_code=status.HTTP_404_NOT_FOUND,
-                detail={
-                    "response": "Conversation not found",
-                    "cause": f"Conversation {conversation_id} could not be deleted: no sessions found",
-                },
+            # If no sessions are found, do not raise an error, just return a success response
+            logger.info("No sessions found for conversation %s", conversation_id)
+            return ConversationDeleteResponse(
+                conversation_id=conversation_id,
+                success=True,
+                response="Conversation deleted successfully",
             )
 
         session_id = str(agent_sessions[0].get("session_id"))

src/utils/endpoints.py

@@ -109,16 +109,17 @@ async def get_agent(
         await client.agents.delete(agent_id=orphan_agent_id)
         sessions_response = await client.agents.session.list(agent_id=conversation_id)
         logger.info("session response: %s", sessions_response)
-        if not sessions_response or not sessions_response.data:
+        try:
+            session_id = str(sessions_response.data[0]["session_id"])
+        except IndexError as e:
             logger.error("No sessions found for conversation %s", conversation_id)
             raise HTTPException(
                 status_code=status.HTTP_404_NOT_FOUND,
                 detail={
                     "response": "Conversation not found",
                     "cause": f"Conversation {conversation_id} could not be retrieved.",
                 },
-            )
-        session_id = str(sessions_response.data[0]["session_id"])
+            ) from e
     else:
         conversation_id = agent.agent_id
         session_id = await agent.create_session(get_suid())

tests/unit/app/endpoints/test_conversations.py

@@ -490,6 +490,10 @@ async def test_successful_conversation_deletion(self, mocker, setup_configuratio
 
         # Mock AsyncLlamaStackClientHolder
         mock_client = mocker.AsyncMock()
+        # Ensure the endpoint sees an existing session so it proceeds to delete
+        mock_client.agents.session.list.return_value = mocker.Mock(
+            data=[{"session_id": VALID_CONVERSATION_ID}]
+        )
         mock_client.agents.session.delete.return_value = None  # Successful deletion
         mock_client_holder = mocker.patch(
             "app.endpoints.conversations.AsyncLlamaStackClientHolder"