fix: Fix pagination of list_sessions in VertexAiSessionService

Resolves https://github.com/google/adk-python/issues/2860

PiperOrigin-RevId: 804511401

src/google/adk/sessions/vertex_ai_session_service.py

@@ -275,36 +275,47 @@ class VertexAiSessionService(BaseSessionService):
     reasoning_engine_id = self._get_reasoning_engine_id(app_name)
     api_client = self._get_api_client()
 
-    path = f'reasoningEngines/{reasoning_engine_id}/sessions'
-    if user_id:
-      parsed_user_id = urllib.parse.quote(f'''"{user_id}"''', safe='')
-      path = path + f'?filter=user_id={parsed_user_id}'
-
-    list_sessions_api_response = await api_client.async_request(
-        http_method='GET',
-        path=path,
-        request_dict={},
-    )
-    list_sessions_api_response = _convert_api_response(
-        list_sessions_api_response
-    )
-
-    # Handles empty response case
-    if not list_sessions_api_response or list_sessions_api_response.get(
-        'httpHeaders', None
-    ):
-      return ListSessionsResponse()
-
+    base_path = f'reasoningEngines/{reasoning_engine_id}/sessions'
     sessions = []
-    for api_session in list_sessions_api_response['sessions']:
-      session = Session(
-          app_name=app_name,
-          user_id=user_id,
-          id=api_session['name'].split('/')[-1],
-          state=api_session.get('sessionState', {}),
-          last_update_time=isoparse(api_session['updateTime']).timestamp(),
+    page_token = None
+    while True:
+      path = base_path
+      query_params = {}
+      if user_id:
+        query_params['filter'] = f'user_id="{user_id}"'
+      if page_token:
+        query_params['pageToken'] = page_token
+
+      if query_params:
+        path = f'{path}?{urllib.parse.urlencode(query_params)}'
+
+      list_sessions_api_response = await api_client.async_request(
+          http_method='GET',
+          path=path,
+          request_dict={},
       )
-      sessions.append(session)
+      converted_api_response = _convert_api_response(list_sessions_api_response)
+
+      # Handles empty response case
+      if not converted_api_response or converted_api_response.get(
+          'httpHeaders', None
+      ):
+        break
+
+      for api_session in converted_api_response.get('sessions', []):
+        session = Session(
+            app_name=app_name,
+            user_id=user_id,
+            id=api_session['name'].split('/')[-1],
+            state=api_session.get('sessionState', {}),
+            last_update_time=isoparse(api_session['updateTime']).timestamp(),
+        )
+        sessions.append(session)
+
+      page_token = converted_api_response.get('nextPageToken')
+      if not page_token:
+        break
+
     return ListSessionsResponse(sessions=sessions)
 
   async def delete_session(

tests/unittests/sessions/test_vertex_ai_session_service.py

@@ -19,6 +19,7 @@ from typing import List
 from typing import Optional
 from typing import Tuple
 from unittest import mock
+from urllib import parse
 
 from dateutil.parser import isoparse
 from google.adk.events.event import Event
@@ -107,6 +108,22 @@ MOCK_EVENT_JSON_3 = [
         'timestamp': '2024-12-12T12:12:12.123456Z',
     },
 ]
+MOCK_SESSION_JSON_PAGE1 = {
+    'name': (
+        'projects/test-project/locations/test-location/'
+        'reasoningEngines/123/sessions/page1'
+    ),
+    'updateTime': '2024-12-15T12:12:12.123456Z',
+    'userId': 'user_with_pages',
+}
+MOCK_SESSION_JSON_PAGE2 = {
+    'name': (
+        'projects/test-project/locations/test-location/'
+        'reasoningEngines/123/sessions/page2'
+    ),
+    'updateTime': '2024-12-16T12:12:12.123456Z',
+    'userId': 'user_with_pages',
+}
 
 MOCK_SESSION = Session(
     app_name='123',
@@ -157,9 +174,7 @@ MOCK_SESSION_2 = Session(
 
 
 SESSION_REGEX = r'^reasoningEngines/([^/]+)/sessions/([^/]+)$'
-SESSIONS_REGEX = (  # %22 represents double-quotes in a URL-encoded string
-    r'^reasoningEngines/([^/]+)/sessions\?filter=user_id=%22([^%]+)%22.*$'
-)
+SESSIONS_REGEX = r'^reasoningEngines/([^/]+)/sessions\?.*$'
 EVENTS_REGEX = (
     r'^reasoningEngines/([^/]+)/sessions/([^/]+)/events(?:\?pageToken=([^/]+))?'
 )
@@ -188,12 +203,28 @@ class MockApiClient:
           else:
             raise ValueError(f'Session not found: {session_id}')
       elif re.match(SESSIONS_REGEX, path):
-        match = re.match(SESSIONS_REGEX, path)
+        parsed_url = parse.urlparse(path)
+        query_params = parse.parse_qs(parsed_url.query)
+        filter_val = query_params.get('filter', [''])[0]
+        user_id_match = re.search(r'user_id="([^"]+)"', filter_val)
+        if not user_id_match:
+          raise ValueError(f'Could not find user_id in filter: {filter_val}')
+        user_id = user_id_match.group(1)
+
+        if user_id == 'user_with_pages':
+          page_token = query_params.get('pageToken', [None])[0]
+          if page_token == 'my_token':
+            return {'sessions': [MOCK_SESSION_JSON_PAGE2]}
+          else:
+            return {
+                'sessions': [MOCK_SESSION_JSON_PAGE1],
+                'nextPageToken': 'my_token',
+            }
         return {
             'sessions': [
                 session
                 for session in self.session_dict.values()
-                if session['userId'] == match.group(2)
+                if session['userId'] == user_id
             ],
         }
       elif re.match(EVENTS_REGEX, path):
@@ -271,6 +302,8 @@ def mock_get_api_client():
       '1': MOCK_SESSION_JSON_1,
       '2': MOCK_SESSION_JSON_2,
       '3': MOCK_SESSION_JSON_3,
+      'page1': MOCK_SESSION_JSON_PAGE1,
+      'page2': MOCK_SESSION_JSON_PAGE2,
   }
   api_client.event_dict = {
       '1': (MOCK_EVENT_JSON, None),
@@ -358,6 +391,18 @@ async def test_list_sessions():
   assert sessions.sessions[1].id == '2'
 
 
+@pytest.mark.asyncio
+@pytest.mark.usefixtures('mock_get_api_client')
+async def test_list_sessions_with_pagination():
+  session_service = mock_vertex_ai_session_service()
+  sessions = await session_service.list_sessions(
+      app_name='123', user_id='user_with_pages'
+  )
+  assert len(sessions.sessions) == 2
+  assert sessions.sessions[0].id == 'page1'
+  assert sessions.sessions[1].id == 'page2'
+
+
 @pytest.mark.asyncio
 @pytest.mark.usefixtures('mock_get_api_client')
 async def test_create_session():