chore(langgraph): Log when no values event is emitted from RemoteGraph (#6140)

libs/langgraph/langgraph/pregel/remote.py

@@ -1,5 +1,6 @@
 from __future__ import annotations
 
+import logging
 from collections.abc import AsyncIterator, Iterator, Sequence
 from dataclasses import asdict
 from typing import (
@@ -61,6 +62,8 @@ from langgraph.types import (
     StreamMode,
 )
 
+logger = logging.getLogger(__name__)
+
 __all__ = ("RemoteGraph", "RemoteException")
 
 _CONF_DROPLIST = frozenset(
@@ -950,6 +953,7 @@ class RemoteGraph(PregelProtocol):
         try:
             return chunk
         except UnboundLocalError:
+            logger.warning("No events received from remote graph")
             return None
 
     async def ainvoke(
@@ -990,6 +994,7 @@ class RemoteGraph(PregelProtocol):
         try:
             return chunk
         except UnboundLocalError:
+            logger.warning("No events received from remote graph")
             return None
 
 

libs/langgraph/tests/test_pregel.py

@@ -8383,6 +8383,7 @@ def test_get_graph_nonterminal_last_step_source(snapshot: SnapshotAssertion) ->
 
     assert json.dumps(graph_json, indent=2, sort_keys=True) == snapshot
 
+
 def test_null_resume_disallowed_with_multiple_interrupts(
     sync_checkpointer: BaseCheckpointSaver,
 ) -> None: