checkpoint-sqlite/postgres: handle calling .list on async checkpointer (#3019)

libs/checkpoint-postgres/langgraph/checkpoint/postgres/aio.py

@@ -380,6 +380,18 @@ class AsyncPostgresSaver(BasePostgresSaver):
         Yields:
             Iterator[CheckpointTuple]: An iterator of matching checkpoint tuples.
         """
+        try:
+            # check if we are in the main thread, only bg threads can block
+            # we don't check in other methods to avoid the overhead
+            if asyncio.get_running_loop() is self.loop:
+                raise asyncio.InvalidStateError(
+                    "Synchronous calls to AsyncSqliteSaver are only allowed from a "
+                    "different thread. From the main thread, use the async interface. "
+                    "For example, use `checkpointer.alist(...)` or `await "
+                    "graph.ainvoke(...)`."
+                )
+        except RuntimeError:
+            pass
         aiter_ = self.alist(config, filter=filter, before=before, limit=limit)
         while True:
             try:
@@ -410,7 +422,7 @@ class AsyncPostgresSaver(BasePostgresSaver):
             if asyncio.get_running_loop() is self.loop:
                 raise asyncio.InvalidStateError(
                     "Synchronous calls to AsyncPostgresSaver are only allowed from a "
-                    "different thread. From the main thread, use the async interface."
+                    "different thread. From the main thread, use the async interface. "
                     "For example, use `await checkpointer.aget_tuple(...)` or `await "
                     "graph.ainvoke(...)`."
                 )

libs/checkpoint-sqlite/langgraph/checkpoint/sqlite/aio.py

@@ -159,7 +159,7 @@ class AsyncSqliteSaver(BaseCheckpointSaver[str]):
             if asyncio.get_running_loop() is self.loop:
                 raise asyncio.InvalidStateError(
                     "Synchronous calls to AsyncSqliteSaver are only allowed from a "
-                    "different thread. From the main thread, use the async interface."
+                    "different thread. From the main thread, use the async interface. "
                     "For example, use `await checkpointer.aget_tuple(...)` or `await "
                     "graph.ainvoke(...)`."
                 )
@@ -191,6 +191,18 @@ class AsyncSqliteSaver(BaseCheckpointSaver[str]):
         Yields:
             Iterator[CheckpointTuple]: An iterator of matching checkpoint tuples.
         """
+        try:
+            # check if we are in the main thread, only bg threads can block
+            # we don't check in other methods to avoid the overhead
+            if asyncio.get_running_loop() is self.loop:
+                raise asyncio.InvalidStateError(
+                    "Synchronous calls to AsyncSqliteSaver are only allowed from a "
+                    "different thread. From the main thread, use the async interface. "
+                    "For example, use `checkpointer.alist(...)` or `await "
+                    "graph.ainvoke(...)`."
+                )
+        except RuntimeError:
+            pass
         aiter_ = self.alist(config, filter=filter, before=before, limit=limit)
         while True:
             try: