fix(checkpoint): update blob access to support JSON path syntax (#117)

Modified the AsyncRedisSaver to access the blob attribute using JSON path syntax. Enhanced the sorting mechanism for parent checkpoints and ensured the results map correctly extracts type and blob pairs, accommodating both direct and JSON path access. This improves compatibility and consistency in data handling.

Author: JHSeo-git

langgraph/checkpoint/redis/aio.py

@@ -1724,7 +1724,7 @@ async def _abatch_load_pending_sends(
                 return_fields=[
                     "checkpoint_id",
                     "type",
-                    "blob",
+                    "$.blob",
                     "task_path",
                     "task_id",
                     "idx",
@@ -1745,20 +1745,27 @@ async def _abatch_load_pending_sends(
             # Sort and format results for each parent checkpoint
             for parent_checkpoint_id in parent_checkpoint_ids:
                 batch_key = (thread_id, checkpoint_ns, parent_checkpoint_id)
-                docs = writes_by_checkpoint.get(parent_checkpoint_id, [])
-
-                # Sort for deterministic order
-                sorted_docs = sorted(
-                    docs,
-                    key=lambda d: (
-                        getattr(d, "task_path", ""),
-                        getattr(d, "task_id", ""),
-                        getattr(d, "idx", 0),
+                writes = writes_by_checkpoint.get(parent_checkpoint_id, [])
+
+                # Sort results by task_path, task_id, idx
+                sorted_writes = sorted(
+                    writes,
+                    key=lambda x: (
+                        getattr(x, "task_path", ""),
+                        getattr(x, "task_id", ""),
+                        getattr(x, "idx", 0),
                     ),
                 )
 
-                # Convert to expected format
-                results_map[batch_key] = [(d.type, d.blob) for d in sorted_docs]
+                # Extract type and blob pairs
+                # Handle both direct attribute access and JSON path access
+                results_map[batch_key] = [
+                    (
+                        getattr(doc, "type", ""),
+                        getattr(doc, "$.blob", getattr(doc, "blob", b"")),
+                    )
+                    for doc in sorted_writes
+                ]
 
         return results_map