fix: make JSON serialization work with Callable objects (#4302)

Enhance JSON serialization with custom encoder for Callable objects

src/backend/base/langflow/events/event_manager.py

@@ -8,6 +8,7 @@ from functools import partial
 from fastapi.encoders import jsonable_encoder
 from typing_extensions import Protocol
 
+from langflow.schema.artifact import CUSTOM_ENCODERS
 from langflow.schema.log import LoggableType
 
 
@@ -53,7 +54,7 @@ class EventManager:
         self.events[name] = _callback
 
     def send_event(self, *, event_type: str, data: LoggableType) -> None:
-        jsonable_data = jsonable_encoder(data)
+        jsonable_data = jsonable_encoder(data, custom_encoder=CUSTOM_ENCODERS)
         json_data = {"event": event_type, "data": jsonable_data}
         event_id = uuid.uuid4()
         str_data = json.dumps(json_data) + "\n\n"

src/backend/base/langflow/schema/artifact.py

@@ -1,4 +1,4 @@
-from collections.abc import Generator
+from collections.abc import Callable, Generator
 from enum import Enum
 
 from fastapi.encoders import jsonable_encoder
@@ -51,6 +51,13 @@ def get_artifact_type(value, build_result=None) -> str:
     return result.value
 
 
+def encode_callable(obj: Callable):
+    return obj.__name__ if hasattr(obj, "__name__") else str(obj)
+
+
+CUSTOM_ENCODERS = {Callable: encode_callable}
+
+
 def post_process_raw(raw, artifact_type: str):
     if artifact_type == ArtifactType.STREAM.value:
         raw = ""
@@ -65,10 +72,10 @@ def post_process_raw(raw, artifact_type: str):
     elif artifact_type == ArtifactType.UNKNOWN.value and raw is not None:
         if isinstance(raw, BaseModel | dict):
             try:
-                raw = jsonable_encoder(raw)
+                raw = jsonable_encoder(raw, custom_encoder=CUSTOM_ENCODERS)
                 artifact_type = ArtifactType.OBJECT.value
             except Exception:  # noqa: BLE001
-                logger.opt(exception=True).debug("Error converting to json")
+                logger.opt(exception=True).debug(f"Error converting to json: {raw} ({type(raw)})")
                 raw = "Built Successfully ✨"
         else:
             raw = "Built Successfully ✨"