fix: make errors in build_flow function use the standardized ErrorMessage schema (#5199)

* fix: enhance error handling in build_flow function by utilizing ErrorMessage schema

- Introduced ErrorMessage schema to standardize error reporting in the build_flow function.
- Updated error handling to include flow_id, session_id, and trace_name for better context in error messages.
- Improved clarity and maintainability of error handling logic across multiple exception cases.

* Remove session_id from ErrorMessage in chat endpoint

* fix: enhance error handling in build_flow function by checking for custom component existence

Updated the error handling logic in the build_flow function to safely access the trace_name of the custom component. This change ensures that if the custom component is not present, the trace_name will be set to None, improving the robustness of error reporting.

* fix: update ErrorMessage schema to allow optional session_id and source

- Modified the ErrorMessage class to accept optional parameters for session_id and source, enhancing flexibility in error reporting.
- Updated the initialization logic to handle None values for sender and component attributes, ensuring robustness in cases where source may not be provided.

* fix: improve error handling in build_flow function by using getattr for trace_name

Updated the error handling logic in the build_flow function to utilize getattr for safely accessing the trace_name attribute of the custom component. This change ensures that if the custom component is not present, trace_name will default to None, enhancing the robustness of error reporting.

src/backend/base/langflow/api/v1/chat.py

@@ -39,6 +39,7 @@ from langflow.events.event_manager import EventManager, create_default_event_man
 from langflow.exceptions.component import ComponentBuildError
 from langflow.graph.graph.base import Graph
 from langflow.graph.utils import log_vertex_build
+from langflow.schema.message import ErrorMessage
 from langflow.schema.schema import OutputValue
 from langflow.services.cache.utils import CacheMiss
 from langflow.services.chat.service import ChatService
@@ -376,10 +377,11 @@ async def build_flow(
                 vertices_task.cancel()
                 return
             except Exception as e:
-                if isinstance(e, HTTPException):
-                    event_manager.on_error(data={"error": str(e.detail), "statusCode": e.status_code})
-                    raise
-                event_manager.on_error(data={"error": str(e)})
+                error_message = ErrorMessage(
+                    flow_id=flow_id,
+                    exception=e,
+                )
+                event_manager.on_error(data=error_message.data)
                 raise
 
             ids, vertices_to_run, graph = vertices_task.result()
@@ -387,10 +389,11 @@ async def build_flow(
             try:
                 ids, vertices_to_run, graph = await build_graph_and_get_order()
             except Exception as e:
-                if isinstance(e, HTTPException):
-                    event_manager.on_error(data={"error": str(e.detail), "statusCode": e.status_code})
-                    raise
-                event_manager.on_error(data={"error": str(e)})
+                error_message = ErrorMessage(
+                    flow_id=flow_id,
+                    exception=e,
+                )
+                event_manager.on_error(data=error_message.data)
                 raise
         event_manager.on_vertices_sorted(data={"ids": ids, "to_run": vertices_to_run})
         await client_consumed_queue.get()
@@ -408,7 +411,15 @@ async def build_flow(
             return
         except Exception as e:
             logger.error(f"Error building vertices: {e}")
-            event_manager.on_error(data={"error": str(e)})
+            custom_component = graph.get_vertex(vertex_id).custom_component
+            trace_name = getattr(custom_component, "trace_name", None)
+            error_message = ErrorMessage(
+                flow_id=flow_id,
+                exception=e,
+                session_id=graph.session_id,
+                trace_name=trace_name,
+            )
+            event_manager.on_error(data=error_message.data)
             raise
         event_manager.on_end(data={})
         await event_manager.queue.put((None, None, time.time))

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

@@ -371,10 +371,10 @@ class ErrorMessage(Message):
     def __init__(
         self,
         exception: BaseException,
-        session_id: str,
-        source: Source,
+        session_id: str | None = None,
+        source: Source | None = None,
         trace_name: str | None = None,
-        flow_id: str | None = None,
+        flow_id: UUID | str | None = None,
     ) -> None:
         # This is done to avoid circular imports
         if exception.__class__.__name__ == "ExceptionWithMessageError" and exception.__cause__ is not None:
@@ -400,8 +400,8 @@ class ErrorMessage(Message):
 
         super().__init__(
             session_id=session_id,
-            sender=source.display_name,
-            sender_name=source.display_name,
+            sender=source.display_name if source else None,
+            sender_name=source.display_name if source else None,
             text=reason,
             properties=Properties(
                 text_color="red",
@@ -420,7 +420,7 @@ class ErrorMessage(Message):
                     contents=[
                         ErrorContent(
                             type="error",
-                            component=source.display_name,
+                            component=source.display_name if source else None,
                             field=str(exception.field) if hasattr(exception, "field") else None,
                             reason=reason,
                             solution=str(exception.solution) if hasattr(exception, "solution") else None,