From 9f5591639efdad29f5d6f94fded93d69a24330bf Mon Sep 17 00:00:00 2001
From: Gabriel Luiz Freitas Almeida <gabriel@logspace.ai>
Date: Tue, 13 Jun 2023 20:41:58 -0300
Subject: [PATCH] =?UTF-8?q?=F0=9F=90=9B=20fix(chat.py):=20handle=20excepti?=
 =?UTF-8?q?ons=20while=20building=20the=20flow=20and=20add=20a=20final=20r?=
 =?UTF-8?q?esponse=20to=20the=20event=20stream=20The=20code=20now=20handle?=
 =?UTF-8?q?s=20exceptions=20that=20may=20occur=20while=20building=20the=20?=
 =?UTF-8?q?flow.=20A=20final=20response=20is=20added=20to=20the=20event=20?=
 =?UTF-8?q?stream=20to=20indicate=20the=20end=20of=20the=20stream.?=
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Content-Type: text/plain; charset=UTF-8
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---
 src/backend/langflow/api/v1/chat.py | 78 +++++++++++++++--------------
 1 file changed, 41 insertions(+), 37 deletions(-)

diff --git a/src/backend/langflow/api/v1/chat.py b/src/backend/langflow/api/v1/chat.py
index 04b93bd9e..a8f6a2101 100644
--- a/src/backend/langflow/api/v1/chat.py
+++ b/src/backend/langflow/api/v1/chat.py
@@ -69,44 +69,48 @@ async def stream_build(flow_id: str):
     """Stream the build process based on stored flow data."""
 
     async def event_stream(flow_id):
-        if flow_id not in flow_data_store:
-            error_message = "Invalid session ID"
-            yield f"data: {json.dumps({'error': error_message})}\n\n"
-            return
-
-        graph_data = flow_data_store[flow_id].get("data")
-
-        if not graph_data:
-            error_message = "No data provided"
-            yield f"data: {json.dumps({'error': error_message})}\n\n"
-            return
-
-        logger.debug("Building langchain object")
-        graph = Graph.from_payload(graph_data)
-        for node in graph.generator_build():
-            try:
-                node.build()
-                params = node._built_object_repr()
-                valid = True
-                logger.debug(
-                    f"Building node {params[:50]}{'...' if len(params) > 50 else ''}"
-                )
-            except Exception as exc:
-                params = str(exc)
-                valid = False
-
-            response = json.dumps(
-                {
-                    "valid": valid,
-                    "params": params,
-                    "id": node.id,
-                }
-            )
-            yield f"data: {response}\n\n"  # SSE format
-
-        chat_manager.set_cache(flow_id, graph.build())
         final_response = json.dumps({"end_of_stream": True})
-        yield f"data: {final_response}\n\n"  # SSE format
+        try:
+            if flow_id not in flow_data_store:
+                error_message = "Invalid session ID"
+                yield f"data: {json.dumps({'error': error_message})}\n\n"
+                return
+
+            graph_data = flow_data_store[flow_id].get("data")
+
+            if not graph_data:
+                error_message = "No data provided"
+                yield f"data: {json.dumps({'error': error_message})}\n\n"
+                return
+
+            logger.debug("Building langchain object")
+            graph = Graph.from_payload(graph_data)
+            for node in graph.generator_build():
+                try:
+                    node.build()
+                    params = node._built_object_repr()
+                    valid = True
+                    logger.debug(
+                        f"Building node {params[:50]}{'...' if len(params) > 50 else ''}"
+                    )
+                except Exception as exc:
+                    params = str(exc)
+                    valid = False
+
+                response = json.dumps(
+                    {
+                        "valid": valid,
+                        "params": params,
+                        "id": node.id,
+                    }
+                )
+                yield f"data: {response}\n\n"
+
+            chat_manager.set_cache(flow_id, graph.build())
+        except Exception:
+            logger.error("Error while building the flow")
+        finally:
+            yield f"data: {final_response}\n\n"
 
     try:
         return StreamingResponse(event_stream(flow_id), media_type="text/event-stream")