feat: Improve formatting in print streaming chunk (#9431)

* Improve formatting in print streaming chunk

* Add reno

* Fix mypy

* PR comments

Author: sjrl

haystack/components/generators/utils.py

@@ -2,6 +2,8 @@
 #
 # SPDX-License-Identifier: Apache-2.0
 
+from typing import Any, Dict
+
 from openai.types.chat.chat_completion_chunk import ChoiceDeltaToolCall
 
 from haystack.dataclasses import StreamingChunk
@@ -23,23 +25,31 @@ def print_streaming_chunk(chunk: StreamingChunk) -> None:
         tool results.
     """
     # Print tool call metadata if available (from ChatGenerator)
-    if chunk.meta.get("tool_calls"):
-        for tool_call in chunk.meta["tool_calls"]:
-            if isinstance(tool_call, ChoiceDeltaToolCall) and tool_call.function:
-                # print the tool name
-                if tool_call.function.name and not tool_call.function.arguments:
-                    print("[TOOL CALL]\n", flush=True, end="")
-                    print(f"Tool: {tool_call.function.name} ", flush=True, end="")
+    if tool_calls := chunk.meta.get("tool_calls"):
+        for tool_call in tool_calls:
+            # Convert to dict if tool_call is a ChoiceDeltaToolCall
+            tool_call_dict: Dict[str, Any] = (
+                tool_call.to_dict() if isinstance(tool_call, ChoiceDeltaToolCall) else tool_call
+            )
+
+            if function := tool_call_dict.get("function"):
+                if name := function.get("name"):
+                    print("\n\n[TOOL CALL]\n", flush=True, end="")
+                    print(f"Tool: {name} ", flush=True, end="")
                     print("\nArguments: ", flush=True, end="")
 
-                # print the tool arguments
-                if tool_call.function.arguments:
-                    print(tool_call.function.arguments, flush=True, end="")
+                if arguments := function.get("arguments"):
+                    print(arguments, flush=True, end="")
 
     # Print tool call results if available (from ToolInvoker)
-    if chunk.meta.get("tool_result"):
-        print(f"\n\n[TOOL RESULT]\n{chunk.meta['tool_result']}\n\n", flush=True, end="")
+    if tool_result := chunk.meta.get("tool_result"):
+        print(f"\n\n[TOOL RESULT]\n{tool_result}", flush=True, end="")
 
     # Print the main content of the chunk (from ChatGenerator)
-    if chunk.content:
-        print(chunk.content, flush=True, end="")
+    if content := chunk.content:
+        print(content, flush=True, end="")
+
+    # End of LLM assistant message so we add two new lines
+    # This ensures spacing between multiple LLM messages (e.g. Agent)
+    if chunk.meta.get("finish_reason") is not None:
+        print("\n\n", flush=True, end="")

haystack/components/tools/tool_invoker.py

@@ -508,6 +508,10 @@ def run(
                         )
                     )
 
+        # We stream one more chunk that contains a finish_reason if tool_messages were generated
+        if len(tool_messages) > 0 and streaming_callback is not None:
+            streaming_callback(StreamingChunk(content="", meta={"finish_reason": "tool_call_results"}))
+
         return {"tool_messages": tool_messages, "state": state}
 
     @component.output_types(tool_messages=List[ChatMessage], state=State)
@@ -609,6 +613,10 @@ async def run_async(
                         )
                     )  # type: ignore[misc] # we have checked that streaming_callback is not None and async
 
+        # We stream one more chunk that contains a finish_reason if tool_messages were generated
+        if len(tool_messages) > 0 and streaming_callback is not None:
+            await streaming_callback(StreamingChunk(content="", meta={"finish_reason": "tool_call_results"}))  # type: ignore[misc] # we have checked that streaming_callback is not None and async
+
         return {"tool_messages": tool_messages, "state": state}
 
     def to_dict(self) -> Dict[str, Any]:

releasenotes/notes/improve-print-streaming-chunk-1b3f389e30967208.yaml

@@ -0,0 +1,6 @@
+---
+enhancements:
+  - |
+    - Updates StreamingChunk construction in ToolInvoker to also stream a chunk with a finish reason. This is useful when using the print_streaming_chunk utility method
+    - Update the print_streaming_chunk to have better formatting of messages especially when using it with Agent.
+    - Also updated to work with the current version of the AWS Bedrock integration by working with the dict representation of ChoiceDeltaToolCall