fix: fix print_streaming_chunk + add tests (#9579)

* fix: fix print_streaming_chunk + add tests

* rel note

Author: anakin87

haystack/components/generators/utils.py

@@ -44,7 +44,7 @@ def print_streaming_chunk(chunk: StreamingChunk) -> None:
                 if chunk.index and tool_call.index > chunk.index:
                     print("\n\n", flush=True, end="")
 
-                print("[TOOL CALL]\nTool: {tool_call.tool_name} \nArguments: ", flush=True, end="")
+                print(f"[TOOL CALL]\nTool: {tool_call.tool_name} \nArguments: ", flush=True, end="")
 
             # print the tool arguments
             if tool_call.arguments:

releasenotes/notes/fix-print-streaming-chunk-501aaa208354d211.yaml

@@ -0,0 +1,3 @@
+---
+fixes:
+  - Fixed a bug in the `print_streaming_chunk` utility function that prevented tool call name from being printed.

test/components/generators/test_utils.py

@@ -3,9 +3,10 @@
 # SPDX-License-Identifier: Apache-2.0
 
 from openai.types.chat import chat_completion_chunk
+from unittest.mock import patch, call
 
-from haystack.components.generators.utils import _convert_streaming_chunks_to_chat_message
-from haystack.dataclasses import ComponentInfo, StreamingChunk, ToolCallDelta
+from haystack.components.generators.utils import _convert_streaming_chunks_to_chat_message, print_streaming_chunk
+from haystack.dataclasses import ComponentInfo, StreamingChunk, ToolCall, ToolCallDelta, ToolCallResult
 
 
 def test_convert_streaming_chunks_to_chat_message_tool_calls_in_any_chunk():