fix: Enhance OpenAI client to handle additional stop reasons and impr…

…ove tool call validation in tests to address empty tool_calls list. (microsoft#5223)

Resolves microsoft#5222

python/packages/autogen-ext/src/autogen_ext/models/openai/_openai_client.py

@@ -336,6 +336,10 @@ def normalize_stop_reason(stop_reason: str | None) -> FinishReasons:
     stop_reason = stop_reason.lower()
 
     KNOWN_STOP_MAPPINGS: Dict[str, FinishReasons] = {
+        "stop": "stop",
+        "length": "length",
+        "content_filter": "content_filter",
+        "function_calls": "function_calls",
         "end_turn": "stop",
         "tool_calls": "function_calls",
     }
@@ -552,7 +556,7 @@ async def create(
         content: Union[str, List[FunctionCall]]
         if choice.message.function_call is not None:
             raise ValueError("function_call is deprecated and is not supported by this model client.")
-        elif choice.message.tool_calls is not None:
+        elif choice.message.tool_calls is not None and len(choice.message.tool_calls) > 0:
             if choice.finish_reason != "tool_calls":
                 warnings.warn(
                     f"Finish reason mismatch: {choice.finish_reason} != tool_calls "

python/packages/autogen-ext/tests/models/test_openai_model_client.py

@@ -600,6 +600,25 @@ async def test_tool_calling(monkeypatch: pytest.MonkeyPatch) -> None:
             object="chat.completion",
             usage=CompletionUsage(prompt_tokens=10, completion_tokens=5, total_tokens=0),
         ),
+        # Should not be returning tool calls when the tool_calls are empty
+        ChatCompletion(
+            id="id5",
+            choices=[
+                Choice(
+                    finish_reason="stop",
+                    index=0,
+                    message=ChatCompletionMessage(
+                        content="I should make a tool call.",
+                        tool_calls=[],
+                        role="assistant",
+                    ),
+                )
+            ],
+            created=0,
+            model=model,
+            object="chat.completion",
+            usage=CompletionUsage(prompt_tokens=10, completion_tokens=5, total_tokens=0),
+        ),
     ]
     mock = _MockChatCompletion(chat_completions)
     monkeypatch.setattr(AsyncCompletions, "create", mock.mock_create)
@@ -652,6 +671,11 @@ async def test_tool_calling(monkeypatch: pytest.MonkeyPatch) -> None:
         assert create_result.content == [FunctionCall(id="1", arguments=r'{"input": "task"}', name="_pass_function")]
         assert create_result.finish_reason == "function_calls"
 
+    # Should not be returning tool calls when the tool_calls are empty
+    create_result = await model_client.create(messages=[UserMessage(content="Hello", source="user")], tools=[pass_tool])
+    assert create_result.content == "I should make a tool call."
+    assert create_result.finish_reason == "stop"
+
 
 async def _test_model_client(model_client: OpenAIChatCompletionClient) -> None:
     # Test basic completion