[Frontend][Responses API] Function call streaming

tests/v1/entrypoints/openai/responses/test_function_call.py

@@ -194,3 +194,107 @@ def get_weather(latitude: float, longitude: float) -> str:
                                                input=input_messages)
     # check the output
     assert len(response_2.output_text) > 0
+
+
+@pytest.mark.asyncio
+@pytest.mark.parametrize("model_name", [MODEL_NAME])
+async def test_function_calling_with_streaming_expected_arguments(
+        client: openai.AsyncOpenAI, model_name: str):
+
+    tools = [{
+        "type": "function",
+        "name": "get_weather",
+        "description":
+        "Get current temperature for provided location in celsius.",
+        "parameters": {
+            "type": "object",
+            "properties": {
+                "location": {
+                    "type": "string"
+                },
+            },
+            "required": ["location"],
+            "additionalProperties": False
+        },
+        "strict": True
+    }]
+
+    stream_response = await client.responses.create(
+        model=model_name,
+        input="Can you tell me what the current weather is in Berlin?",
+        tools=tools,
+        stream=True,
+    )
+
+    tool_call_item = None
+    async for event in stream_response:
+        if (event.type == 'response.output_item.added'
+                and event.item.type == "function_call"):
+            tool_call_item = event.item
+        elif (event.type == 'response.function_call_arguments.delta'
+              and tool_call_item):
+            tool_call_item.arguments += event.delta
+
+    assert tool_call_item is not None
+    assert tool_call_item.type == "function_call"
+    assert tool_call_item.name == "get_weather"
+    args = json.loads(tool_call_item.arguments)
+    assert "location" in args
+    assert args["location"] is not None
+
+
+@pytest.mark.asyncio
+@pytest.mark.parametrize("model_name", [MODEL_NAME])
+async def test_function_calling_with_streaming_types(
+        client: openai.AsyncOpenAI, model_name: str):
+
+    # this links the "done" type with the "start" type
+    # so every "done" type should have a corresponding "start" type
+    # and every open block should be closed by the end of the stream
+    pairs_of_event_types = {
+        "response.completed":
+        "response.created",
+        "response.output_item.done":
+        "response.output_item.added",
+        "response.output_text.done":
+        "response.output_text.delta",
+        "response.content_part.done":
+        "response.content_part.added",
+        "response.reasoning_text.done":
+        "response.reasoning_text.delta",
+        "response.reasoning_part.done":
+        "response.reasoning_part.added",
+        "response.function_call_arguments.done":
+        "response.function_call_arguments.delta",  # noqa
+    }
+
+    input_list = [{
+            "role": "user",
+            "content":
+            "Can you tell me what the current weather is in Berlin and the "\
+            "forecast for the next 5 days, in fahrenheit?"
+        }]
+    stream_response = await client.responses.create(
+        model=model_name,
+        input=input_list,
+        tools=tools,
+        stream=True,
+    )
+
+    stack_of_event_types = []
+    async for event in stream_response:
+        if event.type == 'response.created':
+            stack_of_event_types.append(event.type)
+        elif event.type == 'response.completed':
+            assert stack_of_event_types[-1] == pairs_of_event_types[event.type]
+            stack_of_event_types.pop()
+        if event.type.endswith("added"):
+            stack_of_event_types.append(event.type)
+        elif event.type.endswith("delta"):
+            if stack_of_event_types[-1] == event.type:
+                continue
+            stack_of_event_types.append(event.type)
+        elif event.type.endswith("done"):
+            assert stack_of_event_types[-1] == pairs_of_event_types[event.type]
+            stack_of_event_types.pop()
+    assert len(stack_of_event_types) == 0