vllm - 💡(How to fix) Fix [Bug]: DeepSeek V4 DSML tool calls fake-stream arguments instead of incremental deltas [1 pull requests]

import json
from unittest.mock import MagicMock

from vllm.entrypoints.openai.chat_completion.protocol import ChatCompletionRequest, ChatCompletionToolsParam
from vllm.tool_parsers.deepseekv4_tool_parser import DeepSeekV4ToolParser

mock_tokenizer = MagicMock()
mock_tokenizer.get_vocab.return_value = {}

TC_START = "<｜DSML｜tool_calls>"
TC_END = "</｜DSML｜tool_calls>"
INV_START = '<｜DSML｜invoke name="'
INV_END = "</｜DSML｜invoke>"
PARAM_START = '<｜DSML｜parameter name="'
PARAM_END = "</｜DSML｜parameter>"

tool = ChatCompletionToolsParam(
    type="function",
    function={
        "name": "plan_trip",
        "parameters": {
            "type": "object",
            "properties": {
                "days": {"type": "integer"},
                "flexible": {"type": "boolean"},
                "cities": {"type": "array", "items": {"type": "string"}},
                "notes": {"type": "string"},
            },
            "required": ["days", "flexible", "cities", "notes"],
        },
    },
)

full_text = (
    f'{TC_START}\n{INV_START}plan_trip">\n'
    f'{PARAM_START}days" string="false">3{PARAM_END}\n'
    f'{PARAM_START}flexible" string="false">false{PARAM_END}\n'
    f'{PARAM_START}cities" string="false">["Beijing","Shanghai","Tokyo","New York"]{PARAM_END}\n'
    f'{PARAM_START}notes" string="true">靠窗座位{PARAM_END}\n'
    f'{INV_END}\n{TC_END}'
)

parser = DeepSeekV4ToolParser(mock_tokenizer, tools=[tool])
request = ChatCompletionRequest(model="m", messages=[], tools=[tool])
prev = ""
deltas = []
for start in range(0, len(full_text), 4):
    delta_text = full_text[start:start + 4]
    curr = prev + delta_text
    delta = parser.extract_tool_calls_streaming(prev, curr, delta_text, [], [], [1], request)
    prev = curr
    if delta is not None:
        deltas.append(delta)

arg_chunks = [
    tc.function.arguments
    for d in deltas
    for tc in (d.tool_calls or [])
    if tc.function and tc.function.arguments is not None
]

print(len(arg_chunks), [len(c) for c in arg_chunks])
print(json.loads("".join(arg_chunks)))

---

1 [103]
{'days': 3, 'flexible': False, 'cities': ['Beijing', 'Shanghai', 'Tokyo', 'New York'], 'notes': '靠窗座位'}