[Bugfix][Frontend] Prevent IndexError in MiniMax M2 tool parser during...

[Bugfix][Frontend] Prevent IndexError in MiniMax M2 tool parser during streaming extraction (#30555)
Signed-off-by: WangErXiao <863579016@qq.com>

tests/tool_use/test_minimax_m2_tool_parser.py

+# SPDX-License-Identifier: Apache-2.0
+# SPDX-FileCopyrightText: Copyright contributors to the vLLM project
+
+import json
+
+import pytest
+
+from vllm.tool_parsers.minimax_m2_tool_parser import (
+    MinimaxM2ToolParser,
+)
+
+pytestmark = pytest.mark.cpu_test
+
+
+class FakeTokenizer:
+    """Minimal fake tokenizer that exposes the attributes used by the
+    parser: a truthy model_tokenizer marker and a vocab mapping for the
+    special tokens.
+    """
+
+    def __init__(self):
+        self.model_tokenizer = True
+        # The parser will look up start/end tokens by their literal strings
+        self.vocab = {
+            "<minimax:tool_call>": 1,
+            "</minimax:tool_call>": 2,
+        }
+
+    def get_vocab(self):
+        return self.vocab
+
+
+@pytest.fixture
+def minimax_m2_tool_parser():
+    return MinimaxM2ToolParser(FakeTokenizer())
+
+
+def test_extract_tool_calls_streaming_incremental(minimax_m2_tool_parser):
+    parser = minimax_m2_tool_parser
+    parser._reset_streaming_state()
+    chunks = [
+        "<minimax:tool_call>",
+        '<invoke name="get_weather">',
+        '<parameter name="city">',
+        "Seattle</parameter>",
+        "</invoke></minimax:tool_call>",
+    ]
+    previous = ""
+    for chunk in chunks:
+        current = previous + chunk
+        delta = chunk
+        parser.extract_tool_calls_streaming(
+            previous_text=previous,
+            current_text=current,
+            delta_text=delta,
+            previous_token_ids=[],
+            current_token_ids=[],
+            delta_token_ids=[],
+            request=None,
+        )
+        previous = current
+
+    assert len(parser.prev_tool_call_arr) == 1
+    entry = parser.prev_tool_call_arr[0]
+
+    assert entry["name"] == "get_weather"
+    args = entry["arguments"]
+    assert args["city"] == "Seattle"
+
+
+def test_streaming_minimax_m2_multiple_invokes(minimax_m2_tool_parser):
+    parser = minimax_m2_tool_parser
+    parser._reset_streaming_state()
+
+    chunks = [
+        "<minimax:tool_call>",
+        '<invoke name="search_web">',
+        '<parameter name="query_tag">',
+        '["technology", "events"]</parameter>',
+        '<parameter name="query_list">',
+        '["OpenAI", "latest", "release"]</parameter>',
+        "</invoke>",
+        '<invoke name="search_web">',
+        '<parameter name="query_tag">',
+        '["technology", "events"]</parameter>',
+        '<parameter name="query_list">',
+        '["Gemini", "latest", "release"]</parameter>',
+        "</invoke>",
+        "</minimax:tool_call>",
+    ]
+    previous = ""
+    for chunk in chunks:
+        current = previous + chunk
+        delta = chunk
+        parser.extract_tool_calls_streaming(
+            previous_text=previous,
+            current_text=current,
+            delta_text=delta,
+            previous_token_ids=[],
+            current_token_ids=[],
+            delta_token_ids=[],
+            request=None,
+        )
+        previous = current
+
+    assert len(parser.prev_tool_call_arr) == 2
+
+    for entry, expect_model in zip(parser.prev_tool_call_arr, ["OpenAI", "Gemini"]):
+        assert entry["name"] == "search_web"
+        args = json.dumps(entry["arguments"])
+        assert "technology" in args and "events" in args
+        assert expect_model in args
+
+    # check streamed_args_for_tool for serving_chat.py
+    for index in range(2):
+        expected_call = parser.prev_tool_call_arr[index].get("arguments", {})
+        expected_call = json.dumps(expected_call)
+        actual_call = parser.streamed_args_for_tool[index]
+        assert expected_call == actual_call

vllm/tool_parsers/minimax_m2_tool_parser.py

@@ -122,6 +122,8 @@ class MinimaxM2ToolParser(ToolParser):
         self.streaming_request = None
         # Clear previous tool call history to avoid state pollution
         self.prev_tool_call_arr.clear()
+        # Reset streamed args tracking
+        self.streamed_args_for_tool.clear()
 
     def _extract_name(self, name_str: str) -> str:
         """Extract name from quoted string."""
@@ -421,9 +423,12 @@ class MinimaxM2ToolParser(ToolParser):
                         self.prev_tool_call_arr.append(
                             {
                                 "name": self.current_function_name,
-                                "arguments": "{}",  # Placeholder, will be updated later
+                                "arguments": {},  # Placeholder, will be updated later
                             }
                         )
+                        # Initialize streamed_args_for_tool for this tool call
+                        if len(self.streamed_args_for_tool) <= self.current_tool_index:
+                            self.streamed_args_for_tool.append("")
 
                     # Send header with function info
                     return DeltaMessage(
@@ -445,6 +450,9 @@ class MinimaxM2ToolParser(ToolParser):
             # Send opening brace if not sent yet
             if self.in_function and not self.json_started:
                 self.json_started = True
+                # Update streamed_args_for_tool for opening brace
+                if self.current_tool_index < len(self.streamed_args_for_tool):
+                    self.streamed_args_for_tool[self.current_tool_index] += "{"
                 return DeltaMessage(
                     tool_calls=[
                         DeltaToolCall(
@@ -493,7 +501,7 @@ class MinimaxM2ToolParser(ToolParser):
                                 args = parsed_tool.function.arguments
                                 self.prev_tool_call_arr[self.current_tool_index][
                                     "arguments"
-                                ] = args
+                                ] = json.loads(args)
                         except Exception:
                             pass  # Ignore parsing errors during streaming
 
@@ -505,7 +513,9 @@ class MinimaxM2ToolParser(ToolParser):
                             )
                         ]
                     )
-
+                    # Update streamed_args_for_tool for closing brace
+                    if self.current_tool_index < len(self.streamed_args_for_tool):
+                        self.streamed_args_for_tool[self.current_tool_index] += "}"
                     # Reset state for next tool
                     self.json_closed = True
                     self.in_function = False
@@ -630,7 +640,11 @@ class MinimaxM2ToolParser(ToolParser):
                             )
 
                         self.param_count += 1
-
+                        # Update streamed_args_for_tool for this tool call
+                        if self.current_tool_index < len(self.streamed_args_for_tool):
+                            self.streamed_args_for_tool[self.current_tool_index] += (
+                                json_fragment
+                            )
                         return DeltaMessage(
                             tool_calls=[
                                 DeltaToolCall(