[BugFix] Enforce Mistral ToolCall id constraint when using the Mistral tool call parser (#9020)

Author: gcalmettes

tests/tool_use/test_parallel_tool_calls.py

@@ -45,7 +45,7 @@ async def test_parallel_tool_calls(client: openai.AsyncOpenAI,
         assert tool_call.type == "function"
         assert tool_call.function is not None
         assert isinstance(tool_call.id, str)
-        assert len(tool_call.id) > 16
+        assert len(tool_call.id) >= 9
 
         # make sure the weather tool was called correctly
         assert tool_call.function.name == WEATHER_TOOL["function"]["name"]
@@ -108,7 +108,7 @@ async def test_parallel_tool_calls(client: openai.AsyncOpenAI,
             if tool_call.id:
                 tool_call_id_count += 1
                 assert (isinstance(tool_call.id, str)
-                        and (len(tool_call.id) > 16))
+                        and (len(tool_call.id) >= 9))
 
             # if parts of the function start being streamed
             if tool_call.function:

tests/tool_use/test_tool_calls.py

@@ -33,7 +33,7 @@ async def test_tool_call_and_choice(client: openai.AsyncOpenAI):
     assert tool_calls[0].type == 'function'
     assert tool_calls[0].function is not None
     assert isinstance(tool_calls[0].id, str)
-    assert len(tool_calls[0].id) > 16
+    assert len(tool_calls[0].id) >= 9
 
     # make sure the weather tool was called (classic example) with arguments
     assert tool_calls[0].function.name == WEATHER_TOOL["function"]["name"]
@@ -106,7 +106,7 @@ async def test_tool_call_and_choice(client: openai.AsyncOpenAI):
 
     assert finish_reason_count == 1
     assert role_name == 'assistant'
-    assert isinstance(tool_call_id, str) and (len(tool_call_id) > 16)
+    assert isinstance(tool_call_id, str) and (len(tool_call_id) >= 9)
 
     # validate the name and arguments
     assert function_name == WEATHER_TOOL["function"]["name"]

vllm/entrypoints/openai/tool_parsers/mistral_tool_parser.py

@@ -1,9 +1,12 @@
 import json
 import re
+from random import choices
+from string import ascii_letters, digits
 from typing import Dict, List, Sequence, Union
 
 import partial_json_parser
 from partial_json_parser.core.options import Allow
+from pydantic import Field
 
 from vllm.entrypoints.openai.protocol import (DeltaFunctionCall, DeltaMessage,
                                               DeltaToolCall,
@@ -19,6 +22,19 @@
 
 logger = init_logger(__name__)
 
+ALPHANUMERIC = ascii_letters + digits
+
+
+class MistralToolCall(ToolCall):
+    id: str = Field(
+        default_factory=lambda: MistralToolCall.generate_random_id())
+
+    @staticmethod
+    def generate_random_id():
+        # Mistral Tool Call Ids must be alphanumeric with a maximum length of 9.
+        # https://github.com/mistralai/mistral-common/blob/21ee9f6cee3441e9bb1e6ed2d10173f90bd9b94b/src/mistral_common/protocol/instruct/validator.py#L299
+        return "".join(choices(ALPHANUMERIC, k=9))
+
 
 class MistralToolParser(ToolParser):
     """
@@ -71,8 +87,8 @@ def extract_tool_calls(self,
             # load the JSON, and then use it to build the Function and
             # Tool Call
             function_call_arr = json.loads(raw_tool_call)
-            tool_calls: List[ToolCall] = [
-                ToolCall(
+            tool_calls: List[MistralToolCall] = [
+                MistralToolCall(
                     type="function",
                     function=FunctionCall(
                         name=raw_function_call["name"],