[Bugfix] Support missing tool parameters in mistral tokenizer (#12884)

Signed-off-by: Florian Greinacher <florian.greinacher@siemens.com>

tests/tokenization/test_mistral_tokenizer.py

+# SPDX-License-Identifier: Apache-2.0
+
+import pytest
+from mistral_common.protocol.instruct.messages import UserMessage
+from mistral_common.protocol.instruct.request import ChatCompletionRequest
+from mistral_common.protocol.instruct.tool_calls import Function, Tool
+
+from vllm.transformers_utils.tokenizers.mistral import (
+    make_mistral_chat_completion_request)
+
+
+# yapf: enable
+@pytest.mark.parametrize(
+    "openai_request,expected_mistral_request",
+    [(
+        {
+            "messages": [{
+                "role": "user",
+                "content": "What is the current local date and time?",
+            }],
+            "tools": [{
+                "type": "function",
+                "function": {
+                    "description": "Fetch the current local date and time.",
+                    "name": "get_current_time",
+                },
+            }],
+        },
+        ChatCompletionRequest(
+            messages=[
+                UserMessage(content="What is the current local date and time?")
+            ],
+            tools=[
+                Tool(
+                    type="function",
+                    function=Function(
+                        name="get_current_time",
+                        description="Fetch the current local date and time.",
+                        parameters={},
+                    ),
+                )
+            ],
+        ),
+    )],
+)
+def test_make_mistral_chat_completion_request(openai_request,
+                                              expected_mistral_request):
+    assert (make_mistral_chat_completion_request(
+        openai_request["messages"],
+        openai_request["tools"]) == expected_mistral_request)

vllm/transformers_utils/tokenizers/mistral.py

@@ -104,6 +104,42 @@ def find_tokenizer_file(files: List[str]):
     return matched_files[0]
 
 
+def make_mistral_chat_completion_request(
+        messages: List["ChatCompletionMessageParam"],
+        tools: Optional[List[Dict[str,
+                                  Any]]] = None) -> "ChatCompletionRequest":
+    last_message = cast(Dict[str, Any], messages[-1])
+    if last_message["role"] == "assistant":
+        last_message["prefix"] = True
+
+        last_message = cast(Dict[str, Any], messages[-1])
+        if last_message["role"] == "assistant":
+            last_message["prefix"] = True
+
+    # mistral-common requires AssistantMessage content to be string [1].
+    #
+    # [1]: https://github.com/mistralai/mistral-common/blob/f4a06998b75ed78bbf5aaf569590b772ea26c9f6/src/mistral_common/protocol/instruct/messages.py#L80
+    for message in messages:
+        if message.get("role") == "assistant":
+            content = message.get("content")
+            if isinstance(content, list):
+                content = "\n".join(chunk.get("text") for chunk in content)
+                message["content"] = content
+
+    # The Mistral client, in comparison to the OpenAI client, requires the
+    # "parameters" dict to be present, even if it's empty.
+    if tools:
+        for function in [
+                tool["function"] for tool in tools
+                if tool["type"] == "function"
+        ]:
+            function.setdefault("parameters", {})
+
+    from mistral_common.protocol.instruct.request import ChatCompletionRequest
+    return ChatCompletionRequest(messages=messages,
+                                 tools=tools)  # type: ignore[type-var]
+
+
 class MistralTokenizer:
 
     def __init__(self, tokenizer: "PublicMistralTokenizer") -> None:
@@ -283,27 +319,10 @@ class MistralTokenizer:
 
     def apply_chat_template(self,
                             messages: List["ChatCompletionMessageParam"],
-                            tools: Optional[Dict[str, Any]] = None,
+                            tools: Optional[List[Dict[str, Any]]] = None,
                             **kwargs) -> List[int]:
 
-        last_message = cast(Dict[str, Any], messages[-1])
-        if last_message["role"] == "assistant":
-            last_message["prefix"] = True
-
-        from mistral_common.protocol.instruct.request import (
-            ChatCompletionRequest)
-
-        # mistral-common requires AssistantMessage content to be string [1].
-        #
-        # [1]: https://github.com/mistralai/mistral-common/blob/f4a06998b75ed78bbf5aaf569590b772ea26c9f6/src/mistral_common/protocol/instruct/messages.py#L80
-        for message in messages:
-            if message.get("role") == "assistant":
-                content = message.get("content")
-                if isinstance(content, list):
-                    content = "\n".join(chunk.get("text") for chunk in content)
-                    message["content"] = content
-        request = ChatCompletionRequest(messages=messages,
-                                        tools=tools)  # type: ignore[type-var]
+        request = make_mistral_chat_completion_request(messages, tools)
         encoded = self.mistral.encode_chat_completion(request)
 
         # encode-decode to get clean prompt