fix: support missing tool parameters in mistral tokenizer

The Mistral schema is a bit more restrictive and does not accept
functions without parameter dictionary. This is no problem with the
OpenAI schema though, so the Mistral tokenizer should adapt the request
before passing it on.

Signed-off-by: Florian Greinacher <[email protected]>

Author: fgreinacher

tests/tokenization/test_mistral_tokenizer.py

@@ -0,0 +1,50 @@
+# 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 @@ def encode(self, prompt: str) -> List[int]:
 
     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