[FRONTEND] OpenAI tools support named functions (#5032)

vllm/model_executor/guided_decoding/__init__.py

@@ -1,7 +1,8 @@
 from typing import Optional, Union
 
-from vllm.entrypoints.openai.protocol import (ChatCompletionRequest,
-                                              CompletionRequest)
+from vllm.entrypoints.openai.protocol import (
+    ChatCompletionNamedToolChoiceParam, ChatCompletionRequest,
+    CompletionRequest)
 from vllm.model_executor.guided_decoding.lm_format_enforcer_decoding import (
     get_lm_format_enforcer_guided_decoding_logits_processor)
 from vllm.model_executor.guided_decoding.outlines_decoding import (
@@ -13,6 +14,8 @@ async def get_guided_decoding_logits_processor(
         guided_decoding_backend: str, request: Union[CompletionRequest,
                                                      ChatCompletionRequest],
         tokenizer) -> Optional[LogitsProcessor]:
+    request = _adapt_request_for_tool_use(request)
+
     if guided_decoding_backend == 'outlines':
         return await get_outlines_guided_decoding_logits_processor(
             request, tokenizer)
@@ -23,3 +26,26 @@ async def get_guided_decoding_logits_processor(
     raise ValueError(
         f"Unknown guided decoding backend '{guided_decoding_backend}'. "
         "Must be one of 'outlines, 'lm-format-enforcer'")
+
+
+def _adapt_request_for_tool_use(request: Union[CompletionRequest,
+                                               ChatCompletionRequest]):
+    # the legacy completion API does not support tool use
+    if type(request) is CompletionRequest:
+        return request
+
+    # user has chosen to not use any tool
+    if request.tool_choice == "none":
+        return request
+
+    # user has chosen to use a named tool
+    if type(request.tool_choice) is ChatCompletionNamedToolChoiceParam:
+        tool_name = request.tool_choice.function.name
+        tools = {tool.function.name: tool.function for tool in request.tools}
+        if tool_name not in tools:
+            raise ValueError(
+                f"Tool '{tool_name}' has not been passed in `tools`.")
+        tool = tools[tool_name]
+        request.guided_json = tool.parameters
+
+    return request