Fix: `AttributeError` in OpenAI-compatible server (#3018)

vllm/entrypoints/openai/protocol.py

@@ -57,7 +57,7 @@ class UsageInfo(BaseModel):
 
 class ChatCompletionRequest(BaseModel):
     model: str
-    messages: Union[str, List[Dict[str, str]]]
+    messages: List[Dict[str, str]]
     temperature: Optional[float] = 0.7
     top_p: Optional[float] = 1.0
     n: Optional[int] = 1

vllm/entrypoints/openai/serving_chat.py

@@ -80,7 +80,7 @@ class OpenAIServingChat(OpenAIServing):
         if request.add_generation_prompt:
             return self.response_role
         else:
-            return request.messages[-1].role
+            return request.messages[-1]["role"]
 
     async def chat_completion_stream_generator(
             self, request: ChatCompletionRequest,