[Bugfix] Internal Server Error when tool_choice is incorrect. (#10567)

Signed-off-by: Varun Shenoy <varun.vinayak.shenoy@oracle.com>

tests/entrypoints/openai/test_chat.py

@@ -829,6 +829,20 @@ async def test_inconsistent_tool_choice_and_tools(client: openai.AsyncOpenAI,
                     "name": "nondefined_function_name"
                 }
             })
+    with pytest.raises(openai.BadRequestError):
+        await client.chat.completions.create(
+            model=MODEL_NAME,
+            messages=messages,
+            max_completion_tokens=1000,
+            tools=[{
+                "type": "function",
+                "function": {
+                    "name": "dummy_function_name",
+                    "description": "This is a dummy function",
+                    "parameters": sample_json_schema
+                }
+            }],
+            tool_choice={})
 
 
 @pytest.mark.asyncio

vllm/entrypoints/openai/protocol.py

@@ -478,17 +478,17 @@ class ChatCompletionRequest(OpenAIBaseModel):
             # it matches a valid tool
             if isinstance(data["tool_choice"], dict):
                 valid_tool = False
-                specified_function = data["tool_choice"]["function"]
+                specified_function = data["tool_choice"].get("function")
                 if not specified_function:
                     raise ValueError(
-                        "Incorrectly formatted `tool_choice`. Should be like "
-                        "`{\"type\": \"function\","
+                        "Expected field `function` in `tool_choice`."
+                        " Correct usage: `{\"type\": \"function\","
                         " \"function\": {\"name\": \"my_function\"}}`")
-                specified_function_name = specified_function["name"]
+                specified_function_name = specified_function.get("name")
                 if not specified_function_name:
                     raise ValueError(
-                        "Incorrectly formatted `tool_choice`. Should be like "
-                        "`{\"type\": \"function\", "
+                        "Expected field `name` in `function` in `tool_choice`."
+                        "Correct usage: `{\"type\": \"function\", "
                         "\"function\": {\"name\": \"my_function\"}}`")
                 for tool in data["tools"]:
                     if tool["function"]["name"] == specified_function_name: