[Misc] Enhance warning information to user-defined chat template (#15408)

Signed-off-by: wwl2755 <wangwenlong2755@gmail.com>

tests/entrypoints/test_chat_utils.py

@@ -9,11 +9,11 @@ from transformers import __version__ as TRANSFORMERS_VERSION
 
 from vllm.assets.image import ImageAsset
 from vllm.config import ModelConfig
-from vllm.entrypoints.chat_utils import (_resolve_hf_chat_template,
-                                         _try_extract_ast, load_chat_template,
+from vllm.entrypoints.chat_utils import (_try_extract_ast, load_chat_template,
                                          parse_chat_messages,
                                          parse_chat_messages_futures,
-                                         resolve_chat_template_content_format)
+                                         resolve_chat_template_content_format,
+                                         resolve_hf_chat_template)
 from vllm.entrypoints.llm import apply_hf_chat_template
 from vllm.multimodal import MultiModalDataDict
 from vllm.multimodal.utils import encode_image_base64
@@ -747,7 +747,7 @@ def test_resolve_hf_chat_template(sample_json_schema, model, use_tools):
     }] if use_tools else None
 
     # Test detecting the tokenizer's chat_template
-    chat_template = _resolve_hf_chat_template(
+    chat_template = resolve_hf_chat_template(
         tokenizer,
         chat_template=None,
         tools=tools,
@@ -781,7 +781,7 @@ def test_resolve_content_format_hf_defined(model, expected_format):
     tokenizer = tokenizer_group.tokenizer
 
     # Test detecting the tokenizer's chat_template
-    chat_template = _resolve_hf_chat_template(
+    chat_template = resolve_hf_chat_template(
         tokenizer,
         chat_template=None,
         tools=None,

vllm/entrypoints/chat_utils.py

@@ -306,7 +306,24 @@ def _detect_content_format(
         return "openai"
 
 
-def _resolve_hf_chat_template(
+def resolve_mistral_chat_template(
+    chat_template: Optional[str],
+    **kwargs: Any,
+) -> Optional[str]:
+    if chat_template is not None:
+        logger.warning_once(
+            "'chat_template' cannot be overridden for mistral tokenizer.")
+    if "add_generation_prompt" in kwargs:
+        logger.warning_once(
+            "'add_generation_prompt' is not supported for mistral tokenizer, "
+            "so it will be ignored.")
+    if "continue_final_message" in kwargs:
+        logger.warning_once(
+            "'continue_final_message' is not supported for mistral tokenizer, "
+            "so it will be ignored.")
+    return None
+
+def resolve_hf_chat_template(
     tokenizer: Union[PreTrainedTokenizer, PreTrainedTokenizerFast],
     chat_template: Optional[str],
     tools: Optional[list[dict[str, Any]]],
@@ -352,7 +369,7 @@ def _resolve_chat_template_content_format(
     trust_remote_code: bool,
 ) -> _ChatTemplateContentFormat:
     if isinstance(tokenizer, (PreTrainedTokenizer, PreTrainedTokenizerFast)):
-        hf_chat_template = _resolve_hf_chat_template(
+        hf_chat_template = resolve_hf_chat_template(
             tokenizer,
             chat_template=chat_template,
             trust_remote_code=trust_remote_code,
@@ -1140,7 +1157,7 @@ def apply_hf_chat_template(
     tokenize: bool = False,  # Different from HF's default
     **kwargs: Any,
 ) -> str:
-    hf_chat_template = _resolve_hf_chat_template(
+    hf_chat_template = resolve_hf_chat_template(
         tokenizer,
         chat_template=chat_template,
         tools=tools,
@@ -1169,17 +1186,12 @@ def apply_mistral_chat_template(
     tools: Optional[list[dict[str, Any]]],
     **kwargs: Any,
 ) -> list[int]:
-    if chat_template is not None:
-        logger.warning_once(
-            "'chat_template' cannot be overridden for mistral tokenizer.")
-    if "add_generation_prompt" in kwargs:
-        logger.warning_once(
-            "'add_generation_prompt' is not supported for mistral tokenizer, "
-            "so it will be ignored.")
-    if "continue_final_message" in kwargs:
-        logger.warning_once(
-            "'continue_final_message' is not supported for mistral tokenizer, "
-            "so it will be ignored.")
+    # The return value of resolve_mistral_chat_template is always None,
+    # and we won't use it.
+    resolve_mistral_chat_template(
+        chat_template=chat_template,
+        **kwargs,
+    )
 
     return tokenizer.apply_chat_template(
         messages=messages,

vllm/entrypoints/openai/api_server.py

@@ -35,7 +35,9 @@ from vllm.engine.async_llm_engine import AsyncLLMEngine  # type: ignore
 from vllm.engine.multiprocessing.client import MQLLMEngineClient
 from vllm.engine.multiprocessing.engine import run_mp_engine
 from vllm.engine.protocol import EngineClient
-from vllm.entrypoints.chat_utils import load_chat_template
+from vllm.entrypoints.chat_utils import (load_chat_template,
+                                         resolve_hf_chat_template,
+                                         resolve_mistral_chat_template)
 from vllm.entrypoints.launcher import serve_http
 from vllm.entrypoints.logger import RequestLogger
 from vllm.entrypoints.openai.cli_args import (make_arg_parser,
@@ -84,6 +86,7 @@ from vllm.entrypoints.utils import load_aware_call, with_cancellation
 from vllm.logger import init_logger
 from vllm.transformers_utils.config import (
     maybe_register_config_serialize_by_value)
+from vllm.transformers_utils.tokenizer import MistralTokenizer
 from vllm.usage.usage_lib import UsageContext
 from vllm.utils import (Device, FlexibleArgumentParser, get_open_zmq_ipc_path,
                         is_valid_ipv6_address, set_ulimit)
@@ -883,8 +886,26 @@ async def init_app_state(
 
     resolved_chat_template = load_chat_template(args.chat_template)
     if resolved_chat_template is not None:
-        logger.info("Using supplied chat template:\n%s",
-                    resolved_chat_template)
+        # Get the tokenizer to check official template
+        tokenizer = await engine_client.get_tokenizer()
+
+        if isinstance(tokenizer, MistralTokenizer):
+            # The warning is logged in resolve_mistral_chat_template.
+            resolved_chat_template = resolve_mistral_chat_template(
+                chat_template=resolved_chat_template)
+        else:
+            hf_chat_template = resolve_hf_chat_template(
+                tokenizer,
+                chat_template=None,
+                tools=None,
+                trust_remote_code=model_config.trust_remote_code)
+
+            if hf_chat_template != resolved_chat_template:
+                logger.warning(
+                    "Using supplied chat template: %s\n"
+                    "It is different from official chat template '%s'. "
+                    "This discrepancy may lead to performance degradation.",
+                    resolved_chat_template, args.model)
 
     state.openai_serving_models = OpenAIServingModels(
         engine_client=engine_client,