[Bugfix] Always apply MM processor even when no MM items are passed (#26240)

Signed-off-by: DarkLight1337 <tlleungac@connect.ust.hk>

tests/conftest.py

@@ -46,7 +46,6 @@ from vllm.connections import global_http_connection
 from vllm.distributed import (cleanup_dist_env_and_memory,
                               init_distributed_environment,
                               initialize_model_parallel)
-from vllm.inputs import TextPrompt
 from vllm.logger import init_logger
 from vllm.logprobs import Logprob
 from vllm.multimodal.utils import fetch_image
@@ -760,17 +759,24 @@ class VllmRunner:
         images: Optional[PromptImageInput] = None,
         videos: Optional[PromptVideoInput] = None,
         audios: Optional[PromptAudioInput] = None,
-    ) -> list[TextPrompt]:
-
+    ) -> list[dict[str, Any]]:
         if any(x is not None and len(x) != len(prompts)
                for x in [images, videos, audios]):
             raise ValueError(
                 "All non-None multimodal inputs must have the same length as "
                 "prompts")
 
-        inputs = []
+        inputs = list[dict[str, Any]]()
         for i, prompt in enumerate(prompts):
-            multi_modal_data = {}
+            prompt_dict = dict[str, Any]()
+            if isinstance(prompt, str):
+                prompt_dict["prompt"] = prompt
+            elif isinstance(prompt, list):
+                prompt_dict["prompt_token_ids"] = prompt
+            else:
+                prompt_dict["prompt_embeds"] = prompt
+
+            multi_modal_data = dict[str, Any]()
             if images is not None and (image := images[i]) is not None:
                 multi_modal_data["image"] = image
             if videos is not None and (video := videos[i]) is not None:
@@ -778,17 +784,10 @@ class VllmRunner:
             if audios is not None and (audio := audios[i]) is not None:
                 multi_modal_data["audio"] = audio
 
-            text_prompt_kwargs: dict[str, Any] = {
-                "multi_modal_data": multi_modal_data or None
-            }
-            if isinstance(prompt, str):
-                text_prompt_kwargs["prompt"] = prompt
-            elif isinstance(prompt, list):
-                text_prompt_kwargs["prompt_token_ids"] = prompt
-            else:
-                text_prompt_kwargs["prompt_embeds"] = prompt
+            if multi_modal_data:
+                prompt_dict["multi_modal_data"] = multi_modal_data
 
-            inputs.append(TextPrompt(**text_prompt_kwargs))
+            inputs.append(prompt_dict)
 
         return inputs
 

tests/test_inputs.py

@@ -3,8 +3,11 @@
 
 import pytest
 
+from vllm.config import ModelConfig
 from vllm.inputs import zip_enc_dec_prompts
 from vllm.inputs.parse import parse_raw_prompts
+from vllm.inputs.preprocess import InputPreprocessor
+from vllm.transformers_utils.tokenizer import init_tokenizer_from_configs
 
 pytestmark = pytest.mark.cpu_test
 
@@ -80,3 +83,50 @@ def test_zip_enc_dec_prompts(mm_processor_kwargs, expected_mm_kwargs):
         assert zipped['encoder_prompt'] == enc
         assert zipped['decoder_prompt'] == dec
         assert zipped['mm_processor_kwargs'] == exp_kwargs
+
+
+@pytest.mark.parametrize("model_id", [
+    "facebook/opt-125m",
+])
+@pytest.mark.parametrize("prompt", [
+    {
+        "prompt": "",
+        "multi_modal_data": {
+            "dummy": []
+        },
+    },
+    {
+        "prompt_token_ids": [],
+        "multi_modal_data": {
+            "dummy": []
+        },
+    },
+])
+def test_preprocessor_text_no_mm_inputs(model_id, prompt):
+    model_config = ModelConfig(model=model_id)
+    tokenizer = init_tokenizer_from_configs(model_config)
+    input_preprocessor = InputPreprocessor(model_config, tokenizer)
+
+    with pytest.raises(ValueError, match="does not support multimodal inputs"):
+        input_preprocessor.preprocess(prompt)
+
+
+@pytest.mark.parametrize("model_id", [
+    "facebook/chameleon-7b",
+])
+@pytest.mark.parametrize("prompt", [
+    "",
+    {
+        "prompt_token_ids": []
+    },
+])
+def test_preprocessor_always_mm_code_path(model_id, prompt):
+    model_config = ModelConfig(model=model_id)
+    tokenizer = init_tokenizer_from_configs(model_config)
+    input_preprocessor = InputPreprocessor(model_config, tokenizer)
+
+    # HF processor adds sep token
+    sep_token_id = tokenizer.vocab[tokenizer.sep_token]
+
+    processed_inputs = input_preprocessor.preprocess(prompt)
+    assert sep_token_id in processed_inputs["prompt_token_ids"]

vllm/inputs/preprocess.py

@@ -314,15 +314,19 @@ class InputPreprocessor:
             parsed_content["prompt_token_ids"], tokenization_kwargs)
 
         inputs: Union[TokenInputs, MultiModalInputs]
-        if multi_modal_data := parsed_content.get("multi_modal_data"):
+        if self.model_config.is_multimodal_model:
             inputs = self._process_multimodal(
                 prompt_token_ids,
-                multi_modal_data,
+                parsed_content.get("multi_modal_data", {}),
                 parsed_content.get("mm_processor_kwargs"),
                 tokenization_kwargs=tokenization_kwargs,
                 mm_uuids=mm_uuids,
             )
         else:
+            if parsed_content.get("multi_modal_data"):
+                raise ValueError(
+                    "This model does not support multimodal inputs")
+
             inputs = token_inputs(prompt_token_ids)
 
         if cache_salt := parsed_content.get("cache_salt"):
@@ -340,15 +344,19 @@ class InputPreprocessor:
         prompt_text = parsed_content["prompt"]
 
         inputs: Union[TokenInputs, MultiModalInputs]
-        if multi_modal_data := parsed_content.get("multi_modal_data"):
+        if self.model_config.is_multimodal_model:
             inputs = self._process_multimodal(
                 prompt_text,
-                multi_modal_data,
+                parsed_content.get("multi_modal_data", {}),
                 parsed_content.get("mm_processor_kwargs"),
                 tokenization_kwargs=tokenization_kwargs,
                 mm_uuids=mm_uuids,
             )
         else:
+            if parsed_content.get("multi_modal_data"):
+                raise ValueError(
+                    "This model does not support multimodal inputs")
+
             prompt_token_ids = self._tokenize_prompt(
                 prompt_text,
                 tokenization_kwargs=tokenization_kwargs,

vllm/model_executor/models/phi3v.py

@@ -507,8 +507,8 @@ class Phi3VMultiModalProcessor(BaseMultiModalProcessor[Phi3VProcessingInfo]):
         )
 
         # Keep the behavior in line with HF processor
-        if token_ids[:2] == tokenizer.encode("<s> <|image|>",
-                                             add_special_tokens=False):
+        if len(mm_prompt_updates) and (token_ids[:2] == tokenizer.encode(
+                "<s> <|image|>", add_special_tokens=False)):
             token_ids = [token_ids[0], *token_ids[2:]]
             placeholders = {
                 modality: [

vllm/model_executor/models/qwen2_5_omni_thinker.py

@@ -331,6 +331,7 @@ class Qwen2_5OmniThinkerMultiModalProcessor(
         """
         mm_item_counts = mm_items.get_all_counts()
         self._validate_mm_kwargs(mm_kwargs, mm_item_counts)
+        self._validate_mm_updates(mm_prompt_updates, mm_item_counts)
 
         use_audio_in_video = False
         if "video" in mm_kwargs:

vllm/multimodal/processing.py

@@ -1946,6 +1946,24 @@ class BaseMultiModalProcessor(ABC, Generic[_I]):
                     "model (usually arising from an inconsistency between "
                     "`_call_hf_processor` and `_get_mm_fields_config`).")
 
+    def _validate_mm_updates(
+        self,
+        mm_updates: MultiModalPromptUpdates,
+        mm_item_counts: Mapping[str, int],
+    ) -> None:
+        for modality, item_count in mm_item_counts.items():
+            placeholders = mm_updates.get(modality, [])
+
+            if len(placeholders) != item_count:
+                raise RuntimeError(
+                    f"Expected there to be {item_count} prompt updates "
+                    f"corresponding to {item_count} {modality} items, but "
+                    f"instead found {len(placeholders)} prompt updates! "
+                    "This is likely because you forgot to include input "
+                    "placeholder tokens (e.g., `<image>`, `<|image_pad|>`) "
+                    "in the prompt. If the model has a chat template, make "
+                    "sure you have applied it before calling `LLM.generate`.")
+
     def _validate_mm_placeholders(
         self,
         mm_placeholders: Mapping[str, list[PlaceholderFeaturesInfo]],
@@ -1955,17 +1973,12 @@ class BaseMultiModalProcessor(ABC, Generic[_I]):
             placeholders = mm_placeholders.get(modality, [])
 
             if len(placeholders) != item_count:
-                # NOTE: If you are a model developer, this can also arise from
-                # an inconsistency between `_call_hf_processor` and
-                # `_get_mm_fields_config` implementations
                 raise RuntimeError(
-                    f"Expected there to be {item_count} prompt updates "
+                    f"Expected there to be {item_count} prompt placeholders "
                     f"corresponding to {item_count} {modality} items, but "
-                    f"instead found {len(placeholders)} prompt updates! "
-                    "This is likely because you forgot to include input "
-                    "placeholder tokens (e.g., `<image>`, `<|image_pad|>`) "
-                    "in the prompt. If the model has a chat template, make "
-                    "sure you have applied it before calling `LLM.generate`.")
+                    f"instead found {len(placeholders)} prompt placeholders! "
+                    "Make sure the implementation of `_call_hf_processor` and "
+                    "`_get_mm_fields_config` are consistent with each other.")
 
     def _maybe_apply_prompt_updates(
         self,
@@ -1977,6 +1990,7 @@ class BaseMultiModalProcessor(ABC, Generic[_I]):
     ) -> tuple[list[int], Mapping[str, list[PlaceholderFeaturesInfo]]]:
         mm_item_counts = mm_items.get_all_counts()
         self._validate_mm_kwargs(mm_kwargs, mm_item_counts)
+        self._validate_mm_updates(mm_prompt_updates, mm_item_counts)
 
         if is_update_applied:
             mm_placeholders = self._find_mm_placeholders(