add_special_tokens=False consistent use

Signed-off-by: NickLucche <nlucches@redhat.com>

Author: NickLucche

vllm_bart_plugin/bart.py

@@ -945,6 +945,21 @@ def get_data_parser(self) -> MultiModalDataParser:
         return TextDataParser()
 
 
+# vLLM >=0.18 moved tokenization defaults from a global enc-dec override
+# (InputPreprocessor._get_tokenization_kw) into per-model ProcessingInfo.
+# The old code forced add_special_tokens=False for every is_encoder_decoder
+# model; replicate that here so the renderer does not inject extra BOS/EOS
+# into the decoder prompt.  On vLLM <0.18 the method does not exist on the
+# base class and is not needed (the global override handles it).
+if hasattr(BaseProcessingInfo, "get_default_tok_params"):
+
+    def _bart_get_default_tok_params(self):
+        return super(BartProcessingInfo, self).get_default_tok_params() \
+            .with_kwargs(add_special_tokens=False)
+
+    BartProcessingInfo.get_default_tok_params = _bart_get_default_tok_params  # type: ignore[attr-defined]
+
+
 class BartDummyInputsBuilder(BaseDummyInputsBuilder[BartProcessingInfo]):
     """Builds dummy inputs for profiling BART models."""
 
@@ -993,14 +1008,9 @@ def _parse_text_data(
         data: ModalityData[str],
     ) -> ModalityDataItems[Any, Any] | None:
         """Parse text data for BART."""
-        if data is None:
-            return TextProcessorItems(None)
-
         # _is_empty was removed in vLLM >=0.18; handle emptiness inline
-        if isinstance(data, str) and not data:
-            return None
-        if isinstance(data, list) and len(data) == 0:
-            return None
+        if data is None or not len(data):
+            return TextProcessorItems(None)
 
         # Text data should be a string or list of strings
         if isinstance(data, str) or is_list_of(data, str):
@@ -1033,10 +1043,22 @@ def create_encoder_prompt(
         prompt: str | list[int],
         mm_data: MultiModalDataDict,
     ) -> str | list[int]:
-        # In vLLM >=0.18, `prompt` here is the DECODER prompt text, not the
-        # encoder text. The encoder content lives in mm_data ("text" key).
-        # Always return [0] as a single placeholder token; _get_prompt_updates
-        # will replace it with the correct number of encoder token slots.
+        # vLLM compatibility:
+        # - Legacy (<0.18): prompt is encoder text (str) — tokenize directly.
+        # - Modern (>=0.18): prompt is decoder token IDs or empty str from
+        #   profiling — return a single [0] placeholder that _get_prompt_updates
+        #   will expand to the real encoder token count.  The placeholder IDs
+        #   are structural (KV-cache sizing); the actual encoder computation
+        #   uses encoder_input_ids from mm_kwargs.
+        if isinstance(prompt, str) and prompt:
+            tokenizer = self.info.get_tokenizer()
+            tokens = tokenizer(
+                prompt,
+                add_special_tokens=False,
+                return_tensors="pt",
+            )["input_ids"].flatten()
+            return tokens.tolist()
+
         return [0]
 
     def create_decoder_prompt(
@@ -1055,10 +1077,16 @@ def _call_hf_processor(
         tok_kwargs: Mapping[str, object],
     ):
         """
-        BART doesn't have a HuggingFace Processor - it only has a tokenizer.
-        We tokenize both the prompt (decoder) and encoder text from mm_data.
+        BART doesn't have a HuggingFace Processor — it only has a tokenizer.
+
+        Produces two sets of token IDs:
+        - ``encoder_input_ids``: tokenized encoder text from ``mm_data["texts"]``
+        - ``input_ids``: tokenized decoder prompt (used by the base class to
+          build ``prompt_token_ids``)
+
+        Encoder text is always tokenized with ``add_special_tokens=False`` to
+        match v0.16 behaviour and stay consistent with ``_get_prompt_updates``.
         """
-        # tok_kwargs["add_special_tokens"] = False
         from transformers.feature_extraction_utils import BatchFeature
 
         tokenizer = self.info.get_tokenizer()
@@ -1068,13 +1096,13 @@ def _call_hf_processor(
         result = {}
 
         if has_encoder_data:
-            # Tokenize the encoder text from mm_data
             encoder_texts = mm_data["texts"]
             encoder_text = encoder_texts[0] if encoder_texts else ""
+            # Tokenize the encoder text from mm_data
             encoder_tokenized = tokenizer(
                 encoder_text,
                 return_tensors="pt",
-                **tok_kwargs,
+                add_special_tokens=False,
             )
             result["encoder_input_ids"] = encoder_tokenized["input_ids"]
 
@@ -1109,6 +1137,13 @@ def _get_prompt_updates(
         hf_processor_mm_kwargs: Mapping[str, object],
         out_mm_kwargs: MultiModalKwargsItems,
     ) -> Sequence[PromptUpdate]:
+        """Replace the single [0] encoder placeholder with N placeholder
+        tokens, where N equals the tokenized length of the encoder text.
+
+        The token count must use ``add_special_tokens=False`` to stay
+        consistent with ``_call_hf_processor`` (which tokenizes the encoder
+        text the same way).
+        """
         from vllm.multimodal.processing import PromptReplacement
 
         # Get the number of text items to determine token count