Add a flag to include stop string in output text (#1976)

Author: yunfeng-scale

vllm/engine/llm_engine.py

@@ -682,9 +682,10 @@ def _check_stop(self, seq: Sequence,
         """Stop the finished sequences."""
         for stop_str in sampling_params.stop:
             if seq.output_text.endswith(stop_str):
-                # Truncate the output text so that the stop string is
-                # not included in the output.
-                seq.output_text = seq.output_text[:-len(stop_str)]
+                if not sampling_params.include_stop_str_in_output:
+                    # Truncate the output text so that the stop string is
+                    # not included in the output.
+                    seq.output_text = seq.output_text[:-len(stop_str)]
                 seq.status = SequenceStatus.FINISHED_STOPPED
                 return
         if seq.get_last_token_id() in sampling_params.stop_token_ids:

vllm/sampling_params.py

@@ -2,6 +2,7 @@
 from enum import IntEnum
 from functools import cached_property
 from typing import Callable, List, Optional, Union
+
 import torch
 
 _SAMPLING_EPS = 1e-5
@@ -70,6 +71,8 @@ class SamplingParams:
         stop_token_ids: List of tokens that stop the generation when they are
             generated. The returned output will contain the stop tokens unless
             the stop tokens are special tokens.
+        include_stop_str_in_output: Whether to include the stop strings in output
+            text. Defaults to False.
         ignore_eos: Whether to ignore the EOS token and continue generating
             tokens after the EOS token is generated.
         max_tokens: Maximum number of tokens to generate per output sequence.
@@ -103,6 +106,7 @@ def __init__(
         early_stopping: Union[bool, str] = False,
         stop: Optional[Union[str, List[str]]] = None,
         stop_token_ids: Optional[List[int]] = None,
+        include_stop_str_in_output: bool = False,
         ignore_eos: bool = False,
         max_tokens: int = 16,
         logprobs: Optional[int] = None,
@@ -140,6 +144,7 @@ def __init__(
         self.skip_special_tokens = skip_special_tokens
         self.spaces_between_special_tokens = spaces_between_special_tokens
         self.logits_processors = logits_processors
+        self.include_stop_str_in_output = include_stop_str_in_output
         self._verify_args()
         if self.use_beam_search:
             self._verify_beam_search()
@@ -227,24 +232,26 @@ def sampling_type(self) -> SamplingType:
         return SamplingType.RANDOM
 
     def __repr__(self) -> str:
-        return (f"SamplingParams(n={self.n}, "
-                f"best_of={self.best_of}, "
-                f"presence_penalty={self.presence_penalty}, "
-                f"frequency_penalty={self.frequency_penalty}, "
-                f"repetition_penalty={self.repetition_penalty}, "
-                f"temperature={self.temperature}, "
-                f"top_p={self.top_p}, "
-                f"top_k={self.top_k}, "
-                f"min_p={self.min_p}, "
-                f"use_beam_search={self.use_beam_search}, "
-                f"length_penalty={self.length_penalty}, "
-                f"early_stopping={self.early_stopping}, "
-                f"stop={self.stop}, "
-                f"stop_token_ids={self.stop_token_ids}, "
-                f"ignore_eos={self.ignore_eos}, "
-                f"max_tokens={self.max_tokens}, "
-                f"logprobs={self.logprobs}, "
-                f"prompt_logprobs={self.prompt_logprobs}, "
-                f"skip_special_tokens={self.skip_special_tokens}, "
-                "spaces_between_special_tokens="
-                f"{self.spaces_between_special_tokens})")
+        return (
+            f"SamplingParams(n={self.n}, "
+            f"best_of={self.best_of}, "
+            f"presence_penalty={self.presence_penalty}, "
+            f"frequency_penalty={self.frequency_penalty}, "
+            f"repetition_penalty={self.repetition_penalty}, "
+            f"temperature={self.temperature}, "
+            f"top_p={self.top_p}, "
+            f"top_k={self.top_k}, "
+            f"min_p={self.min_p}, "
+            f"use_beam_search={self.use_beam_search}, "
+            f"length_penalty={self.length_penalty}, "
+            f"early_stopping={self.early_stopping}, "
+            f"stop={self.stop}, "
+            f"stop_token_ids={self.stop_token_ids}, "
+            f"include_stop_str_in_output={self.include_stop_str_in_output}, "
+            f"ignore_eos={self.ignore_eos}, "
+            f"max_tokens={self.max_tokens}, "
+            f"logprobs={self.logprobs}, "
+            f"prompt_logprobs={self.prompt_logprobs}, "
+            f"skip_special_tokens={self.skip_special_tokens}, "
+            "spaces_between_special_tokens="
+            f"{self.spaces_between_special_tokens})")