Add skip_special_tokens sampling params (#1186)

vllm/engine/llm_engine.py

@@ -387,7 +387,7 @@ class LLMEngine:
             child_seqs.append((parent, parent))
 
         for seq, _ in child_seqs:
-            self._decode_sequence(seq)
+            self._decode_sequence(seq, seq_group.sampling_params)
             self._check_stop(seq, seq_group.sampling_params)
 
         # Non-beam search case
@@ -621,7 +621,8 @@ class LLMEngine:
                     f"CPU KV cache usage: {cpu_cache_usage * 100:.1f}%")
         self.last_logging_time = now
 
-    def _decode_sequence(self, seq: Sequence) -> None:
+    def _decode_sequence(self, seq: Sequence,
+                         sampling_params: SamplingParams) -> None:
         """Decodes the new token for a sequence."""
         (new_tokens, new_output_text, prefix_offset,
          read_offset) = detokenize_incrementally(
@@ -630,7 +631,7 @@ class LLMEngine:
              prev_tokens=seq.tokens,
              prefix_offset=seq.prefix_offset,
              read_offset=seq.read_offset,
-             skip_special_tokens=True,
+             skip_special_tokens=sampling_params.skip_special_tokens,
          )
         if seq.tokens is None:
             seq.tokens = new_tokens