LM Format Enforcer Guided Decoding Support (#3868)

Co-authored-by: Simon Mo <simon.mo@hey.com>

vllm/model_executor/guided_decoding/__init__.py

@@ -0,0 +1,25 @@
+from typing import Optional, Union
+
+from vllm.entrypoints.openai.protocol import (ChatCompletionRequest,
+                                              CompletionRequest)
+from vllm.model_executor.guided_decoding.lm_format_enforcer_decoding import (
+    get_lm_format_enforcer_guided_decoding_logits_processor)
+from vllm.model_executor.guided_decoding.outlines_decoding import (
+    get_outlines_guided_decoding_logits_processor)
+from vllm.sampling_params import LogitsProcessor
+
+
+async def get_guided_decoding_logits_processor(
+        guided_decoding_backend: str, request: Union[CompletionRequest,
+                                                     ChatCompletionRequest],
+        tokenizer) -> Optional[LogitsProcessor]:
+    if guided_decoding_backend == 'outlines':
+        return await get_outlines_guided_decoding_logits_processor(
+            request, tokenizer)
+    if guided_decoding_backend == 'lm-format-enforcer':
+        return await get_lm_format_enforcer_guided_decoding_logits_processor(
+            request, tokenizer)
+
+    raise ValueError(
+        f"Unknown guided decoding backend '{guided_decoding_backend}'. "
+        "Must be one of 'outlines, 'lm-format-enforcer'")