[V1][Structured Output] Move xgrammar related utils to `backend_xgrammar.py` (#16578)

Signed-off-by: shen-shanshan <467638484@qq.com>

tests/v1/structured_output/test_utils.py

@@ -2,7 +2,7 @@
 
 import pytest
 
-from vllm.v1.structured_output.utils import (
+from vllm.v1.structured_output.backend_xgrammar import (
     has_xgrammar_unsupported_json_features)
 
 

vllm/v1/engine/processor.py

@@ -22,8 +22,8 @@ from vllm.v1.engine import EngineCoreRequest
 from vllm.v1.engine.mm_input_cache import MirroredProcessingCache
 from vllm.v1.structured_output.backend_guidance import (
     validate_guidance_grammar)
-from vllm.v1.structured_output.utils import (
-    validate_structured_output_request_xgrammar)
+from vllm.v1.structured_output.backend_xgrammar import (
+    validate_xgrammar_grammar)
 
 
 class Processor:
@@ -165,7 +165,7 @@ class Processor:
         # Request content validation
         if engine_level_backend.startswith("xgrammar"):
             # xgrammar with no fallback
-            validate_structured_output_request_xgrammar(params)
+            validate_xgrammar_grammar(params)
             params.guided_decoding.backend = engine_level_backend
         elif engine_level_backend == "auto":
             # "auto" is an opt-in to opinionated behavior where we try to
@@ -173,7 +173,7 @@ class Processor:
             # default as it is less predictable and subject to change
             # between releases as feature support changes.
             try:
-                validate_structured_output_request_xgrammar(params)
+                validate_xgrammar_grammar(params)
                 params.guided_decoding.backend = "xgrammar"
             except ValueError:
                 # The request includes some jsonschema feature(s) that

vllm/v1/structured_output/backend_xgrammar.py

 # SPDX-License-Identifier: Apache-2.0
 
+import json
 from dataclasses import dataclass, field
-from typing import TYPE_CHECKING
+from typing import TYPE_CHECKING, Any
 
 import torch
 
 import vllm.envs
 from vllm.config import VllmConfig
 from vllm.logger import init_logger
+from vllm.sampling_params import SamplingParams
 from vllm.transformers_utils.tokenizer_group import init_tokenizer_from_configs
 from vllm.transformers_utils.tokenizers.mistral import MistralTokenizer
 from vllm.utils import LazyLoader
 from vllm.v1.structured_output.backend_types import (StructuredOutputBackend,
                                                      StructuredOutputGrammar,
                                                      StructuredOutputOptions)
+from vllm.v1.structured_output.utils import (choice_as_grammar,
+                                             convert_lark_to_ebnf,
+                                             grammar_is_likely_lark)
 
 if TYPE_CHECKING:
     import xgrammar as xgr
@@ -156,3 +161,112 @@ class XgrammarGrammar(StructuredOutputGrammar):
     def reset(self):
         self.num_processed_tokens = 0
         self.matcher.reset()
+
+
+def has_xgrammar_unsupported_json_features(schema: dict[str, Any]) -> bool:
+    """Check if JSON schema contains features unsupported by xgrammar."""
+
+    def check_object(obj: dict[str, Any]) -> bool:
+        if not isinstance(obj, dict):
+            return False
+
+        # Check for pattern restrictions
+        if "pattern" in obj:
+            return True
+
+        # Check for numeric ranges
+        if obj.get("type") in ("integer", "number") and any(
+                key in obj
+                for key in ("minimum", "maximum", "exclusiveMinimum",
+                            "exclusiveMaximum", "multipleOf")):
+            return True
+
+        # Check for array unsupported keywords
+        if obj.get("type") == "array" and any(
+                key in obj
+                for key in ("uniqueItems", "contains", "minContains",
+                            "maxContains", "minItems", "maxItems")):
+            return True
+
+        # Unsupported keywords for strings
+        if obj.get("type") == "string" and "format" in obj:
+            return True
+
+        # Unsupported keywords for objects
+        if obj.get("type") == "object" and any(
+                key in obj for key in ("minProperties", "maxProperties",
+                                       "propertyNames", "patternProperties")):
+            return True
+
+        # Recursively check all nested objects and arrays
+        for value in obj.values():
+            if isinstance(value, dict):
+                if check_object(value):
+                    return True
+            elif isinstance(value, list):
+                for item in value:
+                    if isinstance(item, dict) and check_object(item):
+                        return True
+
+        return False
+
+    return check_object(schema)
+
+
+def validate_xgrammar_grammar(sampling_params: SamplingParams) -> None:
+    """Validate that the request is supported by structured output.
+
+    Raises ValueError if the request is not supported.
+    """
+    if sampling_params.guided_decoding is None:
+        return
+
+    gd_params = sampling_params.guided_decoding
+
+    if gd_params.regex:
+        try:
+            xgr.Grammar.from_regex(gd_params.regex)
+        except Exception as err:
+            raise ValueError("Failed to transform regex into a grammar: "
+                             f"{err}") from err
+
+    if gd_params.choice:
+        choice_grammar = choice_as_grammar(gd_params.choice)
+        try:
+            xgr.Grammar.from_ebnf(choice_grammar)
+        except Exception as err:
+            raise ValueError("Failed to transform choices into a grammar: "
+                             "{err}") from err
+        gd_params.choice = None
+        gd_params.grammar = choice_grammar
+        return
+
+    if gd_params.json:
+        if isinstance(gd_params.json, str):
+            try:
+                schema = json.loads(gd_params.json)
+            except json.JSONDecodeError as e:
+                raise ValueError("Invalid JSON grammar specification.") from e
+        else:
+            schema = gd_params.json
+
+        if has_xgrammar_unsupported_json_features(schema):
+            raise ValueError("The provided JSON schema contains features not "
+                             "supported by xgrammar.")
+        return
+
+    if gd_params.grammar:
+        if grammar_is_likely_lark(gd_params.grammar):
+            # xgrammar supports EBNF grammars only
+            try:
+                gd_params.grammar = convert_lark_to_ebnf(gd_params.grammar)
+            except ValueError as e:
+                raise ValueError(
+                    "Failed to convert the grammar from Lark to EBNF. ") from e
+
+        # Test parsing EBNF grammar, possibly already converted from Lark
+        try:
+            # parse the grammar, but we aren't compiling it.
+            xgr.Grammar.from_ebnf(gd_params.grammar)
+        except Exception as e:
+            raise ValueError("Invalid grammar specification.") from e

vllm/v1/structured_output/utils.py

@@ -2,67 +2,7 @@
 
 from __future__ import annotations
 
-import json
 import re
-from typing import TYPE_CHECKING, Any
-
-from vllm.sampling_params import SamplingParams
-from vllm.utils import LazyLoader
-
-if TYPE_CHECKING:
-    import xgrammar as xgr
-else:
-    xgr = LazyLoader("xgr", globals(), "xgrammar")
-
-
-def has_xgrammar_unsupported_json_features(schema: dict[str, Any]) -> bool:
-    """Check if JSON schema contains features unsupported by xgrammar."""
-
-    def check_object(obj: dict[str, Any]) -> bool:
-        if not isinstance(obj, dict):
-            return False
-
-        # Check for pattern restrictions
-        if "pattern" in obj:
-            return True
-
-        # Check for numeric ranges
-        if obj.get("type") in ("integer", "number") and any(
-                key in obj
-                for key in ("minimum", "maximum", "exclusiveMinimum",
-                            "exclusiveMaximum", "multipleOf")):
-            return True
-
-        # Check for array unsupported keywords
-        if obj.get("type") == "array" and any(
-                key in obj
-                for key in ("uniqueItems", "contains", "minContains",
-                            "maxContains", "minItems", "maxItems")):
-            return True
-
-        # Unsupported keywords for strings
-        if obj.get("type") == "string" and "format" in obj:
-            return True
-
-        # Unsupported keywords for objects
-        if obj.get("type") == "object" and any(
-                key in obj for key in ("minProperties", "maxProperties",
-                                       "propertyNames", "patternProperties")):
-            return True
-
-        # Recursively check all nested objects and arrays
-        for value in obj.values():
-            if isinstance(value, dict):
-                if check_object(value):
-                    return True
-            elif isinstance(value, list):
-                for item in value:
-                    if isinstance(item, dict) and check_object(item):
-                        return True
-
-        return False
-
-    return check_object(schema)
 
 
 def grammar_is_likely_lark(grammar_str: str) -> bool:
@@ -232,63 +172,3 @@ def choice_as_grammar(choice: list[str]) -> str:
     escaped_choices = (escape_ebnf_string(c) for c in choice)
     grammar = ('root ::= ' + ' | '.join(f'"{c}"' for c in escaped_choices))
     return grammar
-
-
-def validate_structured_output_request_xgrammar(
-        sampling_params: SamplingParams) -> None:
-    """Validate that the request is supported by structured output.
-
-    Raises ValueError if the request is not supported.
-    """
-    if sampling_params.guided_decoding is None:
-        return
-
-    gd_params = sampling_params.guided_decoding
-
-    if gd_params.regex:
-        try:
-            xgr.Grammar.from_regex(gd_params.regex)
-        except Exception as err:
-            raise ValueError("Failed to transform regex into a grammar: "
-                             f"{err}") from err
-
-    if gd_params.choice:
-        choice_grammar = choice_as_grammar(gd_params.choice)
-        try:
-            xgr.Grammar.from_ebnf(choice_grammar)
-        except Exception as err:
-            raise ValueError("Failed to transform choices into a grammar: "
-                             "{err}") from err
-        gd_params.choice = None
-        gd_params.grammar = choice_grammar
-        return
-
-    if gd_params.json:
-        if isinstance(gd_params.json, str):
-            try:
-                schema = json.loads(gd_params.json)
-            except json.JSONDecodeError as e:
-                raise ValueError("Invalid JSON grammar specification.") from e
-        else:
-            schema = gd_params.json
-
-        if has_xgrammar_unsupported_json_features(schema):
-            raise ValueError("The provided JSON schema contains features not "
-                             "supported by xgrammar.")
-        return
-
-    if gd_params.grammar:
-        if grammar_is_likely_lark(gd_params.grammar):
-            # xgrammar supports EBNF grammars only
-            try:
-                gd_params.grammar = convert_lark_to_ebnf(gd_params.grammar)
-            except ValueError as e:
-                raise ValueError(
-                    "Failed to convert the grammar from Lark to EBNF. ") from e
-
-        # Test parsing EBNF grammar, possibly already converted from Lark
-        try:
-            # parse the grammar, but we aren't compiling it.
-            xgr.Grammar.from_ebnf(gd_params.grammar)
-        except Exception as e:
-            raise ValueError("Invalid grammar specification.") from e