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[Bugfix][Structured Output] Reject structural_tag and unhandled specs in backend validation (#58862)

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Signed-off-by: Samay <samay.piduru@gmail.com>
Co-authored-by: Artem Perevedentsev <aperevedents@nvidia.com>
This commit is contained in:
samayp01
2026-10-13 13:27:34 +03:00
committed by GitHub
co-authored by Artem Perevedentsev
parent 7173c64e2e
commit 54db759eea
4 changed files with 94 additions and 7 deletions
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tests/v1/structured_output/test_validation.py
+57
View File
@@ -17,6 +17,13 @@ from vllm.sampling_params import (
)
from vllm.tokenizers import mistral as mistral_tokenizers
from vllm.v1.structured_output import backend_guidance
from vllm.v1.structured_output.backend_lm_format_enforcer import (
validate_structured_output_request_lm_format_enforcer,
)
from vllm.v1.structured_output.backend_outlines import (
validate_structured_output_request_outlines,
)
from vllm.v1.structured_output.backend_xgrammar import validate_xgrammar_grammar
pytestmark = pytest.mark.cpu_test
@@ -213,6 +220,9 @@ def test_schema_at_nesting_limit_accepted(field):
INVALID_JSON_SCHEMA = {"type": "object", "properties": {"name": {"type": "str"}}}
STRUCTURAL_TAG = (
'{"type": "structural_tag", "format": {"type": "const_string", "value": "hi"}}'
)
@pytest.mark.parametrize(
@@ -227,6 +237,9 @@ INVALID_JSON_SCHEMA = {"type": "object", "properties": {"name": {"type": "str"}}
("lm-format-enforcer", StructuredOutputsParams(grammar="not a grammar")),
("outlines", StructuredOutputsParams(regex="(")),
("guidance", StructuredOutputsParams(structural_tag='{"nope": 1}')),
("outlines", StructuredOutputsParams(structural_tag=STRUCTURAL_TAG)),
("lm-format-enforcer", StructuredOutputsParams(structural_tag=STRUCTURAL_TAG)),
("outlines", StructuredOutputsParams(json_object=True)),
],
)
def test_unsupported_grammar_is_a_client_error(backend, structured_outputs):
@@ -241,6 +254,50 @@ def test_unsupported_grammar_is_a_client_error(backend, structured_outputs):
)
@pytest.mark.parametrize(
"backend, structured_outputs",
[
("xgrammar", StructuredOutputsParams(json_object=True)),
("xgrammar", StructuredOutputsParams(regex="[0-9]+")),
("xgrammar", StructuredOutputsParams(regex="")),
("xgrammar", StructuredOutputsParams(json={})),
("lm-format-enforcer", StructuredOutputsParams(json_object=True)),
("lm-format-enforcer", StructuredOutputsParams(regex="")),
("lm-format-enforcer", StructuredOutputsParams(json={})),
("outlines", StructuredOutputsParams(regex="")),
("outlines", StructuredOutputsParams(json={})),
],
)
def test_supported_spec_is_not_rejected(backend, structured_outputs):
"""Supported specs, including the falsy but valid regex="" and json={}, must
not reach the validators' final rejection."""
params = SamplingParams(structured_outputs=structured_outputs)
params._validate_structured_outputs(
_StubModelConfig(is_diffusion=False),
StructuredOutputsConfig(backend=backend),
tokenizer=object(),
)
@pytest.mark.parametrize(
"validate",
[
validate_structured_output_request_outlines,
validate_structured_output_request_lm_format_enforcer,
validate_xgrammar_grammar,
],
ids=["outlines", "lm-format-enforcer", "xgrammar"],
)
def test_unhandled_spec_is_a_validation_error(validate):
"""json_object=False is rejected before backend selection, so only a direct
validator call reaches the final branch; it must still be a 400."""
params = SamplingParams(
structured_outputs=StructuredOutputsParams(json_object=False)
)
with pytest.raises(VLLMValidationError, match="does not support this"):
validate(params)
@pytest.mark.parametrize(
"schema, expected_backend",
[
vllm/v1/structured_output/backend_lm_format_enforcer.py
+13 -3
View File
@@ -159,7 +159,7 @@ def validate_structured_output_request_lm_format_enforcer(params: SamplingParams
so_params = params.structured_outputs
if so_params.regex:
if so_params.regex is not None:
try:
compile_regex_with_timeout(
lmformatenforcer.RegexParser,
@@ -170,7 +170,7 @@ def validate_structured_output_request_lm_format_enforcer(params: SamplingParams
f"Failed to compile regex for lm-format-enforcer: {err}"
) from err
return
elif so_params.json:
elif so_params.json is not None:
if isinstance(so_params.json, str):
try:
# make sure schema is valid json
@@ -185,10 +185,20 @@ def validate_structured_output_request_lm_format_enforcer(params: SamplingParams
f"Error serializing structured outputs jsonschema: {e}"
) from e
return
elif so_params.choice:
elif so_params.choice or so_params.json_object:
return
elif so_params.grammar:
raise VLLMValidationError(
"LM Format Enforcer structured outputs backend "
"does not support grammar specifications"
)
elif so_params.structural_tag:
raise VLLMValidationError(
"LM Format Enforcer structured outputs backend "
"does not support structural_tag specifications"
)
else:
raise VLLMValidationError(
"LM Format Enforcer structured outputs backend "
"does not support this structured outputs specification"
)
vllm/v1/structured_output/backend_outlines.py
+12 -2
View File
@@ -198,9 +198,9 @@ def validate_structured_output_request_outlines(params: SamplingParams):
so_params = params.structured_outputs
if so_params.regex:
if so_params.regex is not None:
validate_regex_is_buildable(so_params.regex)
elif so_params.json:
elif so_params.json is not None:
if isinstance(so_params.json, str):
try:
# make sure schema is valid json
@@ -236,6 +236,16 @@ def validate_structured_output_request_outlines(params: SamplingParams):
"Outlines structured outputs backend "
"does not support grammar specifications"
)
elif so_params.structural_tag:
raise VLLMValidationError(
"Outlines structured outputs backend "
"does not support structural_tag specifications"
)
else:
raise VLLMValidationError(
"Outlines structured outputs backend "
"does not support this structured outputs specification"
)
def _prefix_needs_context(parsed) -> bool:
vllm/v1/structured_output/backend_xgrammar.py
+12 -2
View File
@@ -414,7 +414,7 @@ def validate_xgrammar_grammar(sampling_params: SamplingParams) -> None:
so_params = sampling_params.structured_outputs
if so_params.regex:
if so_params.regex is not None:
# A NUL byte is never meaningful in a regex pattern and is not handled
# by xgrammar's native regex converter. Reject it here, before the
# pattern reaches that native code; the try/except below does not cover
@@ -432,6 +432,7 @@ def validate_xgrammar_grammar(sampling_params: SamplingParams) -> None:
raise VLLMValidationError(
f"Failed to transform regex into a grammar: {err}"
) from err
return
if so_params.choice:
choice_grammar = choice_as_grammar(so_params.choice)
@@ -445,7 +446,7 @@ def validate_xgrammar_grammar(sampling_params: SamplingParams) -> None:
so_params.grammar = choice_grammar
return
if so_params.json:
if so_params.json is not None:
check_json_nesting(so_params.json)
if isinstance(so_params.json, str):
try:
@@ -470,6 +471,9 @@ def validate_xgrammar_grammar(sampling_params: SamplingParams) -> None:
) from err
return
if so_params.json_object:
return
if so_params.grammar:
# Parse the grammar with the same syntax `compile_grammar` will use,
# but don't compile it. The grammar is passed on unchanged.
@@ -502,3 +506,9 @@ def validate_xgrammar_grammar(sampling_params: SamplingParams) -> None:
xgr.Grammar.from_structural_tag(so_params.structural_tag)
except Exception as e:
raise VLLMValidationError("Invalid structural tag specification.") from e
return
raise VLLMValidationError(
"XGrammar structured outputs backend "
"does not support this structured outputs specification"
)