chore: import upstream snapshot with attribution

tests/v1/structured_output/test_validation.py

@@ -0,0 +1,71 @@
+# SPDX-License-Identifier: Apache-2.0
+# SPDX-FileCopyrightText: Copyright contributors to the vLLM project
+"""Request-time validation of structured output requests."""
+
+import pytest
+
+from vllm.config import StructuredOutputsConfig
+from vllm.sampling_params import SamplingParams, StructuredOutputsParams
+
+pytestmark = pytest.mark.cpu_test
+
+JSON_SCHEMA = {
+    "type": "object",
+    "properties": {
+        "invoice_id": {"type": "string"},
+        "customer": {"type": "string"},
+    },
+    "required": ["invoice_id", "customer"],
+    "additionalProperties": False,
+}
+
+
+class _StubModelConfig:
+    def __init__(self, is_diffusion: bool):
+        self.is_diffusion = is_diffusion
+
+
+def test_structured_outputs_rejected_for_diffusion_models():
+    """Diffusion LLMs denoise the canvas in parallel, which is incompatible
+    with the token-by-token grammar FSM. The request must fail with a clear
+    validation error instead of an FSM rejection mid-generation (#45436)."""
+    params = SamplingParams(
+        structured_outputs=StructuredOutputsParams(json=JSON_SCHEMA)
+    )
+    with pytest.raises(ValueError, match="not yet supported for diffusion"):
+        params._validate_structured_outputs(
+            _StubModelConfig(is_diffusion=True),
+            StructuredOutputsConfig(),
+            tokenizer=None,
+        )
+
+
+def test_plain_request_allowed_for_diffusion_models():
+    """Requests without structured outputs are unaffected by the guard."""
+    params = SamplingParams()
+    params._validate_structured_outputs(
+        _StubModelConfig(is_diffusion=True),
+        StructuredOutputsConfig(),
+        tokenizer=None,
+    )
+
+
+@pytest.mark.parametrize(
+    "structured_outputs, match",
+    [
+        (StructuredOutputsParams(json_object=False), "json_object must be True"),
+        (StructuredOutputsParams(json=""), "json cannot be an empty string"),
+    ],
+)
+def test_degenerate_structured_outputs_rejected(structured_outputs, match):
+    """json_object=False and an empty json schema pass the `is not None`
+    exclusivity check but resolve to no structured-output key, so they must be
+    rejected at request validation (-> 400) instead of reaching and crashing
+    the engine."""
+    params = SamplingParams(structured_outputs=structured_outputs)
+    with pytest.raises(ValueError, match=match):
+        params._validate_structured_outputs(
+            _StubModelConfig(is_diffusion=False),
+            StructuredOutputsConfig(),
+            tokenizer=object(),
+        )