[diffusion] fix: reject unsupported modelopt checkpoint algorithms (#35182)

test/registered/unit/test_checkpoint_quantization.py

@@ -2,6 +2,8 @@
 
 import unittest
 
+from sglang.srt.layers.modelopt_utils import canonicalize_modelopt_quant_algo
+from sglang.srt.layers.quantization.base_config import QuantizationConfig
 from sglang.srt.model_loader.checkpoint_quantization import (
     CheckpointQuantSpec,
     resolve_checkpoint_quant_spec,
@@ -26,6 +28,34 @@ class _QuantConfigObject:
 
 
 class TestResolveCheckpointQuantSpec(CustomTestCase):
+    def test_modelopt_quant_algo_canonicalization(self):
+        cases = {
+            "FP8": "modelopt_fp8",
+            "mxfp8": "mxfp8",
+            "NVFP4": "modelopt_fp4",
+            "NVFP4_AWQ": "modelopt_fp4",
+            "W4A16_NVFP4": "modelopt_fp4",
+            "FP8_FAKE": None,
+            "MIXED_PRECISION": None,
+            None: None,
+        }
+        for quant_algo, expected in cases.items():
+            with self.subTest(quant_algo=quant_algo):
+                self.assertEqual(canonicalize_modelopt_quant_algo(quant_algo), expected)
+
+    def test_srt_modelopt_override_uses_the_exact_algorithm_allowlist(self):
+        self.assertEqual(
+            QuantizationConfig._modelopt_override_quantization_method(
+                {"quant_algo": "NVFP4"}, "modelopt"
+            ),
+            "modelopt_fp4",
+        )
+        self.assertIsNone(
+            QuantizationConfig._modelopt_override_quantization_method(
+                {"quant_algo": "NVFP4_FAKE"}, "modelopt"
+            )
+        )
+
     def test_top_level_quantization_config(self):
         config = {
             "quantization_config": {