[PD] Fix IB device validation for JSON mappings (#26114)

test/registered/cpu/test_server_args_backend.py

@@ -1,3 +1,6 @@
+import json
+import os
+import tempfile
 import unittest
 from unittest.mock import patch
 
@@ -34,5 +37,63 @@ class TestServerArgsCPUBackend(unittest.TestCase):
         self.assertEqual(server_args.sampling_backend, "pytorch")
 
 
+class TestServerArgsIBDeviceValidation(unittest.TestCase):
+    def _validate_ib_devices(self, device_str, available_devices=None):
+        server_args = ServerArgs.__new__(ServerArgs)
+        available_devices = available_devices or [
+            "mlx5_0",
+            "mlx5_1",
+            "mlx5_2",
+            "mlx5_3",
+        ]
+        real_isdir = os.path.isdir
+        real_listdir = os.listdir
+
+        with patch(
+            "sglang.srt.server_args.os.path.isdir",
+            side_effect=lambda path: (
+                True if path == "/sys/class/infiniband" else real_isdir(path)
+            ),
+        ), patch(
+            "sglang.srt.server_args.os.listdir",
+            side_effect=lambda path: (
+                available_devices
+                if path == "/sys/class/infiniband"
+                else real_listdir(path)
+            ),
+        ):
+            return ServerArgs._validate_ib_devices(server_args, device_str)
+
+    def test_validate_ib_devices_accepts_comma_separated(self):
+        self.assertEqual(
+            self._validate_ib_devices("mlx5_0, mlx5_1"),
+            "mlx5_0,mlx5_1",
+        )
+
+    def test_validate_ib_devices_accepts_json_object(self):
+        result = self._validate_ib_devices(
+            '{"0": "mlx5_0, mlx5_1", "1": "mlx5_2, mlx5_3"}'
+        )
+        self.assertEqual(
+            json.loads(result),
+            {"0": "mlx5_0,mlx5_1", "1": "mlx5_2,mlx5_3"},
+        )
+
+    def test_validate_ib_devices_accepts_json_file(self):
+        with tempfile.NamedTemporaryFile("w", suffix=".json", delete=False) as file:
+            json.dump({"0": "mlx5_0, mlx5_1", "1": "mlx5_2"}, file)
+            json_file = file.name
+
+        try:
+            result = self._validate_ib_devices(json_file)
+        finally:
+            os.unlink(json_file)
+
+        self.assertEqual(
+            json.loads(result),
+            {"0": "mlx5_0,mlx5_1", "1": "mlx5_2"},
+        )
+
+
 if __name__ == "__main__":
     unittest.main()