Avoid modifying original config argument

netjsonconfig/backends/openwrt/openwrt.py

@@ -4,6 +4,7 @@
 import time
 import tarfile
 from io import BytesIO
+from copy import deepcopy
 
 from jsonschema import validate
 from jsonschema.exceptions import ValidationError as JsonSchemaError
@@ -32,7 +33,8 @@ def __init__(self, config, templates=[]):
                           as a base for the main config, defaults to empty list
         :raises TypeError: raised if config is not dict or templates is not a list
         """
-        config = self._load(config)
+        # perform deepcopy to avoid modifying the original config argument
+        config = deepcopy(self._load(config))
         # allow omitting NetJSON type
         if 'type' not in config:
             config.update({'type': 'DeviceConfiguration'})

tests/openwrt/test_backend.py

@@ -12,8 +12,15 @@ class TestBackend(unittest.TestCase, _TabsMixin):
     """
     tests for backends.openwrt.OpenWrt
     """
+    def test_config_copy(self):
+        config = {'interfaces': []}
+        o = OpenWrt(config)
+        o.validate()
+        self.assertDictEqual(config, {'interfaces': []})
+
     def test_json_method(self):
         config = {
+            "type": "DeviceConfiguration",
             "interfaces": [
                 {
                     "name": "lo",