Fix a bug when settings were reset to default after an unsuccessful refresh

Author: aleksey925

src/runtime_config/runtime_config.py

@@ -83,7 +83,7 @@ def _check_inst_initialization(inst: RuntimeConfig, exception: Exception) -> Non
             if not inst._initialized and inst._require_complete_init:
                 raise exception
 
-        extracted_settings = []
+        extracted_settings = None
         try:
             extracted_settings = await self._source.get_settings()
         except ValidationError as exc:
@@ -93,11 +93,12 @@ def _check_inst_initialization(inst: RuntimeConfig, exception: Exception) -> Non
             logger.error('Fetching new settings from a remote source failed', exc_info=True)
             _check_inst_initialization(self, exc)
 
-        try:
-            self._settings = await self._settings_merger.merge(extracted_settings=extracted_settings)
-        except Exception as exc:
-            logger.error('Merge settings error', exc_info=True)
-            _check_inst_initialization(self, exc)
+        if extracted_settings is not None:
+            try:
+                self._settings = await self._settings_merger.merge(extracted_settings=extracted_settings)
+            except Exception as exc:
+                logger.error('Merge settings error', exc_info=True)
+                _check_inst_initialization(self, exc)
 
     def get(self, setting_name: str, default: t.Any = None) -> t.Any:
         return self._settings.get(setting_name, default)

tests/test_runtime_config.py

@@ -1,3 +1,4 @@
+import copy
 import os
 
 import aiohttp
@@ -202,6 +203,28 @@ async def test_refresh__insert_new_settings_in_inner_dict__success(self, mocker:
         # assert
         assert inst._settings == expected_settings
 
+    async def test_refresh__remote_source_not_available__save_previous_setting(
+        self, mocker: MockerFixture, init_settings, source_mock
+    ):
+        # arrange
+        mocker.patch.dict(_instance, clear=True)
+
+        source_mock.get_settings.return_value = [
+            Setting(name='some_var', value=1, value_type=SettingValueType.int, disable=False)
+        ]
+        inst = await RuntimeConfig.create(init_settings=init_settings, source=source_mock)
+        setting_after_init = copy.deepcopy(inst._settings)
+
+        source_mock.get_settings.side_effect = Exception
+        expected_settings = {'some_var': 1, **init_settings}
+
+        # act
+        await inst.refresh()
+
+        # assert
+        assert setting_after_init == expected_settings
+        assert inst._settings == expected_settings
+
     @pytest.mark.parametrize('exception', [ValidationError, Exception])
     async def test_refresh__failed_to_get_settings_from_server__config_is_initialized_with_default_settings(
         self, mocker: MockerFixture, init_settings, source_mock, exception