Fix: don't crash when engine or name is missing in settings.yml

SearXNG crashes if the engine or name fields are missing.
With this commit, the app displays an error in the log and keeps loading.

Close #1951

searx/engines/__init__.py

@@ -106,8 +106,12 @@ def load_engine(engine_data: dict) -> Optional[Engine]:
     - required attribute is not set :py:func:`is_missing_required_attributes`
 
     """
+    # pylint: disable=too-many-return-statements
 
-    engine_name = engine_data['name']
+    engine_name = engine_data.get('name')
+    if engine_name is None:
+        logger.error('An engine does not have a "name" field')
+        return None
     if '_' in engine_name:
         logger.error('Engine name contains underscore: "{}"'.format(engine_name))
         return None
@@ -118,7 +122,10 @@ def load_engine(engine_data: dict) -> Optional[Engine]:
         engine_data['name'] = engine_name
 
     # load_module
-    engine_module = engine_data['engine']
+    engine_module = engine_data.get('engine')
+    if engine_module is None:
+        logger.error('The "engine" field is missing for the engine named "{}"'.format(engine_name))
+        return None
     try:
         engine = load_module(engine_module + '.py', ENGINE_DIR)
     except (SyntaxError, KeyboardInterrupt, SystemExit, SystemError, ImportError, RuntimeError):

tests/unit/test_engines_init.py

@@ -53,3 +53,25 @@ class TestEnginesInit(SearxTestCase):
         self.assertIn('onions', engines.categories)
         self.assertIn('http://engine1.onion', engines.engines['engine1'].search_url)
         self.assertEqual(engines.engines['engine1'].timeout, 120.0)
+
+    def test_missing_name_field(self):
+        settings['outgoing']['using_tor_proxy'] = False
+        engine_list = [
+            {'engine': 'dummy', 'shortcut': 'e1', 'categories': 'general'},
+        ]
+        with self.assertLogs('searx.engines', level='ERROR') as cm:
+            engines.load_engines(engine_list)
+            self.assertEqual(len(engines.engines), 0)
+            self.assertEqual(cm.output, ['ERROR:searx.engines:An engine does not have a "name" field'])
+
+    def test_missing_engine_field(self):
+        settings['outgoing']['using_tor_proxy'] = False
+        engine_list = [
+            {'name': 'engine2', 'shortcut': 'e2', 'categories': 'onions'},
+        ]
+        with self.assertLogs('searx.engines', level='ERROR') as cm:
+            engines.load_engines(engine_list)
+            self.assertEqual(len(engines.engines), 0)
+            self.assertEqual(
+                cm.output, ['ERROR:searx.engines:The "engine" field is missing for the engine named "engine2"']
+            )