bots: Add complete test-coverage for bot_lib.py file.

Also, add error handling for get_bot_handler instead of
throwing an assertion error.

zerver/lib/bot_lib.py

@@ -26,9 +26,10 @@ from zulip_bots.lib import RateLimit
 def get_bot_handler(service_name):
     # type: (str) -> Any
 
-    # Assert that this service is present in EMBEDDED_BOTS.
+    # Check that this service is present in EMBEDDED_BOTS, add exception handling.
-    assert any(service_name == embedded_bot_service.name for embedded_bot_service in EMBEDDED_BOTS)
+    is_present_in_registry = any(service_name == embedded_bot_service.name for embedded_bot_service in EMBEDDED_BOTS)
-
+    if not is_present_in_registry:
+        return None
     bot_module_name = 'zulip_bots.bots.%s.%s' % (service_name, service_name)
     bot_module = importlib.import_module(bot_module_name)  # type: Any
     return bot_module.handler_class()

zerver/tests/test_bots.py

@@ -954,6 +954,18 @@ class BotTest(ZulipTestCase, UploadSerializeMixin):
         result = self.client_post("/json/bots", bot_info)
         self.assert_json_error(result, "Enter a valid URL.")
 
+    def test_get_bot_handler(self):
+        # type: () -> None
+        # Test for valid service.
+        test_service_name = 'converter'
+        test_bot_handler = get_bot_handler(test_service_name)
+        self.assertEqual(str(type(test_bot_handler)), "<class 'zulip_bots.bots.converter.converter.ConverterHandler'>")
+
+        # Test for invalid service.
+        test_service_name = "incorrect_bot_service_foo"
+        test_bot_handler = get_bot_handler(test_service_name)
+        self.assertEqual(test_bot_handler, None)
+
     def test_if_each_embedded_bot_service_exists(self):
         # type: () -> None
         # Each bot has its bot handler class name as Bot_nameHandler. For instance encrypt bot has

zerver/worker/queue_processors.py

@@ -491,7 +491,11 @@ class EmbeddedBotWorker(QueueProcessingWorker):
         # TODO: Do we actually want to allow multiple Services per bot user?
         services = get_bot_services(user_profile_id)
         for service in services:
-            get_bot_handler(str(service.name)).handle_message(
+            bot_handler = get_bot_handler(str(service.name))
+            if bot_handler is None:
+                logging.error("Error: User %s has bot with invalid embedded bot service %s" % (user_profile_id, service.name))
+                continue
+            bot_handler.handle_message(
                 message=message,
                 bot_handler=self.get_bot_api_client(user_profile),
                 state_handler=self.get_state_handler())