catch exceptions in error handlerfor errors that happen during polling (2) (#810)

* catch exceptions in error handlerfor errors that happen during polling

* add tests for error handlers that raise exceptions

telegram/ext/dispatcher.py

@@ -258,8 +258,12 @@ class Dispatcher(object):
         """
         # An error happened while polling
         if isinstance(update, TelegramError):
-            self.dispatch_error(None, update)
+            try:
+                self.dispatch_error(None, update)
+            except Exception:
+                self.logger.exception('An uncaught error was raised while handling the error')
             return
+
         for group in self.groups:
             try:
                 for handler in (x for x in self.handlers[group] if x.check_update(update)):

tests/test_dispatcher.py

@@ -47,6 +47,9 @@ class TestDispatcher(object):
     def error_handler(self, bot, update, error):
         self.received = error.message
 
+    def error_handler_raise_error(self, bot, update, error):
+        raise Exception('Failing bigly')
+
     def callback_increase_count(self, bot, update):
         self.count += 1
 
@@ -78,6 +81,30 @@ class TestDispatcher(object):
         sleep(.1)
         assert self.received is None
 
+    def test_error_handler_that_raises_errors(self, dp):
+        """
+        Make sure that errors raised in error handlers don't break the main loop of the dispatcher
+        """
+        handler_raise_error = MessageHandler(Filters.all, self.callback_raise_error)
+        handler_increase_count = MessageHandler(Filters.all, self.callback_increase_count)
+        error = TelegramError('Unauthorized.')
+
+        dp.add_error_handler(self.error_handler_raise_error)
+
+        # From errors caused by handlers
+        dp.add_handler(handler_raise_error)
+        dp.update_queue.put(self.message_update)
+        sleep(.1)
+
+        # From errors in the update_queue
+        dp.remove_handler(handler_raise_error)
+        dp.add_handler(handler_increase_count)
+        dp.update_queue.put(error)
+        dp.update_queue.put(self.message_update)
+        sleep(.1)
+
+        assert self.count == 1
+
     def test_run_async_multiple(self, bot, dp, dp2):
         def get_dispatcher_name(q):
             q.put(current_thread().name)