From 856b9e864f3c170dcb99fff14f3532a9136d8a6e Mon Sep 17 00:00:00 2001
From: Alex Root Junior <jroot.junior@gmail.com>
Date: Fri, 12 Jan 2018 17:44:54 +0200
Subject: [PATCH] Allow to cancel event from the
 Middleware.on_pre_process_<event type>

---
 aiogram/dispatcher/handler.py | 6 +++++-
 1 file changed, 5 insertions(+), 1 deletion(-)

diff --git a/aiogram/dispatcher/handler.py b/aiogram/dispatcher/handler.py
index c721369b..8972958c 100644
--- a/aiogram/dispatcher/handler.py
+++ b/aiogram/dispatcher/handler.py
@@ -60,7 +60,11 @@ class Handler:
         results = []
 
         if self.middleware_key:
-            await self.dispatcher.middleware.trigger(f"pre_process_{self.middleware_key}", args)
+            try:
+                await self.dispatcher.middleware.trigger(f"pre_process_{self.middleware_key}", args)
+            except CancelHandler:  # Allow to cancel current event
+                return results
+
         for filters, handler in self.handlers:
             if await check_filters(filters, args):
                 try: