Implement bot middleware.

aiogram/contrib/middlewares/bot.py

@@ -0,0 +1,25 @@
+from aiogram.dispatcher.middlewares import BaseMiddleware
+
+
+class BotMiddleware(BaseMiddleware):
+    def __init__(self, context=None):
+        super(BotMiddleware, self).__init__()
+
+        if context is None:
+            context = {}
+        self.context = context
+
+    def update_data(self, data):
+        dp = self.manager.dispatcher
+        data.update(
+            bot=dp.bot,
+            dispatcher=dp,
+            loop=dp.loop
+        )
+        if self.context:
+            data.update(self.context)
+
+    async def trigger(self, action, args):
+        if 'error' not in action and action.startswith('pre_process_'):
+            self.update_data(args[-1])
+            return True