Add context middleware (with example of usage)

aiogram/contrib/middlewares/context.py

@@ -0,0 +1,115 @@
+from aiogram import types
+from aiogram.dispatcher import ctx
+from aiogram.dispatcher.middlewares import BaseMiddleware
+
+OBJ_KEY = '_context_data'
+
+
+class ContextMiddleware(BaseMiddleware):
+    """
+    Allow to store data at all of lifetime of Update object
+    """
+
+    async def on_pre_process_update(self, update: types.Update):
+        """
+        Start of Update lifetime
+
+        :param update:
+        :return:
+        """
+        self._configure_update(update)
+
+    async def on_post_process_update(self, update: types.Update, result):
+        """
+        On finishing of processing update
+
+        :param update:
+        :param result:
+        :return:
+        """
+        if OBJ_KEY in update.conf:
+            del update.conf[OBJ_KEY]
+
+    def _configure_update(self, update: types.Update = None):
+        """
+        Setup data storage
+
+        :param update:
+        :return:
+        """
+        obj = update.conf[OBJ_KEY] = {}
+        return obj
+
+    def _get_dict(self):
+        """
+        Get data from update stored in current context
+
+        :return:
+        """
+        update = ctx.get_update()
+        obj = update.conf.get(OBJ_KEY, None)
+        if obj is None:
+            obj = self._configure_update(update)
+        return obj
+
+    def __getitem__(self, item):
+        """
+        Item getter
+
+        :param item:
+        :return:
+        """
+        return self._get_dict()[item]
+
+    def __setitem__(self, key, value):
+        """
+        Item setter
+
+        :param key:
+        :param value:
+        :return:
+        """
+        data = self._get_dict()
+        data[key] = value
+
+    def __iter__(self):
+        """
+        Iterate over dict
+
+        :return:
+        """
+        return self._get_dict().__iter__()
+
+    def keys(self):
+        """
+        Iterate over dict keys
+
+        :return:
+        """
+        return self._get_dict().keys()
+
+    def values(self):
+        """
+        Iterate over dict values
+
+        :return:
+        """
+        return self._get_dict().values()
+
+    def get(self, key, default=None):
+        """
+        Get item from dit or return default value
+
+        :param key:
+        :param default:
+        :return:
+        """
+        return self._get_dict().get(key, default)
+
+    def export(self):
+        """
+        Export all data s dict
+
+        :return:
+        """
+        return self._get_dict()

aiogram/dispatcher/middlewares.py

@@ -35,6 +35,7 @@ class MiddlewareManager:
         self.applications.append(middleware)
         middleware.setup(self)
         log.debug(f"Loaded middleware '{middleware.__class__.__name__}'")
+        return middleware
 
     async def trigger(self, action: str, args: typing.Iterable):
         """