CallbackContext: Expose dispatcher as a property (#1684)

Co-authored-by: Poolitzer <25934244+Poolitzer@users.noreply.github.com>

telegram/ext/callbackcontext.py

@@ -44,7 +44,14 @@ class CallbackContext(object):
 
     Attributes:
         chat_data (:obj:`dict`, optional): A dict that can be used to keep any data in. For each
-            update from the same chat it will be the same ``dict``.
+            update from the same chat id it will be the same ``dict``.
+
+            Warning:
+                When a group chat migrates to a supergroup, its chat id will change and the
+                ``chat_data`` needs to be transferred. For details see our `wiki page
+                <https://github.com/python-telegram-bot/python-telegram-bot/wiki/
+                Storing-user--and-chat-related-data#chat-migration>`_.
+
         user_data (:obj:`dict`, optional): A dict that can be used to keep any data in. For each
             update from the same user it will be the same ``dict``.
         matches (List[:obj:`re match object`], optional): If the associated update originated from
@@ -80,6 +87,11 @@ class CallbackContext(object):
         self.error = None
         self.job = None
 
+    @property
+    def dispatcher(self):
+        """:class:`telegram.ext.Dispatcher`: The dispatcher associated with this context."""
+        return self._dispatcher
+
     @property
     def chat_data(self):
         return self._chat_data

tests/test_callbackcontext.py

@@ -117,3 +117,7 @@ class TestCallbackContext(object):
             callback_context.user_data = {}
         with pytest.raises(AttributeError):
             callback_context.chat_data = "test"
+
+    def test_dispatcher_attribute(self, cdp):
+        callback_context = CallbackContext(cdp)
+        assert callback_context.dispatcher == cdp