Fix a Bug in ChatMemberUpdated.difference (#2947)

telegram/_chatmemberupdated.py

@@ -125,6 +125,19 @@ class ChatMemberUpdated(TelegramObject):
 
         return data
 
+    def _get_attribute_difference(self, attribute: str) -> Tuple[object, object]:
+        try:
+            old = self.old_chat_member[attribute]
+        except KeyError:
+            old = None
+
+        try:
+            new = self.new_chat_member[attribute]
+        except KeyError:
+            new = None
+
+        return old, new
+
     def difference(
         self,
     ) -> Dict[
@@ -162,10 +175,7 @@ class ChatMemberUpdated(TelegramObject):
         # we can't directly use the values from old_dict ^ new_dict b/c that set is unordered
         attributes = (entry[0] for entry in set(old_dict.items()) ^ set(new_dict.items()))
 
-        result = {
-            attribute: (self.old_chat_member[attribute], self.new_chat_member[attribute])
-            for attribute in attributes
-        }
+        result = {attribute: self._get_attribute_difference(attribute) for attribute in attributes}
         if old_user_dict != new_user_dict:
             result['user'] = (self.old_chat_member.user, self.new_chat_member.user)
 

tests/test_chatmemberupdated.py

@@ -29,6 +29,8 @@ from telegram import (
     Chat,
     ChatMemberUpdated,
     ChatInviteLink,
+    ChatMemberOwner,
+    ChatMemberBanned,
 )
 from telegram._utils.datetime import to_timestamp
 
@@ -210,7 +212,7 @@ class TestChatMemberUpdated:
         )
         assert chat_member_updated.difference() == {'status': ('old_status', 'new_status')}
 
-        # We deliberately change an optional argument here to make sure that comparision doesn't
+        # We deliberately change an optional argument here to make sure that comparison doesn't
         # just happens by id/required args
         new_user = User(1, 'First name', False, last_name='last name')
         new_chat_member.user = new_user
@@ -239,3 +241,19 @@ class TestChatMemberUpdated:
             chat, user, datetime.datetime.utcnow(), old_chat_member, new_chat_member
         )
         assert chat_member_updated.difference() == {optional_attribute: (old_value, new_value)}
+
+    def test_difference_different_classes(self, user, chat):
+        old_chat_member = ChatMemberOwner(user=user, is_anonymous=False)
+        new_chat_member = ChatMemberBanned(user=user, until_date=datetime.datetime(2021, 1, 1))
+        chat_member_updated = ChatMemberUpdated(
+            chat=chat,
+            from_user=user,
+            date=datetime.datetime.utcnow(),
+            old_chat_member=old_chat_member,
+            new_chat_member=new_chat_member,
+        )
+        diff = chat_member_updated.difference()
+        assert diff.pop('is_anonymous') == (False, None)
+        assert diff.pop('until_date') == (None, datetime.datetime(2021, 1, 1))
+        assert diff.pop('status') == (ChatMember.CREATOR, ChatMember.KICKED)
+        assert diff == {}