Different method of upgrading user instances

discord/member.py

@@ -189,11 +189,7 @@ class Member(discord.abc.Messageable, _BaseUser):
     @classmethod
     def _from_message(cls, *, message, data):
         author = message.author
-        data['user'] = {
-            attr: getattr(author, attr)
-            for attr in author.__slots__
-            if attr[0] != '_'
-        }
+        data['user'] = author._to_minimal_user_json()
         return cls(data=data, guild=message.guild, state=message._state)
 
     @classmethod

discord/message.py

@@ -403,9 +403,12 @@ class Message:
         # ourselves to a more "partial" member object.
         author = self.author
         try:
+            # Update member reference
             if author.joined_at is None:
                 author.joined_at = utils.parse_time(member.get('joined_at'))
         except AttributeError:
+            # It's a user here
+            # TODO: consider adding to cache here
             self.author = Member._from_message(message=self, data=member)
 
     def _handle_mentions(self, mentions):

discord/user.py

@@ -112,6 +112,15 @@ class BaseUser(_BaseUser):
 
         return self
 
+    def _to_minimal_user_json(self):
+        return {
+            'name': self.name,
+            'id': self.id,
+            'avatar': self.avatar,
+            'discriminator': self.discriminator,
+            'bot': self.bot,
+        }
+
     @property
     def avatar_url(self):
         """Returns an :class:`Asset` for the avatar the user has.