Refetch ChatAction service message to get input users

telethon/events/chataction.py

@@ -344,20 +344,10 @@ class ChatAction(EventBuilder):
                 return []
 
             if self._users is None or len(self._users) != len(self._user_peers):
-                have, missing = [], []
-                for peer in self._user_peers:
-                    user = self._entities.get(utils.get_peer_id(peer))
-                    if user:
-                        have.append(user)
-                    else:
-                        missing.append(peer)
-
-                try:
-                    missing = await self._client.get_entity(missing)
-                except (TypeError, ValueError):
-                    missing = []
-
-                self._users = have + missing
+                await self.action_message._reload_message()
+                self._users = [
+                    u for u in self.action_message.action_entities
+                    if isinstance(u, (types.User, types.UserEmpty))]
 
             return self._users
 
@@ -381,8 +371,15 @@ class ChatAction(EventBuilder):
             """
             Returns `input_users` but will make an API call if necessary.
             """
-            # TODO Maybe we could re-fetch the message
-            return self.input_users
+            self._input_users = None
+            if self._input_users is None:
+                await self.action_message._reload_message()
+                self._input_users = [
+                    utils.get_input_peer(u)
+                    for u in self.action_message.action_entities
+                    if isinstance(u, (types.User, types.UserEmpty))]
+
+            return self._input_users or []
 
         @property
         def user_ids(self):

telethon/tl/custom/message.py

@@ -177,6 +177,7 @@ class Message(ChatGetter, SenderGetter, TLObject, abc.ABC):
         self._sender_id = from_id
         self._sender = None
         self._input_sender = None
+        self._action_entities = None
 
         if not out and isinstance(to_id, types.PeerUser):
             self._chat_peer = types.PeerUser(from_id)
@@ -220,6 +221,23 @@ class Message(ChatGetter, SenderGetter, TLObject, abc.ABC):
         if self.fwd_from:
             self._forward = Forward(self._client, self.fwd_from, entities)
 
+        if self.action:
+            if isinstance(self.action, (types.MessageActionChatAddUser,
+                                        types.MessageActionChatCreate)):
+                self._action_entities = [entities.get(i)
+                                         for i in self.action.users]
+            elif isinstance(self.action, types.MessageActionChatDeleteUser):
+                self._action_entities = [entities.get(self.action.user_id)]
+            elif isinstance(self.action, types.MessageActionChatJoinedByLink):
+                self._action_entities = [entities.get(self.action.inviter_id)]
+            elif isinstance(self.action, types.MessageActionChatMigrateTo):
+                self._action_entities = [entities.get(utils.get_peer_id(
+                    types.PeerChannel(self.action.channel_id)))]
+            elif isinstance(
+                    self.action, types.MessageActionChannelMigrateFrom):
+                self._action_entities = [entities.get(utils.get_peer_id(
+                    types.PeerChat(self.action.chat_id)))]
+
     # endregion Initialization
 
     # region Public Properties
@@ -432,6 +450,22 @@ class Message(ChatGetter, SenderGetter, TLObject, abc.ABC):
         """
         return self._document_by_attribute(types.DocumentAttributeSticker)
 
+    @property
+    def action_entities(self):
+        """
+        Returns a list of entities that can took part in this action.
+
+        Possible cases for this are :tl:`MessageActionChatAddUser`,
+        :tl:`types.MessageActionChatCreate`, :tl:`MessageActionChatDeleteUser`,
+        :tl:`MessageActionChatJoinedByLink` :tl:`MessageActionChatMigrateTo`
+        and :tl:`MessageActionChannelMigrateFrom).
+
+        If the action is neither of those, the result will be ``None``.
+        If some entities could not be retrieved, the list may contain
+        some ``None`` items in it.
+        """
+        return self._action_entities
+
     # endregion Public Properties
 
     # region Public Methods
@@ -670,6 +704,7 @@ class Message(ChatGetter, SenderGetter, TLObject, abc.ABC):
         self._input_sender = msg._input_sender
         self._chat = msg._chat
         self._input_chat = msg._input_chat
+        self._action_entities = msg._action_entities
 
     async def _refetch_sender(self):
         await self._reload_message()