Return produced service message with pin_message

Fixes #1394.

telethon/client/messageparse.py

@@ -131,7 +131,14 @@ class MessageParseMethods:
             elif isinstance(update, (
                     types.UpdateNewChannelMessage, types.UpdateNewMessage)):
                 update.message._finish_init(self, entities, input_chat)
-                id_to_message[update.message.id] = update.message
+
+                # Pinning a message with `updatePinnedMessage` seems to
+                # always produce a service message we can't map so return
+                # it directly.
+                if hasattr(request, 'random_id'):
+                    id_to_message[update.message.id] = update.message
+                else:
+                    return update.message
 
             elif (isinstance(update, types.UpdateEditMessage)
                   and helpers._entity_type(request.peer) != helpers._EntityType.CHANNEL):

telethon/client/messages.py

@@ -1246,11 +1246,24 @@ class MessageMethods:
         """
         message = utils.get_message_id(message) or 0
         entity = await self.get_input_entity(entity)
-        await self(functions.messages.UpdatePinnedMessageRequest(
+        request = functions.messages.UpdatePinnedMessageRequest(
             peer=entity,
             id=message,
             silent=not notify
-        ))
+        )
+        result = await self(request)
+
+        # Unpinning does not produce a service message, and technically
+        # users can pass negative IDs which seem to behave as unpinning too.
+        if message <= 0:
+            return
+
+        # Pinning in User chats (just with yourself really) does not produce a service message
+        if helpers._entity_type(entity) == helpers._EntityType.USER:
+            return
+
+        # Pinning a message that doesn't exist would RPC-error earlier
+        return self._get_response_message(request, result, entity)
 
     # endregion
 

telethon/events/album.py

@@ -259,7 +259,7 @@ class Album(EventBuilder):
             `telethon.client.messages.MessageMethods.pin_message`
             with both ``entity`` and ``message`` already set.
             """
-            await self.messages[0].pin(notify=notify)
+            return await self.messages[0].pin(notify=notify)
 
         def __len__(self):
             """

telethon/tl/custom/message.py

@@ -898,7 +898,7 @@ class Message(ChatGetter, SenderGetter, TLObject, abc.ABC):
         #      maybe just make it illegal to call messages from raw API?
         #      That or figure out a way to always set it directly.
         if self._client:
-            await self._client.pin_message(
+            return await self._client.pin_message(
                 await self.get_input_chat(), self.id, notify=notify)
 
     # endregion Public Methods