Add option to disable removing avatars from Telegram ghosts

There's no way to determine whether an avatar is removed or just hidden
from some users, so avatars are not removed by default.

mautrix_telegram/config.py

@@ -83,6 +83,7 @@ class Config(BaseBridgeConfig):
 
         copy("bridge.displayname_preference")
         copy("bridge.displayname_max_length")
+        copy("bridge.allow_avatar_remove")
 
         copy("bridge.max_initial_member_sync")
         copy("bridge.sync_channel_members")

mautrix_telegram/example-config.yaml

@@ -121,6 +121,10 @@ bridge:
     - phone number
     # Maximum length of displayname
     displayname_max_length: 100
+    # Remove avatars from Telegram ghost users when removed on Telegram. This is disabled by default
+    # as there's no way to determine whether an avatar is removed or just hidden from some users. If
+    # you're on a single-user instance, this should be safe to enable.
+    allow_avatar_remove: false
 
     # Maximum number of members to sync per portal when starting up. Other members will be
     # synced when they send messages. The maximum is 10000, after which the Telegram server

mautrix_telegram/portal/metadata.py

@@ -1,5 +1,5 @@
 # mautrix-telegram - A Matrix-Telegram puppeting bridge
-# Copyright (C) 2019 Tulir Asokan
+# Copyright (C) 2020 Tulir Asokan
 #
 # This program is free software: you can redistribute it and/or modify
 # it under the terms of the GNU Affero General Public License as published by
@@ -695,6 +695,8 @@ class PortalMetadata(BasePortal, ABC):
             loc = None
         else:
             raise ValueError(f"Unknown photo type {type(photo)}")
+        if self.peer_type == "user" and not photo_id and not config["bridge.allow_avatar_remove"]:
+            return False
         if self.photo_id != photo_id:
             if not photo_id:
                 await self._try_set_state(sender, EventType.ROOM_AVATAR,

mautrix_telegram/puppet.py

@@ -1,5 +1,5 @@
 # mautrix-telegram - A Matrix-Telegram puppeting bridge
-# Copyright (C) 2019 Tulir Asokan
+# Copyright (C) 2020 Tulir Asokan
 #
 # This program is free software: you can redistribute it and/or modify
 # it under the terms of the GNU Affero General Public License as published by
@@ -300,6 +300,8 @@ class Puppet(CustomPuppetMixin):
         else:
             self.log.warning(f"Unknown user profile photo type: {type(photo)}")
             return False
+        if not photo_id and not config["bridge.allow_avatar_remove"]:
+            return False
         if self.photo_id != photo_id:
             if not photo_id:
                 self.photo_id = ""