Better handling of odd PLs during room upgrades

changelog.d/4091.feature

@@ -0,0 +1 @@
+Support for replacing rooms with new ones

changelog.d/4099.feature

@@ -0,0 +1 @@
+Support for replacing rooms with new ones

synapse/api/constants.py

@@ -61,6 +61,7 @@ class LoginType(object):
 class EventTypes(object):
     Member = "m.room.member"
     Create = "m.room.create"
+    Tombstone = "m.room.tombstone"
     JoinRules = "m.room.join_rules"
     PowerLevels = "m.room.power_levels"
     Aliases = "m.room.aliases"

synapse/handlers/register.py

@@ -50,7 +50,6 @@ def __init__(self, hs):
         self._auth_handler = hs.get_auth_handler()
         self.profile_handler = hs.get_profile_handler()
         self.user_directory_handler = hs.get_user_directory_handler()
-        self.room_creation_handler = self.hs.get_room_creation_handler()
         self.captcha_client = CaptchaServerHttpClient(hs)
 
         self._next_generated_user_id = None
@@ -241,7 +240,10 @@ def register(
                     else:
                         # create room expects the localpart of the room alias
                         room_alias_localpart = room_alias.localpart
-                        yield self.room_creation_handler.create_room(
+
+                        # getting the RoomCreationHandler during init gives a dependency
+                        # loop
+                        yield self.hs.get_room_creation_handler().create_room(
                             fake_requester,
                             config={
                                 "preset": "public_chat",