SYN-154: Tweak how the m.room.create check is done.

Don't perform the check in auth.is_host_in_room but instead do it in _do_join
and also assert that there are no m.room.members in the room before doing so.

synapse/api/auth.py

@@ -98,16 +98,7 @@ class Auth(object):
         defer.returnValue(member)
 
     @defer.inlineCallbacks
-    def check_host_in_room(self, room_id, host, context=None):
-        if context:
-            # XXX: check_host_in_room should really return True for a new
-            # room created by this home server. There are no m.room.member
-            # join events yet so we need to check for the m.room.create event
-            # instead.
-            if (u"m.room.create", u"") in context.auth_events:
-                defer.returnValue(True)
-                return
-
+    def check_host_in_room(self, room_id, host):
         curr_state = yield self.state.get_current_state(room_id)
 
         for event in curr_state:

synapse/handlers/room.py

@@ -423,9 +423,18 @@ class RoomMemberHandler(BaseHandler):
 
         is_host_in_room = yield self.auth.check_host_in_room(
             event.room_id,
-            self.hs.hostname,
-            context=context
+            self.hs.hostname
         )
+        if not is_host_in_room:
+            # is *anyone* in the room?
+            room_member_keys = [
+                v for (k,v) in context.current_state.keys() if k == "m.room.member"
+            ]
+            if len(room_member_keys) == 0:
+                # has the room been created so we can join it?
+                create_event = context.current_state.get(("m.room.create", ""))
+                if create_event:
+                    is_host_in_room = True
 
         if is_host_in_room:
             should_do_dance = False