Refactor get_or_register_3pid_guest

synapse/handlers/register.py

@@ -446,16 +446,34 @@ def auth_handler(self):
         return self.hs.get_auth_handler()
 
     @defer.inlineCallbacks
-    def guest_access_token_for(self, medium, address, inviter_user_id):
+    def get_or_register_3pid_guest(self, medium, address, inviter_user_id):
+        """Get a guest access token for a 3PID, creating a guest account if
+        one doesn't already exist.
+
+        Args:
+            medium (str)
+            address (str)
+            inviter_user_id (str): The user ID who is trying to invite the
+                3PID
+
+        Returns:
+            Deferred[(str, str)]: A 2-tuple of `(user_id, access_token)` of the
+            3PID guest account.
+        """
         access_token = yield self.store.get_3pid_guest_access_token(medium, address)
         if access_token:
-            defer.returnValue(access_token)
+            user_info = yield self.auth.get_user_by_access_token(
+                access_token
+            )
 
-        _, access_token = yield self.register(
+            defer.returnValue((user_info["user"].to_string(), access_token))
+
+        user_id, access_token = yield self.register(
             generate_token=True,
             make_guest=True
         )
         access_token = yield self.store.save_or_get_3pid_guest_access_token(
             medium, address, access_token, inviter_user_id
         )
-        defer.returnValue(access_token)
+
+        defer.returnValue((user_id, access_token))

synapse/handlers/room_member.py

@@ -735,20 +735,16 @@ def _ask_id_server_for_third_party_invite(
         }
 
         if self.config.invite_3pid_guest:
-            registration_handler = self.registration_handler
-            guest_access_token = yield registration_handler.guest_access_token_for(
+            rh = self.registration_handler
+            guest_user_id, guest_access_token = yield rh.get_or_register_3pid_guest(
                 medium=medium,
                 address=address,
                 inviter_user_id=inviter_user_id,
             )
 
-            guest_user_info = yield self.auth.get_user_by_access_token(
-                guest_access_token
-            )
-
             invite_config.update({
                 "guest_access_token": guest_access_token,
-                "guest_user_id": guest_user_info["user"].to_string(),
+                "guest_user_id": guest_user_id,
             })
 
         data = yield self.simple_http_client.post_urlencoded_get_json(