Fixed set a user as an admin with the new API

changelog.d/6910.bugfix

@@ -0,0 +1 @@
+Fixed set a user as an admin with the admin API `PUT /_synapse/admin/v2/users/<user_id>`. Contributed by @dklimpel.

synapse/rest/admin/users.py

@@ -211,9 +211,7 @@ async def on_PUT(self, request, user_id):
                     if target_user == auth_user and not set_admin_to:
                         raise SynapseError(400, "You may not demote yourself.")
 
-                    await self.admin_handler.set_user_server_admin(
-                        target_user, set_admin_to
-                    )
+                    await self.store.set_server_admin(target_user, set_admin_to)
 
             if "password" in body:
                 if (
@@ -651,6 +649,6 @@ async def on_PUT(self, request, user_id):
         if target_user == auth_user and not set_admin_to:
             raise SynapseError(400, "You may not demote yourself.")
 
-        await self.store.set_user_server_admin(target_user, set_admin_to)
+        await self.store.set_server_admin(target_user, set_admin_to)
 
         return 200, {}

synapse/storage/data_stores/main/registration.py

@@ -301,12 +301,16 @@ def set_server_admin(self, user, admin):
             admin (bool): true iff the user is to be a server admin,
                 false otherwise.
         """
-        return self.db.simple_update_one(
-            table="users",
-            keyvalues={"name": user.to_string()},
-            updatevalues={"admin": 1 if admin else 0},
-            desc="set_server_admin",
-        )
+
+        def set_server_admin_txn(txn):
+            self.db.simple_update_one_txn(
+                txn, "users", {"name": user.to_string()}, {"admin": 1 if admin else 0}
+            )
+            self._invalidate_cache_and_stream(
+                txn, self.get_user_by_id, (user.to_string(),)
+            )
+
+        return self.db.runInteraction("set_server_admin", set_server_admin_txn)
 
     def _query_for_auth(self, txn, token):
         sql = (