Group logic detecting user, ensure rsync_opts is a list if omitted. Fixes #40483

lib/ansible/modules/files/synchronize.py

@@ -366,7 +366,7 @@ def main():
             group=dict(type='bool'),
             set_remote_user=dict(type='bool', default=True),
             rsync_timeout=dict(type='int', default=0),
-            rsync_opts=dict(type='list'),
+            rsync_opts=dict(type='list', default=[]),
             ssh_args=dict(type='str'),
             partial=dict(type='bool', default=False),
             verify_host=dict(type='bool', default=False),

lib/ansible/plugins/action/__init__.py

@@ -583,7 +583,7 @@ class ActionBase(with_metaclass(ABCMeta, object)):
                 expand_path = '~%s' % self._play_context.become_user
             else:
                 # use remote user instead, if none set default to current user
-                expand_path = '~%s' % self._play_context.remote_user or self._connection.default_user or ''
+                expand_path = '~%s' % (self._play_context.remote_user or self._connection.default_user or '')
 
         # use shell to construct appropriate command and execute
         cmd = self._connection._shell.expand_user(expand_path)