source:
  functions:
    - isUser(uid): root.authUserIndex[auth.userid] === uid || isShopper()
    - isShopper(): root.users[root.authUserIndex[auth.uid]].isShopper === true

  schema: {}
  access:
    - location: /
      write: isUser($userid)

expected: {"rules":{".write":"(((root.child('authUserIndex').child(auth.userid).val()===$userid||root.child('users').child(root.child('authUserIndex').child(auth.$userid).val()).child('isShopper').val()===true)))",".read":"false"}}