title: How to fix Vue error `[Vue warn]: data functions should return an object`?
body: <p>I still get this error</p>
  
  <p><code>[Vue warn]: data functions should return an object:</code></p>
  
  <p>even after making my <code>data</code> property a function to return a copy of my global state:</p>
  
  <pre><code>new Vue({
      'el': '#app',
      'data': function getState() { return _.cloneDeep(state); },
      'router': router,
      'template': '&lt;Welcome /&gt;',
      'components': { Welcome }
  });
  </code></pre>
  
  <p>What more does Vue want from me?</p>