How to return Ajax data inside Ember computed property

I'm trying to return data from an Ajax call in a computed property. I understand because of the asynchronous nature, I can't do the following. However, I can't return a promise because I need to return the data in a particular format of an array with objects with a property and label.

options: Ember.computed('name', function() {
    const url = '/testUrl';
    let optionArray = [];
    Ember.$.ajax({
      url: url,
      type: 'GET',
    }).then((response) => {
      let arr = JSON.parse(response);
      for (let idx = 0; idx < arr.length; idx++) {
        optionArray.addObject({
          property: idx,
          label: arr[idx]
        });
      }
      return optionArray;
    });
  })

How do I return the data from the Ajax call in the format specified above?