<a-tree
  show-icon
  :icon="getIcon"
  :tree-data="treeData"
>
</a-tree>

getIcon (props) {
  const { expanded } = props
  if (!props.children) {
    return <a-icon class="file" type="file-text" />
  }
  return <a-icon type={expanded ? 'folder-open' : 'folder'} theme="filled" style="color: #ffbf00;" />
},