你需要做一些其他的事情，因为你的前两个都是无效的HTML。你有几个选择，从最好到最坏：
方案一：

<ul>
  <li>
    <your-custom-element/>
  </li>
</ul>

备选方案二：
在自定义元素的shadow DOM中管理整个<ul>，或者将<ul>作为它的根。
选项3，您应该避免。

<div role="list">
  <your-custom-element role="list-item"/>
</div>

The best would be my option 1. It works because you can put anything you like inside `<li>`.

You should avoid my option 3 if you can, for several reasons:

- Avoid using ARIA unless it's really necessary
- No ARIA is better than bad ARIA
- It's not very clear if specifying the role on a custom element will work as expected, or if you have to report it yourself to the top element of your shadow DOM. It depends on what the browser / accessibility tree pass to assistive tools, and, as far as I know, it isn't very well defined, since custom elements are pretty new

这是3）

<div role="list">
    <my-li role="listitem"></my-li>
</div>

它不能是1）或2），因为两者都违反HTML规范。
3）HTML规范和所有需求都得到满足。