After knowing that a list-item element cannot be display: flex at the same time, I wrap my contents with a container, then put the container inside the <li />.
Things go right for elements with content.
However, if the first element in the container has no child nodes, the marker of the <li /> is unexpectedly located at the bottom.
Though in my case I can simply add a display: none to workaround, I'm still confused:
How can …