Flexbox / Grid取决于子项百分比高度（Firefox / Edge）

Question

我一直在尝试从表格布局切换到更现代的布局。我的布局需要“固定”页眉和粘滞页脚。为了实现它，我决定通过稍微改变页面的工作方式，而不是让整个页面滚动，而是创建一个滚动div作为正文/页脚区域。这样一来，在模仿典型页面滚动方式的同时，标题就可以保持动态顶部。

但是，我在flexbox和grid中都遇到了相同的问题。只要没有基于百分比的子元素，我就可以使用该布局。如果有，似乎flexbox会根据孩子的大小进行调整。例如，如果将一个子级中的div高度设置为100％，它将显示div，但溢出后其他任何内容都会显示页脚。这对我来说似乎有点违反直觉，我希望有人可以解释其背后的设计选择？是否有任何变通办法允许这种功能？

我基本上认为flexbox系统可以填充剩余的空间（用于身体），但也可以根据需要扩展以包围所有孩子。

我写了一个快速样本来说明我在说什么。见下文，谢谢！

编辑：这似乎仅在Firefox和Edge中发生，而不在Chrome中发生。

html, body {
  height: 100%;
  width: 100%;
  margin: 0;
  padding: 0;
}

.container {
  display: inline-block;
  height: 100%;
  width: 50%;
  max-height: 100%;
  overflow: auto;
}

.bg {
  background-color: gray;
}

.span {
  width: 100%;
  height: 100%;
}

.flex {
  display: flex;
  flex-direction: column;
  min-height: 100%;
}

.flex > .main {
  flex: 1;
}

<div class="container">
  <div class="flex">
    <div class="main">
      <ul>
        <li>This is a spacer</li>
        <li>This is a spacer</li>
        <li>This is a spacer</li>
        <li>This is a spacer</li>
        <li>This is a spacer</li>
        <li>This is a spacer</li>
        <li>This is a spacer</li>
        <li>This is a spacer</li>
        <li>This is a spacer</li>
        <li>This is a spacer</li>
        <li>This is a spacer</li>
        <li>This is a spacer</li>
        <li>This is a spacer</li>
        <li>This is a spacer</li>
        <li>This is a spacer</li>
        <li>This is a spacer</li>
        <li>This is a spacer</li>
        <li>This is a spacer</li>
        <li>This is a spacer</li>
        <li>This is a spacer</li>
        <li>This is a spacer</li>
        <li>This is a spacer</li>
        <li>This is a spacer</li>
        <li>This is a spacer</li>
        <li>This is a spacer</li>
        <li>This is a spacer</li>
        <li>This is a spacer</li>
        <li>This is a spacer</li>
        <li>This is a spacer</li>
        <li>This is a spacer</li>
        <li>This is a spacer</li>
        <li>This is a spacer</li>
        <li>This is a spacer</li>
        <li>This is a spacer</li>
        <li>This is a spacer</li>
        <li>This is a spacer</li>
        <li>This is a spacer</li>
        <li>This is a spacer</li>
        <li>This is a spacer</li>
        <li>This is a spacer</li>
        <li>This is a spacer</li>
        <li>This is a spacer</li>
        <li>This is a spacer</li>
        <li>This is a spacer</li>
        <li>This is a spacer</li>
        <li>This is a spacer</li>
        <li>This is a spacer</li>
        <li>This is a spacer</li>
        <li>This is a spacer</li>
        <li>This is a spacer</li>
        <li>This is a spacer</li>
        <li>This is a spacer</li>
        <li>This is a spacer</li>
        <li>This is a spacer</li>
        <li>This is a spacer</li>
        <li>This is a spacer</li>
        <li>This is a spacer</li>
        <li>This is a spacer</li>
        <li>This is a spacer</li>
      </ul>
    </div>
    <footer>
      This should be a sticky footer
    </footer>
  </div>
</div><div class="container">
  <div class="flex">
    <div class="main">
      <div class="bg span">
        This breaks the page
      </div>
      <ul>
        <li>This is a spacer</li>
        <li>This is a spacer</li>
        <li>This is a spacer</li>
        <li>This is a spacer</li>
        <li>This is a spacer</li>
        <li>This is a spacer</li>
        <li>This is a spacer</li>
        <li>This is a spacer</li>
        <li>This is a spacer</li>
        <li>This is a spacer</li>
        <li>This is a spacer</li>
        <li>This is a spacer</li>
        <li>This is a spacer</li>
        <li>This is a spacer</li>
        <li>This is a spacer</li>
        <li>This is a spacer</li>
        <li>This is a spacer</li>
        <li>This is a spacer</li>
        <li>This is a spacer</li>
        <li>This is a spacer</li>
        <li>This is a spacer</li>
        <li>This is a spacer</li>
        <li>This is a spacer</li>
        <li>This is a spacer</li>
        <li>This is a spacer</li>
        <li>This is a spacer</li>
        <li>This is a spacer</li>
        <li>This is a spacer</li>
        <li>This is a spacer</li>
        <li>This is a spacer</li>
        <li>This is a spacer</li>
        <li>This is a spacer</li>
        <li>This is a spacer</li>
        <li>This is a spacer</li>
        <li>This is a spacer</li>
        <li>This is a spacer</li>
        <li>This is a spacer</li>
        <li>This is a spacer</li>
        <li>This is a spacer</li>
        <li>This is a spacer</li>
        <li>This is a spacer</li>
        <li>This is a spacer</li>
        <li>This is a spacer</li>
        <li>This is a spacer</li>
        <li>This is a spacer</li>
        <li>This is a spacer</li>
        <li>This is a spacer</li>
        <li>This is a spacer</li>
        <li>This is a spacer</li>
        <li>This is a spacer</li>
        <li>This is a spacer</li>
        <li>This is a spacer</li>
        <li>This is a spacer</li>
        <li>This is a spacer</li>
        <li>This is a spacer</li>
        <li>This is a spacer</li>
        <li>This is a spacer</li>
        <li>This is a spacer</li>
        <li>This is a spacer</li>
      </ul>
    </div>
    <footer>
      This should be a sticky footer
    </footer>
  </div>
</div>