Content loss when copying or pasting lists with an empty first list item

[James Toohey]

Created attachment 436596 [details]
A simple HTML file to replicate the bug

Hi team,

We discovered some cases where copying or pasting content in Safari 14 would cause content loss.

Context: Google Docs uses a `b` element to wrap their content with the document id when copying content e.g. `<b id="docs-internal-guid-[uuid goes here]">`. When creating a Google Doc with an empty line or empty list item as the first element, Safari converts this element into a style and strips other elements.

I have attached a very simple HTML reproduction case with the following example:

Input (clipboard content):
<b data-important-attr="xyz">
  <ul>
    <li></li>
    <li>text</li>
  </ul>
</b>

Output (result from paste):
<br>
<div>
  <span style="font-weight: bold;">text</span>
</div>

Adding any content into the first list item results in the expected output:

Input (clipboard content):
<b data-important-attr="xyz">
  <ul>
    <li>text</li>
    <li>text</li>
  </ul>
</b>

Output (result from paste):
<b data-important-attr="xyz">
  <ul>
    <li>text</li>
    <li>text</li>
  </ul>
</b>

It is also worth noting that this occurs even without the wrapping `b` element:

Input (clipboard content):
<ul>
  <li></li>
  <li>text</li>
</ul>

Output (result from paste):
<br>
<div>text</div>

[Radar WebKit Bug Importer]

<rdar://problem/82701564>