Table's figcaption/caption elements are not persisted when pasted into the editor

[codebymikey]

Description

When pasting raw HTML into the editor, the figcaption element isn't properly persisted.

This appears to be because the figure element isn't included when pasted in the first place, and this piece of code should have logic in place which attempts to move figcaptions into a figure element if one does exist.

Step-by-step reproduction instructions

1. Copy following HTML into a tool like https://www.onlinehtmleditor.net/
2. Copy and paste the formatted HTML into the Gutenberg editor
3. The figcaption element is moved outside of the original figure element.

The behaviour is also replicable by pasting the formatted HTML into https://wordpress.org/gutenberg/

Expected behaviour

The figcaption should be present as a child of the figure.

Actual behaviour

The figcaption is without a parent and subsequently converted into a p tag.

WordPress information

• WordPress version: "5.8.0"
• Gutenberg version: "9.4.0"
• Are all plugins except Gutenberg deactivated? "Yes"
• Are you using a default theme (e.g. Twenty Twenty-One)? "Yes"

Device information

• Device: "Desktop"
• Operating system: "Windows 10"
• Browser: "Chrome 86.0"

[dhruvkb]

Reproduced. Looks like the code responsible for this is

gutenberg/packages/blocks/src/api/raw-handling/figure-content-reducer.js

Line 24 in 5a06916

if ( tag === 'figcaption' || isTextContent( node ) ) {

Strangely enough, the markup generated for the table after adding the caption from the UI is identical to the one pasted into the editor.

[joedolson]

Just want to draw attention to #24205, and note that the table caption really shouldn't be using the figcaption element, as well.

[codebymikey]

This issue also affects normal caption elements too. e.g.

<table>
  <caption><h3>Monthly savings</h3></caption>
  <tr>
    <th>Month</th>
    <th>Savings</th>
  </tr>
  <tr>
    <td>January</td>
    <td>$100</td>
  </tr>
</table>

We need a way to transform table captions into equivalent figcaptions.