Unsupported element causes JS error instead of being filtered out

[jswiderski]

📝 Provide detailed reproduction steps (if any)

1. First you need to open ZD support ticket no. 64940 where you will find SampleEmail_SendToCKEditor.html and unnamed_attachment_1.eml.
2. Please download these files and open .eml in email client and the .htm in MS Word as well as browser e.g. new Edge.
3. Copy the contents (Ctrl+A/Ctrl+C) and paste them into CKEditor

✔️ Expected result

Content gets pasted

❌ Actual result

Content doesn't get pasted and JS error is being thrown.

emittermixin.js:242 Uncaught TypeError: Cannot read property 'childCount' of null
at UpcastDispatcher.dispatcher.on.priority (upcasttable.js:103)
at UpcastDispatcher.fire (emittermixin.js:209)
at UpcastDispatcher._convertItem (upcastdispatcher.js:249)
at UpcastDispatcher._convertChildren (upcastdispatcher.js:282)
at UpcastDispatcher.<anonymous> (upcasthelpers.js:454)
at UpcastDispatcher.fire (emittermixin.js:209)
at UpcastDispatcher._convertItem (upcastdispatcher.js:249)
at UpcastDispatcher._convertChildren (upcastdispatcher.js:282)
at UpcastDispatcher.<anonymous> (upcasthelpers.js:454)
at UpcastDispatcher.fire (emittermixin.js:209)

The problem is that template contains div elements which wrap the table and are inside the table element. Instead of being filtered out they cause JS error (once you add div plugin the error is gone).

📃 Other details

• Browser: Any
• OS: Any
• CKEditor version: 22.0.0
• Installed CKEditor plugins: All Features

---

If you'd like to see this fixed sooner, add a 👍 reaction to this post.

[jswiderski]

In order to work around this problem one needs to implement div plugin e.g. https://ckeditor.com/docs/ckeditor5/latest/framework/guides/deep-dive/conversion/conversion-preserving-custom-content.html#loading-content-with-all-attributes.

Once plugins supporting divs is added to the build template no longer produces errors.

[Reinmar]

It'd be good to first bisect this as it may give us some pointers.

[pomek]

It's a regression. Bisect: aa6f0ba.

[pomek]

Minimal HTML snippet that triggers the error:

<table>
   <tbody>
      <tr>
         <td>
            <div align="center">
               <table>
                  <tbody>
                     <tr>
                        <td style="border: 2px solid rgb(242, 242, 242);">
                           <p>Test</p>
                        </td>
                     </tr>
                  </tbody>
               </table>
            </div>
         </td>
      </tr>
   </tbody>
</table>

After removing the div element or the td[style] attribute, everything works.