<summary> not handled correctly — incorrect DTD?

[Wim Leers]

Steps to reproduce

Originally reported at ​https://www.drupal.org/node/2656566.

1. Disable ACF.
2. Enter source mode and paste

   <details>
   	<summary>
   		<div>summary</div>
   	</summary>
   	<div>content</div>
   </details>
   

3. Exit source mode.
4. Enter source mode again.

Expected result

Markup is identical to the pasted markup.

Actual result

<details><summary></summary>

<div>summary</div>

<div>content</div>
</details>

Note how <summary> is empty.

Suspected cause: <summary> incorrectly defined in CKEditor's DTD?

Other details (browser, OS, CKEditor version, installed plugins)

Drupal 8 (8.0.3 or 8.1.x). Go to /node/add/article, choose the "Full HTML" text format (to disable ACF) and then apply the STR above.

[Jakub Ś]

According to spec: ​https://www.w3.org/TR/html-markup/summary.html#summary or ​https://html.spec.whatwg.org/multipage/forms.html#the-summary-element, the summary element may only contain Phrasing Content or Phrasing and Heading Conent.

Div is part of the Flow content so the editor behaviour is correct in this case. Disallowed content is removed from the tag.

[Wim Leers]

Oh, great!

Thank you, and apologies for the invalid bug report.