Bug 271645 – Declarative shadow DOM does not work for XHTML

• Component: DOM
• Status: RESOLVED INVALID

[Jonathan Heathcote]

Browser: Epiphany 45.3 on Arch Linux.

The Declarative shadow DOM function does not work for XHTML documents (though it does for plain HTML ones).


# Steps to reproduce:

Paste the following XHTML snippet into the address bar:

data:application/xhtml+xml,<div xmlns="http://www.w3.org/1999/xhtml"><template shadowrootmode="open">OpenDeclarativeShadowDOMsupported</template></div>


# Actual results:

An empty page is shown (and the developer tool DOM tree shows the <template> element is not removed, the template contents aren't moved into the parent and no shadow DOM is created.


# Expected results:

I would have expected the same (working) behaviour we see for equivalent HTML documents (see snippet below):

data:text/html,<div><templateshadowrootmode="open">OpenDeclarativeShadowDOMsupported</template></div>

This shows "OpenDeclarativeShadowDOMsupported" when opened in a browser.


# Other browsers

The same bug also appears to effect:

* Firefox: https://bugzilla.mozilla.org/show_bug.cgi?id=1887436
* Chromium: https://issues.chromium.org/issues/330967152

[Radar WebKit Bug Importer]

<rdar://problem/125716107>

[Sam Sneddon [:gsnedders]]

As per the Chromium bug, this is intended behaviour: specific shadow DOM treatment requires changes to the parser, and the XML parser doesn't do this.

The discussion on the Chromium bug has ended up with https://github.com/whatwg/html/issues/10237 against the HTML spec, and it probably makes sense to keep the discussion there.