Implement :has-slotted

[Westbrook]

Description

<slot> elements can have content ::slotted(*) into them, but historically a developer could not know whether there were elements or text nodes addressed to those slots. The :has-slotted pseudo-class makes the presence of slotted content testable in the CSS context, which will end the need for a widely duplicated set of JS features.

Currently this feature is in Chrome Canary behind a flag and there was wide interest in bringing this to the web platform at various TPAC sessions in September.

Specification

https://drafts.csswg.org/css-scoping/?utm_source=recordnotfound.com#the-has-slotted-pseudo

Additional Signals

WPTs
Chrome bug