[css-shadow-parts][css-pseudo] ::part* and *::before* and *::after* pseudo elements

[frivoal]

(Split from issue #3467, reported by @stefsullrew)

It appears the ::before and ::after pseudo elements/selectors do not function with ::part. Is this intentionally blocked, if so why? If not are there plans to add this functionality in the future?

// add an asterisk prefix to the title part
x-foo::part(title)::before {
    content: '*';
    color: red;
    margin-right: 0.25rem;
}

[lilles]

That sounds like a bug. Also, iterating more on that you should probably be able to say:

::slotted(component)::part(title)::before

but not (only possible if a slot element is exposed as a part):

part(title)::slotted(div)::before

[lilles]

For reference, the spec says ::before/::after is allowed after ::part: https://drafts.csswg.org/css-shadow-parts/#part

[fergald]

This was a chrome implementation issue that has now been fixed (along with ::placeholder). Web Platform tests have also been added for all 3.

[frivoal]

(marking as invalid + commenter satisfied as that this was not a spec bug, and that the implementation bug was resolved the way the commenter asked.)