[css-pseudo-4][css-scoping] Can ::slotted() be followed with element-backed pseudo-elements?

[nt1m]

E.g. is ::slotted(*)::details-content allowed?

https://drafts.csswg.org/css-scoping/#slotted-pseudo only allows tree-abiding pseudo-elements behind ::slotted(), so ::slotted(*)::details-content would actually not work (the definition of element-backed pseudo-elements does not inherit from tree-abiding pseudo-elements).

cc @dbaron @fantasai @tabatkins

[nt1m]

Also ::file-selector-button was changed from tree-abiding to element-backed (without any resolution AFAIK), so ::slotted(*)::file-selector-button also "regressed" spec-wise as a result.

[dbaron]

I think there was previously prose in the spec that said all element-backed pseudo-elements were also tree-abiding. Either it was supposed to be there and was never actually written, or it somehow got removed in an editing error...

[dbaron]

The relevant wording was removed in 24eda7a (search for "subset"); I think that was an editing error.

[nt1m]

Thanks!

I submitted a few WPT PRs for this in case you want to review them:

• Add tests for ::slotted(*)::details-content web-platform-tests/wpt#49408
• Add tests for ::slotted(*)::file-selector-button web-platform-tests/wpt#49407