[css-pseudo-4] Should parent and element attributes of CSSPseudoElement interface be nullable?

[danielsakhapov]

https://drafts.csswg.org/css-pseudo-4/#CSSPseudoElement-interface has

readonly attribute Element element;
readonly attribute (Element or CSSPseudoElement) parent;

but, given the outcome of #3607, and e.g.

fc = div.firstChild;
div.removeChild(fc);
fc.parentElement; <-- is null.

I would expect the following to return null:

.beforePseudo::before { content: "before"; }

before = target.pseudo("::before");
div.classList.remove("beforePseudo");
before.parent; <-- should be null, since the pseudo is now ~"detached from DOM"?

So, I guess that parent and element attributes of CSSPseudoElement interface should be nullable?

@emilio @fantasai ?

[emilio]

Maybe? I think ::before / ::after's relationship with the DOM is not super well defined. Implementation wise we do remove them, but I think per spec they're supposed to be always present?

[danielsakhapov]

Would you expect it to behave the same as for the first child example?

[emilio]

Not sure, I think we need to define whether changing / removing the content property removes the pseudo element or not. Same for display. Also same for elements that don't generate these like input elements. What does the spec say for those?

[emilio]

The problem with your class list example is that it'd require .parent to synchronously run styling right? Which is a bit surprising at least, and a perf footgun

[danielsakhapov]

Right, sorry, I forgot to mention that I didn't include synchronisation lines (like offsetTop) between actions, just to show the need for nullability.