<seletedcontent> behavior in disconnected <select>

[annevk]

What is the issue with the HTML Standard?

The last subtest of https://wpt.fyi/results/html/semantics/forms/the-select-element/customizable-select/selectedcontent.html expects that <select>'s value setter does not update the <selectedcontent> element when they are both disconnected, but I don't see anything in the specification that enforces that?

It's not clear that simply adding an "is connected" check here is sufficient as there are other code paths that lead to manipulation.

[josepharhar]

Thanks for spotting this, I am fixing the test here: https://chromium-review.googlesource.com/c/chromium/src/+/7127725

The test has two checks for the selectedcontent element being updated in a disconnected subtree which seem to have different behavior because the selectedcontent element only gets updated on insertion if it gets connected to the document since it is using the post-insertion steps instead of the insertion steps.

To elaborate:

const select = document.createElement('select');
select.innerHTML =
`<option>one</option>
<option>two</option>`;

const selectedcontent = document.createElement('selectedcontent');
select.appendChild(selectedcontent);
// selectedcontent does NOT get updated here because the element is not
// connected to the document so the post-connection steps do not run.

select.value = 'two';
// selectedcontent does get updated here because the select.value setter steps
// update the selectedcontent regardless of whether it is connected or not.