Consider allowing aria-setsize at the container level

[scottaohara]

Working with a product team today, they were getting an automated flag for their misuse of aria-setsize. they used it directly on a role=listbox element, rather than every option within their listbox.

testing with chrome/edge - setting the aria-setsize once on the element with role=listbox will update the max count for all options within a listbox.

testing with firefox and safari (desktop), the aria-setsize is ignored if not set to the option element itself.

it seems like it'd be far easier from a development perspective to define this attribute once, and update just that (if necessary) than to have to declare it for each element within a set.

i can understand that this might not be 100% sufficient for instances of where there may be groups of items, and those might need to have their own setsize/posinset. but, arguably guidance could be written around when to declare at the parent level vs needing to declare on every item.

[spectranaut]

Discussed during triage: https://www.w3.org/2025/05/08-aria-minutes.html#e3dd

[MarioBatusic]

From the beginning, I wondered why a container property actually needs to be recorded on all members. In our Fabasoft Cloud, users sometimes fill the object list box with thousands of entries, and the list would load faster the less data is recorded per entry.

Besides, it would be much more logical to record a container property directly on the container.