Inconsistency between spec and APG for aria-controls required on combobox

[carmacleod]

The ARIA spec says aria-controls is required on combobox.

The APG Roles, States and Properties section of the combobox pattern says:

The combobox element has aria-controls set to a value that refers to the element that serves as the popup. Note that aria-controls only needs to be set when the popup is visible. However, it is valid to reference an element that is not visible.

The 2nd sentence is problematic. It seems to be implying that aria-controls is not always required, i.e. authors can leave it off when the popup is not visible.

This may lead to confusion, with authors thinking, "Well, is it required or not?".
It also complicates processing for validator tools, making it less likely that tooling will catch incorrectly marked up comboboxes.

Consider rewriting the above point in the APG to say:

The combobox element has aria-controls set to a value that refers to the element that serves as the popup. Note that it is valid for aria-controls to reference an element that is not visible.

[JAWS-test]

In my opinion, the requirement that aria-controls must be present in combobox, even if there is no content to which aria-controls refers, is absurd. This forces the developers to insert e.g. an empty, invisible listbox into the source code even when a combobox is closed. However, empty listboxes are not allowed according to the ARIA specification (Required Owned Elements).
That's why I'm more in favor of aria-controls only being mandatory when the combobox is open. When closed, aria-controls can point to an invisible listbox (grid, dialog, tree), but it does not have to be

[JAWS-test]

See w3c/aria#1334, so this issue can be closed

[carmacleod]

Agreed that the fix for w3c/aria#1334 (in PR w3c/aria#1335) is a better fix.
Closing.