Checkboxes and radios that conditionally reveal content use aria-expanded which is not a valid aria-attribute for those roles

Originally raised by @injms on alphagov/govuk-design-system

The aXe accessiblity tool flags two issues when using the conditional reveal radio component. Running aXe on the example page shows the following issues:

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Elements must only use allowed ARIA attributes

<input class="govuk-radios__input" id="how-contacted-conditional-1" name="how-contacted" type="radio" value="email" aria-controls="conditional-how-contacted-conditional-1" aria-expanded="false">

To solve this violation, you need to:

Fix the following:

• ARIA attribute is not allowed: aria-expanded=“false”

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I think the expected behaviour would be to have no critical issues flagged by aXe - unless this is a false alarm or is found not to have any impact after testing in the empathy lab.

@36degrees:

(For context, this is something that’s come up before in alphagov/govuk_elements#455, but we don’t currently have it recorded on the Frontend repo)

edit: Split https://github.com/alphagov/govuk-frontend/issues/1591 into a separate issue

[NickColley]

The Design System team met and discussed these findings.

This pattern has been through a lot of user research by different service teams and we have not had any feedback to suggest that this is not working for real users of assistive technologies.

We will ask the community for more research with real users of assistive technologies to understand if there are any barriers.

We know that users of the screen reader JAWs and VoiceOver on Mac (Checkboxes only) are not helped by aria-expanded, so based on the feedback we get from the community we can try to understand if removing these attributes entirely will cause barriers.

This means we will:

• not remove these aria attributes, pending more feedback from user research
• document this as a known issue
• consider approaching the ARIA working group to suggest broadening the scope of aria-expanded.

[domoscargin]

Update: the ARIA proposal milestone has been moved to ARIA 1.4: https://github.com/w3c/aria/issues/1404#issuecomment-1151969396