Chromium/VoiceOver: Chromium misreports radio button numbering on conditional reveals

[querkmachine]

Upstream bug: https://bugs.chromium.org/p/chromium/issues/detail?id=1428008
Date: 2023-03-27
Reported by: @querkmachine
Related to: alphagov/govuk-frontend#2346

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Overview

Radio buttons, when announced by VoiceOver, include information about the number of radio buttons in the group and the current radio button's position in the group. For example, it may announce "Email address, radio button, 1 of 3."

When the radio button group includes conditional fields (form fields that are only displayed when the related radio button has been checked), and one of these fields is visible, Chromium browsers start to misreport the number of radio buttons in the group and the placement of the checked radio button.

Expected result

VoiceOver announces "Email address, selected, radio button, 1 of 3." when the first radio button in a group of 3 is checked.

This works as expected in Firefox and Safari.

Actual result

VoiceOver announces "Email address, selected, radio button, 2 of 4." when the first radio button in a group of 3 is checked.

This happens in all Chromium-based browsers tested: Chrome, Edge and Opera.

Related Design System example: https://design-system.service.gov.uk/components/radios/conditional-reveal/index.html
Reduced test case: https://jsfiddle.net/querkmachine/2ecsyd9v/