RadioGroup isn't keyboard accessible when RadioGroup.Item is disabled and selected

[Kashkin]

Describe the bug

The entire RadioGroup is removed from the tab order. It should remain available, allowing keyboard users to select another option.

Using a mouse, it is possible to select a different option, restoring normal function.

Reproduction

https://stackblitz.com/edit/oohjsspd?file=src%2Froutes%2F%2Bpage.svelte

Logs

System Info

System:
    OS: Linux 5.0 undefined
    CPU: (8) x64 Intel(R) Core(TM) i9-9880H CPU @ 2.30GHz
    Memory: 0 Bytes / 0 Bytes
    Shell: 1.0 - /bin/jsh
  Binaries:
    Node: 20.19.1 - /usr/local/bin/node
    Yarn: 1.22.19 - /usr/local/bin/yarn
    npm: 10.8.2 - /usr/local/bin/npm
    pnpm: 8.15.6 - /usr/local/bin/pnpm
  npmPackages:
    @sveltejs/kit: ^2.16.0 => 2.21.4 
    bits-ui: 2.6.0 => 2.6.0 
    svelte: ^5.0.0 => 5.34.1

Severity

annoyance

[huntabyte]

Why would a disabled item ever be selected? I guess my question is how does it even get into that state?

[Kashkin]

It's a reasonable question! I can see a use-case in a form with interdependent fields, where a new selection makes an existing selection invalid. That said, I only discovered this while testing styling in Storybook, which is why I left it tagged as "annoyance".

Also, after some more research, this seems to be an unresolved problem for native radio groups in most browsers?

[huntabyte]

Yeah the issue stems from the fact that a disabled item is selected. Since we use the roving tabindex/focus pattern here, the selected item gets tabindex="0" to be focusable - but if that item is disabled, it becomes unfocusable, and the whole group drops out of the tab order.

This is technically valid HTML, but it's an anti-pattern. A selected item should never be disabled - if an option becomes unavailable, it should first be deselected or replaced with a new valid selection.

We’ll consider adding a dev-time warning to catch this specific scenario, but at the library level it feels wrong to do anything further, as the options would be to forcefully deselect which could also be undesired in certain circumstances.

However, this does bring up something we probably should do, which is provide an option to make the radio group readonly, which would allow focusing but not changing. I'll look into that.