Broken aria-describedby in radios and checkboxes

Following on from @codebymikey's point #29 I've also identified this happens to the 'container' element too, (albeit with the caveat that the container element does not support the #description attribute):

$form['element'] = [
      '#type' => 'container',
      '#description' => 'A description added to the container.'
];

This will result in a container wrapper being rendered with an incorrect 'aria-describedby' attribute.

Following on from @andrewmacpherson's comment #22, I agree there needs to be a more extensible way to declare a form element as a composite form element. But there are also needs to be some consideration for other render elements which get the 'aria-describedby' attribute added.

Liam Morland → made their first commit to this issue’s fork.

I have made a merge request with patch 17 rebased onto 11.x.

Added stack trace

I agree with #25, that we should use something more extensible. However, I don't think either of the suggestions is enough information for making it work. The issue is in the FormBuilder class, and at that point, you don't have instances of ElementInterface, you have a render array. So you can't do an instanceof test.

It might be easier to add an attribute #is_composite to the render array?

Or if I'm wrong, then I would say it's probably better to have CompositeFormElementInterface, because there is also a CompositeFormElementTrait. So you could even put isComposite in the trait, and it would be added to any contrib/custom classes using the trait as well.