New ChildrenBuilder breaking React.Children.only

It seems like Children.only does not work anymore with ChildrenBuilder. Indeed, instead of an opaque structure, PropsWithChildren now has an Array for children, which cause Children.only to always fail.

This failure can be understood through the reading of its implementation which depends on isValidElement.

As a workaround I now use:

const val ReactOnlyChildError = "React.Children.only expected to receive a single React element child"

fun onlyChild(children: ReadonlyArray<ReactNode>?): ReactElement {
    if ((children?.size ?: 0) > 1) error("$ReactOnlyChildError (more than one were provided).")
    return children?.getOrNull(0)?.asElementOrNull() ?: error("$ReactOnlyChildError (none were provided).")
}

However, maybe Children.only should be removed and replaced by a working usage (such as the one above). I also wonder if there are other cases where the new ChildrenBuilder breaks functions provided by React.

[turansky]

Since pre.283 children is ReactNode

[turansky]

It depends on your component - no silver bullet.