Allow binding to <details> open attribute

[LostKobrakai]

<details bind:open={variable} is not supported right now. It would be nice if it would be.

Toggling can be observed using an event listener for the toggle event:
https://developer.mozilla.org/en-US/docs/Web/HTML/Element/details#Events

[Rich-Harris]

Released in 3.4.3! https://svelte.dev/repl/386984e76c904955b085c3f282c03473?version=3.4.3

[JohnRSim]

Styling doesn't appear to work for the

tag when opened.
When the browser adds the open attribute on click of summary - the css is not generated for details[open] {} only for details {}

details[open] {
   background:red;
}
details {
   background:blue;
}

[LostKobrakai]

Seems like svelte doesn't know that details tags might get a open attribute (it's not reactively added), which requires :global(…) to be used.

[JohnRSim]

thanks that did the trick :)

[Conduitry]

I think it would make sense for the compiler to be able to see that bind:open might result in an open attribute being present, so it can scope the styles appropriately.

[Conduitry]

Opened #3281.