next: Select breaks when using transition on content

[jjones315]

Describe the bug

When using a transition on the select content, the select is no longer part of the form after a selection is made.

Reproduction. (you made need to npm install --force)
The page has 3 selects,
The first has no transition, select a value and hit submit, the form values will display and log to the console.
The second has a transition with the {#snippet child({...})} Pattern, select a value and it will be removed from the form values.
The third has a global transition, select a value and it will be removed from the form values.

Reproduction

https://stackblitz.com/edit/github-shpwk7-zlxesb?file=src%2Froutes%2F%2Bpage.svelte

Logs

No response

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: 18.20.3 - /usr/local/bin/node
    Yarn: 1.22.19 - /usr/local/bin/yarn
    npm: 10.2.3 - /usr/local/bin/npm
    pnpm: 8.15.6 - /usr/local/bin/pnpm
  npmPackages:
    @sveltejs/kit: ^2.0.0 => 2.6.3 
    bits-ui: ^1.0.0-next.15 => 1.0.0-next.15 
    svelte: ^5.0.0-next.262 => 5.0.0-next.262

Severity

blocking an upgrade

[huntabyte]

Hmm, I actually don't think this one is fully fixable with the Select using the child snippet and a conditional. You'll miss functionality like the typeahead portal link and such. I'm considering dropping the Select in favor of just having the Listbox; I just need to figure out how to handle the typeahead stuff for that.

It requires a child/children to register the values for each<Select.Items> when they mount. I could probably hack it together but until that open conditional is true, anything within the content isn't mounted and therefore doesn't register.

[jjones315]

That would work for most cases, I have a few where items are visually grouped, so it’s nice to be able to provide a top level content child, could the components just accept a items/options prop with an array of label/value to be used?

[huntabyte]

Yep! That's exactly what I'm implementing now 😃