fix: ensure bound input content is resumed on hydration

[trueadm]

Fixes #1755.

Before:

Screen.Recording.2024-06-10.at.13.06.17.mov

After:

Screen.Recording.2024-06-10.at.13.05.11.mov

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Latest commit: 3fd07ae

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[dummdidumm]

Does it make sense / is it possible to apply this logic to other inputs? bind:value for the select and bind:group come to mind.

[Rich-Harris]

Fixes #1755.

Finally! I think we probably do need to apply it to other form elements, yeah, if it doesn't already work. I also wonder if we need to fire change/input events in these cases. It might seem odd if bind:value works correctly when hydrating an input but oninput doesn't, especially if you need to refactor from one to the other to implement some validation or whatever.

[trueadm]

I added a test case that shows hydration working correctly :)

[dummdidumm]

Test adjustment looks great! Can you add a test for bind:group aswell? And did you look into whether or not it's feasible to handle <select bind:value />?

[trueadm]

And did you look into whether or not it's feasible to handle <select bind:value />?

Seems to work already. I didn't need to change anything.

[j]

@trueadm I'm seeing a few things.

<script>
  let checked = $state(false);
</script>

<input type="checkbox" bind:checked />

Will reset to initial value on a slow connection. As soon as all JS loads, it'll reset back to being unchecked.