Svelte 5: spreading attributes on a input changes event handlers behaviour

[hawk93]

Describe the bug

Hi, I made a simple component to wrap a checkbox and his style. I realized that if you use rest props while destructing $props rune, the onchange event is triggered with the wrong value.

When calling onchange checked value is wrong

<script>
	let { checked = $bindable(), children, onchange, ...rest } = $props();
</script>

<p>
	<label><input type="checkbox" {onchange} {...rest} bind:checked /> {@render children()}</label>
</p>

When calling onchange checked value is right

<script>
	let { checked = $bindable(), children, onchange, disabled } = $props();
</script>

<p>
	<label><input type="checkbox" {onchange} {disabled} bind:checked /> {@render children()}</label>
</p>

Reproduction

https://svelte-5-preview.vercel.app/#H4sIAAAAAAAACrWSTUvEMBCG_8oQFraF2t7XNCgeRIRdUMGD9ZA2s7vBNAlJVpTS_y5xu-t-KR70kENmMu888046MpcKPZk8dUTzFsmEXFpLMhLebbz4V1QBSUa8WbkmRqhvnLSBVboKsrXGBbhaYvNSm7c79AHmzrQwzovdYL6WGZ-omZqTVevwbl08CgNwKGHkAw-YzLnymJ5_5erjnKbFF7Cmll2Z1hqNOkBY8gArjx7yPHeRYmSdsT5J4Qymswd4nN3d3kyvaWFZpenelEY3S64XWHZJCiWDxmhvFObKLBKe9lBLLSZNrEBRdrxnnO458g2NMOj1-JPqFFQEuj_AGQz8Cag-Aqp7VtMDs1mlSUZaI-RcoiCT4FbYZ9tvsUv_2_8Rd9LB0DXuJlLwWmGSZtAspRIOdbZlz7Yz9_HxMPeJHUZtqniNilGp7SpAxCkr0gyQFYFuo9pDN8juuwAFg-7CoRbotjBJ2tNirRzb2l-asnbw32wR0se0-GtfNrp_Zcxz_wEjEgCuUAQAAA==

Logs

No response

System Info

Repl

Severity

blocking all usage of svelte

[hawk93]

I made a slightly different reproduction of the problem repl because I found that the problem is not about destructuring $props with a rest variable, but spreading attributes on the input.
Whenever you do it the event handlers attached to it are fired in a different moment, giving different results

[dummdidumm]

The behavior for this is non-deterministic, because it depends on which events fire in what order. Generally bindings need to happen after attributes have updated, and the spread puts the change event into the same bucket as the spread into one render effect.
I'm tempted to mark this as "won't fix" and instead add a note in the documentation about this.

[hawk93]

If you just add it to the documentation a simple input wrapper like this becomes a lot more verbose