Input of type `file` does not update when you set the bound `files` prop to `undefined`

[kran6a]

Describe the bug

I would expect that for some markup like this

<input type="file" bind:files={files} />

Setting the files variable to undefined would update the input element state to have no selected files just as it is when the files variable has an initial value of undefined.

Reproduction

https://svelte.dev/playground/hello-world?version=5.38.1#H4sIAAAAAAAACm2PMWvDQAyF_4oQGWwwSbq6cSDQoUvp0q3X4eyTmwNFZ3xy0mD838vZTUqhaBB8enp6GlHsibDEZ2IOcAk9O8jIeSWXY4GtZ4pYvo-o1y7pEsDitnXounU8E2titY30H2-CKIlGLHEXm953ujdilElhtocKVlGtUpY_psGK2pYazbK82o8JGPUtZLM2_wFGI-mbP1EY_ghTNUFiYFpz-MzM8gGcbe9tzQQ-goQLDOKo9UIO6kFBjwRPry9ATCcShaieGY72TEtCg0uypW6h7x732VTAw3a7vYmn1KbcyG7z-7fsvHTp5rWjaolnEGovrpyNq3FuE2z2RrBApS_FUvuBpo8C1Xq-eHFYtpYjTd_hmLCmwAEAAA==

Logs

System Info

Does not matter

Severity

annoyance

[Prinzhorn]

https://svelte.dev/docs/svelte/bind#input-bind:files

<script>
	let files = $state();

	function clear() {
		files = new DataTransfer().files; // null or undefined does not work
	}
</script>

<label for="avatar">Upload a picture:</label>
<input accept="image/png, image/jpeg" bind:files id="avatar" name="avatar" type="file" />
<button onclick={clear}>clear</button>

#13156

[kran6a]

Closing. I still believe that undefined as it works with other input types (text, number) despite the "real" input value being "" when the variable is undefined. Another option would be throwing an error when receiving undefined in bind:files so you know it won't work and it is not a bug.