Svelte 5: A snippet default value is inconsistent

[fcrozatier]

Describe the bug

When providing a default value in a snippet with a function call the value is not consistent (it's recomputed), breaking expectations.

Reproduction

The default value id=randId() is not consistent, resulting in broken labels (only the second one set manually works)

https://svelte-5-preview.vercel.app/#H4sIAAAAAAAAE22PQU_EIBSE_8rzeWmT1sbrSpv16MHEu3jA8rolS4EAXdcl_e-GbaPReGT4Zt5MwkFpCrh7TWjERLjDR-ewwvjp8iOcSEfCCoOdfZ8VFnqvXOy44bG3JkTwwsgnCS0UZds9izjeZcVORfnADWt-eJNug1HOUQQVaSpOQs9UgcreNaQoyyUHs5u6Tvs1_tf3AnFUAT6sPwao62sLpoybI-TGLcd-pP74bs8cISm5QLpeWSCvazkevJ0dR2hWqxbvpGGwvs1wt8GsueodN6nZGudahg2KtAwUNzMdyMjuRV0uAqyLyprAmk3NRNp7MpL8OpcjnaMX0I9EgTiuU_8ya44RGqJ1TpkDxwru_2eD0EKuQaz57oYVTlaqQZHEXfQzLW_LF6lPfzzoAQAA

Logs

No response

System Info

preview

Severity

annoyance

[7nik]

A bit more demonstrative version.

[brunnerh]

Or just:

{#snippet item(id = Math.random())}
	<div>{id} {id} {id}</div>
{/snippet}

{@render item()}
{@render item(1)}
{@render item()}

REPL

(Btw, for random IDs I would use crypto.randomUUID().)

[dummdidumm]

Problem also applies to each blocks example