Alternative to #16190, with the distinction that using declarations at the top level of a component are only disposed when the component unmounts.

I think I prefer this — it's more useful and more intuitive. Demo here.

On the server it doesn't transform anything, meaning resources are correctly disposed of once rendering is complete. Obviously all this is of limited use until support is sufficiently widespread, but I don't see any reason to hold it back until then. (The demo above actually works in all browsers, because top-level using gets compiled away for client code, but that doesn't apply to server code or non-top-level using.)

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Latest commit: 8f5a073

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Preview: https://svelte-dev-git-preview-svelte-16192-svelte.vercel.app/

Playground

pnpm add https://pkg.pr.new/svelte@16192

Fun idea from bsky — using x = $derived(...). Like regular using this would also be disposed on component unmount, but would additionally be disposed when the derived updated. Not quite sure what would happen outside the top level of a component though... maybe it would be forbidden to use it with unowned deriveds

Fun idea from bsky — using x = $derived(...). Like regular using this would also be disposed on component unmount, but would additionally be disposed when the derived updated. Not quite sure what would happen outside the top level of a component though... maybe it would be forbidden to use it with unowned deriveds

So that would be like a 1 time $derived value?