$derived() with Promise

[5P5]

I fully expected this ⬇️ to work after reading Basic Svelte / Logic / Await blocks:
update Y from a promis function's resolve when X changes.
e.g.

x=$state()
y=$derived(<Promise>func(x))

I tired various version, see repl
none work 😢

What am I doing wrong?

N.B.: await block is not an option, as the described functionality is in a shared context object.
Also async/await is not what I want, as I expect the promises to run concurrently.

[brunnerh]

[5P5]

😕
the a in const prom=(a)=>{} is just a random function parameter, not a dependency to be tracked.
in the $derived(prom(…)), the prom() function should re-run whenever its argument changes.
So the arguments is the dependency I want tracked, see #14606 (comment)

this obviously works, but is not my issue at all.

[brunnerh]

Your question is not particularly clear. You show a $derived holding a promise but your comment suggest that you don't want a promise at all but just the results of an async operation.

If that is the case you need a $state updated via an $effect. You could set that up in the constructor of the class if you need it to be contained. If the $effect should be independent from any component lifetime, you will need to create an $effect.root around it.

[5P5]

tyvm. that is what I tried to achieve.
I made a working example for anyone trying the same 😃