Effect wrapped in $effect.root cannot be used in teardown

[thes01]

Describe the bug

I thought $effect.root could be used as a "safe environment" for housing effects when you do the care with cleaning up.
However, if that happens to be in onDestroy, then any effect will throw a runtime error regardless it's wrapped in an effect root or not.

To illustrate the use case let's say I have the following function:

export async function get_when_ready(
	getter,  // getter to a reactive value
	predicate,
) {
	const { promise, resolve } = Promise.withResolvers();
	
	const cleanup = $effect.root(() => {
		$effect.pre(() => {
			const value = getter();
			if (predicate(value)) {
				resolve(value);
			}
		});
	});

	// clean the $effect.root after the promise has resolved/rejected
	promise.catch(() => {}).finally(cleanup);

	return promise;
}

Firstly, I don't know if the function is implemented correctly, if not, I'll be glad for any hints. I haven't seen it implemented elsewhere, but also I haven't looked thoroughly.

Given the above utility function and an API that calls it internally, I ran into a situation, where I called the API in the onDestroy of a component.

Reproduction

The REPL is here: https://svelte.dev/playground/d96d1b9b36264a6a83685b0e99552969?version=5.19.9

Note that it doesn't make much sense for the API (MyContext.delete_feature) to call the utility function there, but I hope it's sufficient to illustrate the problem.

I wonder if it's a false positive error or there's some underlying issue there.

System Info

System:
    OS: Windows 11 10.0.26100
    CPU: (16) x64 AMD Ryzen 7 PRO 6850U with Radeon Graphics
    Memory: 5.61 GB / 14.76 GB
  Binaries:
    Node: 22.9.0 - ~\AppData\Local\fnm_multishells\5844_1739017727831\node.EXE
    Yarn: 4.6.0 - ~\AppData\Local\fnm_multishells\5844_1739017727831\yarn.CMD
    npm: 10.9.0 - ~\AppData\Local\fnm_multishells\5844_1739017727831\npm.CMD
    bun: 1.2.1 - E:\designer\node_modules\.bin\bun.CMD
  Browsers:
    Edge: Chromium (131.0.2903.146)
    Internet Explorer: 11.0.26100.1882

Severity

annoyance

[Ocean-OS]

The error tells you why, you can't create a $effect in any way when an effect is being torn down (eg during a component destruction)

[thes01]

Ok, so in my understanding, there's currently no way to correctly implement the get_when_ready function using effects that would work even in the destroying context, right?

Would adding a new rune $effect.destroying be an option? I understand that probably the use case is too niche though..

EDIT: I just realized that I could just do with try-catching the effect since this awaiting stuff is probably only temporary and the API should be refactored not to use it.