[Full-stack Signals] Cannot update a signal that you're not subscribed to

[Legioth]

Describe the bug

Trying to manipulate a signal for which you don't have an open subscription will lead to an exception like java.lang.IllegalStateException: Signal not found for client signal: MXbPB5IqFiJzkzI1v7W0m.

Aside from offline cases that are described in https://github.com/vaadin/hilla/issues/2653, this does also happen if you want to e.g. increment a counter already before it has been shown. This might be the case if you want to count how many times a view has been opened or if you build a poll where you only see the results after you have submitted your own choice.

Expected-behavior

Expected that signal operations can be submitted even without an active subscription as long as the access control check passes for the server-side service method. This means that the service method would have to be invoked again for each operation when there's no subscription but that should be fine since we are anyways expecting such methods to be deterministic.

Reproduction

const counter = StatsService.counter();

export default function Counter() {
    const subscribe = useSignal(false);

    return <VerticalLayout>
        <Button onClick={() => counter.increment()}>Increment</Button>
        <Checkbox checked={subscribe.value} onCheckedChanged={(event) => subscribe.value = event.detail.value} label="Subscribed" />
        {subscribe.value ? <>Live value: {counter}</> : <>Peeked value: {counter.peek()} </>}
    </VerticalLayout>
}

System Info

Hilla 24.5.0.alpha13

[platosha]

Note: we could solve this by creating a temporary subscription for processing any preliminary operations. However, we would also need to close such subscriptions immediately to avoid memory leaks.

[platosha]

Let's get back to this after having thenable operations, see #2712