NG0602 when using RxDB reactivity factory

Question

My use case: Use a reactive rxDB.collection.find().$$() inside a computed angular signal. I am quite sure I am misreading the current documentation :/

Reading the current RxDB documentation I can see that I can make RxDB provide Angular Signals via the reactivityFactory (awesome!!!). If I follow the documentation I end up with an NG0602 error since we cannot create signals within a reactive context. See: https://stackblitz.com/edit/rxdb-15-angular-17-playground-azqzjo?file=src%2Fapp%2Fapp.component.ts

The issue comes from the fact, that

protected cars = computed(() => {
    if (this.isLoading()) return [];
    return this.db.cars.find().$$();
  });

internally calls the reactivityFactory.

If I work around this issue e.g. by using the toLazySignal util from ngxtension it creates a signal everytime a collection change happens, see https://stackblitz.com/edit/rxdb-15-angular-17-playground-1ky4q9?file=src%2Fapp%2Fapp.component.ts (open the browser console)

How should I implement the reactivityFactory corretly so that my use case works?

Answer 1

Solved! The issue was a total different one. The observable actually returned an error, which was swallowed by toSignal.

The error:

Error (QU13): RxError (QU13):
A top level field of the query is not included in the schema
Given parameters: {
schema:{
  "additionalProperties": false,
  "encrypted": [],
  "indexes": [
...

That was the reason why the signal got create again immediately which created an endless loop that ended in a browser crash. Adding rejectErrors: true to the toSignal options helped a lot.

So the reactivity factory should be something like this:

export function createReactivityFactory(injector: Injector): RxReactivityFactory<Signal<any>> {
  return {
    fromObservable(observable$, initialValue: any) {
      return untracked(() =>
        toSignal(observable$, {
          initialValue,
          injector,
          rejectErrors: true
        })
      );
    }
  };
}

Edit: The updated documentation: https://rxdb.info/reactivity.html#adding-a-custom-reactivity-factory-in-angular-projects