Rxjs toPromise() deprecated

Why is this happening?

As mentioned here, these are the main reasons why toPromise is being deprecated:

1. One goal was to remove it from the Observable prototype and turn it into a standalone util function.

2. The naming of toPromise is not the best. Especially when used in combination with await it does not read very well: await categories$.toPromise() vs await lastValueFrom(categories$)

3. The type information of toPromise is wrong. When the source Observable completed without ever emitting a single value – it
   resolved with undefined. It should reject in that case. A Promise is a
   “promise” that when it resolves a value will be there – and be it
   undefined. But when the stream completes without ever emitting a value
   you can’t differentiate between a stream that a emitted undefined on
   purpose and a stream that completed without ever emitting anymore

What should you use next?

If you really insist doing it the promise way, lastValueFrom/firstValueFrom. Otherwise switching to reactive programming would be the way to go.

Using toPromise ( deprecated ) –

public async loadCategories() {
    this.categories = await this.inventoryService
      .getCategories()
      .toPromise()
}

Using lastValueFrom ( new ) –

import { lastValueFrom } from 'rxjs';

public async loadCategories() {
    const categories$ = this.inventoryService.getCategories();
    this.categories = await lastValueFrom(categories$);
} 

This link should help –

https://indepth.dev/posts/1287/rxjs-heads-up-topromise-is-being-deprecated