Debugging utilities / ways to hook into core lifecycle

[csenio]

There are a ton of attempts at creating tooling for rxjs, but they all have to hack into rxjs in some way, usually by overriding class prototypes.
From what I can see, the most common desires are

1. To label observable instances -> achievable by adding some an id or similar prop to Observable, Subscriber and Subject
2. To trace the dependencies of observables -> achievable by tracing Observable, Subscriber and Subject constructors and .subscribe calls
3. To trace observable emissions -> achievable by tracing Subscriber and Subject .next calls

I made a super simple demo here: https://stackblitz.com/edit/typescript-qm8iww?file=index.ts,observable.ts

Is there any interest from the rxjs team to support something like this? I think the library could greatly benefit from better tooling, and this would open the door for that. We also already have onStoppedNotification and onUnhandledError which we could extend for this.

[csenio]

@voliva Esp. curious on your take here. I saw that rxjs-traces relied on custom call stacks instead of the Observable / Subscriber relationship, is this because Subscriber didn't exist yet or is there a limitation to that approach?