tc39 proposal compatible fromObservable for better ecosystem interop.

[jessekelly881]

What is the problem this feature would solve?

It would be nice to add a Stream.fromObservable fn to better interop. w/ rxjs and other libs which use Observables.

https://github.com/tc39/proposal-observable

What is the feature you are proposing to solve the problem?

import { range, Observable } from "rxjs";
import { Effect, Stream } from "effect";

/**
 * Creates a `Stream` from an `Observable` instance.
 * @since 3.2.0
 * @see https://tc39.es/proposal-observable/
 */
export const fromObservable = <T>(observable: Observable<T>) =>
	Stream.async((emit) => {
		const subscription = observable.subscribe((value) =>
			emit.single(value)
		);
		return Effect.sync(() => subscription.unsubscribe());
	});

fromObservable(range(0, 10)).pipe(
	Stream.runForEach((s) => Effect.log(s)),
	Effect.runPromise
);

Observable type could be simplified to a compatible ObservableLike.

interface ObservableLike<T> {
	subscribe: (_: (_: T) => any) => { unsubscribe: () => void };
}

[gcanti]

I think we should wait until it reaches stage 3 and is officially supported by TypeScript.

[jessekelly881]

The spec might never make it into typescript but there are still quite a few libraries that adhere to the proposed type: rxjs, xstate, redux, facebook's relay being a few of them. A simplified interface ObservableLike { subscribe: (_: (_: T) => void) => { unsubscribe: () => void }; } should be enough to be compatible w/ them w/o having to use the full type.

https://github.com/search?q=proposal-observable&type=code

[mikearnaldi]

The spec might never make it into typescript but there are still quite a few libraries that adhere to the proposed type: rxjs, xstate, redux, facebook's relay being a few of them. A simplified interface ObservableLike { subscribe: (_: (_: T) => void) => { unsubscribe: () => void }; } should be enough to be compatible w/ them w/o having to use the full type.

https://github.com/search?q=proposal-observable&type=code

Unless we introduce an Observable module I would avoid using the name, there is also the risk that the tc39 spec ends up in a different direction. I'd wait and see