Injecting Streams?

index_injecting.ts

import xs, { Stream } from 'xstream';
import { initModule, MyMsg } from './module_injecting';

// Stuff

init(
  xs.create({
    start: function(listener) {
      someSource$.subscribe(msg => {
        // do stuff with someSource$ to get it in shape
        listener.next(msg);
      });
    },
    stop: function() {
      someSource$.unsubscribe();
    }
  })
);

index_notinjecting.ts

import xs, { Stream } from 'xstream';
import { initModule, MyMsg } from './module_injecting';

// Stuff

export const myMsg$: Stream<MyMsg> = // do something with someSource$
initModule();

module_injecting.ts

import xs, { Stream } from 'xstream';

export type MyMsg = {msgType: 'MyMsg', data: any};

export function initModule(msg$: Stream<MyMsg>): void {
  msg$.addListener({
    next: msg => update(msg),
    error: err => console.error(err),
    complete: () => console.log('completed')
  });
}

module_notinjecting.ts

import xs, { Stream } from 'xstream';

// This
import { myMsg$ } from './index_notinjecting.ts';

export type MyMsg = {msgType: 'MyMsg', data: any};

export function initModule(): void {
  myMsg$.addListener({
    next: msg => update(msg),
    error: err => console.error(err),
    complete: () => console.log('completed')
  });
}