RxJs5 lifecycle debug operator

debug.ts

import 'rxjs/add/observable/empty';
import 'rxjs/add/operator/do';
import 'rxjs/add/operator/concat';
import 'rxjs/add/operator/finally';
import { Observable } from "rxjs";

/**
 *
 * Lifecycle debugging for your stream, sub/unsubscribe,complete and values
 *
 * @param this Observable
 * @param identifier label to be outputted to console
 */
function debug<T> (this: Observable<T>, identifier: string): Observable<T> {
  return Observable.empty<any>()
    .do(_ => {}, undefined, () => console.log(`[${identifier}] subscribed`))
    .concat(
      this.do(
        (val) => console.log(`[${identifier}] nextVal: ${val}`),
        (err) => console.log(`[${identifier}] error: ${err.message}`),
        () => console.log(`[${identifier}] completed`)
      )
    )
    .finally(() => console.log(`[${identifier}] unsubscribed`));
};

Observable.prototype.debug = debug;

declare module "rxjs/Observable" {
  interface Observable<T> {
    debug: typeof debug;
  }
}

usage.ts

import { Observable } from 'rxjs/Rx';
import "./debug";

const stream = Observable.interval(1000)
  .take(3)
  .debug("my-stream")
  .subscribe()
  ;

/* outputs:
[my-stream] subscribed
[my-stream] nextVal: 0
[my-stream] nextVal: 1
[my-stream] nextVal: 2
[my-stream] nextVal: 3
[my-stream] completed
[my-stream] unsubscribed
*/