angular: Error thrown by rxjs observer not always sent to ErrorHandler.handleError

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Current behavior Error thrown in an observable is not sent to the ErrorHandler.handleError method when observeOn(Scheduler.asap) is used.

Take the following example that DOES result in an error being sent:

    const ticks$ = Observable.interval(1000).take(10);
    
    this.mapped$ = ticks$.map(value => {
      if (value === 3) {
        throw new Error('oops');
      }
      return { value };
    });

<h4>Mapped ticks from an observable... {{mapped$ | async | json}}</h4>

The following example that does NOT result in an error being sent:

    const ticks$ = Observable.interval(1000).take(10)
      .observeOn(Scheduler.asap);
      
    this.mapped$ = ticks$.map(value => {
      if (value === 3) {
        throw new Error('oops');
      }
      return { value };
    });

Expected behavior

An error thrown by an observer scheduled with Scheduler.asap is sent to ErrorHandler.handleError

Minimal reproduction of the problem with instructions*

I’ve reproduced the problem in a new angular seed project generated by the latest vs of angular-cli (1.0.0-beta.30).

To run:

• Clone the repo: https://github.com/christianacca/rxjs-err-async-pipe.git
• npm install
• npm start
• browse to http://localhost:4200/

Notice that the error thrown by the map operator is logged to the console, but not sent to DelegatingErrorHandler.handleError (a custom ErrorHandler)

What is the motivation / use case for changing the behavior?

Using observeOn(Scheduler.asap) is a workaround to a problem with rxjs as documented here:

https://medium.com/@benlesh/on-the-subject-of-subjects-in-rxjs-2b08b7198b93#3114

Please tell us about your environment:

• Windows 10

• Visual Studio code

• Angular version: 2.4.6

• Browser: [all | Chrome XX | Firefox XX | IE XX | Safari XX | Mobile Chrome XX | Android X.X Web Browser | iOS XX Safari | iOS XX UIWebView | iOS XX WKWebView ]

Only tried in Chrome 55.0.2883.87

• Language: [all | TypeScript X.X | ES6/7 | ES5]

TypeScript 2.0.10