Declaration Merging not Working in Angular 2 Project

Question

I am trying to implement a custom RxJS operator as described in this answer. Here are the relevant snippets in my application:

rxjs-extensions.ts

import { Observable } from 'rxjs/Observable';

function restrictToCommand<T>(this: Observable<T>): Observable<T> {
    console.log('works');
    return Observable.empty()
}

declare module 'rxjs/Observable' {
    interface Observable<T> {
        restrictToCommand: typeof restrictToCommand;
    }
}

Observable.prototype.restrictToCommand = restrictToCommand;

consumer.ts

import { Observable } from 'rxjs/Observable';
import '../../rxjs-extensions';
...
export class MyComponent {    

...

    private load(): void {
        Observable.of(1).restrictToCommand();
    }

...

}

When load() is called, I receive the following exception:

EXCEPTION: Uncaught (in promise): Error: Error in ./MyParentComponent class MyParentComponent - inline template:2:4 caused by: __WEBPACK_IMPORTED_MODULE_2_rxjs_Observable__.Observable.of(...).restrictToCommand is not a function
TypeError: __WEBPACK_IMPORTED_MODULE_2_rxjs_Observable__.Observable.of(...).restrictToCommand is not a function
    at MyComponent .load (eval at <anonymous> (http://localhost:8080/app.js:3530:1), <anonymous>:45:75)
    at MyComponent .ngOnInit (eval at <anonymous> (http://localhost:8080/app.js:3530:1), <anonymous>:63:14)
    at Wrapper_MyComponent .ngDoCheck (/AppModule/JobsPanelComponent/wrapper.ngfactory.js:22:53)
    at CompiledTemplate.proxyViewClass.View_MyParentComponent 0.detectChangesInternal (/AppModule/MyParentComponent/component.ngfactory.js:62:32)
    at CompiledTemplate.proxyViewClass.AppView.detectChanges (eval at <anonymous> (http://localhost:8080/app.js:3185:1), <anonymous>:301:14)
    at CompiledTemplate.proxyViewClass.DebugAppView.detectChanges (eval at <anonymous> (http://localhost:8080/app.js:3185:1), <anonymous>:394:44)
    at CompiledTemplate.proxyViewClass.View_MyParentComponentt_Host0.detectChangesInternal (/AppModule/MyParentComponent/host.ngfactory.js:29:19)
    at CompiledTemplate.proxyViewClass.AppView.detectChanges (eval at <anonymous> (http://localhost:8080/app.js:3185:1), <anonymous>:301:14)
    at CompiledTemplate.proxyViewClass.DebugAppView.detectChanges (eval at <anonymous> (http://localhost:8080/app.js:3185:1), <anonymous>:394:44)
    at ViewRef_.detectChanges (eval at <anonymous> (http://localhost:8080/app.js:1708:1), <anonymous>:136:20)

I am using Angular 2, Webpack 2, and TypeScript 2.0.3.

Answer 1

To fix this issue, I had to add import './rxjs-extensions' to my app.module.ts, where I was already importing ./rxjs-imports, a file that contained all of the RXJS operators that I was using in my application.

Unfortunately, I still don't fully understand what is happening. I will update the answer if I ever gain a clearer understanding.