How to cancel current request in interceptor - Angular 4

I think all you have to do to cut the interceptor chain is to simply return an empty Observable like so:

import { EMPTY } from 'rxjs';intercept(request: HttpRequest<any>, next: HttpHandler): Observable<HttpEvent<any>> {  if (stopThisRequest) {    return EMPTY;  }  return next.handle(request);}

Inspired by @RVP answer I have found out that it's possible to cut the chain with an error in the same simple way using Observable.throw()

//...intercept(req: HttpRequest<any>, next: HttpHandler): Observable<HttpEvent<any>> {    if (stopThisRequestWithError) {        return Observable.throw('Error message');    } else {        return next.handle(req);    }}

This avoids fulfilling response promises with undefined values.

This is just a slight variant of RVP's answer

import { NEVER } from 'rxjs';intercept(request: HttpRequest<any>, next: HttpHandler): Observable<HttpEvent<any>> {  if (stopThisRequest) {    return NEVER;  }  return next.handle(request);}

I used NEVER instead of EMPTY to avoid dealing with undefined values in my subscriptions (or promises).

Use NEVER if you don't want your subscription callback to be invoked