Angular httpClient interceptor error handling

Question

after reading the documentation on angular about http client error handling, I still don't understand why I don't catch a 401 error from the server with the code below:

export class interceptor implements HttpInterceptor {
    intercept(request: HttpRequest<any>, next: HttpHandler): Observable<HttpEvent<any>> {
        console.log('this log is printed on the console!');

        return next.handle(request).do(() => (err: any) => {
            console.log('this log isn't');
            if (err instanceof HttpErrorResponse) {
                if (err.status === 401) {
                    console.log('nor this one!');
                }
            }
        });
    }
}

on the console log, I also get this:

zone.js:2969 GET http://localhost:8080/test 401 ()

core.js:1449 ERROR HttpErrorResponse {headers: HttpHeaders, status: 401, statusText: "OK", url: "http://localhost:8080/test", ok: false, …}

Answer 1

Your error handler needs to return a new Observable<HttpEvent<any>>()

return next.handle(request)
    .pipe(catchError((err: any) => {
        console.log('this log isn't');
        if (err instanceof HttpErrorResponse) {
            if (err.status === 401) {
                console.log('Unauthorized');
            }
        }

      return new Observable<HttpEvent<any>>();
    }));