Empty headers in HTTP Response with Angular 4.3's HttpInterceptor

I’m submitting a…

[ ] Regression (a behavior that used to work and stopped working in a new release)
[x] Bug report  
[ ] Feature request
[ ] Documentation issue or request
[ ] Support request => Please do not submit support request here, instead see https://github.com/angular/angular/blob/master/CONTRIBUTING.md#question

Current behavior

This is how I send my HTTP request: return this.http.get(url, { observe: 'response' })

I would like to read the HTTP headers of a HttpResponse in my HttpInterceptor:

intercept(request: HttpRequest<any>, next: HttpHandler): Observable<HttpEvent<any>> {
        return next.handle(request)
            .do(event => {
                if (event instanceof HttpResponse) {
                    this.logger.logDebug(event); // Headers are missing here
                }
            })
            .catch((err: HttpErrorResponse) => {
            // Do stuff
    }
}

The event seems to have no headers, and even in the Chrome Dev Console I cannot see any headers:

However, when using Postman, I can see the headers in the response (as expected)

Connection →keep-alive Content-Length →14766 Content-Type →application/json Date →Fri, 04 Aug 2017 14:50:46 GMT Server →WildFly/10 X-Powered-By →Undertow/1

The official docs for HTTP says to get the headers like this:

http
  .get<MyJsonData>('/data.json', {observe: 'response'})
  .subscribe(resp => {
    // Here, resp is of type HttpResponse<MyJsonData>.
    // You can inspect its headers:
    console.log(resp.headers.get('X-Custom-Header'));
    // And access the body directly, which is typed as MyJsonData as requested.
    console.log(resp.body.someField);
  });

Expected behavior

I was expecting to see the same headers in Angular as with Postman

Environment

Angular version: 4.3.3

Browser:
- [x] Chrome (desktop) version XX

[TheParad0X]

@robwormald You were right. It was a CORS problem. I needed to explicitely expose my custom header. Thank you

[alxhub]

Can you share the code you’re using to actually read the headers? Logging the HttpHeaders instance is going to be misleading - headers are lazily parsed from the response header string on first access. It looks like your instance has a lazyInit function and is poised to perform this parsing when the headers are first accessed.