typescript - I get "Http failure response for (unknown url): 0 Unknown Error" instead of actual error message in Angular

Question

I'm using Angular 4 HttpClient to send requests to external service. It is a very standard setup:

this.httpClient.get(url).subscribe(response => {
  //do something with response
}, err => {
  console.log(err.message);
}, () => {
  console.log('completed');
}

The problem is, when the request fails I see a generic Http failure response for (unknown url): 0 Unknown Error message in console. Meanwhile, when I inspect the failed request in chrome I can see the response status is 422, and in the "preview" tab I see the actual message desribing failure cause.

How do I access the actual response message I can see in chrome dev tools?

Here's a screenshot demonstrating the problem:

Answer 1

The problem was related to CORS. I noticed that there was another error in Chrome console:

No 'Access-Control-Allow-Origin' header is present on the requested resource. Origin 'http://localhost:4200' is therefore not allowed access. The response had HTTP status code 422.`

This means the response from backend server was missing Access-Control-Allow-Origin header even though backend nginx was configured to add those headers to the responses with add_header directive.

However, this directive only adds headers when response code is 20X or 30X. On error responses the headers were missing. I needed to use always parameter to make sure header is added regardless of the response code:

add_header 'Access-Control-Allow-Origin' 'http://localhost:4200' always;

Once the backend was correctly configured I could access actual error message in Angular code.