HttpClient 'Http failure during parsing' error for valid json

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

Request throws an error when trying to parse a response of "ok" which is considered valid json according to https://jsonlint.com/

---

request:

    const requestOptions = Object.assign(
      {}, 
      { responseType: 'json' }, 
      { observe: 'body' as HttpObserve }
    );

    this.httpClient.request('GET', './mockjson.json', requestOptions)
    ...

---

error: "Unexpected token o in JSON at position 0"

Expected behavior

No error should be thrown for a response of "ok"

Minimal reproduction of the problem with instructions

https://embed.plnkr.co/klPNUS/

What is the motivation / use case for changing the behavior?

Environment

Angular version: 4.3.2


Browser:
- [x] Chrome (desktop) version XX
- [ ] Chrome (Android) version XX
- [ ] Chrome (iOS) version XX
- [ ] Firefox version XX
- [ ] Safari (desktop) version XX
- [ ] Safari (iOS) version XX
- [ ] IE version XX
- [ ] Edge version XX
 
For Tooling issues:
- Node version: XX  
- Platform:  

Others:

[dyh333]

this.http.get(url, {responseType: ‘text’})

it works as well.

[leojkwan]

Ran into same problem making a put request to my endpoint. I realized I was sending 200 without a response body. Sending status code 204 made angular http 5.2.8 stop complaining. This problem should not be happening even with a 200, but 204 is the correct code for empty responses.