Not work spread when I set options to HttpClient.get after migrate to v.6

I’m submitting a…

[ ] Regression (a behavior that used to work and stopped working in a new release)
[x ] Bug report 
[ ] Performance issue
[ ] 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
[ ] Other... Please describe:

Current behavior

I call my base function:

protected get(url: string, options?: any): Observable<HttpResponse<any>> {
    return this.http.get(url, {...options, observe: 'response'});
}

When http is HttpClient. I get error:

Type ‘Observable<ArrayBuffer>’ is not assignable to type ‘Observable<HttpResponse<any>>’.

I try change call of function, added <any>:

this.http.get<any>(url, {...options, observe: 'response'})

And get error:

Type ‘Observable<HttpEvent<any>>’ is not assignable to type ‘Observable<HttpResponse<any>>’.

Expected behavior

But, if I remove options and spread: this.http.get(url, {observe: 'response'}) It works as expected and in v.5 and latter…

Environment

Angular version: 6.1.8

Browser:
- [x] Chrome (desktop) version last
- [ ] 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: 8.11.1
- Platform:  Windows

[alxhub]

This is some strange behavior, for sure!! It took me a moment to realize what was happening.

What’s actually happening is that because your options object has type any, then the result of the spread operation {...options, observe: 'response'} actually has type any as well. any is pretty infectious in TypeScript. This means that TS will just take the first signature of get (because any matches anything!) which happens to return an Observable<ArrayBuffer>.

What you should do is type the options parameter to your function more aggressively - I always try to avoid any where possible in my TS code. If you give this parameter a correct type, your spread operation will work as expected.

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