ajax() returns Observable<{}> instead of Observable<AjaxResponse>

[billba]

RxJS version: 5.0.0-beta.9

Code to reproduce:

const source = Observable.ajax({ method:"GET", url: "myurl" });

Expected behavior:

Mouse over source to see that it's type Observable<AjaxResponse>

Actual behavior:

It's type Observable<{}>.

Additional information:

What might be going on is that AjaxObservable<T>.create has

      return new AjaxObservable(urlOrRequest);

and I think it should be:

      return new AjaxObservable<AjaxResponse>(urlOrRequest);

As a workaround I was able to do:

const source = Observable.ajax<AjaxResponse>({ method:"GET", url: "myurl" });

... but ajax shouldn't really take a type at all and I'm not sure why it even can.

[kwonoj]

Seems it makes sense. Let me look bit more and create PR if necessary.

[benlesh]

cc/ @david-driscoll

[kwonoj]

I've looked this into bit more to see if it's possible to get rid of generics for ajax creation method, found it's bit tricky.

but ajax shouldn't really take a type at all and I'm not sure why it even can.

: Main reason for this is AjaxRequest allows resultSelector makes AjaxObservable to emit other than AjaxResponse, Observable.ajax<AjaxResponse>({ method:"GET", url: "myurl" }) is actually valid way to specify types.

While it's expected to allow generics to AjaxObservable I'm also feeling type definitions can be improved bit better to work with resultSelector as well as default, not sure about immediate changes though. I'll leave this open for couple of more days to get idea around.

[billba]

Ah but here's the thing -- ajax, which is to say AjaxObservable.create -- isn't written as a generic function. That's why it's so weird that you can even give it a type. I think what's happening is that TypeScript "needs" a type for that AjaxObservable constructor, and so it lets you add one farther up the stack. Which sure sounds like a bug in TypeScript, but that's a different issue for a different rep.

On the larger subject, my two cents is this: let ajax continue to return the full AjaxResponse, just like in jQuery. It shouldn't be a generic.

If you want to access a REST JSON response as a type, you don't need to resort to resultSelector. You can just do:

const source = Observable.ajax({ method:"GET", url: "myurl" }).map(ajaxResponse => ajaxResponse.response as TheTypeOfTheRestResponse);

Ditto if you just want part of the response:

const source = Observable.ajax({ method:"GET", url: "myurl" }).map(ajaxResponse => ajaxResponse.response["foo"]);

Both are simpler and clearer (and more Rx-y) than the equivalent resultSelector code, no?

tl;dr: let ajax be ajax, death to resultSelector

[david-driscoll]

I don't personally see a ton of value in the result selector (after looking at the code) which would make this problem very easy to solve.

I'll leave it up to @Blesh and @kwonoj though.

[kwonoj]

I'm also leaning towards to drop off resultSelector, just unsure if there's solid usecases for those. (But as @billba mentioned, most cases map can resolve selections..)

[kwonoj]

I've filed PR #1813 to leverage as discussion point. Basically PR drops resultSelector and ensure type delivered to subscription, encourage to use map where selection needed.