forkJoin operator doesn't accept an array of observables

[sumigoma]

ForkJoin doesn't seem to maintain the behavior from Rx4 of supporting both .forkJoin(a,b,c) and .forkJoin([a,b,c]). If you try to do the latter (an array of observables) it gives the exception

TypeError: observables[i].subscribe is not a function
    at ForkJoinObservable.execute.ForkJoinObservable._subscribe (ForkJoinObservable.ts:19)

[endash]

I'm just gonna comment here because my issue is virtually identical. This is also an issue with combineLatest. In Rx4 you could pass an array of observables followed by a projection function. In Rx5 you can only use the arguments list. It is very common to have an array of observables rather than a set number of variables of type Observable.

[trxcllnt]

@Blesh I also think this is a concern. Unfortunately, TypeScript isn't exactly helpful in this regard. The only solution is to splat the Array when you call forkJoin/combineLatest, which you can only do in es6/ typescript.

I would be ok with a call to "flatten" arguments into a flat list of Observables, no matter how deeply-nested.

[kwonoj]

I was thinking about this bit, as @trxcllnt mentioned it requires some additional code to make it work with typescript. Trying to create some changes to trigger perf comparison to see if it's not hurting.

[benlesh]

I'm sort of indifferent about this one.

We can try adding the checks and see how it affects the performance. If it's a hit, then I say we don't do it, and people can just use .apply like they would on any other function in JavaScript.

[kwonoj]

how it affects the performance

: That's I'd like to verify :) if changes does not hurt performance, supporting this would be good. I should come up with numbers.

[kwonoj]

Initial attempt blocked due to same reason as #660, property based stub does not allow overload. Trying some other approaches.