zip does not do anything if passed all iterators

[benlesh]

Ages ago, I had this amazing idea to give zip special handling for iterables, such that, as it was "zipping" it would attempt to only next out values from the iterable as needed.

Unfortunately, this has introduced a lot of complexity in that operator as well as a bug...

zip('abc', 'def').subscribe(x => console.log); // this does nothing.

It should yield:

['a', 'd']
['b', 'e']
['c', 'f']

But it does nothing.

While it seemed like a clever idea at the time, I now think it deviates from the "push only" nature of RxJS, and this behavior should be removed in the upcoming v7.

[benlesh]

Core team: Agree to go back to v4 style behavior and doing from on the iterable passed in.