'cache()' should allow subscribe after unsubscribe

[alex-novikov-1990]

RxJS version: Latest
Code to reproduce:

var cached = Observable.timer(200).cache();
var subscription = cached.subscribe(v => console.log(v));
setTimeout(() => {
    subscription.unsubscribe();
    cached.subscribe(v => console.log(v));
}, 100);

Expected behavior:
"0" in console.
Actual behavior:
Nothing in console.
Additional information:
Subject should be nulled on outerSub unsubscribtion
https://github.com/ReactiveX/rxjs/blob/master/src/operator/cache.ts#L55

[benlesh]

... and here's another issue that leads me to believe cache should be removed from v5 until we more specifically bikeshed it's behavior.

[alex-novikov-1990]

Oh, it's probably a dupe of #1959
Use case from my project (serviceCall is angular 2 http.post with retry logic):

cache.observable = serviceCall
    .expand(() => Observable.timer(period).concatMap(() => serviceCall))
    .cache(1, period);

[jayphelps]

@newsash we ended up removing the .cache() operator for RC1 because in it's current state it was too confusing and [poorly] trying to solve too many problems.

We do plan to revisit in the future and possibly provide one or more operators that have differing forms of caching.

Everyone has differing opinions and use cases for what "caching" should mean and it's far more complex that it may seem at first. Some additional thoughts can be found here.

[lock]

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