MemoryStream doesn't immediately return the cached value to a new subscriber

[tomazy]

I'm trying to use xstream streams as a store in a React project and I'm quite happy with it. The only issue I have is with MemoryStreams not working as I would expect with regards to caching.

I'm not sure if this is a bug or per design.

When I subscribe to a memory stream as the first subscriber (for the first time) the chain of computation starts and I eventually get a value, that the stream will cache for all the subsequent subscribers.

Now, when all the subscribers unsubscribe, the stream knows the latest computed value.

But when I subscribe again to it, it will start the chain of computation again, even though it already has the value for me.

Is this expected behaviour?

I see in the code that in MemoryStream#_stopNow method you explicitly tell the stream that the value is stale via _has flag:

xstream/src/index.ts

Line 2010 in 61f364a

this._has = false;

Could anyone explain the rationale behind it please?

EDIT: Here is a demo of the problem: https://glitch.com/edit/#!/polar-cry

[wclr]

Now, when all the subscribers unsubscribe, the stream knows the latest computed value.

I believe it is expected. After there no subscriptions anymore a stream actually completes (and "forgets" everything, actually it dies). If you subscribe again it will resurrect, but will not give you the latest value from its past life.