Unset oldValue after being done with it

[ccantill]

fixes #771

[bigopon]

@ccantill thanks. I see what you meant. I'll have a look to see whether we need to be carefully setting initial value of old value to something else or simply null would suffice

[bigopon]

I think this is fine. As the observer always deals with outside using currentValue. We may need this for v2 as well cc @fkleuver @EisenbergEffect

[fkleuver]

Actually I already solved this in v2 (unintentionally) when I was doing perf optimizations: https://github.com/aurelia/aurelia/blob/master/packages/runtime/src/observation/setter-observer.ts#L61

I think we can do it the same way in v1; just change this:

  call() {
    let oldValue = this.oldValue;
    let newValue = this.currentValue;
    this.oldValue = null;

    this.queued = false;

    this.callSubscribers(newValue, oldValue);
  }

To this:

  call() {
    let oldValue = this.oldValue;
    let newValue = this.oldValue = this.currentValue;

    this.queued = false;

    this.callSubscribers(newValue, oldValue);
  }

It won't matter much, but it can be slightly better for perf in otherwise monomorphic hot paths.

[bigopon]

That looks good to me, I was thinking of that too but wouldn't want to bother too much with non-outcome requests 😛 @ccantill can you please help with that?

[ccantill]

I've changed it in my PR.

[ccantill]

@bigopon any idea on when this can be merged/released?

[bigopon]

@ccantill oops, sorry missed this. pinging @fkleuver @EisenbergEffect for a merge & release

[fkleuver]

@ccantill It's released now. Thank you!