Ember 2.10.0 helper recompute bug

[ssured]

Calling recompute on a helper does not recompute in 2.10.0

Twiddle: https://ember-twiddle.com/3afc1bda1c824f4ed141b666e5521320?openFiles=helpers.my-helper.js%2C

When you change the dependency to 2.9 this code works, for 2.10 it does not work. It might be related to Glimmer update?

[rwjblue]

Definitely seems funky, I agree. The work around for now is to ensure the recompute is done within a run-loop (which fixes the twiddle):

export default Ember.Helper.extend({
  count: 0,
  compute() {
    if (!this.timer) {
      this.timer = window.setInterval(() => {
        Ember.run.join(() => {
          this.incrementProperty('count');
          console.log('call recompute', this.get('count'));
      	  this.recompute();
        });
      }, 500);
    }    
    return "count = " + this.get('count');
  }
});

Off the top of my head, I am not sure why a run-loop is required for it to function, but wrapping sets/rerenders in a run.join like this is almost certainly better for testing (would prevent an auto-run assertion in tests) so it is a reasonable solution.

[ssured]

My fault, I did not think of the runloop. Would a solution be to wrap

ember.js/packages/ember-glimmer/lib/helper.js

Line 85 in 9e2514e

this[RECOMPUTE_TAG].dirty();

in a run.join to prevent this for future users?

[youroff]

Why is this closed? Seems like an actual bug or what's the rationale behind the need of manually wrapping recompute call in run.join?

[pixelhandler]

@locks @rwjblue @ssured @youroff is this still an issue, perhaps we should close or create a new reproduction of this, what do you think?

[boris-petrov]

@pixelhandler - we just hit the same issue in Ember 3.4.5. So it is still valid. We had to wrap the call to recompute in a run. I created another issue a few days ago which is very similar to this problem that we face here. I.e. the code we had was:

export default Helper.extend
  compute: ([a, b]) ->
    pendingResult = @get('_pendingResult')
    if pendingResult?
      @set('_pendingResult', undefined)
      return pendingResult

    result = a.someMethodWithNativeAwaitsInside(b)

    result.then (result) =>
      @set('_pendingResult', result)
      @recompute()

    false

And this "blocked" when recompute was called - i.e. it didn't call compute again. And this started appearing only after we changed our code to use native promises instead of RSVP promises (or most of it - because of the other issue I mentioned). So there is some inconsistency between RSVP promises and native promises (under the latest Chrome) - and because of it, stuff breaks.

Any ideas?

P.S. I tried creating a reproduction but couldn't do it for now. But I'm pretty sure that fixing the other issue will also fix this.

[rwjblue]

The solution here is to ensure we run.join inside the recompute code (as @ssured mentioned in a prior comment).

[boris-petrov]

@rwjblue - yes, this is also how we worked around the issue, but the original problem is still there. Please check the reproduction repo I've given in the other GitHub issue.

[rwjblue]

I don't understand what you mean @boris-petrov. I'm saying that Ember.Helper's implementation of recompute should be using run.join not that your user-land helper code should...

[boris-petrov]

Ah, sorry, I thought you meant putting “run” around the “recompute” call in the user code as your initial suggestion. I misread, sorry! But the other issue still remains.

[xg-wang]

This issue can be worked around by creating a new runloop as explained in adopted-ember-addons/ember-router-helpers#126.
@rwjblue should recompute's internal impl be using runloop or just let userland code doing the run.join workaround?

[buschtoens]

I also just ran into this, because ember-on-modifier does not create a new runloop. I'm not really sure, whether we should consider this a bug in the framework or expected behavior.

[rwjblue]

Definitely a bug in the framework. We need to fix 😢.

[buschtoens]

I'm saying that Ember.Helper's implementation of recompute should be using run.join not that your user-land helper code should...

Easy PR right there! I'll take it tomorrow, if nobody else signs up. 😏