[BUGFIX release] Fix #12475

[mmun]

Fixes #12475 by reverting the ArrayProxy code to use before-observers. In order to re-remove these before observers we will need to remove the @array:before event (AKA the willChange part of array.addArrayObserver({ willChange, didChange }))

For more details see #12860 (comment).

[stefanpenner]

good hunting, I'm sorta sad about the fix. But... as discussed it appears a better fix may be a breaking change.

also would like @krisselden 👀 on this

[mmun]

Me too 😭

[rwjblue]

OK, 🍏 build now...

[krisselden]

I'm definitely sad about the fix, I think we can do something else but we have to fix the regression in the mean time.

[stefanpenner]

@krisselden good to merge for now?

[mmun]

@stefanpenner: @krisselden approved on Slack.

I believe your solution is best for now @mmun

[runspired]

many tears are shed.

[mmun]

On the plus side, this bug got me more familiar with ember-metal. I'm going to spike out lazy array observers and see how bad it breaks my apps :)

[lozjackson]

Thankyou very much @mmun for fixing this.. I've been stuck on 2.0.3 because of this bug. I'm now on 2.4.1 and much happier. :)