Implement + enable array Helper Feature

[rwjblue]

This is a tracking issue to enable the array helper as proposed in emberjs/rfcs#318.

• Implement
• API Docs
• Guides
• Enable by default
• Author a polyfill (e.g. ember-array-helper-polyfill)?

[josemarluedke]

🔒 I will give this implementation a try.

[rwjblue]

Some general implementation notes, I believe this should roughly be implemented the same way as the hash helper (but using positional args instead of named args).

• a helper like this one but with args.positional.capture()
• add to this array of built-ins
• add a slew of tests like

[kanongil]

I really think you need to revisit the an entirely new array is returned on changes thing on this (and the hash helper). The ember component system is not geared for this, as any change to any property, or sub-property, of any element triggers a re-validation of the whole array.

[rwjblue]

@kanongil - I'm not sure that I agree, the point is that revalidating the full array is not expensive.

[kanongil]

That is not my experience from the hash helper. I can’t see why this would be different.

[rwjblue]

Added a few more todo items:

• Guides
• Enable by default

[rwjblue]

@josemarluedke - Interested in picking up the guides work also?

[YoranBrondsema]

@rwjblue Saw this issue and don't think that @josemarluedke had picked up the guide yet. So wrote a short blurb in the guide in ember-learn/guides-source#209.

[rwjblue]

Nice, thank you!

[SergeAstapov]

https://github.com/kellyselden/ember-array-helper may be considered as polyfill

[rwjblue]

@SergeAstapov - It certainly could be, but it would need some changes. Specifically, it would need to be updated to do nothing when it detects the newer Ember version that ships the helper by default.

[kategengler]

@kellyselden Any interest in updating your ember-array-helper addon (mentioned above) to be a polyfill?

[kellyselden]

Of course. I can donate it or just add people, whatever need be.

[locks]

This is le done.