Deprecate all of Ember Classic

[wagenet]

@chriskrycho is actively planning to write this RFC so I feel comfortable making an issue here.

While this should not be seen as a comprehensive list, significant effort has been put into discussing the deprecation of classic features and is noted below for incorporation into this future RFC:

• Deprecate PromiseProxyMixin, PromiseArray, and PromiseObject #721
• Deprecate "old class binding" syntax #665
• Intent to RFC: Deprecate Libraries + Namespaces #540
• Deprecate Ember.Namespace #376
• Intent to RFC: Deprecate Observers #533
• Intent to RFC: Deprecate Computed Properties #536
• Thoughts on deprecating prototype extensions? #684
• Intent to RFC: Deprecate RSVP #539
• Intent to RFC: Deprecate {{action}} #537
• Intent to RFC: Deprecate EmberObject #535
• Intent to RFC: Deprecate Mixins #534
• Deprecate computed().meta() #441
• Deprecate Events #528
• Deprecate using tracked in classic classes #728
• Deprecate string based actions #632

[chriskrycho]

Don’t panic, everybody. 😅 This will happen with ample time for migrations! I’m waiting in part to get to a decision on #830, so I can target the deprecations for an appropriately generous timeframe!

[runspired]

I've brought this up with core team members in the past but I think I may as well lay it out here.

Ember can't deprecate classic unless ember-data deprecates it first. We've got a chicken-egg problem and it seems better for ember-data to absorb the break first because otherwise it has to somehow support ember both with and without classic support and in doing so would be flooding folks with deprecations they couldn't resolve.

For ember-data to stop using classic APIs we'd have to drop support for classic ourselves, most notably Mixins, Reopen, computed properties, and observers. We began this work with #738 and #793. The rough idea is to break lockstep and target releasing our own major in which we drop support for pre-4.0 ember + all classic ember APIs (e.g. our support matrix will be tighter than simply 4.0 ember, it would also limit what ember we supported to soley the class+tracked world)

[chriskrycho]

(For what it’s worth, I’m one of those members who has had that conversation and I agree. @runspired and I and many others are talking about the path forward here, including multiple discussions at Framework team meetings throughout the spring, and I think we’re getting toward consensus. That RFC will likely need to come before or in parallel with this one.)

[runspired]

We should get the ball moving on "ember-data controls its history / ember-data timeline" though. Roughly we would like to major ember-data around late early December and that would be the release in which we drop support for classic.

[chriskrycho]

Agreed! You and I should sync up next week and work on that!

[runspired]

Not the RFCs, but basically the roadmap for EmberData's next major is now here: warp-drive-data/warp-drive#8086