Deprecate Computed

[wagenet]

Deprecate Computed

Rendered

Summary

This pull request is proposing a new RFC.

To succeed, it will need to pass into the Exploring Stage, followed by the Accepted Stage.

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Upon merging this PR, automation will open a draft PR for this RFC to move to the Ready for Released Stage.

Exploring Stage Description

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Checklist to move to Exploring

• The team believes the concepts described in the RFC should be pursued.
• The label S-Proposed is removed from the PR and the label S-Exploring is added.
• The Ember team is willing to work on the proposal to get it to Accepted

Checklist to move to Accepted

• This PR has had the Final Comment Period label has been added to start the FCP
• The RFC is announced in #news-and-announcements in the Ember Discord.
• The RFC has complete prose, is well-specified and ready for implementation.
  • All sections of the RFC are filled out.
  • Any unanswered questions are outlined and expected to be answered before Ready for Release.
  • "How we teach this?" is sufficiently filled out.
• The RFC has a champion within one of the relevant teams.
• The RFC has consensus after the FCP period.

[wagenet]

Deprecation Guides: ember-learn/deprecation-app#1412

[IgnaceMaes]

FYI There is already a codemod available. I built one a while ago to completely migrate a codebase off macros: https://github.com/OTA-Insight/ember-computed-macro-codemod/

It does not cover all macro's though, so there's room to extend it.

[wagenet]

Well that's a great start!

[apellerano-pw]

Is there a way to provide computed properties as an addon, for continued compatibility?

There is only a subset of computed property usage that is easy to automate away - when the dependent key exists in the same context as the computed property. But computed properties can be dependent on state anywhere in the system, such as Services or other singleton or global patterns. The set call mutations happen 'at a distance' and make a rewrite hard or impossible to automate.

My main concern is that this deprecation will produce an amount of manual effort so great, it will rival the Ember 3->4 migration and create another pit to further fracture the userbase.

Ember is particularly incoherent right now, and the level of incoherence at the time of Ember 6.12 could become crystalized if the 6->7 migration pathway is too labor intensive.

I don't know much about the inner workings of the computed property system. Could the 'brains' be moved into a Service, and classes that uses computed properties decorated? I think the decorator would have to splash onto anything that needs the set function, and could be a good halfway step on the way to tracked properties.

I don't think there would be a need for a get call? IIRC there's only a narrow use case that still requires them, which should be eliminated by RFC 1112 (deprecate Ember Proxies)

[NullVoxPopuli]

it may be possible to provide a babel plugin that:

• uses a new version of computed built on top of tracked (behavior may still be subtly different, not sure yet)
• essentially undeprecating things for your app and all your addons

Your tech debt then becomes a list of babel plugins, which are easy to burn down over time (fewer babel plugins = better build perf? idk)