Merge pull request #1116 from wagenet/deprecate-mixins

Deprecate Mixin Support

Author: ef4

text/1116-deprecate-mixins.md

@@ -0,0 +1,60 @@
+---
+stage: accepted
+start-date: 2025-06-20T00:00:00.000Z
+release-date:
+release-versions:
+teams: # delete teams that aren't relevant
+  - cli
+  - framework
+  - learning
+  - typescript
+prs:
+  accepted: https://github.com/emberjs/rfcs/pull/1116
+project-link:
+---
+
+# Deprecating Mixin Support
+
+## Summary
+
+Deprecate all Mixin support.
+
+## Motivation
+
+For a while now, Ember has not recommended the use of Mixins. We should actually fully
+deprecate this.
+
+## Transition Path
+
+All existing public Ember mixins will be deprecated:
+
+- [Ember.Mixin](https://github.com/emberjs/rfcs/pull/1111) (from `@ember/object/mixin`)
+- [Ember.PromiseProxyMixin](https://github.com/emberjs/rfcs/pull/1112) (from `@ember/object/promise-proxy-mixin`)
+- [Ember.Comparable](https://github.com/emberjs/rfcs/pull/1113) (from `@ember/object/comparable`)
+- [Ember.Enumerable](https://github.com/emberjs/rfcs/pull/1114) (from `@ember/object/enumerable`)
+- [Ember.Observable](https://github.com/emberjs/rfcs/pull/1115) (from `@ember/object/observable`)
+
+For users that still want mixin-like functionality, we should recommend class
+decorators. If this feels less ergonimic that we would desire, we can consider
+providing an addon that adds some sugar around this.
+
+## Exploration
+
+To validate this deprecation, I've tried removing all Mixins in this PR: https://github.com/emberjs/ember.js/pull/20923
+
+## How We Teach This
+
+We should remove all references from the guides and provide a [deprecation guide](https://github.com/ember-learn/deprecation-app/pull/1408).
+
+## Drawbacks
+
+Some users probably rely on this functionality. However, it's almost certainly
+something that we don't need to keep in Ember itself.
+
+## Alternatives
+
+None
+
+## Unresolved questions
+
+None