Deprecation Guide for Use ember-copy addon instead of copy method and Copyable mixin.

Since Ember's earliest days, the copy function and Copyable mixin from @ember/object/internals were intended to be treated as an Ember internal mechanism. The Copyable mixin, in particular, has always been marked private, and it is required in order to use copy with any Ember Object-derived class without receiving an assertion.

Copyable hasn't been used by any code inside of Ember for a very long time, except for the NativeArray mixin, inherited by Ember arrays. The deprecated copy function now handles array copies directly, no longer delegating to NativeArray.copy. With this deprecation, NativeArray no longer inherits from Copyable and its implementation of copy is also deprecated.

For shallow copies of data where you use copy(x) or copy(x, false), the ES6 Object.assign({}, x) will provide the desired effect. For deep copies, copy(x, true), the most efficient and concise approach varies with the situation, but several options are available in open source.

For those whose code is deeply dependent upon the existing implementation, copy and Copyable have been extracted to the ember-copy addon . If you are only using documented methods, this will only require adjusting your import statements to use the methods from ember-copy instead of @ember/object/internals. The code in the addon should work identically to what you were using before.