Decorators recently became a first class part of Ember.js API! They've been accepted in RFC, and will be released in an upcoming version soon. A polyfill has been created as well.
Ember Decorators used to provide decorators like @computed and @service, but
now that Ember has first class support for these, it no longer does. However,
there are still some helpful decorators in this library that were not upstreamed
to Ember, and remain available for folks to use! These decorators are mainly for
compatibility with older Ember classes and features, specifically classic
components, observers, and event listeners.