Summary

Support for component eventMangers is a seldom used feature and should be deprecated.

Motivation

We should strive to simplify the Ember API and source code where possible. As the custom eventManager feature is rarely used in apps, we should deprecate it.

Detailed design

We'll introduce a deprecation warning which will be displayed when a component defines an eventManager property or when canDispatchToEventManager is set to true on EventDispatcher. The warning will have a target version of 3.0.

If required, we can create an addon which extends the EventDispatcher allowing for opt-in custom eventManagers in Ember apps.

How We Teach This

As this is a seldom used feature, we can simply note the deprecation in a future release blog post.

Drawbacks

This adds a little more churn for apps that rely on this feature.

Alternatives

This feature was recently made pay-as-you-go, so the immediate performance concerns have been addressed. We could decide to leave this in the framework as an opt-in feature.