Async creation of components

Is there any intention to support async creation of components? For example, a connection to db should not be injected into another component until it is actually established (something that can be confirmed only asynchronously).

Ideally, a component could return a promise and creation of dependent components should be conditioned on the fulfillment of that promise.

The issue names no files, tests, or entry points. Begin by locating component creation and dependency-injection code, then check how asynchronous initialization is currently handled. Done would require an agreed API and tests showing dependent components wait for a fulfilled promise.

Written by the indexing model from the issue text.