Push API should recommend implementing ServiceWorkerRegistration.showNotification

[johnmellor]

Web developers using the Push API, and subscribing from a document context, will typically check !!window.Notification to see whether the Notifications API is implemented, since they cannot easily check from a document context whether the Notifications Service Worker API (especially ServiceWorkerRegistration.showNotification and ServiceWorkerGlobalScope.onnotificationclick) is implemented.

Thus the spec should recommend that UAs which implement the Push API either:
a) do not implement the Notifications API at all; or
b) implement and ship Notifications Service Worker API before or together with shipping the Push API.

[beverloo]

The Push API does not have a dependency on the Notification API. I don't think this makes sense unless we decide to add such a dependency, e.g. implement an option bag for subscribe()/hasPermission(), which is a larger issue.

On a tangent, ServiceWorkerRegistration.prototype.hasOwnProperty('showNotification') works on both documents and workers.

[johnmellor]

Good point - if developers check that ServiceWorkerRegistration.prototype contains showNotification this won't be an issue.