Move unregister() to PushRegistration.

[mounirlamouri]

This is also changing the type of returned Promise and how it is
expected to behave.

[mounirlamouri]

Fixes issue #94.

[mvano]

I think we were still considering whether this should return true, right?

[mounirlamouri]

How so?

[mvano]

For the case where unregister is called twice. The desired result was achieved: you are unregistered. That sounds more like true than false.

[mounirlamouri]

I disagree. The entire idea of returning a boolean is to point that nothing actually happen. This is also what we do for ServiceWorker.

[mvano]

I think it's weird, but I don't feel too strongly about it and aligning with sw is good. lgtm

[mounirlamouri]

Thanks! \o/

[martinthomson]

Why do you need to know if there was something to unregister? If there is a use case, I'd be interested in learning of it.

[mounirlamouri]

Do we really need a use case to expose an information that can anyway be accessed by other means?

[martinthomson]

Even more so then. If you have other means of getting this information, I think that raises the bar. Can you justify why this returns a boolean over Promise<undefined>?

[mounirlamouri]

Because then you can easily check if the call was a no-op or not... If you have a pushRegistration instance, you can just call pushRegistration.unregister().then(function(b) {...}); and use b to know whether the unregistration happened instead of doing navigator.push.getRegistration().then(function(r) { return r ? r.unregister() : null; }).then(function() { ... });.

[martinthomson]

Why do you need to know if the call was a no-op?

[mounirlamouri]

Should we wait for the need to arise before exposing that simple boolean? I'm not sure. Exposing this doesn't cost us anything and could help developers. Is there an implementation concern?

[martinthomson]

we don't add API points without need usually, that's all

[mvano]

If we later decided that we wanted the boolean, there would be some subtlety in the backward compatibility. Authors would need to distinguish between (false) and (undefined or zero arguments).

[martinthomson]

Yes, this closes certain avenues if we later determine that information like this is useful. That's not a reason to add features.