2.x: Scheduler implement a Clock interface

[davidmoten]

I have frequently passed through a Scheduler instance to a class that only uses the now method (and does no scheduling). In the interests of clarity in my code (and to leverage compile time checking) I'd prefer to pass through a Clock instance (without creating another object to wrap the Scheduler). Would you mind if I submitted a PR with the addition of a new interface Clock that would be implemented by Scheduler?

[artem-zinnatullin]

Well that sounds like wrong abstraction, scheduler shouldn't be source of time, it should depend on some source of time

See #3295

[akarnokd]

Standard Schedulers return System.currentTimeMillis() and the TestScheduler returns an artificial value. Why is a wrapper so costly for you?

[davidmoten]

The wrapper is not costly, just more code to write or a dependency to add. If we had the interface we can use it internally as well, but this is just a convenience request that I'm assuming comes at little cost (?) and doesn't break apis.

[akarnokd]

I'm not fond of the idea. We have no use for this type of abstraction in RxJava and you'd still have to use RxJava as dependency to access such abstraction. You could simply not fully implement a Scheduler, making the other methods throw UnsupportedOperationException.

[davidmoten]

Ok, I'll close