Remove Provider.Watch

[aeneasr]

Method Watch(func(event interface{}, err error)) error is actually not used by Koanf (unlike Load and ReadBytes) itself and serves no purpose except for adding bloat to providers who do not support Watching (e.g. env or flags). As an implementer of my own Provider I want to use a different watch mechanism with channels (instead of a callback) which means I have to implement two watchers, or not use channels.

[knadh]

The file provider Watch(). While the interface{}, err callback is a bit awkward because it's modeled primarily for filesystem events, it's still is generic enough for any sort of event triggers.

A Provider is meant to be generic, so while async updates might be irrelevant to env and flags, it may be relevant to other config sources like HTTP, Redis, PubSub, Consul etc. Having that one extra function on the interface that can be left empty is not really bloat (in any quantifiable way either) but a fair compromise for a universal Provider interface, I would say.

[aeneasr]

But the interface method is not used by Koanf (the struct) itself - it serves thus no purpose. See also: https://mobile.twitter.com/davecheney/status/942593128355192832?lang=en

The file provider's Watch method is called directly (see README)!

If we are expecting to call the watch (or whatever other) methods on the provider structs directly, it should be removed IMO.

[knadh]

You're right. koanf internally has no use for Watch() and it is used externally either way. I mis-read it the first time. Merged #46

[aeneasr]

Thank you for listening to my ideas! :)