Config options remain in hookenv.config() even when unset

[Casey Marshall]

Steps to reproduce:

With a charm that has a config option without a default value,

- Set the value to something: `juju config mycharm foo=100`
- Observe the config-changed hook fires, and the option is set in hookenv.config()
- Now, unset the value: `juju config --reset mycharm foo`
- When config-changed fires, hookenv.config() still shows {foo: 100}
- However, `juju config mycharm` will show the value is unset. And, I've also confirmed this in the Juju DB.

The problem seems to be that keys are never removed from `/var/lib/juju/agents/unit-mycharm-0/charm/.juju-persistent-config` even when unset.

[Casey Marshall (cmars)]

This was with charmhelpers-0.9.1.tar.gz btw

[Cory Johns (johnsca)]

Per https://code.launchpad.net/~simonklb/charm-helpers/include-empty-config-options/+merge/309105 I think the correct behavior would be to have hookenv.config() always return all config options and their values, even if those values are default.

Any objection to supporting that behavior instead?