Charm should be reinitialized at every hook execution in Harness

More specifically, before every hook execution. Point is: when a ‘real’ charm runs, it is reinitialized afresh. While if you do fire eventA and eventB on the harness, the harness won’t reinitialize the charm it holds in between, which may result in some major behavioural differences between a live charm and a harness’d charm.

Use cases include:

class Charm(CharmBase):
     def __init__(self):
         self.relation1 = relation1 = RelationRequirer()
         self.relation2 = RelationProvider(relation1.data[self.unit])

class Charm(CharmBase):
     def __init__(self):
         if self.container.can_connect():
             self.framework.observe(self.on.foo, self._foo)

Concrete example of an affected charm: https://github.com/canonical/prometheus-k8s-operator/blob/main/src/charm.py

[rwcarlsen]

Defer also sneaks its way into this. Deferred evens are run together on the same charm instance/setup as the event that comes in and triggers them.

[jameinel]

(at a minimum, relating A to B should not require that B knows the names of the endpoints of charm A. That is certainly an abstraction break)