AppDelegate fault action

[loudej]

option a - draft 5 and in code

• AppDelegate has a third, fault action passed in

option b - for consideration

• fault action added to environment because it's passed all over the place

option c - for consideration

• merge result and fault actions in AppDelegate, so ResultDelegate would have a nullable Exception argument added

Submitted by Duncan Pierce:

It would be interesting to see how things work out if the fault action were attached to the environment rather than passed as a parameter to the app delegate. We've evolved our own framework of wrappers that work as extension methods around the delegates, which probably biases our view. What we find is that fault gets passed around a lot and yet is hardly ever used in our code. (The framework code does use it though and could in most cases pick it up from environment without user code having to pass it).

[loudej]

Discussed as part of https://github.com/owin/owin/wiki/Meeting---20-jun-2012

Plan of record is to go with C, so all callbacks will have an optional Exception parameter as the final argument