Apichange beforeafter

[da-h]

Api-Change for: Before/After Events

This PR changes the way before_eventname/after_eventname events communicate with their caller (namely the event with the according name eventname.

Attention: This is a breaking change.

Reason for this change is that these kinds of events could not switch position (change execution from before to after or vice versa) and could not be used as a standalone without changing the function signatures. This PR solves this issue by improving the API of these events.

API-Proposal:

• Any before_/after_ event gets called with a unique event object, that behaves just like the normal event object.
• This new event-object has a dict-attribute .hook
• before_-events can read and manipulate the function call arguments before the actual event will be called using event.hook["args"] and event.hook["kwargs"]
• after_-events can read the function call arguments after the actual event has been called with (including the changes of potential before_-hooks using event.hook["args"] and event.hook["kwargs"]
  (Note: Any modification will only change the arguments for future after_-events but not for the function call itself.)
• after_-events can additionally alternate the return value of the event by modifying event.hook["result"].
• both event types can access the name of the actual event-name using event.hook["name"]

---

Example Module:

def dosomething(val):
    print("event called with value: %i" % val)
    return val

def main(event):
    print("event returned value: %i" % event.dosomething(42))

def before_dosomething(event):
    print("before_-event called")
    event.hook["args"][0] *= 2

def after_dosomethingl(event):
    print("after_-event called")
    event.hook["result"] += 1

def register(mf):
    mf.register_event('dosomething', dosomething)
    mf.register_event('main', main)
    mf.register_event('before_dosomething', before_dosomething, unique=False)
    mf.register_event('after_dosomething', after_dosomething, unique=False)

Running this module should result in the following output:

before_-event called
event called with value: 84
after_-event called
event returned value: 85