The Event class is not fully supported in State.Compound #643

The documentation section Declaring events states that event can be declared with the Event class "for better IDE support (autocompletion, type checking) or to set a human-readable display name". It seems these advantages can not be used when the Event class is used inside the State.Compound class. When the event = Event(<transition>) form is used inside this class, the event is ignored, and <transition> becomes eventless.

I didn’t find any example in the documentation where events or transitions would be declared using the Event(<transition>) or event = Event(<transition>) forms inside the State.Compound class. However, I also didn’t find any restrictions regarding this.

Let's look at example from the Compound states section with and without Event(...) declaration.

• The original example:

  from statemachine import State, StateChart
  
  class Journey(StateChart):
      class shire(State.Compound):
          bag_end = State(initial=True)
          green_dragon = State()
          visit_pub = bag_end.to(green_dragon)
      road = State(final=True)
      depart = shire.to(road)
  

• And the same example, but with events visit_pub and depart declared using Event(...):

  class QuirkyJourney(StateChart):
      class shire(State.Compound):
          bag_end = State(initial=True)
          green_dragon = State()
          visit_pub = Event(bag_end.to(green_dragon))
      road = State(final=True)
      depart = Event(shire.to(road))
  

The following snippet shows that these machines are not identical:

j = Journey()
qj = QuirkyJourney()

print("Journey SM:")
print(f"  Configuration:  {j.configuration}")
print(f"  Enabled events: {j.enabled_events()}")
j._graph().write_png("j.png")

print("QuirkyJourney SM:")
print(f"  Configuration:  {qj.configuration}")
print(f"  Enabled events: {qj.enabled_events()}")
qj._graph().write_png("qj.png")

Output:

Journey SM:
  Configuration:  {Shire, Bag end}
  Enabled events: [BoundEvent('depart', delay=0, internal=False), BoundEvent('visit_pub', delay=0, internal=False)]
QuirkyJourney SM:
  Configuration:  {Shire, Green dragon}
  Enabled events: [BoundEvent('depart', delay=0, internal=False)]

Images:

• Journey SM:
  

• QuirkyJourney SM:
  

As you can see, the qj transitions to the green_dragon state without receiving the visit_pub event.

I checked the given example with python-statemachine 3.0.0, 3.1.0, 3.2.0 and 3.2.1. All have the same behavior.