How to express Compound and Parallel states?

[fgmacedo]

The thing that I like the most when using this lib is how you can directly map and express a statemachine into code, in a way that when you're reading the Statemachine you're also learning about the available states and transitions in a clear and concise code.

How we may express Compound and Parallel states in code with a pythonic API?

Here's my first thoughs, let me know what do you think about this speudo code. I'm using the microwave example on the scxml docs:

from statemachine import StateMachine, State, Parallel, Compound


class Microwave(StateMachine):
    oven = State('Green', initial=True)
    yellow = State('Yellow')
    red = State('Red')

    @Parallel
    class oven:

        @Compound
        class engine: # tracks the microwave state and timer
            off = State(initial=True)

            @Compound
            class on:
                iddle = State(initial=True)
                cooking = State()

                cooking.to(idle, cond=is_open)
                idle.to(cooking, cond=is_closed)

            on.to(iddle)
            on.to(off, cond=cook_time_is_over)

            turn_on = off.to(on)
            turn_off = on.to(off)
            
        @Compound
        class door:  # tracks the microwave door state
            closed = State(initial=True)
            open = State()

            door_open = closed.to(open)
            door_close = open.to(closed)

[rafaelrds]

I really enjoy this work at first glance. ❤️. I'll read the docs more thoroughly before giving a second opinion.
A question here is if we want to aim for full compatibility with SCXML? That might be nice for exporting State Machines into SCXML since it has lots of applications in the industry.

[fgmacedo]

I think that full compatibility would be nice. For export purposes, we don't need full support, as statemachines are a subset of statecharts/scxml.

[brunolnetto]

I find this syntax suitable for the issue related to nested state machines. It suits also for parallel state machines, but the developer must be aware on running blocking conditions. In this case, it is suggestive to validate the whole against these blocking parallel pathways.