More granular action sequencing

[emptierset]

Thank you for your help with my last question.

I've reproduced the order of actions from RTD for our convenience:

Validators
Conditions
Before (transition)
Exit (state)
On (transition)

Current state is updated.

Enter (state)
After (transition)

Is there a way to sequence the on actions or to insert actions between on and enter? I have some actions that produce logging that I want to run last among the on actions. My original idea was to run them after, but that is after the state change, and many things could have happened on enter that I wouldn't want to happen beforehand.

[fgmacedo]

Hi @emptierset , how are you?

Eventually, one day, all actions in the same "group" could run in parallel. Currently, they run in sequence in the sync engine and concurrently on the asynchronous engine (using asyncio.gather).

Assuming that you are using the sync engine (no async callbacks), there's a second level of priority that you can use, but it's still an implementation detail that can change in the future: It's the Callback priority order by how they are registered. All the priorities are in the example: https://python-statemachine.readthedocs.io/en/latest/auto_examples/all_actions_machine.html#testing

The priorities:

python-statemachine/statemachine/callbacks.py

Lines 26 to 31 in 4449a9c

	class CallbackPriority(IntEnum):
	GENERIC = 0
	INLINE = 10
	DECORATOR = 20
	NAMING = 30
	AFTER = 40

This means that the callbacks of the same group are ordered when inserted on the list, and for the sync engine they are executed sequentially, so callbacks of generic name convention like on_transition are executed before the specific on_<event> ones, and before registered by using the decorator syntax, and so on, just for example.

The short answer is that there's not yet a Public contract in an order, but if you can rely on an implementation detail, they are ordered.

Best!

[emptierset]

Thanks for the info. I ended up just smooshing multiple on actions into the same function to get orderedness guarantees.