Improve isolation in HSM (for reuse and export) - Githubissues

pytransitions / transitions

A lightweight, object-oriented finite state machine implementation in Python with many extensions

MIT License

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Improve isolation in HSM (for reuse and export) #362

Closed aleneum closed 4 years ago

aleneum commented 4 years ago

Currently, it can be tough to reuse modules if the content and state names are not known (see #332).

Current Issues

name collision: Since all callbacks/convenience functions are added to the same (set of) model(s), there is a risk of
configuration is tricky: you cannot just assign a machine as a substate and be done with it

Required (currently available) features

dispatch: unknown events in submachine should be dispatched to parents
override: it should be possible to hook into submachine events and override behaviour

New Features

it should not be necessary to tinker with models when adding a machine to an HSM
nested models could be used to avoid collisions
Machine.states may only contain root level states and forwards event_handling to NestedState if necessary

NestedState:
    name: 'StateName'
    states: []  # list of NestedState
    models: []  # list of local models

aleneum commented 4 years ago

I opted for (shared) nested states and events and used context managers to readjust the current scope of a Machine. This leads to recursive code and frequent tree searches. "Deep-first" vs "Breadth-first" strategies had to be applied to get the callback execution order (hopefully) right.