Initiating a hierarchical state machine in a nested state does not work in version 0.8.3

[oliver-goetz]

In version 0.8.3 it is not possible to start the state machine in a nested state. Instead an exception is raised. The error can be reproduced using a modified version of the example from README.md

from transitions.extensions import HierarchicalMachine as Machine

states = ['standing', 'walking', {'name': 'caffeinated', 'children':['dithering', 'running']}]
transitions = [
  ['walk', 'standing', 'walking'],
  ['stop', 'walking', 'standing'],
  ['drink', '*', 'caffeinated'],
  ['walk', ['caffeinated', 'caffeinated_dithering'], 'caffeinated_running'],
  ['relax', 'caffeinated', 'standing']
]

machine = Machine(states=states, transitions=transitions, initial='caffeinated_dithering', ignore_invalid_triggers=True)

Creating the instance of Machine raises an exception with this trace:

Traceback (most recent call last):
  File "/usr/local/Cellar/python@3.8/3.8.5/Frameworks/Python.framework/Versions/3.8/lib/python3.8/runpy.py", line 194, in _run_module_as_main
    return _run_code(code, main_globals, None,
  File "/usr/local/Cellar/python@3.8/3.8.5/Frameworks/Python.framework/Versions/3.8/lib/python3.8/runpy.py", line 87, in _run_code
    exec(code, run_globals)
  File "/Users/username/.vscode/extensions/ms-python.python-2020.9.112786/pythonFiles/lib/python/debugpy/__main__.py", line 45, in <module>
    cli.main()
  File "/Users/username/.vscode/extensions/ms-python.python-2020.9.112786/pythonFiles/lib/python/debugpy/../debugpy/server/cli.py", line 430, in main
    run()
  File "/Users/username/.vscode/extensions/ms-python.python-2020.9.112786/pythonFiles/lib/python/debugpy/../debugpy/server/cli.py", line 267, in run_file
    runpy.run_path(options.target, run_name=compat.force_str("__main__"))
  File "/usr/local/Cellar/python@3.8/3.8.5/Frameworks/Python.framework/Versions/3.8/lib/python3.8/runpy.py", line 265, in run_path
    return _run_module_code(code, init_globals, run_name,
  File "/usr/local/Cellar/python@3.8/3.8.5/Frameworks/Python.framework/Versions/3.8/lib/python3.8/runpy.py", line 97, in _run_module_code
    _run_code(code, mod_globals, init_globals,
  File "/usr/local/Cellar/python@3.8/3.8.5/Frameworks/Python.framework/Versions/3.8/lib/python3.8/runpy.py", line 87, in _run_code
    exec(code, run_globals)
  File "/Users/username/development/localhost/python-transitions-0.8.3-test/test.py", line 12, in <module>
    machine = Machine(states=states, transitions=transitions, initial='caffeinated_dithering', ignore_invalid_triggers=True)
  File "/Users/username/.virtualenvs/transitions-venv/lib/python3.8/site-packages/transitions/extensions/nesting.py", line 337, in __init__
    _super(HierarchicalMachine, self).__init__(*args, **kwargs)
  File "/Users/username/.virtualenvs/transitions-venv/lib/python3.8/site-packages/transitions/core.py", line 568, in __init__
    self.initial = initial
  File "/Users/username/.virtualenvs/transitions-venv/lib/python3.8/site-packages/transitions/core.py", line 639, in initial
    self.add_state(state_name)
  File "/Users/username/.virtualenvs/transitions-venv/lib/python3.8/site-packages/transitions/core.py", line 740, in add_state
    self.add_states(*args, **kwargs)
  File "/Users/username/.virtualenvs/transitions-venv/lib/python3.8/site-packages/transitions/extensions/nesting.py", line 434, in add_states
    self.add_states(domains[1], on_enter=on_enter, on_exit=on_exit, ignore_invalid_triggers=ignore_invalid_triggers, **kwargs)
  File "/Users/username/.virtualenvs/transitions-venv/lib/python3.8/site-packages/transitions/extensions/nesting.py", line 437, in add_states
    raise ValueError("State {0} cannot be added since it already exists.".format(state))
ValueError: State dithering cannot be added since it already exists.

Up to version 0.7.2 it was possible to start a state machine in a nested state and I would except the same for the newer versions.

[aleneum]

This should work with 0.8.4 now. Feel free to comment if issues still persist. I will reopen this ticket when required.

[oliver-goetz]

I can confirm, that it is working in version 0.8.4. Thank you 😄