# machina-factory-bugcase

A demonstration of a bug in machina v2.0.2, where a child FSM factory is called erroneously during any `handle` command that's received by a child FSM, even if no state transition takes place in the parent.

What should happen:

```
(fsm.0) Parent state 1 reached
Creating child for state 2
(fsm.1) Child state A reached
(fsm.0) Parent state 2 reached
(fsm.1) Child state B reached
Creating child for state 3
(fsm.2) Child state A reached
(fsm.0) Parent state 3 reached
(fsm.2) Child state B reached
Parent done! Returning to state 2 one last time...
Creating child for state 2
(fsm.3) Child state A reached
(fsm.0) Parent state 2 reached
(fsm.3) Child state B reached
```

What happens instead:

```
(fsm.0) Parent state 1 reached
Creating child for state 2
(fsm.1) Child state A reached
(fsm.0) Parent state 2 reached
Creating child for state 2
(fsm.2) Child state A reached
(fsm.2) Child state B reached
Creating child for state 2
(fsm.3) Child state A reached
Creating child for state 3
(fsm.4) Child state A reached
(fsm.0) Parent state 3 reached
Creating child for state 3
(fsm.5) Child state A reached
(fsm.5) Child state B reached
Creating child for state 3
(fsm.6) Child state A reached
Parent done! Returning to state 2 one last time...
Creating child for state 2
(fsm.7) Child state A reached
(fsm.0) Parent state 2 reached
Creating child for state 2
(fsm.8) Child state A reached
(fsm.8) Child state B reached
Creating child for state 2
(fsm.9) Child state A reached
```

The result is even more wrong when this bug is combined with the duplicate FSM creation bug (as demonstrated in the `master` branch of this repository):

```
(fsm.0) Parent state 1 reached
Creating child for state 2
(fsm.1) Child state A reached
Creating child for state 2
(fsm.2) Child state A reached
(fsm.0) Parent state 2 reached
Creating child for state 2
(fsm.3) Child state A reached
Creating child for state 2
(fsm.4) Child state A reached
(fsm.4) Child state B reached
Creating child for state 2
(fsm.5) Child state A reached
Creating child for state 2
(fsm.6) Child state A reached
Creating child for state 3
(fsm.7) Child state A reached
Creating child for state 3
(fsm.8) Child state A reached
(fsm.0) Parent state 3 reached
Creating child for state 3
(fsm.9) Child state A reached
Creating child for state 3
(fsm.10) Child state A reached
(fsm.10) Child state B reached
Creating child for state 3
(fsm.11) Child state A reached
Creating child for state 3
(fsm.12) Child state A reached
Parent done! Returning to state 2 one last time...
Creating child for state 2
(fsm.13) Child state A reached
Creating child for state 2
(fsm.14) Child state A reached
(fsm.0) Parent state 2 reached
Creating child for state 2
(fsm.15) Child state A reached
Creating child for state 2
(fsm.16) Child state A reached
(fsm.16) Child state B reached
Creating child for state 2
(fsm.17) Child state A reached
Creating child for state 2
(fsm.18) Child state A reached
```