Merge pull request #73 from qmuntal/substatereentry

Don't execute entry action when reentering a state from a super state trigger

statemachine.go

@@ -354,6 +354,10 @@ func (sm *StateMachine) internalFireOne(ctx context.Context, trigger Trigger, ar
 			err = sm.handleTransitioningTrigger(ctx, representativeState, transition, args...)
 		}
 	case *transitioningTriggerBehaviour:
+		if source == t.Destination {
+			// If a trigger was found on a superstate that would cause unintended reentry, don't trigger.
+			break
+		}
 		transition := Transition{Source: source, Destination: t.Destination, Trigger: trigger}
 		err = sm.handleTransitioningTrigger(ctx, representativeState, transition, args...)
 	case *internalTriggerBehaviour:

statemachine_test.go

@@ -1612,3 +1612,28 @@ func assertPanic(t *testing.T, f func()) {
 	}()
 	f()
 }
+
+func TestStateMachineWhenInSubstate_TriggerSuperStateTwiceToSameSubstate_DoesNotReenterSubstate(t *testing.T) {
+	sm := NewStateMachine(stateA)
+	var eCount = 0
+
+	sm.Configure(stateB).
+		OnEntry(func(_ context.Context, _ ...any) error {
+			eCount++
+			return nil
+		}).
+		SubstateOf(stateC)
+
+	sm.Configure(stateA).
+		SubstateOf(stateC)
+
+	sm.Configure(stateC).
+		Permit(triggerX, stateB)
+
+	sm.Fire(triggerX)
+	sm.Fire(triggerX)
+
+	if eCount != 1 {
+		t.Errorf("expected 1, got %d", eCount)
+	}
+}