Add StateMachine.StateWithArgs

statemachine.go

@@ -148,6 +148,12 @@ func (sm *StateMachine) State(ctx context.Context) (State, error) {
 	return state, err
 }
 
+// StateWithArgs returns the current state along with any arguments that were passed to the state mutator.
+// This is useful when using NewStateMachineWithExternalStorageAndArgs to retain additional state information.
+func (sm *StateMachine) StateWithArgs(ctx context.Context) (State, []any, error) {
+	return sm.stateAccessor(ctx)
+}
+
 // MustState returns the current state without the error.
 // It is safe to use this method when used together with NewStateMachine
 // or when using NewStateMachineWithExternalStorage / NewStateMachineWithExternalStorageAndArgs with a state accessor that

statemachine_test.go

@@ -106,6 +106,104 @@ func TestStateMachine_NewStateMachineWithExternalStorageAndArgs(t *testing.T) {
 	}
 }
 
+func TestStateMachine_StateWithArgs(t *testing.T) {
+	sm := NewStateMachine(stateA)
+	sm.Configure(stateA).Permit(triggerX, stateB)
+
+	state, args, err := sm.StateWithArgs(context.Background())
+	if err != nil {
+		t.Errorf("StateWithArgs() error = %v, want nil", err)
+	}
+	if state != stateA {
+		t.Errorf("StateWithArgs() state = %v, want %v", state, stateA)
+	}
+	if args != nil {
+		t.Errorf("StateWithArgs() args = %v, want nil", args)
+	}
+}
+
+func TestStateMachine_StateWithArgs_ExternalStorage(t *testing.T) {
+	var state State = stateB
+	sm := NewStateMachineWithExternalStorage(func(_ context.Context) (State, error) {
+		return state, nil
+	}, func(_ context.Context, s State) error {
+		state = s
+		return nil
+	}, FiringImmediate)
+
+	gotState, gotArgs, err := sm.StateWithArgs(context.Background())
+	if err != nil {
+		t.Errorf("StateWithArgs() error = %v, want nil", err)
+	}
+	if gotState != stateB {
+		t.Errorf("StateWithArgs() state = %v, want %v", gotState, stateB)
+	}
+	if gotArgs != nil {
+		t.Errorf("StateWithArgs() args = %v, want nil", gotArgs)
+	}
+}
+
+func TestStateMachine_StateWithArgs_ExternalStorageAndArgs(t *testing.T) {
+	var state State = stateB
+	var args = []any{"arg1", 42, errors.New("test error")}
+	sm := NewStateMachineWithExternalStorageAndArgs(func(_ context.Context) (State, []any, error) {
+		return state, args, nil
+	}, func(_ context.Context, s State, a ...any) error {
+		state = s
+		args = a
+		return nil
+	}, FiringImmediate)
+	sm.Configure(stateB).Permit(triggerX, stateC)
+
+	gotState, gotArgs, err := sm.StateWithArgs(context.Background())
+	if err != nil {
+		t.Errorf("StateWithArgs() error = %v, want nil", err)
+	}
+	if gotState != stateB {
+		t.Errorf("StateWithArgs() state = %v, want %v", gotState, stateB)
+	}
+	if !reflect.DeepEqual(gotArgs, args) {
+		t.Errorf("StateWithArgs() args = %v, want %v", gotArgs, args)
+	}
+	if got := gotArgs[0].(string); got != "arg1" {
+		t.Errorf("expected arg 0 to be %v, got %v", "arg1", got)
+	}
+	if got := gotArgs[1].(int); got != 42 {
+		t.Errorf("expected arg 1 to be %v, got %v", 42, got)
+	}
+	if got := gotArgs[2].(error).Error(); got != "test error" {
+		t.Errorf("expected arg 2 to be %v, got %v", "test error", got)
+	}
+
+	// Fire a transition with new arguments
+	sm.Fire(triggerX, "arg2", 99)
+	gotState, gotArgs, err = sm.StateWithArgs(context.Background())
+	if err != nil {
+		t.Errorf("StateWithArgs() error = %v, want nil", err)
+	}
+	if gotState != stateC {
+		t.Errorf("StateWithArgs() state = %v, want %v", gotState, stateC)
+	}
+	if got := gotArgs[0].(string); got != "arg2" {
+		t.Errorf("expected arg 0 to be %v, got %v", "arg2", got)
+	}
+	if got := gotArgs[1].(int); got != 99 {
+		t.Errorf("expected arg 1 to be %v, got %v", 99, got)
+	}
+}
+
+func TestStateMachine_StateWithArgs_Error(t *testing.T) {
+	sm := NewStateMachineWithExternalStorage(func(_ context.Context) (State, error) {
+		return nil, errors.New("state accessor error")
+	}, func(_ context.Context, s State) error { return nil }, FiringImmediate)
+
+	_, _, err := sm.StateWithArgs(context.Background())
+	want := "state accessor error"
+	if err == nil || err.Error() != want {
+		t.Errorf("StateWithArgs() error = %v, want %v", err, want)
+	}
+}
+
 func TestStateMachine_Configure_SubstateIsIncludedInCurrentState(t *testing.T) {
 	sm := NewStateMachine(stateB)
 	sm.Configure(stateB).SubstateOf(stateC)