statemachine: Fix state entry bug for parallel state groups

The SCXML spec had a bug that would cause the initial state of a
compound state within a parallel state group to be entered even if
the transition specified another (non-initial) state of the compound
state as its target. This only happened if the transition had
multiple target states.

The bug has been fixed in recent revisions of the SCXML spec. This
commit implements the fix, which is to walk the ancestors of the
transition's target states only after all the target states
themselves have been added, so that the default initial states are
correctly overridden/ignored.

Task-number: QTBUG-25958
Change-Id: Iac532047678c483a4a3996e24dacf30e00f6bbe0
Reviewed-by: Eskil Abrahamsen Blomfeldt <eskil.abrahamsen-blomfeldt@nokia.com>

2 files changed, 37 insertions, 23 deletions

diff --git a/src/corelib/statemachine/qstatemachine.cpp b/src/corelib/statemachine/qstatemachine.cpp
index ccc40ac9b4..5adb6c3fb1 100644
--- a/src/corelib/statemachine/qstatemachine.cpp
+++ b/src/corelib/statemachine/qstatemachine.cpp
@@ -518,6 +518,10 @@ QList<QAbstractState*> QStateMachinePrivate::computeStatesToEnter(const QList<QA
                 QAbstractState *s = lst.at(j);
                 addStatesToEnter(s, lca, statesToEnter, statesForDefaultEntry);
             }
+            for (int j = src ? 1 : 0; j < lst.size(); ++j) {
+                QAbstractState *s = lst.at(j);
+                addAncestorStatesToEnter(s, lca, statesToEnter, statesForDefaultEntry);
+            }
             if (isParallel(lca)) {
                 QList<QAbstractState*> lcac = QStatePrivate::get(lca)->childStates();
                 foreach (QAbstractState* child,lcac) {
@@ -715,32 +719,38 @@ void QStateMachinePrivate::addStatesToEnter(QAbstractState *s, QState *root,
 				return;
 			}
 		}
-		QList<QState*> ancs = properAncestors(s, root);
-		for (int i = 0; i < ancs.size(); ++i) {
-			QState *anc = ancs.at(i);
-			if (!anc->parentState())
-				continue;
-			statesToEnter.insert(anc);
-			if (isParallel(anc)) {
-				QList<QAbstractState*> lst = QStatePrivate::get(anc)->childStates();
-				for (int j = 0; j < lst.size(); ++j) {
-					QAbstractState *child = lst.at(j);
-					bool hasDescendantInList = false;
-					QSet<QAbstractState*>::const_iterator it;
-					for (it = statesToEnter.constBegin(); it != statesToEnter.constEnd(); ++it) {
-						if (isDescendantOf(*it, child)) {
-							hasDescendantInList = true;
-							break;
-						}
-					}
-					if (!hasDescendantInList)
-						addStatesToEnter(child, anc, statesToEnter, statesForDefaultEntry);
-				}
-			}
-		}
 	}
 }
 
+void QStateMachinePrivate::addAncestorStatesToEnter(QAbstractState *s, QState *root,
+                                                    QSet<QAbstractState*> &statesToEnter,
+                                                    QSet<QAbstractState*> &statesForDefaultEntry)
+{
+    QList<QState*> ancs = properAncestors(s, root);
+    for (int i = 0; i < ancs.size(); ++i) {
+        QState *anc = ancs.at(i);
+        if (!anc->parentState())
+            continue;
+        statesToEnter.insert(anc);
+        if (isParallel(anc)) {
+            QList<QAbstractState*> lst = QStatePrivate::get(anc)->childStates();
+            for (int j = 0; j < lst.size(); ++j) {
+                QAbstractState *child = lst.at(j);
+                bool hasDescendantInList = false;
+                QSet<QAbstractState*>::const_iterator it;
+                for (it = statesToEnter.constBegin(); it != statesToEnter.constEnd(); ++it) {
+                    if (isDescendantOf(*it, child)) {
+                        hasDescendantInList = true;
+                        break;
+                    }
+                }
+                if (!hasDescendantInList)
+                    addStatesToEnter(child, anc, statesToEnter, statesForDefaultEntry);
+            }
+        }
+    }
+}
+
 bool QStateMachinePrivate::isFinal(const QAbstractState *s)
 {
     return s && (QAbstractStatePrivate::get(s)->stateType == QAbstractStatePrivate::FinalState);
@@ -1077,6 +1087,7 @@ void QStateMachinePrivate::setError(QStateMachine::Error errorCode, QAbstractSta
     if (currentErrorState != 0) {    
         QState *lca = findLCA(QList<QAbstractState*>() << currentErrorState << currentContext);
         addStatesToEnter(currentErrorState, lca, pendingErrorStates, pendingErrorStatesForDefaultEntry);
+        addAncestorStatesToEnter(currentErrorState, lca, pendingErrorStates, pendingErrorStatesForDefaultEntry);
     } else {
         qWarning("Unrecoverable error detected in running state machine: %s", 
                  qPrintable(errorString));
diff --git a/src/corelib/statemachine/qstatemachine_p.h b/src/corelib/statemachine/qstatemachine_p.h
index 423c077a83..113f17f973 100644
--- a/src/corelib/statemachine/qstatemachine_p.h
+++ b/src/corelib/statemachine/qstatemachine_p.h
@@ -150,6 +150,9 @@ public:
     void addStatesToEnter(QAbstractState *s, QState *root,
                           QSet<QAbstractState*> &statesToEnter,
                           QSet<QAbstractState*> &statesForDefaultEntry);
+    void addAncestorStatesToEnter(QAbstractState *s, QState *root,
+                                  QSet<QAbstractState*> &statesToEnter,
+                                  QSet<QAbstractState*> &statesForDefaultEntry);
 
     static QState *toStandardState(QAbstractState *state);
     static const QState *toStandardState(const QAbstractState *state);