Prevent the root object from being garbage collected.

Passing the root object as a return value from a C++ function could
cause the indestructible flag to be set to false.

Change-Id: Ib70c666f0d0ffbb48bca1996c2517fbccafa5dc1
Reviewed-by: Chris Adams <christopher.adams@nokia.com>

src/qml/qml/qqmlcomponent.cpp

@@ -829,7 +829,10 @@ QQmlComponentPrivate::beginCreate(QQmlContextData *context)
     if (rv) {
         QQmlData *ddata = QQmlData::get(rv);
         Q_ASSERT(ddata);
+        //top level objects should never get JS ownership.
+        //if JS ownership is needed this needs to be explicitly undone (like in component.createObject())
         ddata->indestructible = true;
+        ddata->explicitIndestructibleSet = true;
     }
 
     if (enginePriv->isDebugging && rv) {
@@ -1120,7 +1123,8 @@ void QQmlComponent::createObject(QQmlV8Function *args)
     d->completeCreate();
 
     Q_ASSERT(QQmlData::get(rv));
-    QQmlData::get(rv)->setImplicitDestructible();
+    QQmlData::get(rv)->explicitIndestructibleSet = false;
+    QQmlData::get(rv)->indestructible = false;
 
     if (!rv)
         args->returnValue(v8::Null());
@@ -1255,10 +1259,6 @@ void QQmlComponentPrivate::initializeObjectWithInitialProperties(v8::Handle<v8::
         v8::Handle<v8::Value> args[] = { object, valuemap };
         v8::Handle<v8::Function>::Cast(function)->Call(v8engine->global(), 2, args);
     }
-
-    QQmlData *ddata = QQmlData::get(toCreate);
-    Q_ASSERT(ddata);
-    ddata->setImplicitDestructible();
 }
 
 

src/qml/qml/qqmlincubator.cpp

@@ -293,8 +293,9 @@ void QQmlIncubatorPrivate::incubate(QQmlVME::Interrupt &i)
         if (result) {
             QQmlData *ddata = QQmlData::get(result);
             Q_ASSERT(ddata);
+            //see QQmlComponent::beginCreate for explanation of indestructible
             ddata->indestructible = true;
-
+            ddata->explicitIndestructibleSet = true;
             q->setInitialState(result);
         }
 

src/qml/qml/v8/qqmlbuiltinfunctions.cpp

@@ -1097,7 +1097,9 @@ v8::Handle<v8::Value> createQmlObject(const v8::Arguments &args)
 
     QObject *obj = component.beginCreate(effectiveContext);
     if (obj) {
-        QQmlData::get(obj, true)->setImplicitDestructible();
+        QQmlData::get(obj, true)->explicitIndestructibleSet = false;
+        QQmlData::get(obj)->indestructible = false;
+
 
         obj->setParent(parentArg);
 
@@ -1208,7 +1210,9 @@ v8::Handle<v8::Value> createComponent(const v8::Arguments &args)
     QUrl url = context->resolvedUrl(QUrl(arg));
     QQmlComponent *c = new QQmlComponent(engine, url, compileMode, parentArg);
     QQmlComponentPrivate::get(c)->creationContext = effectiveContext;
-    QQmlData::get(c, true)->setImplicitDestructible();
+    QQmlData::get(c, true)->explicitIndestructibleSet = false;
+    QQmlData::get(c)->indestructible = false;
+
     return v8engine->newQObject(c);
 }
 

tests/auto/qml/qqmlecmascript/data/ownershipConsistency.qml

@@ -0,0 +1,21 @@
+import QtQuick 2.0
+
+Item {
+    Loader {
+        source: "PropertyVarBaseItem.qml"
+        onLoaded: item.destroy()
+    }
+    Loader {
+        Component.onCompleted: setSource("PropertyVarBaseItem.qml", { random: "" })
+        onLoaded: item.destroy()
+    }
+
+    Repeater {
+        model: 1
+        Item { Component.onCompleted: destroy() }
+    }
+    Repeater {
+        model: 1
+        Item { id: me; Component.onCompleted: { setObject(me); getObject().destroy() } }
+    }
+}

tests/auto/qml/qqmlecmascript/data/ownershipRootObject.qml

@@ -0,0 +1,6 @@
+import QtQuick 2.0
+
+QtObject {
+    id: root
+    Component.onCompleted: { setObject(root); getObject() }
+}

tests/auto/qml/qqmlecmascript/tst_qqmlecmascript.cpp

@@ -133,6 +133,8 @@ private slots:
     void ownership();
     void cppOwnershipReturnValue();
     void ownershipCustomReturnValue();
+    void ownershipRootObject();
+    void ownershipConsistency();
     void qlistqobjectMethods();
     void strictlyEquals();
     void compiled();
@@ -2939,6 +2941,72 @@ void tst_qqmlecmascript::ownershipCustomReturnValue()
     QVERIFY(source.value == 0);
 }
 
+//the return value from getObject will be JS ownership,
+//unless strong Cpp ownership has been set
+class OwnershipChangingObject : public QObject
+{
+    Q_OBJECT
+public:
+    OwnershipChangingObject(): object(0) { }
+
+    QPointer<QObject> object;
+
+public slots:
+    QObject *getObject() { return object; }
+    void setObject(QObject *obj) { object = obj; }
+};
+
+void tst_qqmlecmascript::ownershipRootObject()
+{
+    OwnershipChangingObject own;
+    QQmlContext *context = new QQmlContext(engine.rootContext());
+    context->setContextObject(&own);
+
+    QQmlComponent component(&engine, testFileUrl("ownershipRootObject.qml"));
+    QQmlGuard<QObject> object = component.create(context);
+    QVERIFY(object);
+
+    engine.collectGarbage();
+
+    QCoreApplication::sendPostedEvents(0, QEvent::DeferredDelete);
+    QCoreApplication::processEvents();
+
+    QVERIFY(own.object != 0);
+
+    delete context;
+    delete object;
+}
+
+void tst_qqmlecmascript::ownershipConsistency()
+{
+    OwnershipChangingObject own;
+    QQmlContext *context = new QQmlContext(engine.rootContext());
+    context->setContextObject(&own);
+
+    QString expectedWarning = testFileUrl("ownershipConsistency.qml").toString() + QLatin1String(":19: Error: Invalid attempt to destroy() an indestructible object");
+    QTest::ignoreMessage(QtWarningMsg, qPrintable(expectedWarning)); // we expect a meaningful warning to be printed.
+    expectedWarning = testFileUrl("ownershipConsistency.qml").toString() + QLatin1String(":15: Error: Invalid attempt to destroy() an indestructible object");
+    QTest::ignoreMessage(QtWarningMsg, qPrintable(expectedWarning)); // we expect a meaningful warning to be printed.
+    expectedWarning = testFileUrl("ownershipConsistency.qml").toString() + QLatin1String(":6: Error: Invalid attempt to destroy() an indestructible object");
+    QTest::ignoreMessage(QtWarningMsg, qPrintable(expectedWarning)); // we expect a meaningful warning to be printed.
+    expectedWarning = testFileUrl("ownershipConsistency.qml").toString() + QLatin1String(":10: Error: Invalid attempt to destroy() an indestructible object");
+    QTest::ignoreMessage(QtWarningMsg, qPrintable(expectedWarning)); // we expect a meaningful warning to be printed.
+
+    QQmlComponent component(&engine, testFileUrl("ownershipConsistency.qml"));
+    QQmlGuard<QObject> object = component.create(context);
+    QVERIFY(object);
+
+    engine.collectGarbage();
+
+    QCoreApplication::sendPostedEvents(0, QEvent::DeferredDelete);
+    QCoreApplication::processEvents();
+
+    QVERIFY(own.object != 0);
+
+    delete context;
+    delete object;
+}
+
 class QListQObjectMethodsObject : public QObject
 {
     Q_OBJECT