Implement QObject ownership policy for QObject JavaScript wrappers

A parent with C++ ownership keeps its children alive. We know that all
QObject wrappers are kept in a QWeakValue inside the QObject's QQmlData.
As the weak values are registered to the MM, we can traverse there and
mark the children if necessary in one extra pass.

The handleReferenceManagement auto-test that covers this was actually
testing the addGCRelationship implementation as well as the overal behavior.
Some of the tests verify that a handle based overload of addGCRelationship
works, so since those tests don't make sense anymore, I've removed them.

Also fixed some cases where the test ran gc(engine) when it should've called
gc() on the specific local QQmlEngine instance used in the test. This worked
in V8 because the GC was "global".

Change-Id: Ib394b46e034b016196804a9e73682507fa791445
Reviewed-by: Lars Knoll <lars.knoll@digia.com>

1 files changed, 3 insertions, 230 deletions

diff --git a/tests/auto/qml/qqmlecmascript/tst_qqmlecmascript.cpp b/tests/auto/qml/qqmlecmascript/tst_qqmlecmascript.cpp
index 0aec42a811..60a087ec72 100644
--- a/tests/auto/qml/qqmlecmascript/tst_qqmlecmascript.cpp
+++ b/tests/auto/qml/qqmlecmascript/tst_qqmlecmascript.cpp
@@ -182,7 +182,7 @@ private slots:
     void objectPassThroughSignals();
     void objectConversion();
     void booleanConversion();
-//    void handleReferenceManagement();
+    void handleReferenceManagement();
     void stringArg();
     void readonlyDeclaration();
     void sequenceConversionRead();
@@ -5003,10 +5003,8 @@ void tst_qqmlecmascript::booleanConversion()
     delete object;
 }
 
-#if 0
 void tst_qqmlecmascript::handleReferenceManagement()
 {
-
     int dtorCount = 0;
     {
         // Linear QObject reference
@@ -5018,7 +5016,7 @@ void tst_qqmlecmascript::handleReferenceManagement()
         cro->setEngine(&hrmEngine);
         cro->setDtorCount(&dtorCount);
         QMetaObject::invokeMethod(object, "createReference");
-        gc(engine);
+        gc(hrmEngine);
         QCOMPARE(dtorCount, 0); // second has JS ownership, kept alive by first's reference
         delete object;
         hrmEngine.collectGarbage();
@@ -5038,7 +5036,7 @@ void tst_qqmlecmascript::handleReferenceManagement()
         cro->setEngine(&hrmEngine);
         cro->setDtorCount(&dtorCount);
         QMetaObject::invokeMethod(object, "circularReference");
-        gc(engine);
+        gc(hrmEngine);
         QCOMPARE(dtorCount, 2); // both should be cleaned up, since circular references shouldn't keep alive.
         delete object;
         hrmEngine.collectGarbage();
@@ -5047,230 +5045,6 @@ void tst_qqmlecmascript::handleReferenceManagement()
         QCOMPARE(dtorCount, 3);
     }
 
-    dtorCount = 0;
-    {
-        // Linear handle reference
-        QQmlEngine hrmEngine;
-        QQmlComponent component(&hrmEngine, testFileUrl("handleReferenceManagement.handle.1.qml"));
-        QObject *object = component.create();
-        QVERIFY(object != 0);
-        CircularReferenceHandle *crh = object->findChild<CircularReferenceHandle*>("crh");
-        QVERIFY(crh != 0);
-        crh->setEngine(&hrmEngine);
-        crh->setDtorCount(&dtorCount);
-        QMetaObject::invokeMethod(object, "createReference");
-        CircularReferenceHandle *first = object->property("first").value<CircularReferenceHandle*>();
-        CircularReferenceHandle *second = object->property("second").value<CircularReferenceHandle*>();
-        QVERIFY(first != 0);
-        QVERIFY(second != 0);
-        first->addReference(QQmlData::get(second)->v8object); // create reference
-        // now we have to reparent second and make second owned by JS.
-        second->setParent(0);
-        QQmlEngine::setObjectOwnership(second, QQmlEngine::JavaScriptOwnership);
-        gc(engine);
-        QCOMPARE(dtorCount, 0); // due to reference from first to second, second shouldn't be collected.
-        delete object;
-        hrmEngine.collectGarbage();
-        QCoreApplication::sendPostedEvents(0, QEvent::DeferredDelete);
-        QCoreApplication::processEvents();
-        QCOMPARE(dtorCount, 3);
-    }
-
-    dtorCount = 0;
-    {
-        // Circular handle reference
-        QQmlEngine hrmEngine;
-        QQmlComponent component(&hrmEngine, testFileUrl("handleReferenceManagement.handle.2.qml"));
-        QObject *object = component.create();
-        QVERIFY(object != 0);
-        CircularReferenceHandle *crh = object->findChild<CircularReferenceHandle*>("crh");
-        QVERIFY(crh != 0);
-        crh->setEngine(&hrmEngine);
-        crh->setDtorCount(&dtorCount);
-        QMetaObject::invokeMethod(object, "circularReference");
-        CircularReferenceHandle *first = object->property("first").value<CircularReferenceHandle*>();
-        CircularReferenceHandle *second = object->property("second").value<CircularReferenceHandle*>();
-        QVERIFY(first != 0);
-        QVERIFY(second != 0);
-        first->addReference(QQmlData::get(second)->v8object); // create circular reference
-        second->addReference(QQmlData::get(first)->v8object); // note: must be weak.
-        // now we have to reparent and change ownership, and unset the property references.
-        first->setParent(0);
-        second->setParent(0);
-        QQmlEngine::setObjectOwnership(first, QQmlEngine::JavaScriptOwnership);
-        QQmlEngine::setObjectOwnership(second, QQmlEngine::JavaScriptOwnership);
-        object->setProperty("first", QVariant::fromValue<QObject*>(0));
-        object->setProperty("second", QVariant::fromValue<QObject*>(0));
-        gc(engine);
-        QCOMPARE(dtorCount, 2); // despite circular references, both will be collected.
-        delete object;
-        hrmEngine.collectGarbage();
-        QCoreApplication::sendPostedEvents(0, QEvent::DeferredDelete);
-        QCoreApplication::processEvents();
-        QCOMPARE(dtorCount, 3);
-    }
-
-    dtorCount = 0;
-    {
-        // multiple engine interaction - linear reference
-        QQmlEngine hrmEngine1;
-        QQmlEngine hrmEngine2;
-        QQmlComponent component1(&hrmEngine1, testFileUrl("handleReferenceManagement.handle.1.qml"));
-        QQmlComponent component2(&hrmEngine2, testFileUrl("handleReferenceManagement.handle.1.qml"));
-        QObject *object1 = component1.create();
-        QObject *object2 = component2.create();
-        QVERIFY(object1 != 0);
-        QVERIFY(object2 != 0);
-        CircularReferenceHandle *crh1 = object1->findChild<CircularReferenceHandle*>("crh");
-        CircularReferenceHandle *crh2 = object2->findChild<CircularReferenceHandle*>("crh");
-        QVERIFY(crh1 != 0);
-        QVERIFY(crh2 != 0);
-        crh1->setEngine(&hrmEngine1);
-        crh2->setEngine(&hrmEngine2);
-        crh1->setDtorCount(&dtorCount);
-        crh2->setDtorCount(&dtorCount);
-        QMetaObject::invokeMethod(object1, "createReference");
-        QMetaObject::invokeMethod(object2, "createReference");
-        CircularReferenceHandle *first1 = object1->property("first").value<CircularReferenceHandle*>();
-        CircularReferenceHandle *second1 = object1->property("second").value<CircularReferenceHandle*>();
-        CircularReferenceHandle *first2 = object2->property("first").value<CircularReferenceHandle*>();
-        CircularReferenceHandle *second2 = object2->property("second").value<CircularReferenceHandle*>();
-        QVERIFY(first1 != 0);
-        QVERIFY(second1 != 0);
-        QVERIFY(first2 != 0);
-        QVERIFY(second2 != 0);
-        first1->addReference(QQmlData::get(second2)->v8object); // create reference across engines
-        // now we have to reparent second2 and make second2 owned by JS.
-        second2->setParent(0);
-        QQmlEngine::setObjectOwnership(second2, QQmlEngine::JavaScriptOwnership);
-        gc(engine);
-        QCoreApplication::sendPostedEvents(0, QEvent::DeferredDelete);
-        QCoreApplication::processEvents();
-        QCOMPARE(dtorCount, 0); // due to reference from first1 to second2, second2 shouldn't be collected.
-        delete object1;
-        delete object2;
-        hrmEngine1.collectGarbage();
-        hrmEngine2.collectGarbage();
-        QCoreApplication::sendPostedEvents(0, QEvent::DeferredDelete);
-        QCoreApplication::processEvents();
-        QCOMPARE(dtorCount, 6);
-    }
-
-    dtorCount = 0;
-    {
-        // multiple engine interaction - circular reference
-        QQmlEngine hrmEngine1;
-        QQmlEngine hrmEngine2;
-        QQmlComponent component1(&hrmEngine1, testFileUrl("handleReferenceManagement.handle.1.qml"));
-        QQmlComponent component2(&hrmEngine2, testFileUrl("handleReferenceManagement.handle.1.qml"));
-        QObject *object1 = component1.create();
-        QObject *object2 = component2.create();
-        QVERIFY(object1 != 0);
-        QVERIFY(object2 != 0);
-        CircularReferenceHandle *crh1 = object1->findChild<CircularReferenceHandle*>("crh");
-        CircularReferenceHandle *crh2 = object2->findChild<CircularReferenceHandle*>("crh");
-        QVERIFY(crh1 != 0);
-        QVERIFY(crh2 != 0);
-        crh1->setEngine(&hrmEngine1);
-        crh2->setEngine(&hrmEngine2);
-        crh1->setDtorCount(&dtorCount);
-        crh2->setDtorCount(&dtorCount);
-        QMetaObject::invokeMethod(object1, "createReference");
-        QMetaObject::invokeMethod(object2, "createReference");
-        CircularReferenceHandle *first1 = object1->property("first").value<CircularReferenceHandle*>();
-        CircularReferenceHandle *second1 = object1->property("second").value<CircularReferenceHandle*>();
-        CircularReferenceHandle *first2 = object2->property("first").value<CircularReferenceHandle*>();
-        CircularReferenceHandle *second2 = object2->property("second").value<CircularReferenceHandle*>();
-        QVERIFY(first1 != 0);
-        QVERIFY(second1 != 0);
-        QVERIFY(first2 != 0);
-        QVERIFY(second2 != 0);
-        first1->addReference(QQmlData::get(second1)->v8object);  // create linear reference within engine1
-        second1->addReference(QQmlData::get(second2)->v8object); // create linear reference across engines
-        second2->addReference(QQmlData::get(first2)->v8object);  // create linear reference within engine2
-        first2->addReference(QQmlData::get(first1)->v8object);   // close the loop - circular ref across engines
-        // now we have to reparent and change ownership to JS, and remove property references.
-        first1->setParent(0);
-        second1->setParent(0);
-        first2->setParent(0);
-        second2->setParent(0);
-        QQmlEngine::setObjectOwnership(first1, QQmlEngine::JavaScriptOwnership);
-        QQmlEngine::setObjectOwnership(second1, QQmlEngine::JavaScriptOwnership);
-        QQmlEngine::setObjectOwnership(first2, QQmlEngine::JavaScriptOwnership);
-        QQmlEngine::setObjectOwnership(second2, QQmlEngine::JavaScriptOwnership);
-        object1->setProperty("first", QVariant::fromValue<QObject*>(0));
-        object1->setProperty("second", QVariant::fromValue<QObject*>(0));
-        object2->setProperty("first", QVariant::fromValue<QObject*>(0));
-        object2->setProperty("second", QVariant::fromValue<QObject*>(0));
-        gc(engine);
-        QCoreApplication::sendPostedEvents(0, QEvent::DeferredDelete);
-        QCoreApplication::processEvents();
-        QCOMPARE(dtorCount, 4); // circular references shouldn't keep them alive.
-        delete object1;
-        delete object2;
-        hrmEngine1.collectGarbage();
-        hrmEngine2.collectGarbage();
-        QCoreApplication::sendPostedEvents(0, QEvent::DeferredDelete);
-        QCoreApplication::processEvents();
-        QCOMPARE(dtorCount, 6);
-    }
-
-    dtorCount = 0;
-    {
-        // multiple engine interaction - linear reference with engine deletion
-        QQmlEngine *hrmEngine1 = new QQmlEngine;
-        QQmlEngine *hrmEngine2 = new QQmlEngine;
-        QQmlComponent component1(hrmEngine1, testFileUrl("handleReferenceManagement.handle.1.qml"));
-        QQmlComponent component2(hrmEngine2, testFileUrl("handleReferenceManagement.handle.1.qml"));
-        QObject *object1 = component1.create();
-        QObject *object2 = component2.create();
-        QVERIFY(object1 != 0);
-        QVERIFY(object2 != 0);
-        CircularReferenceHandle *crh1 = object1->findChild<CircularReferenceHandle*>("crh");
-        CircularReferenceHandle *crh2 = object2->findChild<CircularReferenceHandle*>("crh");
-        QVERIFY(crh1 != 0);
-        QVERIFY(crh2 != 0);
-        crh1->setEngine(hrmEngine1);
-        crh2->setEngine(hrmEngine2);
-        crh1->setDtorCount(&dtorCount);
-        crh2->setDtorCount(&dtorCount);
-        QMetaObject::invokeMethod(object1, "createReference");
-        QMetaObject::invokeMethod(object2, "createReference");
-        CircularReferenceHandle *first1 = object1->property("first").value<CircularReferenceHandle*>();
-        CircularReferenceHandle *second1 = object1->property("second").value<CircularReferenceHandle*>();
-        CircularReferenceHandle *first2 = object2->property("first").value<CircularReferenceHandle*>();
-        CircularReferenceHandle *second2 = object2->property("second").value<CircularReferenceHandle*>();
-        QVERIFY(first1 != 0);
-        QVERIFY(second1 != 0);
-        QVERIFY(first2 != 0);
-        QVERIFY(second2 != 0);
-        first1->addReference(QQmlData::get(second1)->v8object);  // create linear reference within engine1
-        second1->addReference(QQmlData::get(second2)->v8object); // create linear reference across engines
-        second2->addReference(QQmlData::get(first2)->v8object);  // create linear reference within engine2
-        // now we have to reparent and change ownership to JS.
-        first1->setParent(crh1);
-        second1->setParent(0);
-        first2->setParent(0);
-        second2->setParent(0);
-        QQmlEngine::setObjectOwnership(second1, QQmlEngine::JavaScriptOwnership);
-        QQmlEngine::setObjectOwnership(first2, QQmlEngine::JavaScriptOwnership);
-        QQmlEngine::setObjectOwnership(second2, QQmlEngine::JavaScriptOwnership);
-        gc(*hrmEngine1);
-        gc(*hrmEngine2);
-        QCOMPARE(dtorCount, 0);
-        delete hrmEngine2; // should trigger deletion of objects with JS ownership tracked by this engine
-        gc(*hrmEngine1);
-        QCOMPARE(dtorCount, 2); // first2 and second2 should have been deleted.
-        delete object1;
-        delete object2;
-        gc(*hrmEngine1);
-        QCOMPARE(dtorCount, 6); // deleting object1 and object2 should trigger deletion of first1 and first2.
-        delete hrmEngine1;
-        QCoreApplication::sendPostedEvents(0, QEvent::DeferredDelete);
-        QCoreApplication::processEvents();
-        QCOMPARE(dtorCount, 6); // all objects should have been cleaned up prior to deleting hrmEngine1.
-    }
-
     {
         // Dynamic variant property reference keeps target alive
         QQmlEngine hrmEngine;
@@ -5322,7 +5096,6 @@ void tst_qqmlecmascript::handleReferenceManagement()
         delete object;
     }
 }
-#endif
 
 void tst_qqmlecmascript::stringArg()
 {