tst_qqmlecmascript: Check that parent can defer child class properties

It is arguably a bad idea to defer properties which might get defined in
child classes, but checking it in the engine would be expensive: We
cannot simply check that the property exist, as we might want to defer
attached properties.
So for now, we add a test to document and verify the behavior.

Change-Id: I264b136638c4ecddfa52b6687797cb981d9b531e
Reviewed-by: Ulf Hermann <ulf.hermann@qt.io>

tests/auto/qml/qqmlecmascript/data/deferredPropertiesChild.qml

@@ -0,0 +1,6 @@
+import Qt.test 1.0
+
+DeferredByParentChild {
+    id: root
+    childValue: 10
+}

tests/auto/qml/qqmlecmascript/testtypes.cpp

@@ -469,6 +469,7 @@ void registerTypes()
     qmlRegisterSingletonType<TestTypeCppSingleton>("Test", 1, 0, "TestTypeCppSingleton", testTypeCppProvider);
     qmlRegisterType<MyDeferredObject>("Qt.test", 1,0, "MyDeferredObject");
     qmlRegisterType<DeferredChild>("Qt.test", 1,0, "DeferredChild");
+    qmlRegisterType<DeferredByParentChild>("Qt.test", 1,0, "DeferredByParentChild");
     qmlRegisterType<MyVeryDeferredObject>("Qt.test", 1,0, "MyVeryDeferredObject");
     qmlRegisterType<MyQmlContainer>("Qt.test", 1,0, "MyQmlContainer");
     qmlRegisterExtendedType<MyBaseExtendedObject, BaseExtensionObject>("Qt.test", 1,0, "MyBaseExtendedObject");

tests/auto/qml/qqmlecmascript/testtypes.h

@@ -435,6 +435,32 @@ class DeferredChild : public NonDeferredBased
     Q_CLASSINFO("DeferredPropertyNames", "baseValue")
 };
 
+class ChildDeferringParent : public QObject
+{
+    Q_OBJECT
+    Q_CLASSINFO("DeferredPropertyNames", "childValue")
+};
+
+class DeferredByParentChild : public ChildDeferringParent
+{
+    Q_OBJECT
+    Q_PROPERTY(int childValue READ childValue WRITE setchildValue NOTIFY childValueChanged)
+signals:
+    void childValueChanged();
+public:
+    int childValue() const { return m_childValue; }
+
+    void setchildValue(int i) {
+        if (i == m_childValue)
+            return;
+        m_childValue = i;
+        emit childValueChanged();
+    }
+
+private:
+    int m_childValue = 0;
+};
+
 class MyVeryDeferredObject : public QObject
 {
     Q_OBJECT

tests/auto/qml/qqmlecmascript/tst_qqmlecmascript.cpp

@@ -101,6 +101,7 @@ private slots:
     void dependenciesWithFunctions();
     void deferredProperties();
     void deferredPropertiesParent();
+    void deferredPropertiesByParent();
     void deferredPropertiesErrors();
     void deferredPropertiesInComponents();
     void deferredPropertiesInDestruction();
@@ -1229,6 +1230,20 @@ void tst_qqmlecmascript::deferredPropertiesParent()
     qmlExecuteDeferred(object);
     QCOMPARE(object->baseValue(), 10);
 }
+
+void tst_qqmlecmascript::deferredPropertiesByParent()
+{
+    QQmlEngine engine;
+    QQmlComponent component(&engine, testFileUrl("deferredPropertiesChild.qml"));
+    QScopedPointer<QObject> obj(component.create());
+    QVERIFY2(obj, qPrintable(component.errorString()));
+    DeferredByParentChild *object = qobject_cast<DeferredByParentChild *>(obj.data());
+    QVERIFY(object != nullptr);
+    QCOMPARE(object->childValue(), 0);
+    qmlExecuteDeferred(object);
+    QCOMPARE(object->childValue(), 10);
+}
+
 // Check errors on deferred properties are correctly emitted
 void tst_qqmlecmascript::deferredPropertiesErrors()
 {