Fix writing undefined via QQmlProperty

Just as with QMetaProperty::write, writing an invalid QVariant should
trigger a RESET function if it exists.
This not only helps with consistency, but will be needed to correctly
handle writes of initial properties when doing more work via
QQmlProperty.

Pick-to: 6.10
Task-number: QTBUG-138825
Change-Id: I77058d292bdea34c0b500e6b61b29bca67ff8d99
Reviewed-by: Ulf Hermann <[email protected]>

2 files changed, 41 insertions, 0 deletions

diff --git a/src/qml/qml/qqmlproperty.cpp b/src/qml/qml/qqmlproperty.cpp
index 1829379c34..248f127325 100644
--- a/src/qml/qml/qqmlproperty.cpp
+++ b/src/qml/qml/qqmlproperty.cpp
@@ -1859,6 +1859,11 @@ bool QQmlPropertyPrivate::write(
     } else {
         Q_ASSERT(variantMetaType != propertyMetaType);
 
+        if (property.isResettable() && !value.isValid()) {
+            property.resetProperty(object, flags);
+            return true;
+        }
+
         bool ok = false;
         QVariant v;
         if (variantMetaType == QMetaType::fromType<QString>())
diff --git a/tests/auto/qml/qqmlcomponent/tst_qqmlcomponent.cpp b/tests/auto/qml/qqmlcomponent/tst_qqmlcomponent.cpp
index 6545298b39..66af07af78 100644
--- a/tests/auto/qml/qqmlcomponent/tst_qqmlcomponent.cpp
+++ b/tests/auto/qml/qqmlcomponent/tst_qqmlcomponent.cpp
@@ -1026,9 +1026,45 @@ struct ComponentWithPublicSetInitial : QQmlComponent
     }
 };
 
+class MyObject : public QObject
+{
+    Q_OBJECT
+    Q_PROPERTY(int resettable MEMBER m_resettable RESET resetIt NOTIFY resettableChanged)
+    void resetIt() { resetCalled = true; }
+
+public:
+    MyObject(QObject *parent = nullptr) : QObject(parent) { }
+    int m_resettable;
+    bool resetCalled = false;
+
+signals:
+    void resettableChanged();
+};
+
+
 void tst_qqmlcomponent::testSetInitialProperties()
 {
     QQmlEngine eng;
+    qmlRegisterType<MyObject>("ResetTest", 1, 0, "MyObject");
+    // reset logic
+    {
+        QQmlComponent comp(&eng);
+        comp.loadFromModule("ResetTest", "MyObject");
+        std::unique_ptr<QObject>  obj {comp.createWithInitialProperties({{u"resettable"_s, QVariant() }}) };
+        QVERIFY(obj);
+        QVERIFY(qobject_cast<MyObject *>(obj.get())->resetCalled);
+    }
+    // reset logic - null != undefined
+    {
+        QQmlComponent comp(&eng);
+        comp.loadFromModule("ResetTest", "MyObject");
+        QVariant var = QVariant::fromValue(nullptr);
+        QVERIFY(var.isNull() && var.isValid());
+        QTest::ignoreMessage(QtMsgType::QtWarningMsg, QRegularExpression(".*Could not set initial property resettable"_L1));
+        std::unique_ptr<QObject>  obj {comp.createWithInitialProperties({{u"resettable"_s, var }}) };
+        QVERIFY(obj);
+        QVERIFY(!qobject_cast<MyObject *>(obj.get())->resetCalled);
+    }
     {
         //  QVariant
         ComponentWithPublicSetInitial comp(&eng);