PropertyCache: Fix resolution of forbidden QObject methods

Despite best intentions the code still hid methods of gadgets when those
were derived from other gadgets.

Fixes: QTBUG-84447
Change-Id: I787300b2a22d6557608772d218e73b9af6f79652
Reviewed-by: Fabian Kosmale <fabian.kosmale@qt.io>
(cherry picked from commit 1029b2b9f3d0ff88c0900fbfec2fac873aa6bcd4)
Reviewed-by: Volker Hilsheimer <volker.hilsheimer@qt.io>

3 files changed, 90 insertions, 1 deletions

diff --git a/src/qml/qml/qqmlpropertycache.cpp b/src/qml/qml/qqmlpropertycache.cpp
index 0e5534fc04..0911c06cd0 100644
--- a/src/qml/qml/qqmlpropertycache.cpp
+++ b/src/qml/qml/qqmlpropertycache.cpp
@@ -496,7 +496,9 @@ void QQmlPropertyCache::append(const QMetaObject *metaObject,
     static const int destroyedIdx2 = QObject::staticMetaObject.indexOfSignal("destroyed()");
     static const int deleteLaterIdx = QObject::staticMetaObject.indexOfSlot("deleteLater()");
     // These indices don't apply to gadgets, so don't block them.
-    const bool preventDestruction = metaObject->superClass() || metaObject == &QObject::staticMetaObject;
+    // It is enough to check for QObject::staticMetaObject here because the loop below excludes
+    // methods of parent classes: It starts at metaObject->methodOffset()
+    const bool preventDestruction = (metaObject == &QObject::staticMetaObject);
 
     int methodOffset = metaObject->methodOffset();
     int signalOffset = signalCount - QMetaObjectPrivate::get(metaObject)->signalCount;
diff --git a/tests/auto/qml/qqmlpropertycache/data/derivedGadgetMethod.qml b/tests/auto/qml/qqmlpropertycache/data/derivedGadgetMethod.qml
new file mode 100644
index 0000000000..6f7f4da0d1
--- /dev/null
+++ b/tests/auto/qml/qqmlpropertycache/data/derivedGadgetMethod.qml
@@ -0,0 +1,7 @@
+import QtQml 2.0
+import Test.PropertyCache 1.0
+
+GadgetUser {
+    baseString: base.stringValue()
+    derivedString: derived.stringValue()
+}
diff --git a/tests/auto/qml/qqmlpropertycache/tst_qqmlpropertycache.cpp b/tests/auto/qml/qqmlpropertycache/tst_qqmlpropertycache.cpp
index c9e92cd3c9..00151de34a 100644
--- a/tests/auto/qml/qqmlpropertycache/tst_qqmlpropertycache.cpp
+++ b/tests/auto/qml/qqmlpropertycache/tst_qqmlpropertycache.cpp
@@ -55,11 +55,77 @@ private slots:
     void metaObjectSize();
     void metaObjectChecksum();
     void metaObjectsForRootElements();
+    void derivedGadgetMethod();
 
 private:
     QQmlEngine engine;
 };
 
+class BaseGadget
+{
+    Q_GADGET
+    QML_ANONYMOUS
+public:
+    Q_INVOKABLE QString stringValue() { return QLatin1String("base"); }
+};
+
+Q_DECLARE_METATYPE(BaseGadget)
+
+class DerivedGadget : public BaseGadget
+{
+    Q_GADGET
+    QML_ANONYMOUS
+public:
+    Q_INVOKABLE QString stringValue() { return QLatin1String("derived"); }
+};
+
+Q_DECLARE_METATYPE(DerivedGadget)
+
+class GadgetUser : public QObject
+{
+    Q_OBJECT
+    Q_PROPERTY(BaseGadget base READ base CONSTANT)
+    Q_PROPERTY(DerivedGadget derived READ derived CONSTANT)
+    Q_PROPERTY(QString baseString READ baseString WRITE setBaseString NOTIFY baseStringChanged)
+    Q_PROPERTY(QString derivedString READ derivedString WRITE setDerivedString NOTIFY derivedStringChanged)
+    QML_ELEMENT
+
+public:
+    BaseGadget base() const { return m_base; }
+    DerivedGadget derived() const { return m_derived; }
+    QString baseString() const { return m_baseString; }
+    QString derivedString() const { return m_derivedString; }
+
+public slots:
+    void setBaseString(QString baseString)
+    {
+        if (m_baseString == baseString)
+            return;
+
+        m_baseString = baseString;
+        emit baseStringChanged(m_baseString);
+    }
+
+    void setDerivedString(QString derivedString)
+    {
+        if (m_derivedString == derivedString)
+            return;
+
+        m_derivedString = derivedString;
+        emit derivedStringChanged(m_derivedString);
+    }
+
+signals:
+    void baseStringChanged(QString baseString);
+    void derivedStringChanged(QString derivedString);
+
+private:
+    BaseGadget m_base;
+    DerivedGadget m_derived;
+    QString m_baseString;
+    QString m_derivedString;
+};
+
 class BaseObject : public QObject
 {
     Q_OBJECT
@@ -554,4 +620,18 @@ void tst_qqmlpropertycache::metaObjectsForRootElements()
     QCOMPARE(obj->property("result").toString(), QString::fromLatin1("good"));
 }
 
+void tst_qqmlpropertycache::derivedGadgetMethod()
+{
+    qmlRegisterTypesAndRevisions<BaseGadget, DerivedGadget, GadgetUser>("Test.PropertyCache", 1);
+    QQmlEngine engine;
+    QQmlComponent c(&engine, testFileUrl("derivedGadgetMethod.qml"));
+    QVERIFY(c.isReady());
+    QScopedPointer<QObject> obj(c.create());
+    QVERIFY(!obj.isNull());
+    GadgetUser *gadgetUser = qobject_cast<GadgetUser *>(obj.data());
+    QVERIFY(gadgetUser);
+    QCOMPARE(gadgetUser->baseString(), QString::fromLatin1("base"));
+    QCOMPARE(gadgetUser->derivedString(), QString::fromLatin1("derived"));
+}
+
 QTEST_MAIN(tst_qqmlpropertycache)