QML: Don't try to convert objects with prototypes to QVariant

This is likely to lose some properties.

Fixes: QTBUG-106266
Change-Id: Ib5a2567d61635a5cf7b3abee7cfef0c073d59e63
Reviewed-by: Fabian Kosmale <fabian.kosmale@qt.io>
(cherry picked from commit 4307755655)
Reviewed-by: Qt Cherry-pick Bot <cherrypick_bot@qt-project.org>

src/qml/jsruntime/qv4engine.cpp

@@ -1709,10 +1709,7 @@ static QVariant objectToVariant(const QV4::Object *o, V4ObjectSet *visitedObject
         }
 
         result = list;
-    } else if (const FunctionObject *f = o->as<FunctionObject>()) {
-        // If it's a FunctionObject, we can only save it as QJSValue.
-        result = QVariant::fromValue(QJSValuePrivate::fromReturnedValue(f->asReturnedValue()));
-    } else {
+    } else if (o->getPrototypeOf() == o->engine()->objectPrototype()->d()) {
         QVariantMap map;
         QV4::Scope scope(o->engine());
         QV4::ObjectIterator it(scope, o, QV4::ObjectIterator::EnumerableOnly);
@@ -1730,6 +1727,9 @@ static QVariant objectToVariant(const QV4::Object *o, V4ObjectSet *visitedObject
         }
 
         result = map;
+    } else {
+        // If it's not a plain object, we can only save it as QJSValue.
+        result = QVariant::fromValue(QJSValuePrivate::fromReturnedValue(o->asReturnedValue()));
     }
 
     visitedObjects->remove(o->d());

tests/auto/qml/qqmlcomponent/data/complexObjectArgument.qml

@@ -0,0 +1,10 @@
+import QtQml 2.15
+
+QtObject {
+    id: root
+    Component.onCompleted: {
+        let comp = Qt.createComponent("dynamic.qml");
+        let inst = comp.createObject(root, { testObj: new Set(), });
+        objectName = inst.use();
+    }
+}

tests/auto/qml/qqmlcomponent/data/dynamic.qml

@@ -0,0 +1,6 @@
+import QtQml
+
+QtObject {
+    property var testObj
+    function use() { return testObj.has(1) ? 25 : 26; }
+}

tests/auto/qml/qqmlcomponent/tst_qqmlcomponent.cpp

@@ -146,6 +146,7 @@ private slots:
     void loadFromModuleRequired();
     void loadFromQrc();
     void removeBinding();
+    void complexObjectArgument();
 
 private:
     QQmlEngine engine;
@@ -1450,6 +1451,16 @@ void tst_qqmlcomponent::removeBinding()
     QCOMPARE(o->property("result"), QStringLiteral("42"));
 }
 
+void tst_qqmlcomponent::complexObjectArgument()
+{
+    QQmlEngine e;
+    QQmlComponent c(&e, testFileUrl("complexObjectArgument.qml"));
+    QVERIFY2(c.isReady(), qPrintable(c.errorString()));
+    QScopedPointer<QObject> o(c.create());
+    QVERIFY(!o.isNull());
+    QCOMPARE(o->objectName(), QStringLiteral("26"));
+}
+
 QTEST_MAIN(tst_qqmlcomponent)
 
 #include "tst_qqmlcomponent.moc"