QML: Re-add QMetaType::convert() attempt for argument conversion

There are people who depend on QMetaType to convert their types. This is
not nice, but removing it breaks compatibility.

Fixes: QTBUG-114340
Change-Id: I0a7f54b8fd0f77b71e7e56f65ef7d6f91c876237
Reviewed-by: Fabian Kosmale <fabian.kosmale@qt.io>
Reviewed-by: Qt CI Bot <qt_ci_bot@qt-project.org>
(cherry picked from commit 761b455d47)
Reviewed-by: Qt Cherry-pick Bot <cherrypick_bot@qt-project.org>

src/qml/jsruntime/qv4qobjectwrapper.cpp

@@ -2190,7 +2190,11 @@ bool CallArgument::fromValue(QMetaType metaType, ExecutionEngine *engine, const
     qvariantPtr = new (&allocData) QVariant(metaType);
     type = QVariantWrappedType;
 
-    return ExecutionEngine::metaTypeFromJS(value, metaType, qvariantPtr->data());
+    if (ExecutionEngine::metaTypeFromJS(value, metaType, qvariantPtr->data()))
+        return true;
+
+    const QVariant v = ExecutionEngine::toVariant(value, metaType);
+    return QMetaType::convert(v.metaType(), v.constData(), metaType, qvariantPtr->data());
 }
 
 ReturnedValue CallArgument::toValue(ExecutionEngine *engine)

tests/auto/qml/qqmllanguage/data/unregisteredValueTypeConversion.qml

@@ -2,5 +2,8 @@ import QtQml
 import Test
 
 UnregisteredValueTypeHandler {
-    Component.onCompleted: consume(produce())
+    Component.onCompleted: {
+        consume(produce())
+        consume(produceDerived())
+    }
 }

tests/auto/qml/qqmllanguage/testtypes.cpp

@@ -150,6 +150,7 @@ void registerTypes()
     qmlRegisterTypesAndRevisions<DerivedValueType>("ValueTypes", 1);
     qmlRegisterTypesAndRevisions<GetterObject>("Test", 1);
 
+    QMetaType::registerConverter<UnregisteredValueDerivedType, UnregisteredValueBaseType>();
     qmlRegisterTypesAndRevisions<UnregisteredValueTypeHandler>("Test", 1);
 }
 

tests/auto/qml/qqmllanguage/testtypes.h

@@ -2426,6 +2426,11 @@ struct UnregisteredValueBaseType
     int foo = 12;
 };
 
+struct UnregisteredValueDerivedType: public UnregisteredValueBaseType
+{
+    int bar = 13;
+};
+
 class UnregisteredValueTypeHandler: public QObject
 {
     Q_OBJECT
@@ -2435,6 +2440,7 @@ public:
 
 public slots:
     UnregisteredValueBaseType produce() { return UnregisteredValueBaseType(); }
+    UnregisteredValueDerivedType produceDerived() { return UnregisteredValueDerivedType(); }
     void consume(UnregisteredValueBaseType) { ++consumed; }
 };
 

tests/auto/qml/qqmllanguage/tst_qqmllanguage.cpp

@@ -7920,7 +7920,7 @@ void tst_qqmllanguage::unregisteredValueTypeConversion()
     QVERIFY(!o.isNull());
     UnregisteredValueTypeHandler *handler = qobject_cast<UnregisteredValueTypeHandler *>(o.data());
     Q_ASSERT(handler);
-    QCOMPARE(handler->consumed, 1);
+    QCOMPARE(handler->consumed, 2);
 }
 
 QTEST_MAIN(tst_qqmllanguage)