QML engine: Fix writing function to property through alias

We special case writing functions to properties, only allowing assigning
them to var properties and QJSValue properties.
This would however break when aliases are involved. This commit fixes
the issue by resolving the alias, and then checking and writing to the
resolved property.

Fixes: QTBUG-90373
Pick-to: 5.15 6.0
Change-Id: Ia09ebe92feeaf8359c99ff9aeadc676b9fcfaa07
Reviewed-by: Mitch Curtis <mitch.curtis@qt.io>
Reviewed-by: Ulf Hermann <ulf.hermann@qt.io>

1 files changed, 18 insertions, 1 deletions

diff --git a/src/qml/jsruntime/qv4qobjectwrapper.cpp b/src/qml/jsruntime/qv4qobjectwrapper.cpp
index 200ebfaffd..08d0c6f40e 100644
--- a/src/qml/jsruntime/qv4qobjectwrapper.cpp
+++ b/src/qml/jsruntime/qv4qobjectwrapper.cpp
@@ -463,7 +463,24 @@ void QObjectWrapper::setProperty(ExecutionEngine *engine, QObject *object, QQmlP
     QV4::ScopedFunctionObject f(scope, value);
     if (f) {
         if (!f->isBinding()) {
-            if (!property->isVarProperty() && property->propType().id() != qMetaTypeId<QJSValue>()) {
+            const bool isAliasToAllowed = [&]() {
+                if (property->isAlias()) {
+                    const QQmlPropertyIndex originalIndex(property->coreIndex(), -1);
+                    QObject *targetObject = nullptr;
+                    QQmlPropertyIndex targetIndex;
+                    QQmlPropertyPrivate::findAliasTarget(object, originalIndex, &targetObject, &targetIndex);
+                    Q_ASSERT(targetObject);
+                    QQmlPropertyCache *targetCache = QQmlData::get(targetObject)->propertyCache;
+                    Q_ASSERT(targetCache);
+                    QQmlPropertyData *targetProperty = targetCache->property(targetIndex.coreIndex());
+                    object = targetObject;
+                    property = targetProperty;
+                    return targetProperty->isVarProperty() || targetProperty->propType() == QMetaType::fromType<QJSValue>();
+                } else {
+                    return false;
+                }
+            }();
+            if (!isAliasToAllowed && !property->isVarProperty() && property->propType().id() != qMetaTypeId<QJSValue>()) {
                 // assigning a JS function to a non var or QJSValue property or is not allowed.
                 QString error = QLatin1String("Cannot assign JavaScript function to ");
                 if (!QMetaType(property->propType()).name())