QML: Consider deep aliases when finding binding targets

If we have a deep alias we need to bind to the inner object rather than
the outer one.

Fixes: QTBUG-109417
Change-Id: Iefe8641026cfbbf9199b2bb8d9fa2f5fba591f17
Reviewed-by: Fabian Kosmale <fabian.kosmale@qt.io>
(cherry picked from commit e9b7eaaf6e627c84cf77dc0ea76c9cb40d705711)
Reviewed-by: Sami Shalayel <sami.shalayel@qt.io>

4 files changed, 71 insertions, 16 deletions

diff --git a/src/qml/qml/qqmlbinding.cpp b/src/qml/qml/qqmlbinding.cpp
index 9bebc4c67e..cb0dd2fe25 100644
--- a/src/qml/qml/qqmlbinding.cpp
+++ b/src/qml/qml/qqmlbinding.cpp
@@ -691,14 +691,34 @@ bool QQmlBinding::setTarget(QObject *object, const QQmlPropertyData &core, const
                      valueType ? valueType->coreIndex() : -1);
 }
 
-bool QQmlBinding::setTarget(QObject *object, int coreIndex, bool coreIsAlias, int valueTypeIndex)
+static const QQmlPropertyData *getObjectPropertyData(QObject *object, int coreIndex)
 {
-    m_target = object;
+    QQmlData *data = QQmlData::get(object, true);
+    if (!data)
+        return nullptr;
+    if (!data->propertyCache) {
+        data->propertyCache = QQmlMetaType::propertyCache(object->metaObject());
+        if (!data->propertyCache)
+            return nullptr;
+        data->propertyCache->addref();
+    }
+    const QQmlPropertyData *propertyData = data->propertyCache->property(coreIndex);
+    Q_ASSERT(propertyData);
+    return propertyData;
+}
 
-    if (!object) {
+bool QQmlBinding::setTarget(QObject *object, int coreIndex, bool coreIsAlias, int valueTypeIndex)
+{
+    auto invalidate = [this]() {
+        m_target = nullptr;
         m_targetIndex = QQmlPropertyIndex();
         return false;
-    }
+    };
+
+    if (!object)
+        return invalidate();
+
+    m_target = object;
 
     for (bool isAlias = coreIsAlias; isAlias;) {
         QQmlVMEMetaObject *vme = QQmlVMEMetaObject::getForProperty(object, coreIndex);
@@ -706,21 +726,25 @@ bool QQmlBinding::setTarget(QObject *object, int coreIndex, bool coreIsAlias, in
         int aValueTypeIndex;
         if (!vme->aliasTarget(coreIndex, &object, &coreIndex, &aValueTypeIndex)) {
             // can't resolve id (yet)
-            m_target = nullptr;
-            m_targetIndex = QQmlPropertyIndex();
-            return false;
+            return invalidate();
         }
-        if (valueTypeIndex == -1)
-            valueTypeIndex = aValueTypeIndex;
 
-        QQmlData *data = QQmlData::get(object, false);
-        if (!data || !data->propertyCache) {
-            m_target = nullptr;
-            m_targetIndex = QQmlPropertyIndex();
-            return false;
+        const QQmlPropertyData *propertyData = getObjectPropertyData(object, coreIndex);
+        if (!propertyData)
+            return invalidate();
+        if (aValueTypeIndex != -1) {
+            if (propertyData->propType().flags().testFlag(QMetaType::PointerToQObject)) {
+                // deep alias
+                propertyData->readProperty(object, &object);
+                coreIndex = aValueTypeIndex;
+                valueTypeIndex = -1;
+                propertyData = getObjectPropertyData(object, coreIndex);
+                if (!propertyData)
+                    return invalidate();
+            } else {
+                valueTypeIndex = aValueTypeIndex;
+            }
         }
-        QQmlPropertyData *propertyData = data->propertyCache->property(coreIndex);
-        Q_ASSERT(propertyData);
 
         m_target = object;
         isAlias = propertyData->isAlias();
diff --git a/tests/auto/qml/qqmllanguage/data/MyRectangle.qml b/tests/auto/qml/qqmllanguage/data/MyRectangle.qml
new file mode 100644
index 0000000000..4d5e7c6c8d
--- /dev/null
+++ b/tests/auto/qml/qqmllanguage/data/MyRectangle.qml
@@ -0,0 +1,10 @@
+import QtQuick
+
+Item {
+    property alias rectangle1AnchorsleftMargin: rectangle1.anchors.leftMargin
+
+    Rectangle {
+        id: rectangle1
+        anchors.leftMargin: 250
+    }
+}
diff --git a/tests/auto/qml/qqmllanguage/data/alias.19.qml b/tests/auto/qml/qqmllanguage/data/alias.19.qml
new file mode 100644
index 0000000000..a96c0c694d
--- /dev/null
+++ b/tests/auto/qml/qqmllanguage/data/alias.19.qml
@@ -0,0 +1,11 @@
+import QtQuick
+
+Item {
+    id: myThing
+    width: 1920
+
+    MyRectangle {
+        rectangle1AnchorsleftMargin: myThing.width / 2
+        Component.onCompleted: myThing.height = rectangle1AnchorsleftMargin
+    }
+}
diff --git a/tests/auto/qml/qqmllanguage/tst_qqmllanguage.cpp b/tests/auto/qml/qqmllanguage/tst_qqmllanguage.cpp
index 06b2738c9e..047df2f6d0 100644
--- a/tests/auto/qml/qqmllanguage/tst_qqmllanguage.cpp
+++ b/tests/auto/qml/qqmllanguage/tst_qqmllanguage.cpp
@@ -2257,6 +2257,16 @@ void tst_qqmllanguage::aliasProperties()
         QQmlComponent component(&engine, testFileUrl("alias.18.qml"));
         VERIFY_ERRORS("alias.18.errors.txt");
     }
+
+    // Binding on deep alias
+    {
+        QQmlComponent component(&engine, testFileUrl("alias.19.qml"));
+        VERIFY_ERRORS(0);
+
+        QScopedPointer<QObject> object(component.create());
+        QVERIFY(!object.isNull());
+        QCOMPARE(object->property("height").toInt(), 960);
+    }
 }
 
 // QTBUG-13374 Test that alias properties and signals can coexist