QObject: Do not register an observer when writing objectName property

Observers should only be registered when _reading_ the property.
Otherwise we get binding loops.

Pick-to: 6.6 6.5
Change-Id: I974f6ea444fa7a5d333ed79eea6f34e3d757d169
Reviewed-by: Ivan Solovev <ivan.solovev@qt.io>

2 files changed, 12 insertions, 2 deletions

diff --git a/src/corelib/kernel/qobject.cpp b/src/corelib/kernel/qobject.cpp
index 002b9bcab1..90d1f6745c 100644
--- a/src/corelib/kernel/qobject.cpp
+++ b/src/corelib/kernel/qobject.cpp
@@ -1321,7 +1321,7 @@ void QObject::doSetObjectName(const QString &name)
 
     d->extraData->objectName.removeBindingUnlessInWrapper();
 
-    if (d->extraData->objectName != name) {
+    if (d->extraData->objectName.valueBypassingBindings() != name) {
         d->extraData->objectName.setValueBypassingBindings(name);
         d->extraData->objectName.notify(); // also emits a signal
     }
@@ -1339,7 +1339,7 @@ void QObject::setObjectName(QAnyStringView name)
 
     d->extraData->objectName.removeBindingUnlessInWrapper();
 
-    if (d->extraData->objectName != name) {
+    if (d->extraData->objectName.valueBypassingBindings() != name) {
         d->extraData->objectName.setValueBypassingBindings(name.toString());
         d->extraData->objectName.notify(); // also emits a signal
     }
diff --git a/tests/auto/corelib/kernel/qobject/tst_qobject.cpp b/tests/auto/corelib/kernel/qobject/tst_qobject.cpp
index 31345cc333..a4f761d6b9 100644
--- a/tests/auto/corelib/kernel/qobject/tst_qobject.cpp
+++ b/tests/auto/corelib/kernel/qobject/tst_qobject.cpp
@@ -8197,6 +8197,16 @@ void tst_QObject::objectNameBinding()
     QObject obj;
     QTestPrivate::testReadWritePropertyBasics<QObject, QString>(obj, "test1", "test2",
                                                                 "objectName");
+
+    const QPropertyBinding<QString> binding([]() {
+        QObject obj2;
+        obj2.setObjectName(QLatin1String("no loop"));
+        return obj2.objectName();
+    }, {});
+    obj.bindableObjectName().setBinding(binding);
+
+    QCOMPARE(obj.objectName(), QLatin1String("no loop"));
+    QVERIFY2(!binding.error().hasError(), qPrintable(binding.error().description()));
 }
 
 namespace EmitToDestroyedClass {