QDBusAbstractAdaptor: Send signals using correct interface

When forwarding a signal, associate this signal with its
enclosing metaobject instead of its sender's metaobject.
Those two may be different if the signal is declared in
a base class.

Add a regression test into tst_qdbusconnection.

Fixes: QTBUG-33142
Pick-to: 6.5
Change-Id: I532ab3bb6c0671a480568f46d63fceff0c82c097
Reviewed-by: Thiago Macieira <thiago.macieira@intel.com>
Reviewed-by: Qt CI Bot <qt_ci_bot@qt-project.org>

src/dbus/qdbusabstractadaptor.cpp

@@ -255,8 +255,8 @@ void QDBusAdaptorConnector::relay(QObject *senderObj, int lastSignalIdx, void **
         // QObject signal (destroyed(QObject *)) -- ignore
         return;
 
-    const QMetaObject *senderMetaObject = senderObj->metaObject();
+    QMetaMethod mm = senderObj->metaObject()->method(lastSignalIdx);
-    QMetaMethod mm = senderMetaObject->method(lastSignalIdx);
+    const QMetaObject *senderMetaObject = mm.enclosingMetaObject();
 
     QObject *realObject = senderObj;
     if (qobject_cast<QDBusAbstractAdaptor *>(senderObj))

tests/auto/dbus/qdbusconnection/tst_qdbusconnection.cpp

@@ -1417,6 +1417,34 @@ void tst_QDBusConnection::emptyServerAddress()
     QDBusServer server({}, nullptr);
 }
 
+void tst_QDBusConnection::parentClassSignal()
+{
+    if (!QCoreApplication::instance())
+        QSKIP("Test requires a QCoreApplication");
+
+    const QString path = "/path";
+
+    QDBusConnection con = QDBusConnection::sessionBus();
+    QVERIFY(con.isConnected());
+
+    // register one object at root:
+    MyObject obj;
+    QVERIFY(con.registerObject(path, &obj, QDBusConnection::ExportAllContents));
+    QCOMPARE(con.objectRegisteredAt(path), static_cast<QObject *>(&obj));
+
+    SignalReceiver recv;
+    QVERIFY(con.connect(con.baseService(), path, "local.BaseObject", "baseObjectSignal", &recv,
+                        SLOT(oneSlot())));
+    QVERIFY(con.connect(con.baseService(), path, "local.MyObject", "myObjectSignal", &recv,
+                        SLOT(oneSlot())));
+
+    emit obj.baseObjectSignal();
+    QTRY_COMPARE(recv.signalsReceived, 1);
+
+    emit obj.myObjectSignal();
+    QTRY_COMPARE(recv.signalsReceived, 2);
+}
+
 QString MyObject::path;
 QString MyObjectWithoutInterface::path;
 QString MyObjectWithoutInterface::interface;

tests/auto/dbus/qdbusconnection/tst_qdbusconnection.h

@@ -21,11 +21,14 @@ public:
     BaseObject(QObject *parent = nullptr) : QObject(parent) { }
 public slots:
     void anotherMethod() { }
+signals:
+    void baseObjectSignal();
 };
 
 class MyObject: public BaseObject
 {
     Q_OBJECT
+    Q_CLASSINFO("D-Bus Interface", "local.MyObject")
 public slots:
     void method(const QDBusMessage &msg);
 
@@ -33,6 +36,9 @@ public:
     static QString path;
     int callCount;
     MyObject(QObject *parent = nullptr) : BaseObject(parent), callCount(0) {}
+
+signals:
+    void myObjectSignal();
 };
 
 class MyObjectWithoutInterface: public QObject
@@ -117,6 +123,8 @@ private slots:
 
     void emptyServerAddress();
 
+    void parentClassSignal();
+
 public:
     QString serviceName() const { return "org.qtproject.Qt.Autotests.QDBusConnection"; }
     bool callMethod(const QDBusConnection &conn, const QString &path);