path: root/user/qt5-qtwebchannel/kde-lts.patch

From adfc4bacdf18d9876a1ea908ce6aeb43555b0dbd Mon Sep 17 00:00:00 2001
From: Milian Wolff <milian.wolff@kdab.com>
Date: Fri, 13 Dec 2019 18:07:26 +0100
Subject: [PATCH 1/3] Handle signals in the registered object's thread

Do not call `sender()` from a different thread. As the API documentation
indicates, that is not supported and can lead to crashes as experienced
on the CI frequently.

Instead, we now have per-thread SignalHandlers and use those to get
notified about signals and metacall events.

Moving a registered object into a different thread isn't supported once
it was registered. But the object can be deregistered, moved, and then
re-registered.

[ChangeLog] Signals from objects living in a different thread than the
QWebChannel are now handled correctly.

Task-number: QTBUG-51366
Change-Id: I1edb0694b946a494b6c0d4a8a6dc6b452dcb2c7a
Reviewed-by: Arno Rehn <a.rehn@menlosystems.com>
Reviewed-by: Qt CI Bot <qt_ci_bot@qt-project.org>
(cherry picked from commit 28455e59c0b940200fe0223472a80104ce1a02dd)
---
 src/webchannel/qmetaobjectpublisher.cpp  | 23 +++++++++++++++++------
 src/webchannel/qmetaobjectpublisher_p.h  |  5 ++++-
 src/webchannel/signalhandler_p.h         |  3 +++
 tests/auto/webchannel/tst_webchannel.cpp |  4 +---
 4 files changed, 25 insertions(+), 10 deletions(-)

diff --git a/src/webchannel/qmetaobjectpublisher.cpp b/src/webchannel/qmetaobjectpublisher.cpp
index 536eb5c..e997b75 100644
--- a/src/webchannel/qmetaobjectpublisher.cpp
+++ b/src/webchannel/qmetaobjectpublisher.cpp
@@ -186,7 +186,6 @@ Q_DECLARE_TYPEINFO(OverloadResolutionCandidate, Q_MOVABLE_TYPE);
 QMetaObjectPublisher::QMetaObjectPublisher(QWebChannel *webChannel)
     : QObject(webChannel)
     , webChannel(webChannel)
-    , signalHandler(this)
     , clientIsIdle(false)
     , blockUpdates(false)
     , propertyUpdatesInitialized(false)
@@ -333,6 +332,7 @@ QJsonObject QMetaObjectPublisher::initializeClient(QWebChannelAbstractTransport
 
 void QMetaObjectPublisher::initializePropertyUpdates(const QObject *const object, const QJsonObject &objectInfo)
 {
+    auto *signalHandler = signalHandlerFor(object);
     foreach (const QJsonValue &propertyInfoVar, objectInfo[KEY_PROPERTIES].toArray()) {
         const QJsonArray &propertyInfo = propertyInfoVar.toArray();
         if (propertyInfo.size() < 2) {
@@ -353,14 +353,14 @@ void QMetaObjectPublisher::initializePropertyUpdates(const QObject *const object
 
         // Only connect for a property update once
         if (connectedProperties.isEmpty()) {
-            signalHandler.connectTo(object, signalIndex);
+            signalHandler->connectTo(object, signalIndex);
         }
 
         connectedProperties.insert(propertyIndex);
     }
 
     // also always connect to destroyed signal
-    signalHandler.connectTo(object, s_destroyedSignalIndex);
+    signalHandler->connectTo(object, s_destroyedSignalIndex);
 }
 
 void QMetaObjectPublisher::sendPendingPropertyUpdates()
@@ -590,7 +590,7 @@ void QMetaObjectPublisher::objectDestroyed(const QObject *object)
     // only remove from handler when we initialized the property updates
     // cf: https://bugreports.qt.io/browse/QTBUG-60250
     if (propertyUpdatesInitialized) {
-        signalHandler.remove(object);
+        signalHandlerFor(object)->remove(object);
         signalToPropertyMap.remove(object);
     }
     pendingPropertyUpdates.remove(object);
@@ -913,9 +913,9 @@ void QMetaObjectPublisher::handleMessage(const QJsonObject &message, QWebChannel
                 return;
             transport->sendMessage(createResponse(message.value(KEY_ID), wrapResult(result, transport)));
         } else if (type == TypeConnectToSignal) {
-            signalHandler.connectTo(object, message.value(KEY_SIGNAL).toInt(-1));
+            signalHandlerFor(object)->connectTo(object, message.value(KEY_SIGNAL).toInt(-1));
         } else if (type == TypeDisconnectFromSignal) {
-            signalHandler.disconnectFrom(object, message.value(KEY_SIGNAL).toInt(-1));
+            signalHandlerFor(object)->disconnectFrom(object, message.value(KEY_SIGNAL).toInt(-1));
         } else if (type == TypeSetProperty) {
             setProperty(object, message.value(KEY_PROPERTY).toInt(-1),
                         message.value(KEY_VALUE));
@@ -948,4 +948,15 @@ void QMetaObjectPublisher::timerEvent(QTimerEvent *event)
     }
 }
 
+SignalHandler<QMetaObjectPublisher> *QMetaObjectPublisher::signalHandlerFor(const QObject *object)
+{
+    auto thread = object->thread();
+    auto it = signalHandlers.find(thread);
+    if (it == signalHandlers.end()) {
+        it = signalHandlers.emplace(thread, this).first;
+        it->second.moveToThread(thread);
+    }
+    return &it->second;
+}
+
 QT_END_NAMESPACE
diff --git a/src/webchannel/qmetaobjectpublisher_p.h b/src/webchannel/qmetaobjectpublisher_p.h
index bbd9875..ded0d33 100644
--- a/src/webchannel/qmetaobjectpublisher_p.h
+++ b/src/webchannel/qmetaobjectpublisher_p.h
@@ -60,6 +60,8 @@
 #include <QPointer>
 #include <QJsonObject>
 
+#include <unordered_map>
+
 #include "qwebchannelglobal.h"
 
 QT_BEGIN_NAMESPACE
@@ -272,7 +274,8 @@ private:
     friend class TestWebChannel;
 
     QWebChannel *webChannel;
-    SignalHandler<QMetaObjectPublisher> signalHandler;
+    std::unordered_map<const QThread*, SignalHandler<QMetaObjectPublisher>> signalHandlers;
+    SignalHandler<QMetaObjectPublisher> *signalHandlerFor(const QObject *object);
 
     // true when the client is idle, false otherwise
     bool clientIsIdle;
diff --git a/src/webchannel/signalhandler_p.h b/src/webchannel/signalhandler_p.h
index 27afadb..d77373c 100644
--- a/src/webchannel/signalhandler_p.h
+++ b/src/webchannel/signalhandler_p.h
@@ -56,6 +56,7 @@
 #include <QVector>
 #include <QMetaMethod>
 #include <QDebug>
+#include <QThread>
 
 QT_BEGIN_NAMESPACE
 
@@ -71,6 +72,7 @@ static const int s_destroyedSignalIndex = QObject::staticMetaObject.indexOfMetho
 template<class Receiver>
 class SignalHandler : public QObject
 {
+    Q_DISABLE_COPY(SignalHandler)
 public:
     SignalHandler(Receiver *receiver, QObject *parent = 0);
 
@@ -268,6 +270,7 @@ int SignalHandler<Receiver>::qt_metacall(QMetaObject::Call call, int methodId, v
     if (call == QMetaObject::InvokeMetaMethod) {
         const QObject *object = sender();
         Q_ASSERT(object);
+        Q_ASSERT(QThread::currentThread() == object->thread());
         Q_ASSERT(senderSignalIndex() == methodId);
         Q_ASSERT(m_connectionsCounter.contains(object));
         Q_ASSERT(m_connectionsCounter.value(object).contains(methodId));
diff --git a/tests/auto/webchannel/tst_webchannel.cpp b/tests/auto/webchannel/tst_webchannel.cpp
index 181da9e..7f846f5 100644
--- a/tests/auto/webchannel/tst_webchannel.cpp
+++ b/tests/auto/webchannel/tst_webchannel.cpp
@@ -943,8 +943,6 @@ void TestWebChannel::testInfiniteRecursion()
 
 void TestWebChannel::testAsyncObject()
 {
-    QSKIP("This test is broken. See QTBUG-80729");
-
     QWebChannel channel;
     channel.connectTo(m_dummyTransport);
 
@@ -1082,7 +1080,7 @@ void TestWebChannel::benchInitializeClients()
 
         publisher->propertyUpdatesInitialized = false;
         publisher->signalToPropertyMap.clear();
-        publisher->signalHandler.clear();
+        publisher->signalHandlers.clear();
     }
 }
 
-- 
2.36.0

From 01803a64b0a0b03eb8d9add60008829bc9d5c11e Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?=C3=98ystein=20Heskestad?= <oystein.heskestad@qt.io>
Date: Fri, 7 May 2021 15:23:38 +0200
Subject: [PATCH 2/3] Handle per-transport client idle status

[ChangeLog][QMetaObjectPublisher] Handle per-transport client idle status

Task-number: QTBUG-92927
Change-Id: I5a06261e6dddb0fc0fae9f73b280c61cf5a2b52d
Reviewed-by: Arno Rehn <a.rehn@menlosystems.com>
(cherry picked from commit a7199de7d90f48ce3d95cae795bd9209c39516ce)
---
 src/webchannel/qmetaobjectpublisher.cpp  | 71 ++++++++++++++++++------
 src/webchannel/qmetaobjectpublisher_p.h  | 39 +++++++++++--
 tests/auto/qml/testwebchannel.cpp        |  6 +-
 tests/auto/webchannel/tst_webchannel.cpp | 48 +++++++++++++++-
 tests/auto/webchannel/tst_webchannel.h   |  1 +
 5 files changed, 138 insertions(+), 27 deletions(-)

diff --git a/src/webchannel/qmetaobjectpublisher.cpp b/src/webchannel/qmetaobjectpublisher.cpp
index e997b75..3897c07 100644
--- a/src/webchannel/qmetaobjectpublisher.cpp
+++ b/src/webchannel/qmetaobjectpublisher.cpp
@@ -186,7 +186,6 @@ Q_DECLARE_TYPEINFO(OverloadResolutionCandidate, Q_MOVABLE_TYPE);
 QMetaObjectPublisher::QMetaObjectPublisher(QWebChannel *webChannel)
     : QObject(webChannel)
     , webChannel(webChannel)
-    , clientIsIdle(false)
     , blockUpdates(false)
     , propertyUpdatesInitialized(false)
 {
@@ -300,17 +299,17 @@ QJsonObject QMetaObjectPublisher::classInfoForObject(const QObject *object, QWeb
     return data;
 }
 
-void QMetaObjectPublisher::setClientIsIdle(bool isIdle)
+void QMetaObjectPublisher::setClientIsIdle(bool isIdle, QWebChannelAbstractTransport *transport)
 {
-    if (clientIsIdle == isIdle) {
-        return;
-    }
-    clientIsIdle = isIdle;
-    if (!isIdle && timer.isActive()) {
-        timer.stop();
-    } else if (isIdle && !timer.isActive()) {
-        timer.start(PROPERTY_UPDATE_INTERVAL, this);
-    }
+    transportState[transport].clientIsIdle = isIdle;
+    if (isIdle)
+        sendEnqueuedPropertyUpdates(transport);
+}
+
+bool QMetaObjectPublisher::isClientIdle(QWebChannelAbstractTransport *transport)
+{
+    auto found = transportState.find(transport);
+    return found != transportState.end() && found.value().clientIsIdle;
 }
 
 QJsonObject QMetaObjectPublisher::initializeClient(QWebChannelAbstractTransport *transport)
@@ -365,7 +364,7 @@ void QMetaObjectPublisher::initializePropertyUpdates(const QObject *const object
 
 void QMetaObjectPublisher::sendPendingPropertyUpdates()
 {
-    if (blockUpdates || !clientIsIdle || pendingPropertyUpdates.isEmpty()) {
+    if (blockUpdates) {
         return;
     }
 
@@ -415,18 +414,19 @@ void QMetaObjectPublisher::sendPendingPropertyUpdates()
 
     // data does not contain specific updates
     if (!data.isEmpty()) {
-        setClientIsIdle(false);
-
         message[KEY_DATA] = data;
-        broadcastMessage(message);
+        enqueueBroadcastMessage(message);
     }
 
     // send every property update which is not supposed to be broadcasted
     const QHash<QWebChannelAbstractTransport*, QJsonArray>::const_iterator suend = specificUpdates.constEnd();
     for (QHash<QWebChannelAbstractTransport*, QJsonArray>::const_iterator it = specificUpdates.constBegin(); it != suend; ++it) {
         message[KEY_DATA] = it.value();
-        it.key()->sendMessage(message);
+        enqueueMessage(message, it.key());
     }
+
+    for (auto state = transportState.begin(); state != transportState.end(); ++state)
+        sendEnqueuedPropertyUpdates(state.key());
 }
 
 QVariant QMetaObjectPublisher::invokeMethod(QObject *const object, const QMetaMethod &method,
@@ -572,7 +572,7 @@ void QMetaObjectPublisher::signalEmitted(const QObject *object, const int signal
         }
     } else {
         pendingPropertyUpdates[object][signalIndex] = arguments;
-        if (clientIsIdle && !blockUpdates && !timer.isActive()) {
+        if (!blockUpdates && !timer.isActive()) {
             timer.start(PROPERTY_UPDATE_INTERVAL, this);
         }
     }
@@ -852,6 +852,40 @@ void QMetaObjectPublisher::broadcastMessage(const QJsonObject &message) const
     }
 }
 
+void QMetaObjectPublisher::enqueueBroadcastMessage(const QJsonObject &message)
+{
+    if (webChannel->d_func()->transports.isEmpty()) {
+        qWarning("QWebChannel is not connected to any transports, cannot send message: %s",
+                 QJsonDocument(message).toJson().constData());
+        return;
+    }
+
+    for (auto *transport : webChannel->d_func()->transports) {
+        auto &state = transportState[transport];
+        state.queuedMessages.append(message);
+    }
+}
+
+void QMetaObjectPublisher::enqueueMessage(const QJsonObject &message,
+                                          QWebChannelAbstractTransport *transport)
+{
+    auto &state = transportState[transport];
+    state.queuedMessages.append(message);
+}
+
+void QMetaObjectPublisher::sendEnqueuedPropertyUpdates(QWebChannelAbstractTransport *transport)
+{
+    auto found = transportState.find(transport);
+    if (found != transportState.end() && found.value().clientIsIdle
+        && !found.value().queuedMessages.isEmpty()) {
+        for (auto message : found.value().queuedMessages) {
+            transport->sendMessage(message);
+        }
+        found.value().queuedMessages.clear();
+        found.value().clientIsIdle = false;
+    }
+}
+
 void QMetaObjectPublisher::handleMessage(const QJsonObject &message, QWebChannelAbstractTransport *transport)
 {
     if (!webChannel->d_func()->transports.contains(transport)) {
@@ -866,7 +900,7 @@ void QMetaObjectPublisher::handleMessage(const QJsonObject &message, QWebChannel
 
     const MessageType type = toType(message.value(KEY_TYPE));
     if (type == TypeIdle) {
-        setClientIsIdle(true);
+        setClientIsIdle(true, transport);
     } else if (type == TypeInit) {
         if (!message.contains(KEY_ID)) {
             qWarning("JSON message object is missing the id property: %s",
@@ -931,6 +965,7 @@ void QMetaObjectPublisher::setBlockUpdates(bool block)
     blockUpdates = block;
 
     if (!blockUpdates) {
+        timer.start(PROPERTY_UPDATE_INTERVAL, this);
         sendPendingPropertyUpdates();
     } else if (timer.isActive()) {
         timer.stop();
diff --git a/src/webchannel/qmetaobjectpublisher_p.h b/src/webchannel/qmetaobjectpublisher_p.h
index ded0d33..4713ef1 100644
--- a/src/webchannel/qmetaobjectpublisher_p.h
+++ b/src/webchannel/qmetaobjectpublisher_p.h
@@ -59,6 +59,7 @@
 #include <QBasicTimer>
 #include <QPointer>
 #include <QJsonObject>
+#include <QQueue>
 
 #include <unordered_map>
 
@@ -111,17 +112,36 @@ public:
      */
     void broadcastMessage(const QJsonObject &message) const;
 
+    /**
+     * Enqueue the given @p message to all known transports.
+     */
+    void enqueueBroadcastMessage(const QJsonObject &message);
+
+    /**
+     * Enqueue the given @p message to @p transport.
+     */
+    void enqueueMessage(const QJsonObject &message, QWebChannelAbstractTransport *transport);
+
+    /**
+     * If client for given @p transport is idle, send queued messaged to @p transport and then mark
+     * the client as not idle.
+     */
+    void sendEnqueuedPropertyUpdates(QWebChannelAbstractTransport *transport);
+
     /**
      * Serialize the QMetaObject of @p object and return it in JSON form.
      */
     QJsonObject classInfoForObject(const QObject *object, QWebChannelAbstractTransport *transport);
 
     /**
-     * Set the client to idle or busy, based on the value of @p isIdle.
-     *
-     * When the value changed, start/stop the property update timer accordingly.
+     * Set the client to idle or busy for a single @p transport, based on the value of @p isIdle.
      */
-    void setClientIsIdle(bool isIdle);
+    void setClientIsIdle(bool isIdle, QWebChannelAbstractTransport *transport);
+
+    /**
+     * Check that client is idle for @p transport.
+     */
+    bool isClientIdle(QWebChannelAbstractTransport *transport);
 
     /**
      * Initialize clients by sending them the class information of the registered objects.
@@ -277,8 +297,15 @@ private:
     std::unordered_map<const QThread*, SignalHandler<QMetaObjectPublisher>> signalHandlers;
     SignalHandler<QMetaObjectPublisher> *signalHandlerFor(const QObject *object);
 
-    // true when the client is idle, false otherwise
-    bool clientIsIdle;
+    struct TransportState
+    {
+        TransportState() : clientIsIdle(false) { }
+        // true when the client is idle, false otherwise
+        bool clientIsIdle;
+        // messages to send
+        QQueue<QJsonObject> queuedMessages;
+    };
+    QHash<QWebChannelAbstractTransport *, TransportState> transportState;
 
     // true when no property updates should be sent, false otherwise
     bool blockUpdates;
diff --git a/tests/auto/qml/testwebchannel.cpp b/tests/auto/qml/testwebchannel.cpp
index 9891687..3ca81c2 100644
--- a/tests/auto/qml/testwebchannel.cpp
+++ b/tests/auto/qml/testwebchannel.cpp
@@ -46,7 +46,11 @@ TestWebChannel::~TestWebChannel()
 
 bool TestWebChannel::clientIsIdle() const
 {
-    return QWebChannel::d_func()->publisher->clientIsIdle;
+    for (auto *transport : QWebChannel::d_func()->transports) {
+        if (QWebChannel::d_func()->publisher->isClientIdle(transport))
+            return true;
+    }
+    return false;
 }
 
 QT_END_NAMESPACE
diff --git a/tests/auto/webchannel/tst_webchannel.cpp b/tests/auto/webchannel/tst_webchannel.cpp
index 7f846f5..37f989a 100644
--- a/tests/auto/webchannel/tst_webchannel.cpp
+++ b/tests/auto/webchannel/tst_webchannel.cpp
@@ -785,7 +785,7 @@ void TestWebChannel::testTransportWrapObjectProperties()
     DummyTransport *dummyTransport = new DummyTransport(this);
     channel.connectTo(dummyTransport);
     channel.d_func()->publisher->initializeClient(dummyTransport);
-    channel.d_func()->publisher->setClientIsIdle(true);
+    channel.d_func()->publisher->setClientIsIdle(true, dummyTransport);
 
     QCOMPARE(channel.d_func()->publisher->transportedWrappedObjects.size(), 0);
 
@@ -988,6 +988,50 @@ void TestWebChannel::testAsyncObject()
     thread.wait();
 }
 
+void TestWebChannel::testPropertyMultipleTransports()
+{
+    DummyTransport transport1;
+    DummyTransport transport2;
+
+    QWebChannel channel;
+    QMetaObjectPublisher *publisher = channel.d_func()->publisher;
+
+    TestObject testObj;
+    testObj.setObjectName("testObject");
+    channel.registerObject(testObj.objectName(), &testObj);
+    channel.connectTo(&transport1);
+    channel.connectTo(&transport2);
+
+    testObj.setProp("Hello");
+
+    publisher->initializeClient(&transport1);
+    publisher->initializeClient(&transport2);
+    publisher->setClientIsIdle(true, &transport1);
+    QCOMPARE(publisher->isClientIdle(&transport1), true);
+    QCOMPARE(publisher->isClientIdle(&transport2), false);
+    QVERIFY(transport1.messagesSent().isEmpty());
+    QVERIFY(transport2.messagesSent().isEmpty());
+
+    testObj.setProp("World");
+    QTRY_COMPARE_WITH_TIMEOUT(transport1.messagesSent().size(), 1u, 2000);
+    QCOMPARE(transport2.messagesSent().size(), 0u);
+    publisher->setClientIsIdle(true, &transport2);
+    QTRY_COMPARE_WITH_TIMEOUT(transport2.messagesSent().size(), 1u, 2000);
+    QCOMPARE(publisher->isClientIdle(&transport1), false);
+    QCOMPARE(publisher->isClientIdle(&transport2), false);
+
+    testObj.setProp("!!!");
+    publisher->setClientIsIdle(true, &transport2);
+    QCOMPARE(publisher->isClientIdle(&transport2), true);
+    QCOMPARE(publisher->isClientIdle(&transport1), false);
+    QTRY_COMPARE_WITH_TIMEOUT(transport2.messagesSent().size(), 2u, 2000);
+    QCOMPARE(transport1.messagesSent().size(), 1u);
+    publisher->setClientIsIdle(true, &transport1);
+    QTRY_COMPARE_WITH_TIMEOUT(transport1.messagesSent().size(), 2u, 2000);
+    QCOMPARE(publisher->isClientIdle(&transport1), false);
+    QCOMPARE(publisher->isClientIdle(&transport2), false);
+}
+
 class FunctionWrapper : public QObject
 {
     Q_OBJECT
@@ -1105,7 +1149,7 @@ void TestWebChannel::benchPropertyUpdates()
             obj->change();
         }
 
-        channel.d_func()->publisher->clientIsIdle = true;
+        channel.d_func()->publisher->setClientIsIdle(true, m_dummyTransport);
         channel.d_func()->publisher->sendPendingPropertyUpdates();
     }
 }
diff --git a/tests/auto/webchannel/tst_webchannel.h b/tests/auto/webchannel/tst_webchannel.h
index eae21f4..dd4e690 100644
--- a/tests/auto/webchannel/tst_webchannel.h
+++ b/tests/auto/webchannel/tst_webchannel.h
@@ -348,6 +348,7 @@ private slots:
     void testJsonToVariant();
     void testInfiniteRecursion();
     void testAsyncObject();
+    void testPropertyMultipleTransports();
     void testDeletionDuringMethodInvocation_data();
     void testDeletionDuringMethodInvocation();
 
-- 
2.36.0

From 8c842152da613f941892481d62267c73c4a4f006 Mon Sep 17 00:00:00 2001
From: Arno Rehn <a.rehn@menlosystems.com>
Date: Wed, 8 Dec 2021 22:44:49 +0100
Subject: [PATCH 3/3] QMetaObjectPublisher: Never send stale queued messages

If the client is connected with an in-process transport, it can happen
that a transmitted message triggers a subsequent property change.
In that case, we need to ensure that the queued messages have already
been cleared; otherwise the recursive call will send everythig again.

Case in point: The qmlwebchannel tests fail if we don't clear the
queued messages before sending them out.

For that same reason set the client to "busy" (aka non-idle) just right
before sending out the messages; otherwise a potential "Idle" type
message will not correctly restore the Idle state.

Pick-to: 6.2
Pick-to: 6.3
Change-Id: Idc4afdd5cf4b4e03b8de8953a03d28442d74a3ab
Reviewed-by: Fabian Kosmale <fabian.kosmale@qt.io>
(cherry picked from commit b4bf8f5e043120341cd9caa59f25a2beecd94ad0)
---
 src/webchannel/qmetaobjectpublisher.cpp | 18 +++++++++++++++---
 1 file changed, 15 insertions(+), 3 deletions(-)

diff --git a/src/webchannel/qmetaobjectpublisher.cpp b/src/webchannel/qmetaobjectpublisher.cpp
index 3897c07..898d769 100644
--- a/src/webchannel/qmetaobjectpublisher.cpp
+++ b/src/webchannel/qmetaobjectpublisher.cpp
@@ -878,11 +878,23 @@ void QMetaObjectPublisher::sendEnqueuedPropertyUpdates(QWebChannelAbstractTransp
     auto found = transportState.find(transport);
     if (found != transportState.end() && found.value().clientIsIdle
         && !found.value().queuedMessages.isEmpty()) {
-        for (auto message : found.value().queuedMessages) {
+
+        // If the client is connected with an in-process transport, it can
+        // happen that a message triggers a subsequent property change. In
+        // that case, we need to ensure that the queued messages have already
+        // been cleared; otherwise the recursive call will send everythig again.
+        // Case in point: The qmlwebchannel tests fail if we don't clear the
+        // queued messages before sending them out.
+        // For that same reason set the client to "busy" (aka non-idle) just
+        // right before sending out the messages; otherwise a potential
+        // "Idle" type message will not correctly restore the Idle state.
+        const auto messages = std::move(found.value().queuedMessages);
+        Q_ASSERT(found.value().queuedMessages.isEmpty());
+        found.value().clientIsIdle = false;
+
+        for (const auto &message : messages) {
             transport->sendMessage(message);
         }
-        found.value().queuedMessages.clear();
-        found.value().clientIsIdle = false;
     }
 }
 
-- 
2.36.0