Allow deleting a channel during method invocation

A real-life use case is the session restore page in KDE Falkon or, more
generally, any kind of closeTab() method exposed to JS in a QWebEnginePage.

The approach taken in this patch will only work if the transport can also deal
with deletion during a messageReceived signal emission. Alternatively, method
invocation could be delayed via the event loop, but this would come with an
obvious performance penalty.

Change-Id: I2940f61e07c77365f6e3e7cd29463d4cb5b525a6
Reviewed-by: Milian Wolff <milian.wolff@kdab.com>

1 files changed, 9 insertions, 3 deletions

diff --git a/src/webchannel/qmetaobjectpublisher.cpp b/src/webchannel/qmetaobjectpublisher.cpp
index cfc6ad2..8e83237 100644
--- a/src/webchannel/qmetaobjectpublisher.cpp
+++ b/src/webchannel/qmetaobjectpublisher.cpp
@@ -664,9 +664,15 @@ void QMetaObjectPublisher::handleMessage(const QJsonObject &message, QWebChannel
                 return;
             }
 
-            transport->sendMessage(createResponse(message.value(KEY_ID),
-                wrapResult(invokeMethod(object, message.value(KEY_METHOD).toInt(-1),
-                             message.value(KEY_ARGS).toArray()), transport)));
+            QPointer<QMetaObjectPublisher> publisherExists(this);
+            QPointer<QWebChannelAbstractTransport> transportExists(transport);
+            QVariant result =
+                invokeMethod(object,
+                             message.value(KEY_METHOD).toInt(-1),
+                             message.value(KEY_ARGS).toArray());
+            if (!publisherExists || !transportExists)
+                return;
+            transport->sendMessage(createResponse(message.value(KEY_ID), wrapResult(result, transport)));
         } else if (type == TypeConnectToSignal) {
             signalHandler.connectTo(object, message.value(KEY_SIGNAL).toInt(-1));
         } else if (type == TypeDisconnectFromSignal) {