Remove QtScript connection when receiver QObject has been deleted

We don't want to have to listen to the destroyed() signal for every
receiver object of a connection, and likewise we don't want to create
a QObject to handle each connection; instead, remove the connection
lazily at signal emission time after we've detected that the receiver
has been deleted.

Task-number: QTBUG-7313
Reviewed-by: Simon Hausmann

2 files changed, 31 insertions, 1 deletions

diff --git a/src/script/bridge/qscriptqobject.cpp b/src/script/bridge/qscriptqobject.cpp
index 3f4f6bb..db312bc 100644
--- a/src/script/bridge/qscriptqobject.cpp
+++ b/src/script/bridge/qscriptqobject.cpp
@@ -2220,7 +2220,14 @@ void QObjectConnectionManager::execute(int slotIndex, void **argv)
     JSC::call(exec, slot, callType, callData, thisObject, jscArgs);
 
     if (exec->hadException()) {
-        engine->emitSignalHandlerException();
+        if (slot.inherits(&QtFunction::info) && !static_cast<QtFunction*>(JSC::asObject(slot))->qobject()) {
+            // The function threw an error because the target QObject has been deleted.
+            // The connections list is stale; remove the signal handler and ignore the exception.
+            removeSignalHandler(sender(), signalIndex, receiver, slot);
+            exec->clearException();
+        } else {
+            engine->emitSignalHandlerException();
+        }
     }
 }
 
diff --git a/tests/auto/qscriptextqobject/tst_qscriptextqobject.cpp b/tests/auto/qscriptextqobject/tst_qscriptextqobject.cpp
index de9d37e..b4ce561 100644
--- a/tests/auto/qscriptextqobject/tst_qscriptextqobject.cpp
+++ b/tests/auto/qscriptextqobject/tst_qscriptextqobject.cpp
@@ -532,6 +532,7 @@ private slots:
     void prototypes();
     void objectDeleted();
     void connectToDestroyedSignal();
+    void emitAfterReceiverDeleted();
 
 private:
     QScriptEngine *m_engine;
@@ -3020,5 +3021,27 @@ void tst_QScriptExtQObject::connectToDestroyedSignal()
 #endif
 }
 
+void tst_QScriptExtQObject::emitAfterReceiverDeleted()
+{
+    for (int x = 0; x < 2; ++x) {
+        MyQObject *obj = new MyQObject;
+        QScriptValue scriptObj = m_engine->newQObject(obj);
+        if (x == 0) {
+            // Connecting from JS
+            m_engine->globalObject().setProperty("obj", scriptObj);
+            QVERIFY(m_engine->evaluate("myObject.mySignal.connect(obj, 'mySlot()')").isUndefined());
+        } else {
+            // Connecting from C++
+            qScriptConnect(m_myObject, SIGNAL(mySignal()), scriptObj, scriptObj.property("mySlot"));
+        }
+        delete obj;
+        QSignalSpy signalHandlerExceptionSpy(m_engine, SIGNAL(signalHandlerException(QScriptValue)));
+        QVERIFY(!m_engine->hasUncaughtException());
+        m_myObject->emitMySignal();
+        QCOMPARE(signalHandlerExceptionSpy.count(), 0);
+        QVERIFY(!m_engine->hasUncaughtException());
+    }
+}
+
 QTEST_MAIN(tst_QScriptExtQObject)
 #include "tst_qscriptextqobject.moc"