Allow property observers on readonly properties

This makes it necessary to tolerate evaluate() calls after the engine is
gone. With non-QProperty properties this can't happen as the engine
controls the observers.

Change-Id: Ia700a10ad847b8a174b2346a4ad7a4de7afb0c83
Reviewed-by: Fabian Kosmale <fabian.kosmale@qt.io>

3 files changed, 27 insertions, 13 deletions

diff --git a/src/qml/qml/qqmlboundsignal.cpp b/src/qml/qml/qqmlboundsignal.cpp
index 0dfbf1faee..665d4e6c75 100644
--- a/src/qml/qml/qqmlboundsignal.cpp
+++ b/src/qml/qml/qqmlboundsignal.cpp
@@ -175,12 +175,16 @@ QString QQmlBoundSignalExpression::expression() const
 // Changes made here may need to be made there and vice versa.
 void QQmlBoundSignalExpression::evaluate(void **a)
 {
-    Q_ASSERT (engine());
-
     if (!expressionFunctionValid())
         return;
 
     QQmlEngine *qmlengine = engine();
+
+    // If there is no engine, we have no way to evaluate anything.
+    // This can happen on destruction.
+    if (!qmlengine)
+        return;
+
     QQmlEnginePrivate *ep = QQmlEnginePrivate::get(qmlengine);
     QV4::ExecutionEngine *v4 = qmlengine->handle();
     QV4::Scope scope(v4);
diff --git a/src/qml/qml/qqmljavascriptexpression.cpp b/src/qml/qml/qqmljavascriptexpression.cpp
index 95db27019c..75bc944fee 100644
--- a/src/qml/qml/qqmljavascriptexpression.cpp
+++ b/src/qml/qml/qqmljavascriptexpression.cpp
@@ -178,8 +178,14 @@ void QQmlJavaScriptExpression::refresh()
 
 QV4::ReturnedValue QQmlJavaScriptExpression::evaluate(bool *isUndefined)
 {
-    QV4::ExecutionEngine *v4 = m_context->engine()->handle();
-    QV4::Scope scope(v4);
+    QQmlEngine *qmlengine = engine();
+    if (!qmlengine) {
+        if (isUndefined)
+            *isUndefined = true;
+        return QV4::Encode::undefined();
+    }
+
+    QV4::Scope scope(qmlengine->handle());
     QV4::JSCallArguments jsCall(scope);
 
     return evaluate(jsCall.callData(scope), isUndefined);
@@ -256,10 +262,9 @@ static inline QV4::ReturnedValue thisObject(QObject *scopeObject, QV4::Execution
 
 QV4::ReturnedValue QQmlJavaScriptExpression::evaluate(QV4::CallData *callData, bool *isUndefined)
 {
-    Q_ASSERT(m_context && m_context->engine());
-
+    QQmlEngine *qmlEngine = engine();
     QV4::Function *v4Function = function();
-    if (!v4Function) {
+    if (!v4Function || !qmlEngine) {
         if (isUndefined)
             *isUndefined = true;
         return QV4::Encode::undefined();
@@ -267,7 +272,6 @@ QV4::ReturnedValue QQmlJavaScriptExpression::evaluate(QV4::CallData *callData, b
 
     // All code that follows must check with watcher before it accesses data members
     // incase we have been deleted.
-    QQmlEngine *qmlEngine = m_context->engine();
     QQmlJavaScriptExpressionCapture capture(this, qmlEngine);
 
     QV4::Scope scope(qmlEngine->handle());
@@ -291,11 +295,15 @@ QV4::ReturnedValue QQmlJavaScriptExpression::evaluate(QV4::CallData *callData, b
 
 bool QQmlJavaScriptExpression::evaluate(void **a, const QMetaType *types, int argc)
 {
-    Q_ASSERT(m_context && m_context->engine());
-
     // All code that follows must check with watcher before it accesses data members
     // incase we have been deleted.
-    QQmlEngine *qmlEngine = m_context->engine();
+    QQmlEngine *qmlEngine = engine();
+
+    // If there is no engine, we have no way to evaluate anything.
+    // This can happen on destruction.
+    if (!qmlEngine)
+        return false;
+
     QQmlJavaScriptExpressionCapture capture(this, qmlEngine);
 
     QV4::Scope scope(qmlEngine->handle());
diff --git a/src/qml/qml/qqmlpropertyvalidator.cpp b/src/qml/qml/qqmlpropertyvalidator.cpp
index deb747fa2f..f1826b2f1c 100644
--- a/src/qml/qml/qqmlpropertyvalidator.cpp
+++ b/src/qml/qml/qqmlpropertyvalidator.cpp
@@ -241,9 +241,11 @@ QVector<QQmlError> QQmlPropertyValidator::validateObject(
         }
 
         // Signal handlers were resolved and checked earlier in the signal handler conversion pass.
-        if (binding->flags & QV4::CompiledData::Binding::IsSignalHandlerExpression
-            || binding->flags & QV4::CompiledData::Binding::IsSignalHandlerObject)
+        if (binding->flags & (QV4::CompiledData::Binding::IsSignalHandlerExpression
+                              | QV4::CompiledData::Binding::IsSignalHandlerObject
+                              | QV4::CompiledData::Binding::IsPropertyObserver)) {
             continue;
+        }
 
         if (binding->type == QV4::CompiledData::Binding::Type_AttachedProperty) {
             if (instantiatingBinding && (instantiatingBinding->isAttachedProperty() || instantiatingBinding->isGroupProperty())) {