Correctly set this object when calling scope/context functions

When a function is called that is in a QML scope or a QML context, set
the 'this' object to the QML scope.

Note: this patch is 5.9 specific. 5.11 has a similair issue, but the
implementation is quite different, so that needs a separate fix.

Task-number: QTBUG-59357
Change-Id: Ia78e012d413c40a094e957f4020502cd055ac286
Reviewed-by: Simon Hausmann <simon.hausmann@qt.io>

src/qml/jsruntime/qv4runtime.cpp

@@ -1064,6 +1064,8 @@ ReturnedValue Runtime::method_callQmlScopeObjectProperty(ExecutionEngine *engine
         return engine->throwTypeError(error);
     }
 
+    auto scopeObj = static_cast<const QmlContext &>(callData->thisObject).d()->qml->scopeObject;
+    callData->thisObject = QObjectWrapper::wrap(engine, scopeObj);
     o->call(scope, callData);
     return scope.result.asReturnedValue();
 }
@@ -1077,6 +1079,8 @@ ReturnedValue Runtime::method_callQmlContextObjectProperty(ExecutionEngine *engi
         return engine->throwTypeError(error);
     }
 
+    auto scopeObj = static_cast<const QmlContext &>(callData->thisObject).d()->qml->context->contextData()->contextObject;
+    callData->thisObject = QObjectWrapper::wrap(engine, scopeObj);
     o->call(scope, callData);
     return scope.result.asReturnedValue();
 }

tests/auto/qml/qqmllanguage/data/thisInQmlScope.qml

@@ -0,0 +1,10 @@
+import QtQml 2.2
+QtObject {
+    property int x: 42
+    property int y: 0
+    function g(){
+        y = this.x;
+    }
+    property var f: g
+    Component.onCompleted: f()
+}

tests/auto/qml/qqmllanguage/tst_qqmllanguage.cpp

@@ -273,6 +273,8 @@ private slots:
 
     void lowercaseTypeNames();
 
+    void thisInQmlScope();
+
 private:
     QQmlEngine engine;
     QStringList defaultImportPathList;
@@ -4604,6 +4606,19 @@ void tst_qqmllanguage::lowercaseTypeNames()
     QCOMPARE(qmlRegisterSingletonType<QObject>("Test", 1, 0, "lowerCaseTypeName", nullptr), -1);
 }
 
+void tst_qqmllanguage::thisInQmlScope()
+{
+    QQmlEngine engine;
+
+    QQmlComponent component(&engine, testFileUrl("thisInQmlScope.qml"));
+    QTRY_VERIFY(component.isReady());
+    VERIFY_ERRORS(0);
+    QScopedPointer<QObject> o(component.create());
+    QVERIFY(!o.isNull());
+    QCOMPARE(o->property("x"), QVariant(42));
+    QCOMPARE(o->property("y"), QVariant(42));
+}
+
 QTEST_MAIN(tst_qqmllanguage)
 
 #include "tst_qqmllanguage.moc"