Add a QJSManagedValue

A QJSManagedValue is a view on a QJSValue which always knows the engine
the value belongs to. This allows us to implement the JavaScript
semantics of the various QJSValue methods in a much more rigorous way.

[ChangeLog][QtQml] The new QJSManagedValue should be used instead of
QJSValue for manipulating properties and prototypes of JavaScript
values, as well as for calling JavaScript functions.

Change-Id: I9d445ffcf68dfa72dba9bae0818e83c80665ad66
Reviewed-by: Fabian Kosmale <fabian.kosmale@qt.io>

1 files changed, 15 insertions, 0 deletions

diff --git a/src/qml/jsapi/qjsvalue.cpp b/src/qml/jsapi/qjsvalue.cpp
index ce3ab0076b..5525aee595 100644
--- a/src/qml/jsapi/qjsvalue.cpp
+++ b/src/qml/jsapi/qjsvalue.cpp
@@ -43,6 +43,7 @@
 #include "qjsengine.h"
 #include "qjsvalue.h"
 #include "qjsprimitivevalue.h"
+#include "qjsmanagedvalue.h"
 #include "qjsvalue_p.h"
 #include "qv4value_p.h"
 #include "qv4object_p.h"
@@ -884,6 +885,20 @@ QJSValue::QJSValue(QJSPrimitiveValue &&value)
     Q_UNREACHABLE();
 }
 
+QJSValue::QJSValue(QJSManagedValue &&value)
+{
+    if (!value.d) {
+        d = QV4::Encode::undefined();
+    } else if (value.d->isManaged()) {
+        QJSValuePrivate::setRawValue(this, value.d);
+        value.d = nullptr;
+    } else {
+        d = value.d->asReturnedValue();
+        QV4::PersistentValueStorage::free(value.d);
+        value.d = nullptr;
+    }
+}
+
 static bool js_equal(const QString &string, const QV4::Value &value)
 {
     if (String *s = value.stringValue())