Fix roundtrip conversion between JS var and QVariant

Always convert null to a QVariant(VoidStar) as documented in
QJSValue. Make sure the reverse conversion will lead back to
a null JS value.

Adjusted two test cases that expected an invalid QVariant when
setting the property to null, and added test cases for the
correct conversion.

Task-number: QTBUG-40880
Change-Id: I6eb01f0067f2c89779c53fd2cd0a1193047ed2cc
Reviewed-by: Simon Hausmann <simon.hausmann@digia.com>

1 files changed, 5 insertions, 2 deletions

diff --git a/src/qml/qml/qqmlproperty.cpp b/src/qml/qml/qqmlproperty.cpp
index 42bf0dd657..09b735ae9e 100644
--- a/src/qml/qml/qqmlproperty.cpp
+++ b/src/qml/qml/qqmlproperty.cpp
@@ -1585,11 +1585,14 @@ bool QQmlPropertyPrivate::writeBinding(QObject *object,
                     propertyType = propertyMetaObject.className();
             }
         } else if (value.userType() != QVariant::Invalid) {
-            valueType = QMetaType::typeName(value.userType());
+            if (value.userType() == QMetaType::VoidStar)
+                valueType = "null";
+            else
+                valueType = QMetaType::typeName(value.userType());
         }
 
         if (!valueType)
-            valueType = "null";
+            valueType = "undefined";
         if (!propertyType)
             propertyType = QMetaType::typeName(type);
         if (!propertyType)