Reading QJsonObject property should not modify the object itself.

Before this change such code:

    QJsonObject o;
    o["blah"];

would create property "blah" and assign null value to it, while
this code:

    const QJsonObject o;
    o["blah"];

would not. The change unifies the confusing behavior. Now reading
a non-existing property, is not causing a property to be added
in any visible way.

Internally QJsonObject stores a special hash of undefined, but
referenced values. Such reference is supposed to not live long,
only to the first compacting or assignment.

Change-Id: Ib022acf74ff49bad88d45d65d7093c4281d468f1
Reviewed-by: Thiago Macieira <thiago.macieira@intel.com>
Reviewed-by: Lars Knoll <lars.knoll@digia.com>

1 files changed, 3 insertions, 4 deletions

diff --git a/src/corelib/json/qjsonvalue.cpp b/src/corelib/json/qjsonvalue.cpp
index 4c4838d314..1224a24709 100644
--- a/src/corelib/json/qjsonvalue.cpp
+++ b/src/corelib/json/qjsonvalue.cpp
@@ -669,11 +669,10 @@ void QJsonValue::detach()
     However, they are not explicitly documented here.
 */
 
-
 QJsonValueRef &QJsonValueRef::operator =(const QJsonValue &val)
 {
     if (is_object)
-        o->setValueAt(index, val);
+        UnionHelper::setValueAt(this, val);
     else
         a->replace(index, val);
 
@@ -683,7 +682,7 @@ QJsonValueRef &QJsonValueRef::operator =(const QJsonValue &val)
 QJsonValueRef &QJsonValueRef::operator =(const QJsonValueRef &ref)
 {
     if (is_object)
-        o->setValueAt(index, ref);
+        UnionHelper::setValueAt(this, ref);
     else
         a->replace(index, ref);
 
@@ -704,7 +703,7 @@ QJsonValue QJsonValueRef::toValue() const
 {
     if (!is_object)
         return a->at(index);
-    return o->valueAt(index);
+    return UnionHelper::valueAt(this);
 }
 
 #if !defined(QT_NO_DEBUG_STREAM) && !defined(QT_JSON_READONLY)