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, 2 insertions, 0 deletions

diff --git a/src/corelib/json/qjsonvalue.h b/src/corelib/json/qjsonvalue.h
index 97e20b574d..a00bc0b72f 100644
--- a/src/corelib/json/qjsonvalue.h
+++ b/src/corelib/json/qjsonvalue.h
@@ -149,6 +149,7 @@ public:
         : a(array), is_object(false), index(idx) {}
     QJsonValueRef(QJsonObject *object, int idx)
         : o(object), is_object(true), index(idx) {}
+    inline QJsonValueRef(QJsonObject *object, const QString &key);
 
     inline operator QJsonValue() const { return toValue(); }
     QJsonValueRef &operator = (const QJsonValue &val);
@@ -188,6 +189,7 @@ private:
     };
     uint is_object : 1;
     uint index : 31;
+    struct UnionHelper;
 };
 
 #if !defined(QT_NO_DEBUG_STREAM) && !defined(QT_JSON_READONLY)