QSettings: Special-case serialization of QDateTime.

QDateTime values with a UTC offset are not correctly serialized with
QDataStream::Qt_4_0. So use a newer QDataStream format for this type and
mark it with "@DateTime" instead of "@Variant".

Task-number: QTBUG-46551
Change-Id: I211c89e8cd0211c949ec993e6ffd5192d0eebbb3
Reviewed-by: Joerg Bornemann <joerg.bornemann@theqtcompany.com>

2 files changed, 28 insertions, 5 deletions

diff --git a/src/corelib/io/qsettings.cpp b/src/corelib/io/qsettings.cpp
index da4a02e4e4..b9993c454e 100644
--- a/src/corelib/io/qsettings.cpp
+++ b/src/corelib/io/qsettings.cpp
@@ -453,14 +453,23 @@ QString QSettingsPrivate::variantToString(const QVariant &v)
 
         default: {
 #ifndef QT_NO_DATASTREAM
+            QDataStream::Version version;
+            const char *typeSpec;
+            if (v.type() == QVariant::DateTime) {
+                version = QDataStream::Qt_5_6;
+                typeSpec = "@DateTime(";
+            } else {
+                version = QDataStream::Qt_4_0;
+                typeSpec = "@Variant(";
+            }
             QByteArray a;
             {
                 QDataStream s(&a, QIODevice::WriteOnly);
-                s.setVersion(QDataStream::Qt_4_0);
+                s.setVersion(version);
                 s << v;
             }
 
-            result = QLatin1String("@Variant(");
+            result = QLatin1String(typeSpec);
             result += QString::fromLatin1(a.constData(), a.size());
             result += QLatin1Char(')');
 #else
@@ -480,11 +489,21 @@ QVariant QSettingsPrivate::stringToVariant(const QString &s)
         if (s.endsWith(QLatin1Char(')'))) {
             if (s.startsWith(QLatin1String("@ByteArray("))) {
                 return QVariant(s.toLatin1().mid(11, s.size() - 12));
-            } else if (s.startsWith(QLatin1String("@Variant("))) {
+            } else if (s.startsWith(QLatin1String("@Variant("))
+                       || s.startsWith(QLatin1String("@DateTime("))) {
 #ifndef QT_NO_DATASTREAM
-                QByteArray a(s.toLatin1().mid(9));
+                QDataStream::Version version;
+                int offset;
+                if (s.at(1) == QLatin1Char('D')) {
+                    version = QDataStream::Qt_5_6;
+                    offset = 10;
+                } else {
+                    version = QDataStream::Qt_4_0;
+                    offset = 9;
+                }
+                QByteArray a(s.toLatin1().mid(offset));
                 QDataStream stream(&a, QIODevice::ReadOnly);
-                stream.setVersion(QDataStream::Qt_4_0);
+                stream.setVersion(version);
                 QVariant result;
                 stream >> result;
                 return result;
diff --git a/tests/auto/corelib/io/qsettings/tst_qsettings.cpp b/tests/auto/corelib/io/qsettings/tst_qsettings.cpp
index e2e1d99657..badff20490 100644
--- a/tests/auto/corelib/io/qsettings/tst_qsettings.cpp
+++ b/tests/auto/corelib/io/qsettings/tst_qsettings.cpp
@@ -37,6 +37,7 @@
 #include <QtCore/QSettings>
 #include <private/qsettings_p.h>
 #include <QtCore/QCoreApplication>
+#include <QtCore/QDateTime>
 #include <QtCore/QtGlobal>
 #include <QtCore/QMetaType>
 #include <QtCore/QString>
@@ -1201,6 +1202,9 @@ void tst_QSettings::testVariantTypes()
     QList<QVariant> l4;
     l4 << QVariant(m2) << QVariant(l2) << QVariant(l3);
     testVal("key13", l4, QVariantList, List);
+    QDateTime dt = QDateTime::currentDateTime();
+    dt.setOffsetFromUtc(3600);
+    testVal("key14", dt, QDateTime, DateTime);
 
     // We store key sequences as strings instead of binary variant blob, for improved
     // readability in the resulting format.