Fix QtScript Date <--> QDateTime (local time) conversion

This has already been fixed in 4.7 (QTBUG-9770), but the change is
too big to backport.
The general idea is the same: Only operate on UTC dates internally
(since that's how JS dates are stored), and let QDateTime take care
of converting from/to local dates as necessary.

The fix itself shouldn't be merged to 4.7, but the autotests should.

Task-number: QTBUG-9770
Reviewed-by: Jedrzej Nowacki

2 files changed, 70 insertions, 7 deletions

diff --git a/src/script/utils/qscriptdate.cpp b/src/script/utils/qscriptdate.cpp
index 598025662c..3985adb136 100644
--- a/src/script/utils/qscriptdate.cpp
+++ b/src/script/utils/qscriptdate.cpp
@@ -320,8 +320,9 @@ qsreal FromDateTime(const QDateTime &dt)
         return qSNaN();
     if (!LocalTZA) // ### move
         LocalTZA = getLocalTZA();
-    QDate date = dt.date();
-    QTime taim = dt.time();
+    QDateTime utc = dt.toUTC();
+    QDate date = utc.date();
+    QTime taim = utc.time();
     int year = date.year();
     int month = date.month() - 1;
     int day = date.day();
@@ -331,8 +332,6 @@ qsreal FromDateTime(const QDateTime &dt)
     int ms = taim.msec();
     double t = MakeDate(MakeDay(year, month, day),
                         MakeTime(hours, mins, secs, ms));
-    if (dt.timeSpec() == Qt::LocalTime)
-        t = UTC(t);
     return TimeClip(t);
 }
 
@@ -348,8 +347,6 @@ QDateTime ToDateTime(qsreal t, Qt::TimeSpec spec)
         return QDateTime();
     if (!LocalTZA) // ### move
         LocalTZA = getLocalTZA();
-    if (spec == Qt::LocalTime)
-        t = LocalTime(t);
     int year = int(YearFromTime(t));
     int month = int(MonthFromTime(t) + 1);
     int day = int(DateFromTime(t));
@@ -357,7 +354,7 @@ QDateTime ToDateTime(qsreal t, Qt::TimeSpec spec)
     int mins = MinFromTime(t);
     int secs = SecFromTime(t);
     int ms = msFromTime(t);
-    return QDateTime(QDate(year, month, day), QTime(hours, mins, secs, ms), spec);
+    return QDateTime(QDate(year, month, day), QTime(hours, mins, secs, ms), Qt::UTC).toTimeSpec(spec);
 }
 
 } // namespace QScript
diff --git a/tests/auto/qscriptengine/tst_qscriptengine.cpp b/tests/auto/qscriptengine/tst_qscriptengine.cpp
index bb01a42157..3bb9d17ce7 100644
--- a/tests/auto/qscriptengine/tst_qscriptengine.cpp
+++ b/tests/auto/qscriptengine/tst_qscriptengine.cpp
@@ -166,6 +166,10 @@ private slots:
 
     void qRegExpInport_data();
     void qRegExpInport();
+    void dateRoundtripJSQtJS();
+    void dateRoundtripQtJSQt();
+    void dateConversionJSQt();
+    void dateConversionQtJS();
 };
 
 tst_QScriptEngine::tst_QScriptEngine()
@@ -4895,5 +4899,67 @@ void tst_QScriptEngine::qRegExpInport()
     }
 }
 
+// QScriptValue::toDateTime() returns a local time, whereas JS dates
+// are always stored as UTC. QtScript must respect the current time
+// zone, and correctly adjust for daylight saving time that may be in
+// effect at a given date (QTBUG-9770).
+void tst_QScriptEngine::dateRoundtripJSQtJS()
+{
+    uint secs = QDateTime(QDate(2009, 1, 1)).toUTC().toTime_t();
+    QScriptEngine eng;
+    for (int i = 0; i < 8000; ++i) {
+        QScriptValue jsDate = eng.evaluate(QString::fromLatin1("new Date(%0)").arg(secs * 1000.0));
+        QDateTime qtDate = jsDate.toDateTime();
+        QScriptValue jsDate2 = eng.newDate(qtDate);
+        if (jsDate2.toNumber() != jsDate.toNumber())
+            QFAIL(qPrintable(jsDate.toString()));
+        secs += 2*60*60;
+    }
+}
+
+void tst_QScriptEngine::dateRoundtripQtJSQt()
+{
+    QDateTime qtDate = QDateTime(QDate(2009, 1, 1));
+    QScriptEngine eng;
+    for (int i = 0; i < 8000; ++i) {
+        QScriptValue jsDate = eng.newDate(qtDate);
+        QDateTime qtDate2 = jsDate.toDateTime();
+        if (qtDate2 != qtDate)
+            QFAIL(qPrintable(qtDate.toString()));
+        qtDate = qtDate.addSecs(2*60*60);
+    }
+}
+
+void tst_QScriptEngine::dateConversionJSQt()
+{
+    uint secs = QDateTime(QDate(2009, 1, 1)).toUTC().toTime_t();
+    QScriptEngine eng;
+    for (int i = 0; i < 8000; ++i) {
+        QScriptValue jsDate = eng.evaluate(QString::fromLatin1("new Date(%0)").arg(secs * 1000.0));
+        QDateTime qtDate = jsDate.toDateTime();
+        QString qtUTCDateStr = qtDate.toUTC().toString(Qt::ISODate);
+        QString jsUTCDateStr = jsDate.property("toISOString").call(jsDate).toString();
+        jsUTCDateStr.chop(5); // get rid of milliseconds (".000Z")
+        if (qtUTCDateStr != jsUTCDateStr)
+            QFAIL(qPrintable(jsDate.toString()));
+        secs += 2*60*60;
+    }
+}
+
+void tst_QScriptEngine::dateConversionQtJS()
+{
+    QDateTime qtDate = QDateTime(QDate(2009, 1, 1));
+    QScriptEngine eng;
+    for (int i = 0; i < 8000; ++i) {
+        QScriptValue jsDate = eng.newDate(qtDate);
+        QString jsUTCDateStr = jsDate.property("toISOString").call(jsDate).toString();
+        jsUTCDateStr.chop(5); // get rid of milliseconds (".000Z")
+        QString qtUTCDateStr = qtDate.toUTC().toString(Qt::ISODate);
+        if (jsUTCDateStr != qtUTCDateStr)
+            QFAIL(qPrintable(qtDate.toString()));
+        qtDate = qtDate.addSecs(2*60*60);
+    }
+}
+
 QTEST_MAIN(tst_QScriptEngine)
 #include "tst_qscriptengine.moc"