Clarify handling of unspecified year in two QCalendar methods

[ChangeLog][QtCore] QCalendar::monthsInYear(QCalendar::Unspecified)
now returns maximumMonthsInYear(). QCalendar::daysInYear() now makes
clear that its handling of unspecified year is undefined.

Change-Id: Ifef8723193868c666f6afeb7f190af4929d30dea
Reviewed-by: Paul Wicking <paul.wicking@qt.io>
Reviewed-by: Thiago Macieira <thiago.macieira@intel.com>

2 files changed, 33 insertions, 3 deletions

diff --git a/src/corelib/time/qcalendar.cpp b/src/corelib/time/qcalendar.cpp
index 9d485f181e..32f0a511a3 100644
--- a/src/corelib/time/qcalendar.cpp
+++ b/src/corelib/time/qcalendar.cpp
@@ -1,6 +1,6 @@
 /****************************************************************************
 **
-** Copyright (C) 2019 The Qt Company Ltd.
+** Copyright (C) 2020 The Qt Company Ltd.
 ** Contact: https://www.qt.io/licensing/
 **
 ** This file is part of the QtCore module of the Qt Toolkit.
@@ -750,6 +750,8 @@ int QCalendar::daysInMonth(int month, int year) const
 
 /*!
     Returns the number of days in the given \a year.
+
+    Handling of \c Unspecified as \a year is undefined.
 */
 int QCalendar::daysInYear(int year) const
 {
@@ -758,10 +760,15 @@ int QCalendar::daysInYear(int year) const
 
 /*!
     Returns the number of months in the given \a year.
+
+    If \a year is \c Unspecified, returns the maximum number of months in a
+    year.
+
+    \sa maximumMonthsInYear()
 */
 int QCalendar::monthsInYear(int year) const
 {
-    return d ? d->monthsInYear(year) : 0;
+    return d ? year == Unspecified ? d->maximumMonthsInYear() : d->monthsInYear(year) : 0;
 }
 
 /*!
diff --git a/tests/auto/corelib/time/qcalendar/tst_qcalendar.cpp b/tests/auto/corelib/time/qcalendar/tst_qcalendar.cpp
index 9b41014394..5da69e76a5 100644
--- a/tests/auto/corelib/time/qcalendar/tst_qcalendar.cpp
+++ b/tests/auto/corelib/time/qcalendar/tst_qcalendar.cpp
@@ -1,6 +1,6 @@
 /****************************************************************************
 **
-** Copyright (C) 2018 The Qt Company Ltd.
+** Copyright (C) 2020 The Qt Company Ltd.
 ** Contact: https://www.qt.io/licensing/
 **
 ** This file is part of the test suite of the Qt Toolkit.
@@ -40,6 +40,8 @@ private:
 private slots:
     void basic_data();
     void basic();
+    void unspecified_data() { basic_data(); }
+    void unspecified();
     void nameCase();
     void specific_data();
     void specific();
@@ -145,6 +147,27 @@ void tst_QCalendar::basic()
     NORMALYEAR(cal, year);
 }
 
+void tst_QCalendar::unspecified()
+{
+    QFETCH(QCalendar::System, system);
+    QCalendar cal(system);
+
+    const QDate today = QDate::currentDate();
+    const int thisYear = today.year();
+    QCOMPARE(cal.monthsInYear(QCalendar::Unspecified), cal.maximumMonthsInYear());
+    for (int month = cal.maximumMonthsInYear(); month > 0; month--) {
+        const int days = cal.daysInMonth(month);
+        int count = 0;
+        // 19 years = one Metonic cycle (used by some lunar calendars)
+        for (int i = 19; i > 0; --i) {
+            if (cal.daysInMonth(month, thisYear - i) == days)
+                count++;
+        }
+        // Require a majority of the years tested:
+        QVERIFY2(count > 9, "Default daysInMonth() should be for a normal year");
+    }
+}
+
 void tst_QCalendar::nameCase()
 {
     QVERIFY(QCalendar::availableCalendars().contains(QStringLiteral("Gregorian")));