Add a flag not to update the lastModified field automatically.

autotests/testmemorycalendar.cpp

@@ -448,3 +448,50 @@ void MemoryCalendarTest::testDeleteIncidence()
     QVERIFY(cal->incidence(event->uid(), exception2->recurrenceId()).isNull());
     QVERIFY(cal->incidence(event->uid()).isNull());
 }
+
+void MemoryCalendarTest::testUpdateIncidence()
+{
+    MemoryCalendar::Ptr cal(new MemoryCalendar(QTimeZone::utc()));
+
+    const QDateTime dt(QDate(2021, 02, 25), QTime(14, 0), Qt::UTC);
+    Event::Ptr event(new Event());
+    event->setCreated(dt);
+    event->setLastModified(dt);
+    event->setDtStart(dt);
+    event->setDtEnd(dt.addSecs(3600));
+
+    // Adding event to cal, makes cal an observer of event.
+    QVERIFY(cal->addIncidence(event));
+    QCOMPARE(cal->rawEventsForDate(dt).count(), 1);
+
+    QVERIFY(cal->updateLastModifiedOnChange());
+
+    const QDateTime now = QDateTime::currentDateTimeUtc();
+
+    // Any single modfication is updating the lastModified field.
+    event->setSummary(QString::fromLatin1("test"));
+    QVERIFY(event->lastModified().secsTo(now) < 5);
+
+    // Reset lastModified field.
+    event->setLastModified(dt);
+    QCOMPARE(event->lastModified(), dt);
+
+    // Any modification within a startUpdates()/endUpdates() should not touch
+    // lastModified field, before the changes are completed.
+    event->startUpdates();
+    QVERIFY(cal->rawEventsForDate(dt).isEmpty());
+    event->setSummary(QString::fromLatin1("test again"));
+    QCOMPARE(event->lastModified(), dt);
+    event->endUpdates();
+    QVERIFY(event->lastModified().secsTo(now) < 5);
+    QCOMPARE(cal->rawEventsForDate(dt).count(), 1);
+
+    // Reset lastModified field.
+    event->setLastModified(dt);
+    QCOMPARE(event->lastModified(), dt);
+
+    // Don't update lastModified on change.
+    cal->setUpdateLastModifiedOnChange(false);
+    event->setSummary(QString::fromLatin1("last test"));
+    QCOMPARE(event->lastModified(), dt);
+}

autotests/testmemorycalendar.h

@@ -27,6 +27,7 @@ private Q_SLOTS:
     void testRawEventsForDate();
     void testVisibility();
     void testDeleteIncidence();
+    void testUpdateIncidence();
 };
 
 #endif

src/memorycalendar.cpp

@@ -41,7 +41,7 @@ class Q_DECL_HIDDEN KCalendarCore::MemoryCalendar::Private
 
 public:
     Private(MemoryCalendar *qq)
-        : q(qq), mFormat(nullptr)
+        : q(qq), mFormat(nullptr), mUpdateLastModified(true)
     {
     }
     ~Private()
@@ -51,6 +51,7 @@ class Q_DECL_HIDDEN KCalendarCore::MemoryCalendar::Private
     MemoryCalendar *q;
     CalFormat *mFormat;                    // calendar format
     QString mIncidenceBeingUpdated;        //  Instance identifier of Incidence currently being updated
+    bool mUpdateLastModified;              // Call setLastModified() on incidence modific ations
 
 
     /**
@@ -529,6 +530,16 @@ Alarm::List MemoryCalendar::alarms(const QDateTime &from, const QDateTime &to, b
     return alarmList;
 }
 
+bool MemoryCalendar::updateLastModifiedOnChange() const
+{
+    return d->mUpdateLastModified;
+}
+
+void MemoryCalendar::setUpdateLastModifiedOnChange(bool update)
+{
+    d->mUpdateLastModified = update;
+}
+
 void MemoryCalendar::incidenceUpdate(const QString &uid, const QDateTime &recurrenceId)
 {
     Incidence::Ptr inc = incidence(uid, recurrenceId);
@@ -564,7 +575,9 @@ void MemoryCalendar::incidenceUpdated(const QString &uid, const QDateTime &recur
 
         d->mIncidenceBeingUpdated = QString();
 
-        inc->setLastModified(QDateTime::currentDateTimeUtc());
+        if (d->mUpdateLastModified) {
+            inc->setLastModified(QDateTime::currentDateTimeUtc());
+        }
         // we should probably update the revision number here,
         // or internally in the Event itself when certain things change.
         // need to verify with ical documentation.

src/memorycalendar.h

@@ -293,6 +293,25 @@ class KCALENDARCORE_EXPORT MemoryCalendar : public Calendar
     */
     Q_REQUIRED_RESULT Alarm::List alarmsTo(const QDateTime &to) const; // TODO KF6 remove, already defined in Calendar
 
+    /**
+      Return true if the memory calendar is updating the lastModified field
+      of incidence owned by the calendar on any incidence change.
+
+      @since 5.80
+    */
+    bool updateLastModifiedOnChange() const;
+
+    /**
+      Govern if the memory calendar is changing the lastModified field of incidence
+      it owns, on incidence updates.
+
+      @param update, when true, the lastModified field of an incidence owned by the
+      calendar is set to the current date time on any change of the incidence.
+
+      @since 5.80
+    */
+    void setUpdateLastModifiedOnChange(bool update);
+
     /**
       @copydoc Calendar::incidenceUpdate(const QString &,const QDateTime &)
     */