fix: WithStartDateTimePast now correctly calculates from past time (#897)

Author: JohnRoesler

job.go

@@ -1022,16 +1022,14 @@ type weeklyJob struct {
 }
 
 func (w weeklyJob) next(lastRun time.Time) time.Time {
-	firstPass := true
-	next := w.nextWeekDayAtTime(lastRun, firstPass)
+	next := w.nextWeekDayAtTime(lastRun, true)
 	if !next.IsZero() {
 		return next
 	}
-	firstPass = false
 
 	startOfTheNextIntervalWeek := (lastRun.Day() - int(lastRun.Weekday())) + int(w.interval*7)
 	from := time.Date(lastRun.Year(), lastRun.Month(), startOfTheNextIntervalWeek, 0, 0, 0, 0, lastRun.Location())
-	return w.nextWeekDayAtTime(from, firstPass)
+	return w.nextWeekDayAtTime(from, false)
 }
 
 func (w weeklyJob) nextWeekDayAtTime(lastRun time.Time, firstPass bool) time.Time {

scheduler.go

@@ -508,6 +508,12 @@ func (s *scheduler) selectNewJob(in newJobIn) {
 				next = j.next(s.now())
 			}
 
+			if next.Before(s.now()) {
+				for next.Before(s.now()) {
+					next = j.next(next)
+				}
+			}
+
 			id := j.id
 			j.timer = s.exec.clock.AfterFunc(next.Sub(s.now()), func() {
 				select {
@@ -559,6 +565,11 @@ func (s *scheduler) selectStart() {
 			if next.IsZero() {
 				next = j.next(s.now())
 			}
+			if next.Before(s.now()) {
+				for next.Before(s.now()) {
+					next = j.next(next)
+				}
+			}
 
 			jobID := id
 			j.timer = s.exec.clock.AfterFunc(next.Sub(s.now()), func() {

scheduler_test.go

@@ -2876,3 +2876,34 @@ func TestScheduler_WithMonitor(t *testing.T) {
 		})
 	}
 }
+
+func TestScheduler_WithStartAtDateTimePast(t *testing.T) {
+	defer verifyNoGoroutineLeaks(t)
+
+	// Monday
+	testTime := time.Date(2024, time.January, 1, 9, 0, 0, 0, time.UTC)
+
+	fakeClock := clockwork.NewFakeClockAt(testTime)
+
+	s := newTestScheduler(t, WithClock(fakeClock))
+	j, err := s.NewJob(
+		WeeklyJob(2, NewWeekdays(time.Sunday), NewAtTimes(NewAtTime(10, 0, 0))),
+		NewTask(func() {}),
+		WithStartAt(
+			// The start time is in the past (Dec 30, 2023 9am) which is a Saturday
+			WithStartDateTimePast(testTime.Add(-time.Hour*24*2)),
+		),
+	)
+	require.NoError(t, err)
+
+	s.Start()
+
+	nextRun, err := j.NextRun()
+	require.NoError(t, err)
+
+	require.NoError(t, s.Shutdown())
+
+	// Because the start time was in the past - we expect it to schedule 2 intervals ahead, pasing the first available Sunday
+	// which was in the past Dec 31, 2023, so the next is Jan 7, 2024
+	assert.Equal(t, time.Date(2024, time.January, 7, 10, 0, 0, 0, time.UTC), nextRun)
+}