add a 24 hour bound to _findPreviousDSTJump + test.

lib/time.js

@@ -424,14 +424,27 @@ function CronTime(luxon) {
  * When the jump is found, the range of the jump is investigated to check for acceptable cron times.
  * A pair is returned, whose first is a boolean representing if an acceptable time was found inside the jump,
  * and whose second is a DateTime representing the first millisecond after the jump.
+ *
+ * The input date is expected to be decently close to a DST jump.
+ * Up to a day in the past is checked before an error is thrown.
  * @param date
  */
  _findPreviousDSTJump: function (date) {
  /** @type number */
  let expectedMinute, expectedHour, actualMinute, actualHour;
  /** @type DateTime */
  let maybeJumpingPoint;
+
+ // representing one day of backwards checking. If this is hit, the input must be wrong.
+ const iterationLimit = 60 * 24;
+ let iteration = 0;
  do {
+ if (iteration++ > iterationLimit) {
+ throw new Error(
+ `ERROR: This DST checking related function assumes the input DateTime (${date.toISO()}) is within 24 hours of a DST jump.`
+ );
+ }
+
  expectedMinute = date.minute - 1;
  expectedHour = date.hour - 1;
 

tests/crontime.test.js

@@ -421,7 +421,20 @@ describe('crontime', () => {
  expect(nextDate - currentDate).toEqual(1000 * 60);
  });
  // Do not think a similar test for secondly job is necessary, the minutely one already ensured no double hits in the overlap zone.
-
+ it('Should throw when dates that are not within 24 hours of DST jumps are checked for past DST jumps', () => {
+ const cronTime = new cron.CronTime('* * * * *');
+ const tryFindPastDST = isoTime => () => {
+ const maybeBadDate = luxon.DateTime.fromISO(isoTime, {
+ zone: 'Asia/Amman'
+ });
+ expect(maybeBadDate.invalid).toEqual(null);
+ cronTime._findPreviousDSTJump(maybeBadDate);
+ };
+
+ // This timezone jumps from 0:00 to 1:00 on March 30th, so the cutoff is March 31st 1:00:00
+ expect(tryFindPastDST('2018-03-31T00:59:00')).not.toThrow();
+ expect(tryFindPastDST('2018-03-31T01:00:00')).toThrow();
+ });
  // The following few DST related tests do not need specific dates that are actually DST,
  // the functions they are calling assume the given parameters encapsulate a DST jump,
  // and use the raw hour and minute data to check it from there.