interval.prev(): loops infinitely in Brazilian locale

[m0nzderr]

In Brazil, when it reaches the value of "2017-10-16T00:59:59.999", the operation

CronDate.prototype.subtractDay = function() {
  this._date.subtract(1, 'day').endOf('day');
};

stays at the same date, causing infinite loop.

see issue moment/moment#3132 :

moment("2017-10-16T00:59:59.999").subtract(1,'day').endOf('day')
=> "2017-10-16T00:59:59.999"

Until the issue is not fixed, I'd suggest to add a simple workaround for it, something like detecting the "no change" situation and forcing the date to change.

[harrisiirak]

@m0nzderr thanks for reporting! Can you provide me some example(s)?

Not sure how to reproduce this one. Tried to change the local tz + changed the opts.tz: not getting the infinite loop.

Example code:

const interval = parser.parseExpression('0 0 * * * *', {
  currentDate: '2017-10-16T00:59:59.999',
  tz: 'America/Sao_Paulo'
});

console.log(interval.next().toISOString());
console.log(interval.next().toISOString());
console.log(interval.prev().toISOString());
console.log(interval.next().toISOString());

[m0nzderr]

@harrisiirak , sorry for taking too long to respond.
Here is one of the cases that loops forever:

const parser = require("cron-parser")
const interval = parser.parseExpression('0 0 0 1 1 *', {
  currentDate: 1498359600000,
  tz: 'America/Sao_Paulo'
});

console.log(interval.next().toISOString());
console.log(interval.prev().toISOString()); // it gets stuck here forever around DST switch
console.log(interval.next().toISOString());
console.log(interval.next().toISOString());

In my production code I had to overcome this problem by overriding your methods with a hack that prevents it from getting stuck on the same date:

CronDate.prototype.subtractDay = function () {
    let before = this._date.date();
    this._date.subtract(1, 'day').endOf('day');
    while (this._date.date() === before) {
        this._date.subtract(1, 'h');
    }
};

CronDate.prototype.addDay = function () {
    let before = this._date.date();
    this._date.add(1, 'day').startOf('day');
    while (this._date.date() === before) {
        this._date.add(1, 'h');
    }
};

[santigimeno]

@m0nzderr I think your patch looks good. Could you send a PR?

[m0nzderr]

@santigimeno got it!

[harrisiirak]

@m0nzderr any updates?

[harrisiirak]

Closing this issues as there are no further updates on this.