SETPOS/bySetPositions is not behaving correctly

[jonasbadstuebner]

When testing for #66 to be correct, I ran into an issue, that occurs also without the change I made there, so I open a seperate ticket here.

I tested the following configuration: RRULE:FREQ=WEEKLY;BYDAY=MO,WE;BYSETPOS=2,3

Which corresponds to the following setup:

test('#??: works', () {
  final rrule = RecurrenceRule(
    frequency: Frequency.weekly,
    byWeekDays: [
      ByWeekDayEntry(DateTime.monday),
      ByWeekDayEntry(DateTime.wednesday),
    ],
    bySetPositions: const [2, 3],
  );
  final start = DateTime.utc(2024, 02, 01);

  final instances = rrule.getInstances(start: start).take(5);
  expect(
    instances,
    equals([
      DateTime.utc(2024, 02, 07),
      DateTime.utc(2024, 02, 14),
      DateTime.utc(2024, 02, 21),
      DateTime.utc(2024, 02, 28),
      DateTime.utc(2024, 03, 06),
    ]),
  );
});

I get a test failure:

TestFailure (Expected: [
            DateTime:2024-02-07 00:00:00.000Z,
            DateTime:2024-02-14 00:00:00.000Z,
            DateTime:2024-02-21 00:00:00.000Z,
            DateTime:2024-02-28 00:00:00.000Z,
            DateTime:2024-03-06 00:00:00.000Z
          ]
  Actual: TakeIterable<DateTime>:[
            DateTime:2024-02-07 00:00:00.000Z,
            DateTime:2024-02-14 00:00:00.000Z,
            DateTime:2024-02-12 00:00:00.000Z,
            DateTime:2024-02-21 00:00:00.000Z,
            DateTime:2024-02-19 00:00:00.000Z
          ]

I set a breakpoint here: https://github.com/JonasWanke/rrule/blob/f557fe9e72821c0543b1bf8f56fe5f50d531b07d/lib/src/iteration/set_positions_list.dart#L35

This is on the first hit on the breakpoint:

This is on the second one:

It seems like the setPostion is wrongly calculated. In this setup, setPosition: 3 should never occur, since the events are looked at "on a weekly basis" and a new week starts a new set. Therefore only positions 1 and 2 exist. In this setup, only Wednesdays should be yielded...right?

Environment:

• Package version: main-branch with fix from #67

[jonasbadstuebner]

I double checked with the RFC 5545, but couldn't find anything about that this would be an invalid RRULE. rrule.js seems to be very similar to the current implementation in this package. https://github.com/jkbrzt/rrule/blob/master/src/iter/poslist.ts Yet it does show the correct dates.

Code:

const { datetime, RRule } = require('rrule');

const ruleOptions = RRule.parseString(
  "RRULE:FREQ=WEEKLY;BYDAY=MO,WE;BYSETPOS=2,3;COUNT=5"
)

ruleOptions.dtstart = datetime(2024, 02, 01);

const rule = new RRule(ruleOptions);

console.log(rule.all())

Output:

[
  2024-02-07T00:00:00.000Z,
  2024-02-14T00:00:00.000Z,
  2024-02-21T00:00:00.000Z,
  2024-02-28T00:00:00.000Z,
  2024-03-06T00:00:00.000Z
]

[jonasbadstuebner]

Found the problem, opened a PR.