java.time.temporal.UnsupportedTemporalTypeException: Unsupported unit: Weeks

[KaiSuchomel]

Describe the bug
When using the newest version (4.0.8) the Exception:
java.time.temporal.UnsupportedTemporalTypeException: Unsupported unit: Weeks
occurs.

        Recur recurence = new Recur.Builder()
                .frequency(Frequency.WEEKLY)
                .dayList(List.of(WeekDay.MO, WeekDay.TU, WeekDay.WE, WeekDay.TH, WeekDay.FR))
                .interval(2)
                .until(OffsetDateTime.of(2100, 1, 23, 0, 0, 0, 0, ZoneOffset.UTC))
                .build();
        ZonedDateTime start = ZonedDateTime.of(2100, 1, 2, 6, 0, 0, 0, ZoneId.of("Europe/Berlin"));
        ZonedDateTime end = ZonedDateTime.of(2100, 1, 2, 14, 0, 0, 0, ZoneId.of("Europe/Berlin"));
        VEvent event = new VEvent(start, end, "Test")
                .add(new RandomUidGenerator().generateUid())
                .add(new XProperty("MyId", UUID.randomUUID().toString()))
                .add(new RRule<>(recurence))
                .add(new Transp(Transp.VALUE_OPAQUE));
        Set<Period<Temporal>> calculateRecurrenceSet = event.calculateRecurrenceSet(
                new Period<>(OffsetDateTime.now().minusYears(1).toInstant(),
                        OffsetDateTime.now().plusYears(1).toInstant()));

Using Instants leads to the Exception

To Reproduce
see https://github.com/KaiSuchomel/quarkus-test/tree/ical4j for reproducer.

Expected behavior
With version 4.0.6 the Tests passed.

Environment:

• OS: MACOS
• Java Version: openjdk version "21.0.5" 2024-10-15
• iCal4j Version: 4.0.8

[tananaev]

Same thing is happening with monthly events on the calendar. RRULE example:

RRULE:FREQ=MONTHLY;BYMONTHDAY=1

Getting the following error:

java.time.temporal.UnsupportedTemporalTypeException: Unsupported unit: Months
	at java.base/java.time.Instant.plus(Instant.java:861)
	at java.base/java.time.Instant.minus(Instant.java:983)
	at java.base/java.time.Instant.minus(Instant.java:209)
	at net.fortuna.ical4j.model.Recur$DateSpliterator.<init>(Recur.java:1320)
	at net.fortuna.ical4j.model.Recur.getDatesAsStream(Recur.java:736)
	at net.fortuna.ical4j.model.Recur.getDates(Recur.java:723)
	at net.fortuna.ical4j.model.Recur.getDates(Recur.java:704)
	at net.fortuna.ical4j.model.Component.lambda$calculateRecurrenceSet$1(Component.java:357)
	at java.base/java.util.stream.ReferencePipeline$3$1.accept(ReferencePipeline.java:197)
	at java.base/java.util.ArrayList$ArrayListSpliterator.forEachRemaining(ArrayList.java:1708)
	at java.base/java.util.stream.AbstractPipeline.copyInto(AbstractPipeline.java:509)
	at java.base/java.util.stream.AbstractPipeline.wrapAndCopyInto(AbstractPipeline.java:499)
	at java.base/java.util.stream.ReduceOps$ReduceOp.evaluateSequential(ReduceOps.java:921)
	at java.base/java.util.stream.AbstractPipeline.evaluate(AbstractPipeline.java:234)
	at java.base/java.util.stream.ReferencePipeline.collect(ReferencePipeline.java:682)
	at net.fortuna.ical4j.model.Component.calculateRecurrenceSet(Component.java:359)
        ...

[jbnas]

Appears error was introduced in 4.0.7

[KaiSuchomel]

@benfortuna Will this be fixed?

[benfortuna]

You should always use generics with Recur instances since v4, as some Temporal types won't be supported depending on the rule.

e.g.

 Recur<ZonedDateTime> recurence = new Recur.Builder<ZonedDateTime>()
                .frequency(Frequency.WEEKLY)
                .dayList(List.of(WeekDay.MO, WeekDay.TU, WeekDay.WE, WeekDay.TH, WeekDay.FR))
                .interval(2)
                .until(OffsetDateTime.of(2100, 1, 23, 0, 0, 0, 0, ZoneOffset.UTC))
                .build();

and the input to Component.calculateRecurrenceSet() should be of the same Temporal type as the event, to avoid mismatch such as the error above.

e.g.

Set<Period<Temporal>> calculateRecurrenceSet = event.calculateRecurrenceSet(
                new Period<>(ZonedDateTime.now().minusYears(1), ZonedDateTime.now().plusYears(1)));

[tananaev]

@benfortuna in my case I'm trying to extract all recurring events from a calendar file that happen at specific instant:

            var period = new Period<>(date.toInstant(), Duration.ZERO);
            return calendar.<VEvent>getComponents(CalendarComponent.VEVENT).stream()
                    .flatMap(c -> c.calculateRecurrenceSet(period).stream())
                    .map(p -> new Period<>(temporalToInstant(p.getStart()), temporalToInstant(p.getEnd())))
                    .collect(Collectors.toUnmodifiableSet());

Am I doing this incorrectly? Is there some other way of achieving this?

[benfortuna]

@tananaev the key thing is that you really need to know what date format is used for the DTSTART properties in the events. So they might be just a date, or a floating date-time or a zoned/UTC date-time. This should be used to guide the period you are using to filter recurrences.

e.g. for event with TZID params, use ZonedDateTime, without a TZID, use LocalDateTime, or for dates use LocalDate.

I think Instant will work if they are UTC date-time values, or otherwise use OffsetDateTime.

[tananaev]

@benfortuna what if I don't know the calendar format and I want a generic solution?

[tananaev]

@benfortuna any update on this? I want to be able to operate with abstract generic interfaces. Is that not possible and not planned anymore?