Is organizer really mandatory for publishing a VEVENT?

[ma-we-dev]

Describe the bug
The RFC 2445 states that for VEVENT, the organizer is an optional property, see https://datatracker.ietf.org/doc/html/rfc2445#section-4.6.1.

But for VEVENT with method PUBLISH, the methodValidators of the VEvent-class contain organizer as mandatory field, see

ical4j/src/main/java/net/fortuna/ical4j/model/component/VEvent.java

Line 224 in a2066e5

new ValidationRule<>(One, true, DTSTAMP, ORGANIZER, SUMMARY),

What is the reason for this difference?

To Reproduce
Steps to reproduce the behavior:

1. Create a VEVENT with method PUBLISH without organizer
2. Check validation output

Expected behavior
No validation error when leaving out the optional organizer property.

Environment:

• OS: macOS
• Java Version 17
• iCal4j Version 4.1.0

[benfortuna]

Whilst the ORGANIZER property is optional in the core spec, the iTIP spec which defines the rules for the METHOD property indicate it is mandatory when METHOD=PUBLISH:

https://datatracker.ietf.org/doc/html/rfc5546#section-3.2.1

3.2.1.  PUBLISH

   The "PUBLISH" method in a "VEVENT" calendar component is an
   unsolicited posting of an iCalendar object.  Any CU may add published
   components to their calendar.  The "Organizer" MUST be present in a
   published iCalendar component.  "Attendees" MUST NOT be present.  Its
   expected usage is for encapsulating an arbitrary event as an
   iCalendar object.  The "Organizer" may subsequently update (with
   another "PUBLISH" method), add instances to (with an "ADD" method),
   or cancel (with a "CANCEL" method) a previously published "VEVENT"
   calendar component.