HTTP 415 when uploading jtx Board task: calendar object may only have components with the same UID

[dariopnc]

Problem scope

• I'm sure that this is a DAVx⁵ problem.

App version

• I'm using the latest available DAVx⁵ version.

Android version and device/firmware type

Android 14 (moto g73 5G)

Steps to reproduce

I had DAVx⁵ configured to periodically sync resources with my Nextcloud account.
I just have periodic automatic syncing configured.
I haven't changed any configuration after the update.

Actual result

After installing the latest DAVx⁵ version I started receiving notifications about sync errors, due to HTTP error 415.
My task list «Attività» is not synced, probably due to the error mentioned

Expected result

No syncing error, as it happened before the upgrade

Further info

You can find debug infos at the following link (expires in a few days): https://shared02.opsone-cloud.ch/index.php/s/ofcXjExqo8X7eos

[rfc2822]

Relevant parts of debug info (anonymized):

HTTP REQUEST
PUT .../1d1e0c72-dfab-40f3-9be4-616ee0bad79a.ics

BEGIN:VCALENDAR^M
VERSION:2.0^M
PRODID:DAVx5/4.5.12-gplay ical4j/4.2.5 (at.techbee.jtx)^M
BEGIN:VTODO^M
DTSTAMP:20260520T172633Z^M
UID:1d1e0c72-dfab-40f3-9be4-616ee0bad79a^M
...
DTSTART;TZID=Europe/Rome:20260418T130000^M
RRULE:FREQ=MONTHLY;UNTIL=20270417T110000Z^M
PERCENT-COMPLETE:0^M
DUE;TZID=Europe/Rome:20260419T130000^M
END:VTODO^M
BEGIN:VTODO^M
DTSTAMP:20260520T172633Z^M
END:VTODO^M
BEGIN:VTODO^M
DTSTAMP:20260520T172633Z^M
END:VTODO^M
END:VCALENDAR^M


HTTP RESPONSE
<?xml version="1.0" encoding="utf-8"?>
<d:error xmlns:d="DAV:" xmlns:s="http://sabredav.org/ns">
  <s:exception>Sabre\DAV\Exception\UnsupportedMediaType</s:exception>
  <s:message>Validation error in iCalendar: A calendar object on a CalDAV server may only have components with the same UID.</s:message>
</d:error>

There are VTODOs without any content, these should probably be the exceptions of the recurring vtodo.

@dariopnc Does it work again if you delete the "Check Capra Cornetto Fattormia" task, either on the server or in jtx Board?

[dariopnc]

I removed the task from the server and syncing got back to working again. I still see on jtx Board future occurrences of the recurring task

[deralmas]

Hi, I had a very similar issue with davx5, jtx board and radicale. I can confirm that rolling back to davx5 4.5.10-ose works around the issue.

[rfc2822]

This bug is a result of the changed PropertyList behavior in ical4j 4.x. Existing code (that worked with ical4j 3.x) was used with ical4j 4.x without reflecting the breaking API changes.

Events/tasks.org code is fine, probably because of the tests.

Possible bugs of the same type, all in the (not yet refactored) JtxICalObject.kt:

---

Bug 1 — Alarms: all properties silently dropped

vAlarm.propertyList.apply {
    add(ImmutableAction.DISPLAY)   // ← returns new PropertyList, discarded
    add(Trigger().apply { ... })   // ← same
    add(Summary(it))               // ← same
    addAll(...)                    // ← same
}

PropertyList.add() returns a new list. Calling it inside apply {} on vAlarm.propertyList discards every result. Every VAlarm emitted to the iCalendar has no properties (empty except for the auto-generated DTSTAMP).

---

Bug 2 — Alarms: not added to the parent component at all

calComponent.componentList.add(vAlarm)  // ← returns new ComponentList, discarded

ComponentList.add() also returns a new instance. calComponent.componentList is never updated, so no VAlarm sub-components are emitted in the iCalendar output at all.

(Bugs 1 & 2 together mean alarms are completely invisible in outgoing iCalendar.)