[Bug]: CalDAV issues collection ticket

[miaulalala]

⚠️ This issue respects the following points: ⚠️

• This is a bug, not a question or a configuration/webserver/proxy issue.
• This issue is not already reported on Github (I've searched it).
• Nextcloud Server is up to date. See Maintenance and Release Schedule for supported versions.
• I agree to follow Nextcloud's Code of Conduct.

Bug description

Collecting all bugs that @st3iny and I found when debugging the scheduling:

1. When deleting events from the trashbin a cancelled email is being sent from scheduling
2. When manually cancelling a recurring event, the sent email will be a method="REQUEST" email instead of a method="CANCEL".
3. Something's funky with processing calendar objects from an external client. Could possibly be the ACLs. "Submit my changes anyway" pops up in Thunderbird.
4. Cannot accept recurrences from external client (internal we have not supported that ... yet)

Steps to reproduce

1. Install Thunderbird
2. Add Calendar in Thunderbird
3. Play around with accepting and declining events generated in Nextcloud

Expected behavior

THe correct email method is set
Events from trashbin do not generate emails
etc

Also, stumbled upon this bug when testing too: https://bugzilla.mozilla.org/show_bug.cgi?id=1406402

Installation method

No response

Operating system

No response

PHP engine version

No response

Web server

No response

Database engine version

No response

Is this bug present after an update or on a fresh install?

No response

Are you using the Nextcloud Server Encryption module?

No response

What user-backends are you using?

• Default user-backend (database)
• LDAP/ Active Directory
• SSO - SAML
• Other

Configuration report

No response

List of activated Apps

see c.nc.com config for that

Nextcloud Signing status

No response

Nextcloud Logs

No response

Additional info

No response

[ChristophWurst]

When deleting events from the trashbin a cancelled email is being sent from scheduling

What else is expected? If the organizer discards a meeting, the attendees should be notified, shouldn't they? Would you expect this notification earlier, when the event is moved to the trash bin?

[miaulalala]

When deleting events from the trashbin a cancelled email is being sent from scheduling

What else is expected? If the organizer discards a meeting, the attendees should be notified, shouldn't they? Would you expect this notification earlier, when the event is moved to the trash bin?

yeah, that's exactly the issue. There are two emails being sent - one on moving it to the trashbin, one on deleting it completely.

[miaulalala]

@szaimen thanks for the housekeeping but this needs to stay open

[szaimen]

All right! Then lets add the tech debt label

[sparagi]

1. May now be filed separately as Calendar event invitee emails and links are incorrect as events are deleted and restored from trash. #36051.
2. May be the same issue as Editing / Deleting one occurrence of a recurring calendar event → 2nd invitation IMIT mail is very confusing #21220.

These are getting less likely, but in case it helps:

3. Since you suspect ACLs, a client might want to ask for confirmation in a situation like group member can overwrite private appointment #5551, where a sharee is attempting to edit a calendar object whose details they cannot see. If you confirmed "Submit my changes anyway", and this were the situation, I would expect the calendar object's description to change to "Busy".
4. There are 3 similar (to each other) issues related to clients syncing recurring events. They all sound pretty disruptive, though, and they seem to occur only when recurring events have no valid instances. If syncs weren't failing entirely, the issue you saw is more likely to be different from these.
   • Prevent Sabre\VObject\Recur\NoInstancesException: This recurrence rule does not generate any valid instances from being fatal to CalDAV sync #5641
   • [CalDAV] Nextcloud returns HTTP 500 instead of 403 when POSTing an event without valid instances #30514
   • [Bug]: Syncing acalendar ICS fails HTTP500 - This recurrence rule does not generate any valid instances #1423 #34790