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pimutils / vdirsyncer

📇 Synchronize calendars and contacts.
https://vdirsyncer.pimutils.org/
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[WIP] Handle recurring events with duplicate UIDs #1120

Closed DavidMikeSimon closed 7 months ago

WhyNotHugo commented 7 months ago

What is the issue that you're addressing?

DavidMikeSimon commented 7 months ago

@WhyNotHugo Still working on this, but basically the problem is that UID isn't guaranteed to be unique. See https://stackoverflow.com/questions/62982636/in-what-situations-could-an-ical-vevent-end-up-with-a-duplicated-uid

DavidMikeSimon commented 7 months ago

See also this text from RFC 5546:

  1. The primary key for referencing a particular iCalendar component is the "UID" property value. To reference an instance of a recurring component, the primary key is composed of the "UID" and the "RECURRENCE-ID" properties.
WhyNotHugo commented 7 months ago

If multiple events are instances of the same recurring event, they share the same UID.

From https://www.rfc-editor.org/rfc/rfc4791#section-4.1:

The UID property value of the calendar components contained in a calendar object resource MUST be unique in the scope of the calendar collection in which they are stored.

This implies that is multiple instances of a single event exist, they MUST be stored in the same calendar object resource.

WhyNotHugo commented 7 months ago

E.g.: the would have the same href.

DavidMikeSimon commented 7 months ago

@WhyNotHugo Yeah, I think you're right! I was looking for the problem in the wrong place.

I'm attempting to synchronize events from an ICS from a Google Calendar URL to a local CalDav server. I noticed that some instances of recurring events were not present on the destination.

To narrow it down, I just now tried to reproduce the issue in a sync from the downloaded ICS file as type singlefile to a directory as type filesystem. And I noticed it doing exactly as you said: putting the recurring events with the same UID in the same file. So I believe the problem is not in vdirsyncer but in my receiving server.

Sorry about the distraction, and thank you for the info! I'll go ahead and close this PR.