Propagate subscribed calendars to CalDAV clients

[Sesivany]

Is your feature request related to a problem? Please describe.
I'm using the Nextcloud Calendar mostly in desktop/mobile clients. I'm subscribed to several remote calendars via ical. I can see them in the web interface, but I can't in the clients.

Describe the solution you'd like
It would be great if the calendars I'm subscribed to got propagated to CalDAV clients just like calendars that are located in my Nextcloud.

Describe alternatives you've considered
The alternative is to subscribe to the calendars in each client, but that's additional work in the initial setup and maintenance. I'd rather set them up in one location for all clients.

Additional context
Proprietary competition (Google Calendar, iCloud) supports it.

[tcitworld]

DAVx5 can automatically fetch subscriptions from Nextcloud, if you have ICSx5 installed.

Anyway subscriptions are now cached by Nextcloud server, we just need to expose them to clients.
@georgehrke do we transfer and keep this issue in server?

[georgehrke]

Yes, let's move it to the server.

It's basically about filling this array: https://github.com/nextcloud/server/blob/master/apps/dav/lib/CalDAV/WebcalCaching/Plugin.php#L42

[BernieO]

I just wondered, because if I subscribe to an external webcal calendar in the webinterface of Nextcloud, it is shown (including all events) on my iOS devices. But on a closer look, it looks like iOS fetches the webcal link from Nextcloud via caldav and then directly loads the calendar events from the external resource.

A change in a subscribed calendar is shown in iOS while the Nextcloud calendar-app still shows old data. Obviously the Nextcloud calendar-app doesn‘t refresh the calendar as often as my iOS devices.

So it looks like Nextcloud pushes the webcal link to the clients instead of the cached events.

Nextcloud 16.0.5
iOS 13.2

[tcitworld]

A change in a subscribed calendar is shown in iOS while the Nextcloud calendar-app still shows old data. Obviously the Nextcloud calendar-app doesn‘t refresh the calendar as often as my iOS devices.

Subscribed calendars are currently cached in your browser for two hours when you're using the Calendar app.

[akoyaxd]

I would love this to be implemented. This would improve the experience on Gnome pretty well, especially when you use multiple computers!

[msrn]

Has there any work been done on this? Would love to have this.

[tcitworld]

This feature is a fix for CalDAV clients that doesn't support discovering subscriptions from the endpoint (like DAVx⁵ does for instance).
We can only allow some clients (based on their user-agent) if we know what they are, so please post the clients you use (and if you can, their user-agent).

[msrn]

Currently I'm using Nextcloud Contacts and Calendar with Windows 10 Contacts/Calendar app. When initiating sync, these are the request made to server by the application.

"PROPFIND /remote.php/dav/principals/users/{USER}/ HTTP/1.1" 207 1976 "-" "MSFT-WIN-3/10.0.19041 (gzip)"
"PROPFIND /remote.php/dav/addressbooks/users/{USER}/ HTTP/1.1" 207 1363 "-" "MSFT-WIN-3/10.0.19041 (gzip)"
"PROPFIND /remote.php/dav/principals/users/{USER}/ HTTP/1.1" 207 1217 "-" "MSFT-WIN-3/10.0.19041 (gzip)"
"PROPFIND /remote.php/dav/addressbooks/users/{USER}/ HTTP/1.1" 207 1363 "-" "MSFT-WIN-3/10.0.19041 (gzip)"
"PROPFIND /remote.php/dav/principals/users/{USER}/ HTTP/1.1" 207 1341 "-" "MSFT-WIN-3/10.0.19041 (gzip)"
"PROPFIND /remote.php/dav/calendars/{USER}/ HTTP/1.1" 207 1772 "-" "MSFT-WIN-3/10.0.19041 (gzip)"
"PROPFIND /remote.php/dav/principals/users/{USER}/ HTTP/1.1" 207 1210 "-" "MSFT-WIN-3/10.0.19041 (gzip)"
"PROPFIND /remote.php/dav/calendars/{USER}/ HTTP/1.1" 207 1772 "-" "MSFT-WIN-3/10.0.19041 (gzip)"

User-agent being MSFT-WIN-3/10.0.19041
My current Windows version is 2004. Build 19041.985
Windows 10 contacts app version: 10.1909.12456.0
Windows 10 calendar app version: 16005.13426.20920.0

It seems that the user-agent string is tied to the build version of Windows 10. Would be it appropriate to just match MSFT-WIN-3 with regex?

[tcitworld]

Would be it appropriate to just match MSFT-WIN-3 with regex?

Seems fine. It would be nice to make sure that it's different for the Outlook Caldav Synchronizer. https://caldavsynchronizer.org

[msrn]

Would be it appropriate to just match MSFT-WIN-3 with regex?

Seems fine. It would be nice to make sure that it's different for the Outlook Caldav Synchronizer. https://caldavsynchronizer.org

CalDavSynchronizer has the following UserAgent CalDavSynchronizer/4.1

[msrn]

Would be it appropriate to just match MSFT-WIN-3 with regex?

Tested this to working with expression /^MSFT-WIN-3/. During sync now Windows 10 Calendar shows subscribed calendars from Nextcloud.

Should I submit PR with the addition of this to Plugin-php? @tcitworld

[tcitworld]

Please do.