Adding a shared calendar via link fails if the calendar contains non- compliant VComponents

Steps to reproduce

Add a google calendar via share link.

{
   "reqId":"WPDmb1ev23ZvuZRZGshW",
   "level":2,
   "time":"2022-08-18T12:45:55+00:00",
   "remoteAddr":"127.0.0.1",
   "user":"admin",
   "app":"dav",
   "method":"MKCOL",
   "url":"/remote.php/dav/calendars/admin/calendargooglecom-1",
   "message":"Subscription 2 could not be parsed",
   "userAgent":"Mozilla/5.0 (X11; Linux x86_64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/104.0.0.0 Safari/537.36",
   "version":"25.0.0.5",
   "exception":{
      "Exception":"Sabre\\VObject\\ParseException",
      "Message":"This parser only supports VCARD and VCALENDAR files",
      "Code":0,
      "Trace":[
         {
            "file":"/var/www/nextcloud/3rdparty/sabre/vobject/lib/Parser/MimeDir.php",
            "line":90,
            "function":"parseDocument",
            "class":"Sabre\\VObject\\Parser\\MimeDir",
            "type":"->"
         },
         {
            "file":"/var/www/nextcloud/3rdparty/sabre/vobject/lib/Reader.php",
            "line":47,
            "function":"parse",
            "class":"Sabre\\VObject\\Parser\\MimeDir",
            "type":"->"
         },
         {
            "file":"/var/www/nextcloud/apps/dav/lib/CalDAV/WebcalCaching/RefreshWebcalService.php",
            "line":250,
            "function":"read",
            "class":"Sabre\\VObject\\Reader",
            "type":"::"
         },
         {
            "file":"/var/www/nextcloud/apps/dav/lib/CalDAV/WebcalCaching/RefreshWebcalService.php",
            "line":89,
            "function":"queryWebcalFeed",
            "class":"OCA\\DAV\\CalDAV\\WebcalCaching\\RefreshWebcalService",
            "type":"->"
         },
         {
            "file":"/var/www/nextcloud/apps/dav/lib/Listener/SubscriptionListener.php",
            "line":63,
            "function":"refreshSubscription",
            "class":"OCA\\DAV\\CalDAV\\WebcalCaching\\RefreshWebcalService",
            "type":"->"
         },
         {
            "file":"/var/www/nextcloud/lib/private/EventDispatcher/ServiceEventListener.php",
            "line":87,
            "function":"handle",
            "class":"OCA\\DAV\\Listener\\SubscriptionListener",
            "type":"->"
         },
         {
            "file":"/var/www/nextcloud/3rdparty/symfony/event-dispatcher/EventDispatcher.php",
            "line":251,
            "function":"__invoke",
            "class":"OC\\EventDispatcher\\ServiceEventListener",
            "type":"->"
         },
         {
            "file":"/var/www/nextcloud/3rdparty/symfony/event-dispatcher/EventDispatcher.php",
            "line":73,
            "function":"callListeners",
            "class":"Symfony\\Component\\EventDispatcher\\EventDispatcher",
            "type":"->"
         },
         {
            "file":"/var/www/nextcloud/lib/private/EventDispatcher/EventDispatcher.php",
            "line":88,
            "function":"dispatch",
            "class":"Symfony\\Component\\EventDispatcher\\EventDispatcher",
            "type":"->"
         },
         {
            "file":"/var/www/nextcloud/lib/private/EventDispatcher/EventDispatcher.php",
            "line":100,
            "function":"dispatch",
            "class":"OC\\EventDispatcher\\EventDispatcher",
            "type":"->"
         },
         {
            "file":"/var/www/nextcloud/apps/dav/lib/CalDAV/CalDavBackend.php",
            "line":2453,
            "function":"dispatchTyped",
            "class":"OC\\EventDispatcher\\EventDispatcher",
            "type":"->"
         },
         {
            "file":"/var/www/nextcloud/3rdparty/sabre/dav/lib/CalDAV/CalendarHome.php",
            "line":249,
            "function":"createSubscription",
            "class":"OCA\\DAV\\CalDAV\\CalDavBackend",
            "type":"->"
         },
         {
            "file":"/var/www/nextcloud/apps/dav/lib/CalDAV/CalendarHome.php",
            "line":93,
            "function":"createExtendedCollection",
            "class":"Sabre\\CalDAV\\CalendarHome",
            "type":"->"
         },
         {
            "file":"/var/www/nextcloud/3rdparty/sabre/dav/lib/DAV/Server.php",
            "line":1199,
            "function":"createExtendedCollection",
            "class":"OCA\\DAV\\CalDAV\\CalendarHome",
            "type":"->"
         },
         {
            "file":"/var/www/nextcloud/3rdparty/sabre/dav/lib/DAV/CorePlugin.php",
            "line":560,
            "function":"createCollection",
            "class":"Sabre\\DAV\\Server",
            "type":"->"
         },
         {
            "file":"/var/www/nextcloud/3rdparty/sabre/event/lib/WildcardEmitterTrait.php",
            "line":89,
            "function":"httpMkcol",
            "class":"Sabre\\DAV\\CorePlugin",
            "type":"->"
         },
         {
            "file":"/var/www/nextcloud/3rdparty/sabre/dav/lib/DAV/Server.php",
            "line":472,
            "function":"emit",
            "class":"Sabre\\DAV\\Server",
            "type":"->"
         },
         {
            "file":"/var/www/nextcloud/3rdparty/sabre/dav/lib/DAV/Server.php",
            "line":253,
            "function":"invokeMethod",
            "class":"Sabre\\DAV\\Server",
            "type":"->"
         },
         {
            "file":"/var/www/nextcloud/3rdparty/sabre/dav/lib/DAV/Server.php",
            "line":321,
            "function":"start",
            "class":"Sabre\\DAV\\Server",
            "type":"->"
         },
         {
            "file":"/var/www/nextcloud/apps/dav/lib/Server.php",
            "line":357,
            "function":"exec",
            "class":"Sabre\\DAV\\Server",
            "type":"->"
         },
         {
            "file":"/var/www/nextcloud/apps/dav/appinfo/v2/remote.php",
            "line":35,
            "function":"exec",
            "class":"OCA\\DAV\\Server",
            "type":"->"
         },
         {
            "file":"/var/www/nextcloud/remote.php",
            "line":167,
            "args":[
               "/var/www/nextcloud/apps/dav/appinfo/v2/remote.php"
            ],
            "function":"require_once"
         }
      ],
      "File":"/var/www/nextcloud/3rdparty/sabre/vobject/lib/Parser/MimeDir.php",
      "Line":163,
      "message":"Subscription 2 could not be parsed",
      "exception":{
         
      },
      "CustomMessage":"Subscription 2 could not be parsed"
   }
}

Expected behavior

The parser skips VComponents gracefully and still displays allowed VComponents VCARD and VCALENDAR.

OR

The calendar entry in the left sidebar in calendar shows an error icon that let's the user know there is an issue with this calendar.

Actual behaviour

The parser fails and doesn't show any events at all.

Calendar app version

No response

CalDAV-clients used

Web

Browser

No response

Client operating system

No response

Server operating system

No response

Web server

Apache

Database engine version

MySQL

PHP engine version

PHP 8.0

Nextcloud version

No response

Updated from an older installed version or fresh install

No response

List of activated apps

No response

Nextcloud configuration

No response

Web server error log

No response

Log file

No response

Browser log

No response

Additional info

No response

Start with the stack trace in apps/dav/lib/CalDAV/WebcalCaching/RefreshWebcalService.php, especially queryWebcalFeed and refreshSubscription, and trace how the Sabre VObject reader handles the subscribed feed. Reproduce the Google calendar link failure and verify that allowed VCARD or VCALENDAR components remain available while unsupported components are skipped or the calendar visibly reports an error.