fix(calendar): rely on organizer's event state before updating attendee

When an attendee is adding a new event for which the organizer is local
but doesn't have the event anymore, return a 412 error code.

Fixes #5496

SoObjects/Appointments/SOGoAppointmentObject.m

@@ -1,5 +1,5 @@
 /*
-  Copyright (C) 2007-2020 Inverse inc.
+  Copyright (C) 2007-2022 Inverse inc.
 
   This file is part of SOGo
 
@@ -151,7 +151,8 @@
           if (possibleName)
             {
               object = [folder lookupName: possibleName
-                                inContext: context acquire: NO];
+                                inContext: context
+                                  acquire: NO];
               if ([object isKindOfClass: [NSException class]] || [object isNew])
                 object = nil;
             }
@@ -163,10 +164,9 @@
   if (!object)
     {
       // Create the event in the user's personal calendar.
-      folder = [[SOGoUser userWithLogin: uid]
-                 personalCalendarFolderInContext: context];
+      folder = [[SOGoUser userWithLogin: uid] personalCalendarFolderInContext: context];
       object = [SOGoAppointmentObject objectWithName: nameInContainer
-				                                 inContainer: folder];
+                                         inContainer: folder];
       [object setIsNew: YES];
     }
 
@@ -2528,6 +2528,7 @@ inRecurrenceExceptionsForEvent: (iCalEvent *) theEvent
           iCalEvent *currentMasterEvent;
           NSArray *folders;
           NSEnumerator *e;
+          NSString *organizerUID;
           SOGoAppointmentFolder *folder;
           SOGoAppointmentObject *object;
 
@@ -2555,6 +2556,20 @@ inRecurrenceExceptionsForEvent: (iCalEvent *) theEvent
                     }
                 }
             }
+
+          // Verify if the event is still present in the organizer calendar
+          organizerUID = [[masterEvent organizer] uidInContext: context];
+          if (organizerUID)
+            {
+              object = [self _lookupEvent: [masterEvent uid]
+                                   forUID: organizerUID];
+              if ([object isNew])
+                {
+                  // The event has vanished
+                  return [NSException exceptionWithDAVStatus: 412
+                                                      reason: @"Precondition Failed"];
+                }
+            }
         }
     }
   else

SoObjects/SOGo/SOGoParentFolder.m

@@ -177,7 +177,7 @@ static SoSecurityManager *sm = nil;
       [folder setOCSPath: [NSString stringWithFormat: @"%@/%@", OCSPath, folderName]];
       
       if ([folder create])
-      [subFolders setObject: folder forKey: folderName];
+        [subFolders setObject: folder forKey: folderName];
     }
     else if (folderType == SOGoCollectedFolder)
     {