[Bug]: Irritating behavior: Reminders get send to all users with write access within a shared group.

[dzatoah]

⚠️ 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

Firstly, this is a duplicate of nextcloud/calendar#3946. But it fits in this Repo better, since I think the bug lies in the Reminder background job. (Which is in this repo.)

Event reminders are not only sent to the attendees of an event, but to all members of all shared groups which have write access too. This behavior is very confusing for end users.

Steps to reproduce

1. Go to the user settings. (index.php/settings/users)
2. Create a group with the following members:
   [email protected]
[email protected]
3. Go to the calendar app. (index.php/apps/calendar/timeGridWeek/now )
4. Create new calendar
5. Share the newly created calendar with the new group (with write-access!)
6. Create a new event in the calendar.
7. Activate a reminder: 5 mins before the event.
8. Under attendees -> Invite the following people:
   [email protected]
[email protected]not

Expected behavior

[email protected], [email protected] and the calendar owner should get a reminder notification.
[email protected] and [email protected] should only be able to edit the event and not get a notification, since they're not attendees.

So, only the attendees plus the event owner should get a reminder notification.
But I think that some people also want that group members get a notification too, so this behavior should be configurable in the settings.
And I don't think that write-access should have something to do with who gets reminder notifications and who don't.

Actual behaviour

[email protected], [email protected], [email protected], [email protected] and the calendar owner get notifications.

Also members of groups which don't have write-access don't get reminders!

Possible solution

I imagine a toggle switch in Settings -> Administration -> Groupware:
"Send reminder notifications to attendees and also shared group members."

Installation method

Manual installation (Cloned git repo)

Operating system

Debian/Ubuntu

PHP engine version

PHP 7.4

Web server

Apache (supported)

Database engine version

SQlite

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

Fresh Nextcloud Server install

Are you using the Nextcloud Server Encryption module?

Encryption is Disabled

What user-backends are you using?

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

Configuration report

{
    "system": {
        "instanceid": "***REMOVED SENSITIVE VALUE***",
        "passwordsalt": "***REMOVED SENSITIVE VALUE***",
        "secret": "***REMOVED SENSITIVE VALUE***",
        "trusted_domains": [
            "10.0.2.5"
        ],
        "datadirectory": "***REMOVED SENSITIVE VALUE***",
        "dbtype": "sqlite3",
        "version": "24.0.0.4",
        "overwrite.cli.url": "http:\/\/10.0.2.5",
        "dbname": "***REMOVED SENSITIVE VALUE***",
        "dbhost": "***REMOVED SENSITIVE VALUE***",
        "dbport": "",
        "dbtableprefix": "oc_",
        "installed": true,
        "debug": true,
        "app_install_overwrite": [
            "richdocuments",
            "richdocumentscode",
            "announcementcenter",
            "deck"
        ],
        "mail_smtpmode": "smtp",
        "mail_smtpauthtype": "LOGIN",
        "mail_sendmailmode": "smtp",
        "mail_smtpauth": 1,
        "mail_smtpsecure": "tls",
        "mail_from_address": "***REMOVED SENSITIVE VALUE***",
        "mail_domain": "***REMOVED SENSITIVE VALUE***",
        "mail_smtphost": "***REMOVED SENSITIVE VALUE***",
        "mail_smtpname": "***REMOVED SENSITIVE VALUE***",
        "mail_smtppassword": "***REMOVED SENSITIVE VALUE***",
        "force_language": "en"
    }
}

List of activated Apps

Enabled:
  - accessibility: 1.10.0
  - calendar: 3.1.0-alpha.1
  - cloud_federation_api: 1.7.0
  - comments: 1.14.0
  - contactsinteraction: 1.5.0
  - dashboard: 7.4.0
  - dav: 1.22.0
  - deck: 1.6.0
  - federatedfilesharing: 1.14.0
  - federation: 1.14.0
  - files: 1.19.0
  - files_sharing: 1.16.0
  - files_trashbin: 1.14.0
  - files_versions: 1.17.0
  - lookup_server_connector: 1.12.0
  - oauth2: 1.12.0
  - provisioning_api: 1.14.0
  - settings: 1.6.0
  - sharebymail: 1.14.0
  - systemtags: 1.14.0
  - theming: 1.15.0
  - twofactor_backupcodes: 1.13.0
  - updatenotification: 1.14.0
  - user_status: 1.4.0
  - weather_status: 1.4.0
  - workflowengine: 2.6.0
Disabled:
  - admin_audit
  - bruteforcesettings
  - encryption
  - files_external
  - testing
  - user_ldap

Additional info

I think the issue lies in this file:

server/apps/dav/lib/CalDAV/Reminder/ReminderService.php

Line 148 in 6ab9a13

$users = $this->getAllUsersWithWriteAccessToCalendar($reminder['calendar_id']);

$users = $this->getAllUsersWithWriteAccessToCalendar($reminder['calendar_id']);
$user = $this->getUserFromPrincipalURI($reminder['principaluri']);
if ($user) {
$users[] = $user;
}