Imported events are excluded from notifications

[thebenkahn]

Describe the bug (required)
When you use an external calendar and import events, the Reminders plugin skips notifications for the event if no module types are exluded. In the cron logs I am seeing that the event is skipped because the module type ' ' is excluded. And in the database I can see that imported events have the field 'modulename' null, while manually created user/site events have that value set to 0.

If I set an excluded activity in the plugin settings, E.G. 'workshop' that seems to workaround the issue.

My thought is that the blank DB entry for mdl_event.modulename is being compared to the default empty string for excluded modules and matching.

To Reproduce (required)
Steps to reproduce the behavior:

1. Import a calendar event from an external source (google cal, etc)
   as a user event
2. Manually create a user event at the same time
3. Configure plugin to remind for user events
4. Observe that the manual event gets a reminder and the imported event does not

Expected behavior (required)

1. Imported events should have the same behavior as manually created events.

Cron Logs (required)

testing with a user level event, #380 is external event and #381 is manually created on the test site

 [Local Reminder] Time window: Wednesday, November 3, 2021, 6:48 PM to Wednesday, November 3, 2021, 7:00 PM
   [Local Reminder] Found 2 upcoming events. Continuing...
  [Local Reminder] xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx
  [Local Reminder]   Skipping event #380 in excluded module ''!
  [Local Reminder] xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx
   [Local Reminder] Processing event in ahead of 0.0034722222222222 days.
   [Local Reminder] Processing event#381 [Type: user, inaheadof=0.0034722222222222 days]...
   [Local Reminder] A reminder can be sent for event#381 , detected through custom schedule.
  [Local Reminder] Starting sending reminders for 381 [type: user, mod: 0]

Environment (required):

• Moodle version: 3.10.5
• Database: mariadb
• PHP Version: 7.3.28.1.16.04.1.1
• Plugin version 2.4 2021062000

[isuru89]

@thebenkahn
The plugin cannot continue when the event's modulename is empty if the event type is set to due. The above error message come when trying to send an overdue reminder.

However, course and modulename are mandatory to find out relevant users to send this activity reminder. Without these context information, the plugin cannot proceed.

See here:

moodle-local_reminders/locallib.php

Line 334 in 1572e20

if (isemptystring($event->modulename)) {

And also here:

moodle-local_reminders/locallib.php

Line 157 in 1572e20

function send_overdue_activity_reminders($curtime, $timewindowstart, $activityroleids, $fromuser) {