Scheduled tasks of mod plugins can not be uninstalled

Testing deletion of plugins with scheduled tasks Install a module which defines a task_scheduled e.g. https://moodle.org/plugins/mod_ratingallocate or https://moodle.org/plugins/mod_questionnaire (forum is the only one in core and it can't be removed) Goto administration ► Server ► Scheduled tasks Assert there is at least one scheduled tasks installed for the module. Uninstall the module Goto administration ► Server ► Scheduled tasks Assert there is no scheduled tasks installed for the module. Testing deletion of plugins with message handlers (You'll need an email server that allows IMAP and SMTP connections. We'll use the mod_forum for our tests since it's got inbound message handling.) Set up outbound email settings: Site administration ► Plugins ► Message outputs ► Email Set up inbound email settings: Site administration ► Server ► Incoming mail configuration ► Mail settings Go to Site administration ► Server ► Incoming mail configuration ► Message handlers Set Reply to forum posts to Yes . Check the mdl_messageinbound_handlers table in the database. Confirm that there is a record for mod_forum . Create a course. Enrol some users with valid emails. Create a Single simple discussion forum and set its Subscription mode to Forced subscription . Post a reply to the discussion. Make sure to tick Send forum post notifications with no editing-time delay . On a terminal, go to your moodle root directory and run the following command: php admin/cli/cron.php Check the mdl_messageinbound_datakeys table in the database. Confirm that a key has been added. Edit the is_uninstall_allowed() function in /lib/classes/plugininfo/mod.php and replace its contents with just return true; Go to Site administration ► Plugins ► Plugins overview . Uninstall the following in the given order: block_news_items block_search_forums mod_forum Check the mdl_messageinbound_handlers table in the database. Confirm that the record for mod_forum has been removed. Check the mdl_messageinbound_datakeys table in the database. Confirm that the key that has been added has now been removed.