Use preflight filters added in WP 5.1

[peterwilsoncc]

Task When setting and getting Cron jobs, make use of the new WP filters: pre_schedule_event, pre_reschedule_event, pre_unschedule_event, pre_clear_scheduled_hook, pre_unschedule_hook, pre_get_scheduled_event and pre_get_ready_cron_jobs.

Background In WordPress 5.1, new filters will be added to preflight event scheduling to allow for custom Cron storage systems.

The filters were added in WordPress#32656 (see WordPress/wordpress-develop@a32ea2d35d2fcf7bccf54ff7abfad9a2b49ee360) and WordPress#45797 (see WordPress/wordpress-develop@0bc20594c78369a6778635cd58f2b90c57428d6d).

[peterwilsoncc]

Note: pre_next_scheduled was removed during the WordPress beta period. The logic for getting the next schedule task should now be included as part of the pre_get_scheduled_event filter.

The description of this ticket has been updated to reflect these changes.

[peterwilsoncc]

Notes:

HM\Cavalcade\Plugin\Job class changes:

• :new: query( $event ) Searches for a single registered job depending on the event attributes.
  • no $timestamp return the next event
  • no $hook fail (WP Core should catch this beforehand anyway)
  • no $schedule or $interval search single events
• :new: get_jobs_by_hook( $hook, $args = null )
  • no $hook fail
  • $args === null return all jobs on hook regardless of arguments
• get_by_site()
  • Add parameter for limiting to ready jobs only, default to false

HM\Cavalcade\Plugin\Connector changes

• schedule_event() and schedule_recurring_event()
  • Unchanged for backward compatibility/direct changes to cron array.
• :new: pre_schedule_event( $pre, $event )
  • Search for existing job with Job::get_job_by_attributes()
  • Save/Update via schedule_event() if required
  • Recurring jobs with the same $timestamp but new $schedule/$interval replace existing task
• :new: pre_reschedule_event()
  • Search for existing job with Job::get_job_by_attributes()
  • Modify $timestamp (nextrun + interval, per cavalcade design)
  • Update via schedule_event()
• :new: pre_unschedule_event()
  • Search for existing job with Job::get_job_by_attributes()
  • Job::delete()
• :new: pre_clear_scheduled_hook()
  • also used for pre_unschedule_hook filter
  • Search for existing jobs with Job::get_jobs_by_hook()
  • Delete returned jobs
• :new: pre_get_scheduled_event()
  • Search for existing job with Job::get_job_by_attributes()
  • return it
• :new: pre_get_ready_cron_jobs()
  • return Job::get_by_site() limited to ready jobs only.