hook_flag_reset() has been replaced with the FLAG_RESET event

In Flag 7.x-3.x, hook_flag_reset() was invoked whenever a flag was reset. (Resetting a flag is an action which removes all the flaggings made with that flag, by all users.)

In Flag 8.x-4.x, hook_flag_reset() has been removed. A FLAG_RESET event is now triggered when a flag is resent. The FlagResetEvent class is passed to your event subscriber containing both the flag, and the number of flaggings to delete.

Note that when a flag is reset, this does not result in ENTITY_UNFLAGGED events, only a single reset event.

7.x

<?php
function your_module_flag_reset($flag) {
  // respond to flag reset.
}
?>

8.x

Instead of implementing a hook, create an event subscriber class. Your method must accept a FlagResetEvent object as a single parameter.

<?php
class MyFlagEventSubscriber implements EventSubscriberInterface {

  public function respondToReset(FlagResetEvent $event) {
    //respond to flag reset.
  }

  public function getSubscribedEvents() {
    return [FlagEvents::FLAG_RESET][] = array('respondToReset', 0);
  }

}
?>