Custom Hooks

Drush commands can define custom events that other command files can hook. You can find examples in CacheCommands and SanitizeCommands

First, the command must implement CustomEventAwareInterface and use CustomEventAwareTrait, as described in the dependency injection documentation.

Then, the command may ask the provided hook manager to return a list of handlers with a certain annotation. In the example below, the my-event label is used:

    /**
     * This command uses a custom event 'my-event' to collect data.  Note that
     * the event handlers will not be found unless the hook manager is
     * injected into this command handler object via `setHookManager()`
     * (defined in CustomEventAwareTrait).
     *
     * @command example:command
     */
    public function exampleCommand()
    {
        $myEventHandlers = $this->getCustomEventHandlers('my-event');
        $result = [];
        foreach ($myEventHandlers as $handler) {
            $result[] = $handler();
        }
        sort($result);
        return implode(',', $result);
    }

Other command handlers may provide implementations by implementing @hook on-event my-event.

    /**
     * @hook on-event my-event
     */
    public function hookOne()
    {
        return 'one';
    }