Using Attributes for SilverStripe routing

ImprovedController.php

<?php

trait ImprovedController
{
    /**
     * Override default mechanisms for ease of use
     *
     * @link https://docs.silverstripe.org/en/5/developer_guides/controllers/access_control/
     * @param string $action
     * @return boolean
     */
    public function checkAccessAction($action)
    {
        // Check if we have our attribute
        if (method_exists($this, $action)) {
            $refl = new ReflectionMethod($this, $action);

            // Fetch all action attributes, if we have any, it's valid
            $attributes = $refl->getAttributes(IsAction::class, \ReflectionAttribute::IS_INSTANCEOF);
            if (!empty($attributes)) {
                return true;
            }
        }
        return parent::checkAccessAction($action);
    }
}

IsAction.php

<?php

#[\Attribute]
class IsAction
{
}

SomeController.php

<?php

class MyController extends Controller {

    #[\IsAction]
    public function dosomething(HTTPRequest $req)
    {
       // do something
    }
}