allow actions to throw exception that are shown to the user

inc/Action/Exception/ActionException.php

@@ -15,8 +15,12 @@ namespace dokuwiki\Action\Exception;
  */
 class ActionException extends \Exception {
 
+    /** @var string the new action */
     protected $newaction;
 
+    /** @var bool should the exception's message be shown to the user? */
+    protected $displayToUser = false;
+
     /**
      * ActionException constructor.
      *
@@ -36,4 +40,15 @@ class ActionException extends \Exception {
     public function getNewAction() {
         return $this->newaction;
     }
+
+    /**
+     * Should this Exception's message be shown to the user?
+     *
+     * @param null|bool $set when null is given, the current setting is not changed
+     * @return bool
+     */
+    public function displayToUser($set = null) {
+        if(!is_null($set)) $this->displayToUser = $set;
+        return $set;
+    }
 }

inc/ActionRouter.php

@@ -88,6 +88,11 @@ class ActionRouter {
                 msg('Action disabled: ' . hsc($presetup), -1);
             }
 
+            // some actions may request the display of a message
+            if($e->displayToUser()) {
+                msg(hsc($e->getMessage()), -1);
+            }
+
             // do setup for new action
             $this->transitionAction($presetup, $actionname);