Given the following code

        require_once 'Zend/Filter/Input.php';
        
        require_once 'Zend/Validate/NotEmpty.php';
        
        
        $notEmpty = new Zend_Validate_NotEmpty();
        $notEmpty->setMessage("\"key\" may not be empty", Zend_Validate_NotEmpty::IS_EMPTY);
        
        $filter = New Zend_Filter_Input(array(), array(
            'key' => array($notEmpty)
        ), array('key' => ""));
    
        var_dump($filter->getInvalid());

I expect the following result:

array
  'key' => 
    array
      'isEmpty' => string 'You must give a non-empty value for field 'key''

However, I'm getting the following result

array
  'key' => 
    array
      'isEmpty' => string '"key" may not be empty'

which means that there is no way to actually use the NotEmpty Validator along with a custom error message, since some funny Zend_Filter_Input implementation preceeds my validator configuration.