PHP Fatal error: Call to undefined method can_expose() in views/plugins/views_plugin_display.inc on line 1872

PHP Fatal error: Call to undefined method can_expose() in views/plugins/views_plugin_display.inc on line 1872

This error happens when trying to save the settings form for certain filters. It happened to us with User name filters and Date filters.

This is the original problem, I think. The following code found in views_plugin_display.inc:

  /**
   * Check if the provided identifier is unique.
   */ 
  function is_identifier_unique($id, $identifier) {   
    foreach (views_object_types() as $type => $info) {
      foreach ($this->get_handlers($type) as $key => $handler) {
        if ($handler->can_expose() && $handler->is_exposed()) {
          if ($id != $key && $identifier == $handler->options['expose']['identifier']) {
            return FALSE;
          }
        }
      }
    }
    return TRUE;
  }

views_object_types() is defined in includes/view.inc and looks like this:

function views_object_types() {
  static $retval = NULL;

  // statically cache this so t() doesn't run a bajillion times.
  if (!isset($retval)) {
    $retval = array(
      'field' => array(
        'title' => t('Fields'), // title
        'ltitle' => t('fields'), // lowercase title for mid-sentence
        'stitle' => t('Field'), // singular title
        'lstitle' => t('field'), // singular lowercase title for mid sentence
        'plural' => 'fields',
      ),
      'argument' => array(
        'title' => t('Arguments'),
        'ltitle' => t('arguments'),
        'stitle' => t('Argument'),
        'lstitle' => t('Argument'),
        'plural' => 'arguments',
      ),
      'sort' => array(
        'title' => t('Sort criteria'),
        'ltitle' => t('sort criteria'),
        'stitle' => t('Sort criterion'),
        'lstitle' => t('sort criterion'),
        'plural' => 'sorts',
      ),
      'filter' => array(
        'title' => t('Filters'),
        'ltitle' => t('filters'),
        'stitle' => t('Filter'),
        'lstitle' => t('filter'),
        'plural' => 'filters',
        'options' => 'views_ui_config_filters_form',
      ),
      'relationship' => array(
        'title' => t('Relationships'),
        'ltitle' => t('relationships'),
        'stitle' => t('Relationship'),
        'lstitle' => t('Relationship'),
        'plural' => 'relationships',
      ),
    );
  }

  return $retval;
}

This means the method is_identifier_unique() tries to invoke can_expose() for all handlers of all these types. However, can_expose() is not defined for all handlers.

I have added function can_expose() { return FALSE; } to views_handler class definition temporarily. Though, I'm not 100% sure this is correct.