Chris@0: <?php
Chris@0: 
Chris@0: /**
Chris@0:  * @file
Chris@0:  * Hooks and documentation related to the menu system and links.
Chris@0:  */
Chris@0: 
Chris@0: /**
Chris@0:  * @defgroup menu Menu system
Chris@0:  * @{
Chris@0:  * Define the navigation menus, local actions and tasks, and contextual links.
Chris@0:  *
Chris@0:  * @section sec_overview Overview and terminology
Chris@0:  * The menu system uses routes; see the
Chris@0:  * @link routing Routing API topic @endlink for more information. It is used
Chris@0:  * for navigation menus, local tasks, local actions, and contextual links:
Chris@0:  * - Navigation menus are hierarchies of menu links; links point to routes or
Chris@0:  *   URLs.
Chris@0:  * - Menu links and their hierarchies can be defined by Drupal subsystems
Chris@0:  *   and modules, or created in the user interface using the Menu UI module.
Chris@0:  * - Local tasks are groups of related routes. Local tasks are usually rendered
Chris@0:  *   as a group of tabs.
Chris@0:  * - Local actions are used for operations such as adding a new item on a page
Chris@0:  *   that lists items of some type. Local actions are usually rendered as
Chris@0:  *   buttons.
Chris@0:  * - Contextual links are actions that are related to sections of rendered
Chris@0:  *   output, and are usually rendered as a pop-up list of links. The
Chris@0:  *   Contextual Links module handles the gathering and rendering of contextual
Chris@0:  *   links.
Chris@0:  *
Chris@0:  * The following sections of this topic provide an overview of the menu API.
Chris@0:  * For more detailed information, see
Chris@0:  * https://www.drupal.org/developing/api/8/menu
Chris@0:  *
Chris@0:  * @section sec_links Defining menu links for the administrative menu
Chris@0:  * Routes for administrative tasks can be added to the main Drupal
Chris@0:  * administrative menu hierarchy. To do this, add lines like the following to a
Chris@0:  * module_name.links.menu.yml file (in the top-level directory for your module):
Chris@0:  * @code
Chris@0:  * dblog.overview:
Chris@0:  *   title: 'Recent log messages'
Chris@0:  *   parent: system.admin_reports
Chris@0:  *   description: 'View events that have recently been logged.'
Chris@0:  *   route_name: dblog.overview
Chris@18:  *   options:
Chris@18:  *     query:
Chris@18:  *       uid: 1
Chris@0:  *   weight: -1
Chris@0:  * @endcode
Chris@0:  * Some notes:
Chris@0:  * - The first line is the machine name for your menu link, which usually
Chris@0:  *   matches the machine name of the route (given in the 'route_name' line).
Chris@0:  * - parent: The machine name of the menu link that is the parent in the
Chris@0:  *   administrative hierarchy. See system.links.menu.yml to find the main
Chris@0:  *   skeleton of the hierarchy.
Chris@18:  * - options: Define additional route options such as query parameters. See
Chris@18:  *   https://www.drupal.org/docs/8/api/menu-api/providing-module-defined-menu-links
Chris@18:  *   for more information.
Chris@0:  * - weight: Lower (negative) numbers come before higher (positive) numbers,
Chris@0:  *   for menu items with the same parent.
Chris@0:  *
Chris@0:  * Discovered menu links from other modules can be altered using
Chris@0:  * hook_menu_links_discovered_alter().
Chris@0:  *
Chris@0:  * @todo Derivatives will probably be defined for these; when they are, add
Chris@0:  *   documentation here.
Chris@0:  *
Chris@0:  * @section sec_tasks Defining groups of local tasks (tabs)
Chris@0:  * Local tasks appear as tabs on a page when there are at least two defined for
Chris@0:  * a route, including the base route as the main tab, and additional routes as
Chris@0:  * other tabs. Static local tasks can be defined by adding lines like the
Chris@0:  * following to a module_name.links.task.yml file (in the top-level directory
Chris@0:  * for your module):
Chris@0:  * @code
Chris@0:  * book.admin:
Chris@0:  *   route_name: book.admin
Chris@0:  *   title: 'List'
Chris@0:  *   base_route: book.admin
Chris@0:  * book.settings:
Chris@0:  *   route_name: book.settings
Chris@0:  *   title: 'Settings'
Chris@0:  *   base_route: book.admin
Chris@0:  *   weight: 100
Chris@0:  * @endcode
Chris@0:  * Some notes:
Chris@0:  * - The first line is the machine name for your local task, which usually
Chris@0:  *   matches the machine name of the route (given in the 'route_name' line).
Chris@0:  * - base_route: The machine name of the main task (tab) for the set of local
Chris@0:  *   tasks.
Chris@0:  * - weight: Lower (negative) numbers come before higher (positive) numbers,
Chris@0:  *   for tasks on the same base route. If there is a tab whose route
Chris@0:  *   matches the base route, that will be the default/first tab shown.
Chris@0:  *
Chris@0:  * Local tasks from other modules can be altered using
Chris@0:  * hook_menu_local_tasks_alter().
Chris@0:  *
Chris@0:  * @todo Derivatives are in flux for these; when they are more stable, add
Chris@0:  *   documentation here.
Chris@0:  *
Chris@0:  * @section sec_actions Defining local actions for routes
Chris@0:  * Local actions can be defined for operations related to a given route. For
Chris@0:  * instance, adding content is a common operation for the content management
Chris@0:  * page, so it should be a local action. Static local actions can be
Chris@0:  * defined by adding lines like the following to a
Chris@0:  * module_name.links.action.yml file (in the top-level directory for your
Chris@0:  * module):
Chris@0:  * @code
Chris@0:  * node.add_page:
Chris@0:  *   route_name: node.add_page
Chris@0:  *   title: 'Add content'
Chris@0:  *   appears_on:
Chris@0:  *     - system.admin_content
Chris@0:  * @endcode
Chris@0:  * Some notes:
Chris@0:  * - The first line is the machine name for your local action, which usually
Chris@0:  *   matches the machine name of the route (given in the 'route_name' line).
Chris@0:  * - appears_on: Machine names of one or more routes that this local task
Chris@0:  *   should appear on.
Chris@0:  *
Chris@0:  * Local actions from other modules can be altered using
Chris@0:  * hook_menu_local_actions_alter().
Chris@0:  *
Chris@0:  * @todo Derivatives are in flux for these; when they are more stable, add
Chris@0:  *   documentation here.
Chris@0:  *
Chris@0:  * @section sec_contextual Defining contextual links
Chris@0:  * Contextual links are displayed by the Contextual Links module for user
Chris@0:  * interface elements whose render arrays have a '#contextual_links' element
Chris@0:  * defined. For example, a block render array might look like this, in part:
Chris@0:  * @code
Chris@0:  * array(
Chris@0:  *   '#contextual_links' => array(
Chris@0:  *     'block' => array(
Chris@0:  *       'route_parameters' => array('block' => $entity->id()),
Chris@0:  *     ),
Chris@0:  *   ),
Chris@0:  * @endcode
Chris@0:  * In this array, the outer key 'block' defines a "group" for contextual
Chris@0:  * links, and the inner array provides values for the route's placeholder
Chris@0:  * parameters (see @ref sec_placeholders above).
Chris@0:  *
Chris@0:  * To declare that a defined route should be a contextual link for a
Chris@0:  * contextual links group, put lines like the following in a
Chris@0:  * module_name.links.contextual.yml file (in the top-level directory for your
Chris@0:  * module):
Chris@0:  * @code
Chris@0:  * block_configure:
Chris@0:  *   title: 'Configure block'
Chris@0:  *   route_name: 'entity.block.edit_form'
Chris@0:  *   group: 'block'
Chris@0:  * @endcode
Chris@0:  * Some notes:
Chris@0:  * - The first line is the machine name for your contextual link, which usually
Chris@0:  *   matches the machine name of the route (given in the 'route_name' line).
Chris@0:  * - group: This needs to match the link group defined in the render array.
Chris@0:  *
Chris@0:  * Contextual links from other modules can be altered using
Chris@0:  * hook_contextual_links_alter().
Chris@0:  *
Chris@0:  * @todo Derivatives are in flux for these; when they are more stable, add
Chris@0:  *   documentation here.
Chris@0:  *
Chris@0:  * @section sec_rendering Rendering menus
Chris@0:  * Once you have created menus (that contain menu links), you want to render
Chris@0:  * them. Drupal provides a block (Drupal\system\Plugin\Block\SystemMenuBlock) to
Chris@0:  * do so.
Chris@0:  *
Chris@0:  * However, perhaps you have more advanced needs and you're not satisfied with
Chris@0:  * what the menu blocks offer you. If that's the case, you'll want to:
Chris@0:  * - Instantiate \Drupal\Core\Menu\MenuTreeParameters, and set its values to
Chris@0:  *   match your needs. Alternatively, you can use
Chris@0:  *   MenuLinkTree::getCurrentRouteMenuTreeParameters() to get a typical
Chris@0:  *   default set of parameters, and then customize them to suit your needs.
Chris@0:  * - Call \Drupal\Core\MenuLinkTree::load() with your menu link tree parameters,
Chris@0:  *   this will return a menu link tree.
Chris@0:  * - Pass the menu tree to \Drupal\Core\Menu\MenuLinkTree::transform() to apply
Chris@0:  *   menu link tree manipulators that transform the tree. You will almost always
Chris@0:  *   want to apply access checking. The manipulators that you will typically
Chris@0:  *   need can be found in \Drupal\Core\Menu\DefaultMenuLinkTreeManipulators.
Chris@0:  * - Potentially write a custom menu tree manipulator, see
Chris@0:  *   \Drupal\Core\Menu\DefaultMenuLinkTreeManipulators for examples. This is
Chris@0:  *   only necessary if you want to do things like adding extra metadata to
Chris@0:  *   rendered links to display icons next to them.
Chris@0:  * - Pass the menu tree to \Drupal\Core\Menu\MenuLinkTree::build(), this will
Chris@0:  *   build a renderable array.
Chris@0:  *
Chris@0:  * Combined, that would look like this:
Chris@0:  * @code
Chris@0:  * $menu_tree = \Drupal::menuTree();
Chris@0:  * $menu_name = 'my_menu';
Chris@0:  *
Chris@0:  * // Build the typical default set of menu tree parameters.
Chris@0:  * $parameters = $menu_tree->getCurrentRouteMenuTreeParameters($menu_name);
Chris@0:  *
Chris@0:  * // Load the tree based on this set of parameters.
Chris@0:  * $tree = $menu_tree->load($menu_name, $parameters);
Chris@0:  *
Chris@0:  * // Transform the tree using the manipulators you want.
Chris@0:  * $manipulators = array(
Chris@0:  *   // Only show links that are accessible for the current user.
Chris@0:  *   array('callable' => 'menu.default_tree_manipulators:checkAccess'),
Chris@0:  *   // Use the default sorting of menu links.
Chris@0:  *   array('callable' => 'menu.default_tree_manipulators:generateIndexAndSort'),
Chris@0:  * );
Chris@0:  * $tree = $menu_tree->transform($tree, $manipulators);
Chris@0:  *
Chris@0:  * // Finally, build a renderable array from the transformed tree.
Chris@0:  * $menu = $menu_tree->build($tree);
Chris@0:  *
Chris@16:  * $menu_html = \Drupal::service('renderer')->render($menu);
Chris@0:  * @endcode
Chris@0:  *
Chris@0:  * @}
Chris@0:  */
Chris@0: 
Chris@0: /**
Chris@0:  * @addtogroup hooks
Chris@0:  * @{
Chris@0:  */
Chris@0: 
Chris@0: /**
Chris@0:  * Alters all the menu links discovered by the menu link plugin manager.
Chris@0:  *
Chris@0:  * @param array $links
Chris@0:  *   The link definitions to be altered.
Chris@0:  *
Chris@0:  * @return array
Chris@0:  *   An array of discovered menu links. Each link has a key that is the machine
Chris@0:  *   name, which must be unique. By default, use the route name as the
Chris@0:  *   machine name. In cases where multiple links use the same route name, such
Chris@0:  *   as two links to the same page in different menus, or two links using the
Chris@0:  *   same route name but different route parameters, the suggested machine name
Chris@0:  *   patten is the route name followed by a dot and a unique suffix. For
Chris@0:  *   example, an additional logout link might have a machine name of
Chris@0:  *   user.logout.navigation, and default links provided to edit the article and
Chris@0:  *   page content types could use machine names
Chris@0:  *   entity.node_type.edit_form.article and entity.node_type.edit_form.page.
Chris@0:  *   Since the machine name may be arbitrary, you should never write code that
Chris@0:  *   assumes it is identical to the route name.
Chris@0:  *
Chris@0:  *   The value corresponding to each machine name key is an associative array
Chris@0:  *   that may contain the following key-value pairs:
Chris@0:  *   - title: (required) The title of the menu link. If this should be
Chris@0:  *     translated, create a \Drupal\Core\StringTranslation\TranslatableMarkup
Chris@0:  *     object.
Chris@0:  *   - description: The description of the link. If this should be
Chris@0:  *     translated, create a \Drupal\Core\StringTranslation\TranslatableMarkup
Chris@0:  *     object.
Chris@0:  *   - route_name: (optional) The route name to be used to build the path.
Chris@0:  *     Either the route_name or url element must be provided.
Chris@0:  *   - route_parameters: (optional) The route parameters to build the path.
Chris@0:  *   - url: (optional) If you have an external link use this element instead of
Chris@0:  *     providing route_name.
Chris@0:  *   - parent: (optional) The machine name of the link that is this link's menu
Chris@0:  *     parent.
Chris@0:  *   - weight: (optional) An integer that determines the relative position of
Chris@0:  *     items in the menu; higher-weighted items sink. Defaults to 0. Menu items
Chris@0:  *     with the same weight are ordered alphabetically.
Chris@0:  *   - menu_name: (optional) The machine name of a menu to put the link in, if
Chris@0:  *     not the default Tools menu.
Chris@0:  *   - expanded: (optional) If set to TRUE, and if a menu link is provided for
Chris@0:  *     this menu item (as a result of other properties), then the menu link is
Chris@0:  *     always expanded, equivalent to its 'always expanded' checkbox being set
Chris@0:  *     in the UI.
Chris@0:  *   - options: (optional) An array of options to be passed to
Chris@0:  *     \Drupal\Core\Utility\LinkGeneratorInterface::generate() when generating
Chris@0:  *     a link from this menu item.
Chris@0:  *
Chris@0:  * @ingroup menu
Chris@0:  */
Chris@0: function hook_menu_links_discovered_alter(&$links) {
Chris@0:   // Change the weight and title of the user.logout link.
Chris@0:   $links['user.logout']['weight'] = -10;
Chris@0:   $links['user.logout']['title'] = new \Drupal\Core\StringTranslation\TranslatableMarkup('Logout');
Chris@0:   // Conditionally add an additional link with a title that's not translated.
Chris@0:   if (\Drupal::moduleHandler()->moduleExists('search')) {
Chris@0:     $links['menu.api.search'] = [
Chris@0:       'title' => \Drupal::config('system.site')->get('name'),
Chris@0:       'route_name' => 'menu.api.search',
Chris@0:       'description' => new \Drupal\Core\StringTranslation\TranslatableMarkup('View popular search phrases for this site.'),
Chris@0:       'parent' => 'system.admin_reports',
Chris@0:     ];
Chris@0:   }
Chris@0: }
Chris@0: 
Chris@0: /**
Chris@0:  * Alter local tasks displayed on the page before they are rendered.
Chris@0:  *
Chris@0:  * This hook is invoked by \Drupal\Core\Menu\LocalTaskManager::getLocalTasks().
Chris@0:  * The system-determined tabs and actions are passed in by reference. Additional
Chris@0:  * tabs may be added.
Chris@0:  *
Chris@0:  * The local tasks are under the 'tabs' element and keyed by plugin ID.
Chris@0:  *
Chris@0:  * Each local task is an associative array containing:
Chris@0:  * - #theme: The theme function to use to render.
Chris@0:  * - #link: An associative array containing:
Chris@0:  *   - title: The localized title of the link.
Chris@0:  *   - url: a Url object.
Chris@0:  *   - localized_options: An array of options to pass to
Chris@0:  *     \Drupal\Core\Utility\LinkGeneratorInterface::generate().
Chris@0:  * - #weight: The link's weight compared to other links.
Chris@0:  * - #active: Whether the link should be marked as 'active'.
Chris@0:  *
Chris@0:  * @param array $data
Chris@0:  *   An associative array containing list of (up to 2) tab levels that contain a
Chris@0:  *   list of tabs keyed by their href, each one being an associative array
Chris@0:  *   as described above.
Chris@0:  * @param string $route_name
Chris@0:  *   The route name of the page.
Chris@16:  * @param \Drupal\Core\Cache\RefinableCacheableDependencyInterface $cacheability
Chris@16:  *   The cacheability metadata for the current route's local tasks.
Chris@0:  *
Chris@0:  * @ingroup menu
Chris@0:  */
Chris@16: function hook_menu_local_tasks_alter(&$data, $route_name, \Drupal\Core\Cache\RefinableCacheableDependencyInterface &$cacheability) {
Chris@0: 
Chris@0:   // Add a tab linking to node/add to all pages.
Chris@0:   $data['tabs'][0]['node.add_page'] = [
Chris@0:       '#theme' => 'menu_local_task',
Chris@0:       '#link' => [
Chris@0:           'title' => t('Example tab'),
Chris@0:           'url' => Url::fromRoute('node.add_page'),
Chris@0:           'localized_options' => [
Chris@0:               'attributes' => [
Chris@0:                   'title' => t('Add content'),
Chris@0:               ],
Chris@0:           ],
Chris@0:       ],
Chris@0:   ];
Chris@16:   // The tab we're adding is dependent on a user's access to add content.
Chris@16:   $cacheability->addCacheTags(['user.permissions']);
Chris@0: }
Chris@0: 
Chris@0: /**
Chris@0:  * Alter local actions plugins.
Chris@0:  *
Chris@0:  * @param array $local_actions
Chris@0:  *   The array of local action plugin definitions, keyed by plugin ID.
Chris@0:  *
Chris@0:  * @see \Drupal\Core\Menu\LocalActionInterface
Chris@0:  * @see \Drupal\Core\Menu\LocalActionManager
Chris@0:  *
Chris@0:  * @ingroup menu
Chris@0:  */
Chris@0: function hook_menu_local_actions_alter(&$local_actions) {
Chris@0: }
Chris@0: 
Chris@0: /**
Chris@0:  * Alter local tasks plugins.
Chris@0:  *
Chris@0:  * @param array $local_tasks
Chris@0:  *   The array of local tasks plugin definitions, keyed by plugin ID.
Chris@0:  *
Chris@0:  * @see \Drupal\Core\Menu\LocalTaskInterface
Chris@0:  * @see \Drupal\Core\Menu\LocalTaskManager
Chris@0:  *
Chris@0:  * @ingroup menu
Chris@0:  */
Chris@0: function hook_local_tasks_alter(&$local_tasks) {
Chris@0:   // Remove a specified local task plugin.
Chris@0:   unset($local_tasks['example_plugin_id']);
Chris@0: }
Chris@0: 
Chris@0: /**
Chris@0:  * Alter contextual links before they are rendered.
Chris@0:  *
Chris@0:  * This hook is invoked by
Chris@0:  * \Drupal\Core\Menu\ContextualLinkManager::getContextualLinkPluginsByGroup().
Chris@0:  * The system-determined contextual links are passed in by reference. Additional
Chris@0:  * links may be added and existing links can be altered.
Chris@0:  *
Chris@0:  * Each contextual link contains the following entries:
Chris@0:  * - title: The localized title of the link.
Chris@0:  * - route_name: The route name of the link.
Chris@0:  * - route_parameters: The route parameters of the link.
Chris@0:  * - localized_options: An array of URL options.
Chris@0:  * - (optional) weight: The weight of the link, which is used to sort the links.
Chris@0:  *
Chris@0:  *
Chris@0:  * @param array $links
Chris@0:  *   An associative array containing contextual links for the given $group,
Chris@0:  *   as described above. The array keys are used to build CSS class names for
Chris@0:  *   contextual links and must therefore be unique for each set of contextual
Chris@0:  *   links.
Chris@0:  * @param string $group
Chris@0:  *   The group of contextual links being rendered.
Chris@0:  * @param array $route_parameters
Chris@0:  *   The route parameters passed to each route_name of the contextual links.
Chris@0:  *   For example:
Chris@0:  *   @code
Chris@0:  *   array('node' => $node->id())
Chris@0:  *   @endcode
Chris@0:  *
Chris@0:  * @see \Drupal\Core\Menu\ContextualLinkManager
Chris@0:  *
Chris@0:  * @ingroup menu
Chris@0:  */
Chris@0: function hook_contextual_links_alter(array &$links, $group, array $route_parameters) {
Chris@0:   if ($group == 'menu') {
Chris@0:     // Dynamically use the menu name for the title of the menu_edit contextual
Chris@0:     // link.
Chris@0:     $menu = \Drupal::entityManager()->getStorage('menu')->load($route_parameters['menu']);
Chris@0:     $links['menu_edit']['title'] = t('Edit menu: @label', ['@label' => $menu->label()]);
Chris@0:   }
Chris@0: }
Chris@0: 
Chris@0: /**
Chris@0:  * Alter the plugin definition of contextual links.
Chris@0:  *
Chris@0:  * @param array $contextual_links
Chris@0:  *   An array of contextual_links plugin definitions, keyed by contextual link
Chris@0:  *   ID. Each entry contains the following keys:
Chris@0:  *     - title: The displayed title of the link
Chris@0:  *     - route_name: The route_name of the contextual link to be displayed
Chris@0:  *     - group: The group under which the contextual links should be added to.
Chris@0:  *       Possible values are e.g. 'node' or 'menu'.
Chris@0:  *
Chris@0:  * @see \Drupal\Core\Menu\ContextualLinkManager
Chris@0:  *
Chris@0:  * @ingroup menu
Chris@0:  */
Chris@0: function hook_contextual_links_plugins_alter(array &$contextual_links) {
Chris@0:   $contextual_links['menu_edit']['title'] = 'Edit the menu';
Chris@0: }
Chris@0: 
Chris@0: /**
Chris@0:  * Perform alterations to the breadcrumb built by the BreadcrumbManager.
Chris@0:  *
Chris@0:  * @param \Drupal\Core\Breadcrumb\Breadcrumb $breadcrumb
Chris@0:  *   A breadcrumb object returned by BreadcrumbBuilderInterface::build().
Chris@0:  * @param \Drupal\Core\Routing\RouteMatchInterface $route_match
Chris@0:  *   The current route match.
Chris@0:  * @param array $context
Chris@0:  *   May include the following key:
Chris@0:  *   - builder: the instance of
Chris@0:  *     \Drupal\Core\Breadcrumb\BreadcrumbBuilderInterface that constructed this
Chris@0:  *     breadcrumb, or NULL if no builder acted based on the current attributes.
Chris@0:  *
Chris@0:  * @ingroup menu
Chris@0:  */
Chris@0: function hook_system_breadcrumb_alter(\Drupal\Core\Breadcrumb\Breadcrumb &$breadcrumb, \Drupal\Core\Routing\RouteMatchInterface $route_match, array $context) {
Chris@0:   // Add an item to the end of the breadcrumb.
Chris@0:   $breadcrumb->addLink(\Drupal\Core\Link::createFromRoute(t('Text'), 'example_route_name'));
Chris@0: }
Chris@0: 
Chris@0: /**
Chris@0:  * Alter the parameters for links.
Chris@0:  *
Chris@0:  * @param array $variables
Chris@0:  *   An associative array of variables defining a link. The link may be either a
Chris@0:  *   "route link" using \Drupal\Core\Utility\LinkGenerator::link(), which is
Chris@0:  *   exposed as the 'link_generator' service or a link generated by
Chris@0:  *   \Drupal\Core\Utility\LinkGeneratorInterface::generate(). If the link is a
Chris@0:  *   "route link", 'route_name' will be set; otherwise, 'path' will be set.
Chris@0:  *   The following keys can be altered:
Chris@0:  *   - text: The link text for the anchor tag. If the hook implementation
Chris@0:  *     changes this text it needs to preserve the safeness of the original text.
Chris@17:  *     Using t() or \Drupal\Component\Render\FormattableMarkup with
Chris@0:  *     @placeholder is recommended as this will escape the original text if
Chris@0:  *     necessary. If the resulting text is not marked safe it will be escaped.
Chris@0:  *   - url_is_active: Whether or not the link points to the currently active
Chris@0:  *     URL.
Chris@0:  *   - url: The \Drupal\Core\Url object.
Chris@0:  *   - options: An associative array of additional options that will be passed
Chris@0:  *     to either \Drupal\Core\Utility\UnroutedUrlAssembler::assemble() or
Chris@0:  *     \Drupal\Core\Routing\UrlGenerator::generateFromRoute() to generate the
Chris@0:  *     href attribute for this link, and also used when generating the link.
Chris@0:  *     Defaults to an empty array. It may contain the following elements:
Chris@0:  *     - 'query': An array of query key/value-pairs (without any URL-encoding) to
Chris@0:  *       append to the URL.
Chris@0:  *     - absolute: Whether to force the output to be an absolute link (beginning
Chris@0:  *       with http:). Useful for links that will be displayed outside the site,
Chris@0:  *       such as in an RSS feed. Defaults to FALSE.
Chris@0:  *     - language: An optional language object. May affect the rendering of
Chris@0:  *       the anchor tag, such as by adding a language prefix to the path.
Chris@0:  *     - attributes: An associative array of HTML attributes to apply to the
Chris@0:  *       anchor tag. If element 'class' is included, it must be an array; 'title'
Chris@0:  *       must be a string; other elements are more flexible, as they just need
Chris@0:  *       to work as an argument for the constructor of the class
Chris@0:  *       Drupal\Core\Template\Attribute($options['attributes']).
Chris@0:  *
Chris@0:  * @see \Drupal\Core\Utility\UnroutedUrlAssembler::assemble()
Chris@0:  * @see \Drupal\Core\Routing\UrlGenerator::generateFromRoute()
Chris@0:  */
Chris@0: function hook_link_alter(&$variables) {
Chris@0:   // Add a warning to the end of route links to the admin section.
Chris@0:   if (isset($variables['route_name']) && strpos($variables['route_name'], 'admin') !== FALSE) {
Chris@0:     $variables['text'] = t('@text (Warning!)', ['@text' => $variables['text']]);
Chris@0:   }
Chris@0: }
Chris@0: 
Chris@0: /**
Chris@0:  * @} End of "addtogroup hooks".
Chris@0:  */