Move into nested docroot

web/core/modules/help/help.api.php

@@ -0,0 +1,80 @@
+<?php
+
+/**
+ * @file
+ * Hooks for the Help system.
+ */
+
+/**
+ * @addtogroup hooks
+ * @{
+ */
+
+/**
+ * Provide online user help.
+ *
+ * By implementing hook_help(), a module can make documentation available to
+ * the user for the module as a whole, or for specific pages. Help for
+ * developers should usually be provided via function header comments in the
+ * code, or in special API example files.
+ *
+ * The page-specific help information provided by this hook appears in the
+ * Help block (provided by the core Help module), if the block is displayed on
+ * that page. The module overview help information is displayed by the Help
+ * module. It can be accessed from the page at /admin/help or from the Extend
+ * page. If a module implements hook_help() the help system expects module
+ * overview help to be provided.
+ *
+ * For detailed usage examples of:
+ * - Module overview help, see content_translation_help(). Module overview
+ *   help should follow
+ *   @link https://www.drupal.org/node/632280 the standard help template. @endlink
+ * - Page-specific help using only routes, see book_help().
+ * - Page-specific help using routes and $request, see block_help().
+ *
+ * @param string $route_name
+ *   For page-specific help, use the route name as identified in the
+ *   module's routing.yml file. For module overview help, the route name
+ *   will be in the form of "help.page.$modulename".
+ * @param Drupal\Core\Routing\RouteMatchInterface $route_match
+ *   The current route match. This can be used to generate different help
+ *   output for different pages that share the same route.
+ *
+ * @return string|array
+ *   A render array, localized string, or object that can be rendered into
+ *   a string, containing the help text.
+ */
+function hook_help($route_name, \Drupal\Core\Routing\RouteMatchInterface $route_match) {
+  switch ($route_name) {
+    // Main module help for the block module.
+    case 'help.page.block':
+      return '<p>' . t('Blocks are boxes of content rendered into an area, or region, of a web page. The default theme Bartik, for example, implements the regions "Sidebar first", "Sidebar second", "Featured", "Content", "Header", "Footer", etc., and a block may appear in any one of these areas. The <a href=":blocks">blocks administration page</a> provides a drag-and-drop interface for assigning a block to a region, and for controlling the order of blocks within regions.', array(':blocks' => \Drupal::url('block.admin_display'))) . '</p>';
+
+    // Help for another path in the block module.
+    case 'block.admin_display':
+      return '<p>' . t('This page provides a drag-and-drop interface for assigning a block to a region, and for controlling the order of blocks within regions. Since not all themes implement the same regions, or display regions in the same way, blocks are positioned on a per-theme basis. Remember that your changes will not be saved until you click the <em>Save blocks</em> button at the bottom of the page.') . '</p>';
+  }
+}
+
+/**
+ * Perform alterations on help page section plugin definitions.
+ *
+ * Sections for the page at /admin/help are provided by plugins. This hook
+ * allows modules to alter the plugin definitions.
+ *
+ * @param array $info
+ *   Array of plugin information exposed by hook page section plugins, altered
+ *   by reference.
+ *
+ * @see \Drupal\help\HelpSectionPluginInterface
+ * @see \Drupal\help\Annotation\HelpSection
+ * @see \Drupal\help\HelpSectionManager
+ */
+function hook_help_section_info_alter(&$info) {
+  // Alter the header for the module overviews section.
+  $info['hook_help']['header'] = t('Overviews of modules');
+}
+
+/**
+ * @} End of "addtogroup hooks".
+ */

web/core/modules/help/help.info.yml

@@ -0,0 +1,6 @@
+name: Help
+type: module
+description: 'Manages the display of online help.'
+package: Core
+version: VERSION
+core: 8.x

web/core/modules/help/help.links.menu.yml

@@ -0,0 +1,6 @@
+help.main:
+  title: Help
+  description: 'Reference for usage, configuration, and modules.'
+  route_name: help.main
+  weight: 9
+  parent: system.admin

web/core/modules/help/help.module

@@ -0,0 +1,78 @@
+<?php
+
+/**
+ * @file
+ * Manages displaying online help.
+ */
+
+use Drupal\Core\Block\BlockPluginInterface;
+use Drupal\Core\Routing\RouteMatchInterface;
+
+/**
+ * Implements hook_help().
+ */
+function help_help($route_name, RouteMatchInterface $route_match) {
+  switch ($route_name) {
+    case 'help.main':
+      $output = '<h2>' . t('Getting Started') . '</h2>';
+      $output .= '<p>' . t('Follow these steps to set up and start using your website:') . '</p>';
+      $output .= '<ol>';
+      $output .= '<li>' . t('<strong>Configure your website</strong> Once logged in, visit the <a href=":admin">Administration page</a>, where you may <a href=":config">customize and configure</a> all aspects of your website.', array(':admin' => \Drupal::url('system.admin'), ':config' => \Drupal::url('system.admin_config'))) . '</li>';
+      $output .= '<li>' . t('<strong>Enable additional functionality</strong> Next, visit the <a href=":modules">Extend page</a> and enable modules that suit your specific needs. You can find additional modules at the <a href=":download_modules">Drupal.org modules page</a>.', array(':modules' => \Drupal::url('system.modules_list'), ':download_modules' => 'https://www.drupal.org/project/modules')) . '</li>';
+      $output .= '<li>' . t('<strong>Customize your website design</strong> To change the "look and feel" of your website, visit the <a href=":themes">Appearance page</a>. You may choose from one of the included themes or download additional themes from the <a href=":download_themes">Drupal.org themes page</a>.', array(':themes' => \Drupal::url('system.themes_page'), ':download_themes' => 'https://www.drupal.org/project/themes')) . '</li>';
+      // Display a link to the create content page if Node module is enabled.
+      if (\Drupal::moduleHandler()->moduleExists('node')) {
+        $output .= '<li>' . t('<strong>Start posting content</strong> Finally, you may <a href=":content">add new content</a> to your website.', array(':content' => \Drupal::url('node.add_page'))) . '</li>';
+      }
+      $output .= '</ol>';
+      $output .= '<p>' . t('For more information, refer to the help listed on this page or to the <a href=":docs">online documentation</a> and <a href=":support">support</a> pages at <a href=":drupal">drupal.org</a>.', array(':docs' => 'https://www.drupal.org/documentation', ':support' => 'https://www.drupal.org/support', ':drupal' => 'https://www.drupal.org')) . '</p>';
+      return ['#markup' => $output];
+
+    case 'help.page.help':
+      $output = '';
+      $output .= '<h3>' . t('About') . '</h3>';
+      $output .= '<p>' . t('The Help module generates <a href=":help-page">Help reference pages</a> to guide you through the use and configuration of modules, and provides a Help block with page-level help. The reference pages are a starting point for <a href=":handbook">Drupal.org online documentation</a> pages that contain more extensive and up-to-date information, are annotated with user-contributed comments, and serve as the definitive reference point for all Drupal documentation. For more information, see the <a href=":help">online documentation for the Help module</a>.', array(':help' => 'https://www.drupal.org/documentation/modules/help/', ':handbook' => 'https://www.drupal.org/documentation', ':help-page' => \Drupal::url('help.main'))) . '</p>';
+      $output .= '<h3>' . t('Uses') . '</h3>';
+      $output .= '<dl>';
+      $output .= '<dt>' . t('Providing a help reference') . '</dt>';
+      $output .= '<dd>' . t('The Help module displays explanations for using each module listed on the main <a href=":help">Help reference page</a>.', array(':help' => \Drupal::url('help.main'))) . '</dd>';
+      $output .= '<dt>' . t('Providing page-specific help') . '</dt>';
+      $output .= '<dd>' . t('Page-specific help text provided by modules is displayed in the Help block. This block can be placed and configured on the <a href=":blocks">Block layout page</a>.', array(':blocks' => (\Drupal::moduleHandler()->moduleExists('block')) ? \Drupal::url('block.admin_display') : '#')) . '</dd>';
+      $output .= '</dl>';
+      return ['#markup' => $output];
+  }
+}
+
+/**
+ * Implements hook_theme().
+ */
+function help_theme($existing, $type, $theme, $path) {
+  return [
+    'help_section' => [
+      'variables' => [
+        'title' => NULL,
+        'description' => NULL,
+        'links' => NULL,
+        'empty' => NULL,
+      ],
+    ],
+  ];
+}
+
+/**
+ * Implements hook_preprocess_HOOK() for block templates.
+ */
+function help_preprocess_block(&$variables) {
+  if ($variables['plugin_id'] == 'help_block') {
+    $variables['attributes']['role'] = 'complementary';
+  }
+}
+
+/**
+ * Implements hook_block_view_BASE_BLOCK_ID_alter().
+ */
+function help_block_view_help_block_alter(array &$build, BlockPluginInterface $block) {
+  // Assume that most users do not need or want to perform contextual actions on
+  // the help block, so don't needlessly draw attention to it.
+  unset($build['#contextual_links']);
+}

web/core/modules/help/help.routing.yml

@@ -0,0 +1,15 @@
+help.main:
+  path: '/admin/help'
+  defaults:
+    _controller: '\Drupal\help\Controller\HelpController::helpMain'
+    _title: 'Help'
+  requirements:
+    _permission: 'access administration pages'
+
+help.page:
+  path: '/admin/help/{name}'
+  defaults:
+    _controller: '\Drupal\help\Controller\HelpController::helpPage'
+    _title: 'Help'
+  requirements:
+    _permission: 'access administration pages'

web/core/modules/help/help.services.yml

@@ -0,0 +1,4 @@
+services:
+  plugin.manager.help_section:
+    class: Drupal\help\HelpSectionManager
+    parent: default_plugin_manager

web/core/modules/help/src/Annotation/HelpSection.php

@@ -0,0 +1,60 @@
+<?php
+
+namespace Drupal\help\Annotation;
+
+use Drupal\Component\Annotation\Plugin;
+
+/**
+ * Defines a Plugin annotation object for help page section plugins.
+ *
+ * Plugin Namespace: Plugin\HelpSection
+ *
+ * For a working example, see \Drupal\help\Plugin\HelpSection\HookHelpSection.
+ *
+ * @see \Drupal\help\HelpSectionPluginInterface
+ * @see \Drupal\help\Plugin\HelpSection\HelpSectionPluginBase
+ * @see \Drupal\help\HelpSectionManager
+ * @see hook_help_section_info_alter()
+ * @see plugin_api
+ *
+ * @Annotation
+ */
+class HelpSection extends Plugin {
+
+  /**
+   * The plugin ID.
+   *
+   * @var string
+   */
+  public $id;
+
+  /**
+   * The text to use as the title of the help page section.
+   *
+   * @var \Drupal\Core\Annotation\Translation
+   *
+   * @ingroup plugin_translatable
+   */
+  public $title;
+
+  /**
+   * The description of the help page section.
+   *
+   * @var \Drupal\Core\Annotation\Translation
+   *
+   * @ingroup plugin_translatable
+   */
+  public $description;
+
+  /**
+   * The (optional) permission needed to view the help section.
+   *
+   * Only set if this section needs its own permission, beyond the generic
+   * 'access administration pages' permission needed to see the /admin/help
+   * page itself.
+   *
+   * @var string
+   */
+  public $permission = '';
+
+}

web/core/modules/help/src/Controller/HelpController.php

@@ -0,0 +1,162 @@
+<?php
+
+namespace Drupal\help\Controller;
+
+use Drupal\Core\Cache\CacheableMetadata;
+use Drupal\Core\Controller\ControllerBase;
+use Drupal\Core\Routing\RouteMatchInterface;
+use Drupal\help\HelpSectionManager;
+use Symfony\Component\DependencyInjection\ContainerInterface;
+use Symfony\Component\HttpKernel\Exception\NotFoundHttpException;
+
+/**
+ * Controller routines for help routes.
+ */
+class HelpController extends ControllerBase {
+
+  /**
+   * The current route match.
+   *
+   * @var \Drupal\Core\Routing\RouteMatchInterface
+   */
+  protected $routeMatch;
+
+  /**
+   * The help section plugin manager.
+   *
+   * @var \Drupal\help\HelpSectionManager
+   */
+  protected $helpManager;
+
+  /**
+   * Creates a new HelpController.
+   *
+   * @param \Drupal\Core\Routing\RouteMatchInterface $route_match
+   *   The current route match.
+   * @param \Drupal\help\HelpSectionManager $help_manager
+   *   The help section manager.
+   */
+  public function __construct(RouteMatchInterface $route_match, HelpSectionManager $help_manager) {
+    $this->routeMatch = $route_match;
+    $this->helpManager = $help_manager;
+  }
+
+  /**
+   * {@inheritdoc}
+   */
+  public static function create(ContainerInterface $container) {
+    return new static(
+      $container->get('current_route_match'),
+      $container->get('plugin.manager.help_section')
+    );
+  }
+
+  /**
+   * Prints a page listing various types of help.
+   *
+   * The page has sections defined by \Drupal\help\HelpSectionPluginInterface
+   * plugins.
+   *
+   * @return array
+   *   A render array for the help page.
+   */
+  public function helpMain() {
+    $output = [];
+
+    // We are checking permissions, so add the user.permissions cache context.
+    $cacheability = new CacheableMetadata();
+    $cacheability->addCacheContexts(['user.permissions']);
+
+    $plugins = $this->helpManager->getDefinitions();
+    $cacheability->addCacheableDependency($this->helpManager);
+
+    foreach ($plugins as $plugin_id => $plugin_definition) {
+      // Check the provided permission.
+      if (!empty($plugin_definition['permission']) && !$this->currentuser()->hasPermission($plugin_definition['permission'])) {
+        continue;
+      }
+
+      // Add the section to the page.
+      /** @var \Drupal\help\HelpSectionPluginInterface $plugin */
+      $plugin = $this->helpManager->createInstance($plugin_id);
+      $this_output = [
+        '#theme' => 'help_section',
+        '#title' => $plugin->getTitle(),
+        '#description' => $plugin->getDescription(),
+        '#empty' => $this->t('There is currently nothing in this section.'),
+        '#links' => [],
+      ];
+
+      $links = $plugin->listTopics();
+      if (is_array($links) && count($links)) {
+        $this_output['#links'] = $links;
+      }
+
+      $cacheability->addCacheableDependency($plugin);
+      $output[$plugin_id] = $this_output;
+    }
+
+    $cacheability->applyTo($output);
+    return $output;
+  }
+
+  /**
+   * Prints a page listing general help for a module.
+   *
+   * @param string $name
+   *   A module name to display a help page for.
+   *
+   * @return array
+   *   A render array as expected by drupal_render().
+   *
+   * @throws \Symfony\Component\HttpKernel\Exception\NotFoundHttpException
+   */
+  public function helpPage($name) {
+    $build = array();
+    if ($this->moduleHandler()->implementsHook($name, 'help')) {
+      $module_name = $this->moduleHandler()->getName($name);
+      $build['#title'] = $module_name;
+
+      $info = system_get_info('module', $name);
+      if ($info['package'] === 'Core (Experimental)') {
+        drupal_set_message($this->t('This module is experimental. <a href=":url">Experimental modules</a> are provided for testing purposes only. Use at your own risk.', [':url' => 'https://www.drupal.org/core/experimental']), 'warning');
+      }
+
+      $temp = $this->moduleHandler()->invoke($name, 'help', array("help.page.$name", $this->routeMatch));
+      if (empty($temp)) {
+        $build['top'] = ['#markup' => $this->t('No help is available for module %module.', array('%module' => $module_name))];
+      }
+      else {
+        if (!is_array($temp)) {
+          $temp = ['#markup' => $temp];
+        }
+        $build['top'] = $temp;
+      }
+
+      // Only print list of administration pages if the module in question has
+      // any such pages associated with it.
+      $admin_tasks = system_get_module_admin_tasks($name, system_get_info('module', $name));
+      if (!empty($admin_tasks)) {
+        $links = array();
+        foreach ($admin_tasks as $task) {
+          $link['url'] = $task['url'];
+          $link['title'] = $task['title'];
+          $links[] = $link;
+        }
+        $build['links'] = array(
+          '#theme' => 'links__help',
+          '#heading' => array(
+            'level' => 'h3',
+            'text' => $this->t('@module administration pages', array('@module' => $module_name)),
+          ),
+          '#links' => $links,
+        );
+      }
+      return $build;
+    }
+    else {
+      throw new NotFoundHttpException();
+    }
+  }
+
+}

web/core/modules/help/src/HelpSectionManager.php

@@ -0,0 +1,37 @@
+<?php
+
+namespace Drupal\help;
+
+use Drupal\Core\Cache\CacheBackendInterface;
+use Drupal\Core\Extension\ModuleHandlerInterface;
+use Drupal\Core\Plugin\DefaultPluginManager;
+
+/**
+ * Manages help page section plugins.
+ *
+ * @see \Drupal\help\HelpSectionPluginInterface
+ * @see \Drupal\help\Plugin\HelpSection\HelpSectionPluginBase
+ * @see \Drupal\help\Annotation\HelpSection
+ * @see hook_help_section_info_alter()
+ */
+class HelpSectionManager extends DefaultPluginManager {
+
+  /**
+   * Constructs a new HelpSectionManager.
+   *
+   * @param \Traversable $namespaces
+   *   An object that implements \Traversable which contains the root paths
+   *   keyed by the corresponding namespace to look for plugin implementations.
+   * @param \Drupal\Core\Cache\CacheBackendInterface $cache_backend
+   *   Cache backend instance to use.
+   * @param \Drupal\Core\Extension\ModuleHandlerInterface $module_handler
+   *   The module handler for the alter hook.
+   */
+  public function __construct(\Traversable $namespaces, CacheBackendInterface $cache_backend, ModuleHandlerInterface $module_handler) {
+    parent::__construct('Plugin/HelpSection', $namespaces, $module_handler, 'Drupal\help\HelpSectionPluginInterface', 'Drupal\help\Annotation\HelpSection');
+
+    $this->alterInfo('help_section_info');
+    $this->setCacheBackend($cache_backend, 'help_section_plugins');
+  }
+
+}

web/core/modules/help/src/HelpSectionPluginInterface.php

@@ -0,0 +1,49 @@
+<?php
+
+namespace Drupal\help;
+
+use Drupal\Component\Plugin\PluginInspectionInterface;
+use Drupal\Core\Cache\CacheableDependencyInterface;
+
+/**
+ * Provides an interface for a plugin for a section of the /admin/help page.
+ *
+ * Plugins of this type need to be annotated with
+ * \Drupal\help\Annotation\HelpSection annotation, and placed in the
+ * Plugin\HelpSection namespace directory. They are managed by the
+ * \Drupal\help\HelpSectionManager plugin manager class. There is a base
+ * class that may be helpful:
+ * \Drupal\help\Plugin\HelpSection\HelpSectionPluginBase.
+ */
+interface HelpSectionPluginInterface extends PluginInspectionInterface, CacheableDependencyInterface {
+
+
+  /**
+   * Returns the title of the help section.
+   *
+   * @return string
+   *   The title text, which could be a plain string or an object that can be
+   *   cast to a string.
+   */
+  public function getTitle();
+
+  /**
+   * Returns the description text for the help section.
+   *
+   * @return string
+   *   The description text, which could be a plain string or an object that
+   *   can be cast to a string.
+   */
+  public function getDescription();
+
+  /**
+   * Returns a list of topics to show in the help section.
+   *
+   * @return array
+   *   A sorted list of topic links or render arrays for topic links. The links
+   *   will be shown in the help section; if the returned array of links is
+   *   empty, the section will be shown with some generic empty text.
+   */
+  public function listTopics();
+
+}

web/core/modules/help/src/Plugin/Block/HelpBlock.php

@@ -0,0 +1,115 @@
+<?php
+
+namespace Drupal\help\Plugin\Block;
+
+use Drupal\Core\Block\BlockBase;
+use Drupal\Core\Cache\Cache;
+use Drupal\Core\Extension\ModuleHandlerInterface;
+use Drupal\Core\Plugin\ContainerFactoryPluginInterface;
+use Drupal\Core\Routing\RouteMatchInterface;
+use Symfony\Component\DependencyInjection\ContainerInterface;
+use Symfony\Component\HttpFoundation\Request;
+
+/**
+ * Provides a 'Help' block.
+ *
+ * @Block(
+ *   id = "help_block",
+ *   admin_label = @Translation("Help")
+ * )
+ */
+class HelpBlock extends BlockBase implements ContainerFactoryPluginInterface {
+
+  /**
+   * The module handler.
+   *
+   * @var \Drupal\Core\Extension\ModuleHandlerInterface
+   */
+  protected $moduleHandler;
+
+  /**
+   * The current request.
+   *
+   * @var \Symfony\Component\HttpFoundation\Request
+   */
+  protected $request;
+
+  /**
+   * The current route match.
+   *
+   * @var \Drupal\Core\Routing\RouteMatchInterface
+   */
+  protected $routeMatch;
+
+  /**
+   * Creates a HelpBlock instance.
+   *
+   * @param array $configuration
+   *   A configuration array containing information about the plugin instance.
+   * @param string $plugin_id
+   *   The plugin_id for the plugin instance.
+   * @param mixed $plugin_definition
+   *   The plugin implementation definition.
+   * @param \Symfony\Component\HttpFoundation\Request $request
+   *   The current request.
+   * @param \Drupal\Core\Extension\ModuleHandlerInterface $module_handler
+   *   The module handler.
+   * @param \Drupal\Core\Routing\RouteMatchInterface $route_match
+   *   The current route match.
+   */
+  public function __construct(array $configuration, $plugin_id, $plugin_definition, Request $request, ModuleHandlerInterface $module_handler, RouteMatchInterface $route_match) {
+    parent::__construct($configuration, $plugin_id, $plugin_definition);
+
+    $this->request = $request;
+    $this->moduleHandler = $module_handler;
+    $this->routeMatch = $route_match;
+  }
+
+  /**
+   * {@inheritdoc}
+   */
+  public static function create(ContainerInterface $container, array $configuration, $plugin_id, $plugin_definition) {
+    return new static(
+      $configuration,
+      $plugin_id,
+      $plugin_definition,
+      $container->get('request_stack')->getCurrentRequest(),
+      $container->get('module_handler'),
+      $container->get('current_route_match')
+    );
+  }
+
+  /**
+   * {@inheritdoc}
+   */
+  public function build() {
+    // Do not show on a 403 or 404 page.
+    if ($this->request->attributes->has('exception')) {
+      return [];
+    }
+
+    $implementations = $this->moduleHandler->getImplementations('help');
+    $build = [];
+    $args = [
+      $this->routeMatch->getRouteName(),
+      $this->routeMatch,
+    ];
+    foreach ($implementations as $module) {
+      // Don't add empty strings to $build array.
+      if ($help = $this->moduleHandler->invoke($module, 'help', $args)) {
+        // Convert strings to #markup render arrays so that they will XSS admin
+        // filtered.
+        $build[] = is_array($help) ? $help : ['#markup' => $help];
+      }
+    }
+    return $build;
+  }
+
+  /**
+   * {@inheritdoc}
+   */
+  public function getCacheContexts() {
+    return Cache::mergeContexts(parent::getCacheContexts(), ['route']);
+  }
+
+}

web/core/modules/help/src/Plugin/HelpSection/HelpSectionPluginBase.php

@@ -0,0 +1,34 @@
+<?php
+
+namespace Drupal\help\Plugin\HelpSection;
+
+use Drupal\Core\Cache\UnchangingCacheableDependencyTrait;
+use Drupal\Core\Plugin\PluginBase;
+use Drupal\help\HelpSectionPluginInterface;
+
+/**
+ * Provides a base class for help section plugins.
+ *
+ * @see \Drupal\help\HelpSectionPluginInterface
+ * @see \Drupal\help\Annotation\HelpSection
+ * @see \Drupal\help\HelpSectionManager
+ */
+abstract class HelpSectionPluginBase extends PluginBase implements HelpSectionPluginInterface {
+
+  use UnchangingCacheableDependencyTrait;
+
+  /**
+   * {@inheritdoc}
+   */
+  public function getTitle() {
+    return $this->getPluginDefinition()['title'];
+  }
+
+  /**
+   * {@inheritdoc}
+   */
+  public function getDescription() {
+    return $this->getPluginDefinition()['description'];
+  }
+
+}

web/core/modules/help/src/Plugin/HelpSection/HookHelpSection.php

@@ -0,0 +1,72 @@
+<?php
+
+namespace Drupal\help\Plugin\HelpSection;
+
+use Drupal\Core\Extension\ModuleHandlerInterface;
+use Drupal\Core\Link;
+use Drupal\Core\Plugin\ContainerFactoryPluginInterface;
+use Symfony\Component\DependencyInjection\ContainerInterface;
+
+/**
+ * Provides the module topics list section for the help page.
+ *
+ * @HelpSection(
+ *   id = "hook_help",
+ *   title = @Translation("Module overviews"),
+ *   description = @Translation("Module overviews are provided by modules. Overviews available for your installed modules:"),
+ * )
+ */
+class HookHelpSection extends HelpSectionPluginBase implements ContainerFactoryPluginInterface {
+
+  /**
+   * The module handler.
+   *
+   * @var \Drupal\Core\Extension\ModuleHandlerInterface
+   */
+  protected $moduleHandler;
+
+  /**
+   * Constructs a HookHelpSection object.
+   *
+   * @param array $configuration
+   *   A configuration array containing information about the plugin instance.
+   * @param string $plugin_id
+   *   The plugin_id for the plugin instance.
+   * @param mixed $plugin_definition
+   *   The plugin implementation definition.
+   * @param \Drupal\Core\Extension\ModuleHandlerInterface $module_handler
+   *   The module handler service.
+   */
+  public function __construct(array $configuration, $plugin_id, $plugin_definition, ModuleHandlerInterface $module_handler) {
+    parent::__construct($configuration, $plugin_id, $plugin_definition);
+    $this->moduleHandler = $module_handler;
+  }
+
+  /**
+   * {@inheritdoc}
+   */
+  public static function create(ContainerInterface $container, array $configuration, $plugin_id, $plugin_definition) {
+    return new static(
+      $configuration,
+      $plugin_id,
+      $plugin_definition,
+      $container->get('module_handler')
+    );
+  }
+
+  /**
+   * {@inheritdoc}
+   */
+  public function listTopics() {
+    $topics = [];
+    foreach ($this->moduleHandler->getImplementations('help') as $module) {
+      $title = $this->moduleHandler->getName($module);
+      $topics[$title] = Link::createFromRoute($title, 'help.page', ['name' => $module]);
+    }
+
+    // Sort topics by title, which is the array key above.
+    ksort($topics);
+    return $topics;
+  }
+
+}

web/core/modules/help/templates/help-section.html.twig

@@ -0,0 +1,25 @@
+{#
+/**
+ * @file
+ * Default theme implementation for a section of the help page.
+ *
+ * Available variables:
+ * - title: The section title.
+ * - description: The description text for the section.
+ * - links: Links to display in the section.
+ * - empty: Text to display if there are no links.
+ *
+ * @ingroup themeable
+ */
+#}
+<h2>{{ title }}</h2>
+<p>{{ description }}</p>
+{% if links %}
+  <ul>
+  {% for link in links %}
+    <li>{{ link }}</li>
+  {% endfor %}
+  </ul>
+{% else %}
+  <p>{{ empty }}</p>
+{% endif %}

web/core/modules/help/tests/modules/help_page_test/help_page_test.info.yml

@@ -0,0 +1,7 @@
+name: 'Help Page Test'
+type: module
+description: 'Module to test the help page.'
+package: Testing
+version: VERSION
+core: 8.x
+hidden: true

web/core/modules/help/tests/modules/help_page_test/help_page_test.module

@@ -0,0 +1,29 @@
+<?php
+
+/**
+ * @file
+ * Help Page Test module to test the help page.
+ */
+
+use \Drupal\Core\Routing\RouteMatchInterface;
+
+/**
+ * Implements hook_help().
+ */
+function help_page_test_help($route_name, RouteMatchInterface $route_match) {
+
+  switch ($route_name) {
+    case 'help.page.help_page_test':
+      // Make the help text conform to core standards. See
+      // \Drupal\system\Tests\Module\InstallUninstallTest::assertHelp().
+      return t('Read the <a href=":url">online documentation for the Help Page Test module</a>.', [':url' => 'http://www.example.com']);
+    case 'help_page_test.has_help':
+      return t('I have help!');
+    case 'help_page_test.test_array':
+      return ['#markup' => 'Help text from help_page_test_help module.'];
+  }
+
+  // Ensure that hook_help() can return an empty string and not cause the block
+  // to display.
+  return '';
+}

web/core/modules/help/tests/modules/help_page_test/help_page_test.routing.yml

@@ -0,0 +1,20 @@
+help_page_test.has_help:
+  path: '/help_page_test/has_help'
+  defaults:
+    _controller: '\Drupal\help_page_test\HelpPageTestController::hasHelp'
+  requirements:
+    _access: 'TRUE'
+
+help_page_test.no_help:
+  path: '/help_page_test/no_help'
+  defaults:
+    _controller: '\Drupal\help_page_test\HelpPageTestController::noHelp'
+  requirements:
+    _access: 'TRUE'
+
+help_page_test.test_array:
+  path: '/help_page_test/test_array'
+  defaults:
+    _controller: '\Drupal\help_page_test\HelpPageTestController::testArray'
+  requirements:
+    _access: 'TRUE'

web/core/modules/help/tests/modules/help_page_test/src/HelpPageTestController.php

@@ -0,0 +1,40 @@
+<?php
+
+namespace Drupal\help_page_test;
+
+/**
+ * Provides controllers for testing the help block.
+ */
+class HelpPageTestController {
+
+  /**
+   * Provides a route with help.
+   *
+   * @return array
+   *   A render array.
+   */
+  public function hasHelp() {
+    return ['#markup' => 'A route with help.'];
+  }
+
+  /**
+   * Provides a route with no help.
+   *
+   * @return array
+   *   A render array.
+   */
+  public function noHelp() {
+    return ['#markup' => 'A route without help.'];
+  }
+
+  /**
+   * Provides a route which has multiple array returns from hook_help().
+   *
+   * @return array
+   *   A render array.
+   */
+  public function testArray() {
+    return ['#markup' => 'A route which has multiple array returns from hook_help().'];
+  }
+
+}

web/core/modules/help/tests/modules/help_page_test/src/Plugin/HelpSection/EmptyHelpSection.php

@@ -0,0 +1,24 @@
+<?php
+
+namespace Drupal\help_page_test\Plugin\HelpSection;
+
+use Drupal\help\Plugin\HelpSection\HelpSectionPluginBase;
+
+/**
+ * Provides an empty section for the help page, for testing.
+ *
+ * @HelpSection(
+ *   id = "empty_section",
+ *   title = @Translation("Empty section"),
+ *   description = @Translation("This description should appear."),
+ * )
+ */
+class EmptyHelpSection extends HelpSectionPluginBase {
+  /**
+   * {@inheritdoc}
+   */
+  public function listTopics() {
+    return [];
+  }
+
+}

web/core/modules/help/tests/modules/help_test/help_test.info.yml

@@ -0,0 +1,6 @@
+name: help_test
+type: module
+core: 8.x
+package: Testing
+dependencies:
+  - help

web/core/modules/help/tests/modules/help_test/help_test.module

@@ -0,0 +1,16 @@
+<?php
+
+/**
+ * @file
+ * Test Help module.
+ */
+
+use \Drupal\Core\Routing\RouteMatchInterface;
+
+/**
+ * Implements hook_help().
+ */
+function help_test_help($route_name, RouteMatchInterface $route_match) {
+  // Do not implement a module overview page to test an empty implementation.
+  // @see \Drupal\help\Tests\HelpTest
+}

web/core/modules/help/tests/modules/help_test/src/SupernovaGenerator.php

@@ -0,0 +1,62 @@
+<?php
+
+namespace Drupal\help_test;
+
+use Drupal\Core\Routing\UrlGeneratorInterface;
+use Symfony\Component\Routing\RequestContext;
+
+/**
+ * Implements a URL generator which always thrown an exception.
+ */
+class SupernovaGenerator implements UrlGeneratorInterface {
+
+  /**
+   * {@inheritdoc}
+   */
+  public function setContext(RequestContext $context) {
+    throw new \Exception();
+  }
+
+  /**
+   * {@inheritdoc}
+   */
+  public function getContext() {
+    throw new \Exception();
+  }
+
+  /**
+   * {@inheritdoc}
+   */
+  public function generate($name, $parameters = array(), $referenceType = self::ABSOLUTE_PATH) {
+    throw new \Exception();
+  }
+
+  /**
+   * {@inheritdoc}
+   */
+  public function getPathFromRoute($name, $parameters = array()) {
+    throw new \Exception();
+  }
+
+  /**
+   * {@inheritdoc}
+   */
+  public function generateFromRoute($name, $parameters = array(), $options = array(), $collect_bubbleable_metadata = FALSE) {
+    throw new \Exception();
+  }
+
+  /**
+   * {@inheritdoc}
+   */
+  public function supports($name) {
+    throw new \Exception();
+  }
+
+  /**
+   * {@inheritdoc}
+   */
+  public function getRouteDebugMessage($name, array $parameters = array()) {
+    throw new \Exception();
+  }
+
+}

web/core/modules/help/tests/modules/more_help_page_test/more_help_page_test.info.yml

@@ -0,0 +1,7 @@
+name: 'More Help Page Test'
+type: module
+description: 'Module to test the help page.'
+package: Testing
+version: VERSION
+core: 8.x
+hidden: true

web/core/modules/help/tests/modules/more_help_page_test/more_help_page_test.module

@@ -0,0 +1,20 @@
+<?php
+
+/**
+ * @file
+ * More Help Page Test module to test the help blocks.
+ */
+
+use \Drupal\Core\Routing\RouteMatchInterface;
+
+/**
+ * Implements hook_help().
+ */
+function more_help_page_test_help($route_name, RouteMatchInterface $route_match) {
+
+  switch ($route_name) {
+    // Return help for the same route as the help_page_test module.
+    case 'help_page_test.test_array':
+      return ['#markup' => 'Help text from more_help_page_test_help module.'];
+  }
+}

web/core/modules/help/tests/src/Functional/ExperimentalHelpTest.php

@@ -0,0 +1,56 @@
+<?php
+
+namespace Drupal\Tests\help\Functional;
+
+use Drupal\Tests\BrowserTestBase;
+
+/**
+ * Verifies help for experimental modules.
+ *
+ * @group help
+ */
+class ExperimentalHelpTest extends BrowserTestBase {
+
+  /**
+   * Modules to enable.
+   *
+   * The experimental_module_test module implements hook_help() and is in the
+   * Core (Experimental) package.
+   *
+   * @var array
+   */
+  public static $modules = array('help', 'experimental_module_test', 'help_page_test');
+
+  /**
+   * The admin user.
+   *
+   * @var \Drupal\user\UserInterface
+   */
+  protected $adminUser;
+
+  /**
+   * {@inheritoc}
+   */
+  protected function setUp() {
+    parent::setUp();
+    $this->adminUser = $this->drupalCreateUser(['access administration pages']);
+  }
+
+  /**
+   * Verifies that a warning message is displayed for experimental modules.
+   */
+  public function testExperimentalHelp() {
+    $this->drupalLogin($this->adminUser);
+    $this->drupalGet('admin/help/experimental_module_test');
+    $this->assertText('This module is experimental.');
+
+    // Regular modules should not display the message.
+    $this->drupalGet('admin/help/help_page_test');
+    $this->assertNoText('This module is experimental.');
+
+    // Ensure the actual help page is displayed to avoid a false positive.
+    $this->assertResponse(200);
+    $this->assertText('online documentation for the Help Page Test module');
+  }
+
+}

web/core/modules/help/tests/src/Functional/HelpBlockTest.php

@@ -0,0 +1,50 @@
+<?php
+
+namespace Drupal\Tests\help\Functional;
+
+use Drupal\Tests\BrowserTestBase;
+
+/**
+ * Tests display of help block.
+ *
+ * @group help
+ */
+class HelpBlockTest extends BrowserTestBase {
+
+  /**
+   * {@inheritdoc}
+   */
+  public static $modules = ['help', 'help_page_test', 'block', 'more_help_page_test'];
+
+  /**
+   * The help block instance.
+   *
+   * @var \Drupal\block\Entity\Block
+   */
+  protected $helpBlock;
+
+  protected function setUp() {
+    parent::setUp();
+    $this->helpBlock = $this->placeBlock('help_block');
+  }
+
+  /**
+   * Logs in users, tests help pages.
+   */
+  public function testHelp() {
+    $this->drupalGet('help_page_test/has_help');
+    $this->assertText(t('I have help!'));
+    $this->assertText($this->helpBlock->label());
+
+    $this->drupalGet('help_page_test/no_help');
+    // The help block should not appear when there is no help.
+    $this->assertNoText($this->helpBlock->label());
+
+    // Ensure that if two hook_help() implementations both return a render array
+    // the output is as expected.
+    $this->drupalGet('help_page_test/test_array');
+    $this->assertText('Help text from more_help_page_test_help module.');
+    $this->assertText('Help text from help_page_test_help module.');
+  }
+
+}

web/core/modules/help/tests/src/Functional/HelpTest.php

@@ -0,0 +1,160 @@
+<?php
+
+namespace Drupal\Tests\help\Functional;
+
+use Drupal\Tests\BrowserTestBase;
+
+/**
+ * Verify help display and user access to help based on permissions.
+ *
+ * @group help
+ */
+class HelpTest extends BrowserTestBase {
+
+  /**
+   * Modules to enable.
+   *
+   * The help_test module implements hook_help() but does not provide a module
+   * overview page. The help_page_test module has a page section plugin that
+   * returns no links.
+   *
+   * @var array.
+   */
+  public static $modules = array('help_test', 'help_page_test');
+
+  /**
+   * Use the Standard profile to test help implementations of many core modules.
+   */
+  protected $profile = 'standard';
+
+  /**
+   * The admin user that will be created.
+   */
+  protected $adminUser;
+
+  /**
+   * The anonymous user that will be created.
+   */
+  protected $anyUser;
+
+  protected function setUp() {
+    parent::setUp();
+
+    // Create users.
+    $this->adminUser = $this->drupalCreateUser(array('access administration pages', 'view the administration theme', 'administer permissions'));
+    $this->anyUser = $this->drupalCreateUser(array());
+  }
+
+  /**
+   * Logs in users, tests help pages.
+   */
+  public function testHelp() {
+    // Log in the root user to ensure as many admin links appear as possible on
+    // the module overview pages.
+    $this->drupalLogin($this->rootUser);
+    $this->verifyHelp();
+
+    // Log in the regular user.
+    $this->drupalLogin($this->anyUser);
+    $this->verifyHelp(403);
+
+    // Verify that introductory help text exists, goes for 100% module coverage.
+    $this->drupalLogin($this->adminUser);
+    $this->drupalGet('admin/help');
+    $this->assertRaw(t('For more information, refer to the help listed on this page or to the <a href=":docs">online documentation</a> and <a href=":support">support</a> pages at <a href=":drupal">drupal.org</a>.', array(':docs' => 'https://www.drupal.org/documentation', ':support' => 'https://www.drupal.org/support', ':drupal' => 'https://www.drupal.org')));
+
+    // Verify that hook_help() section title and description appear.
+    $this->assertRaw('<h2>' . t('Module overviews') . '</h2>');
+    $this->assertRaw('<p>' . t('Module overviews are provided by modules. Overviews available for your installed modules:'), '</p>');
+
+    // Verify that an empty section is handled correctly.
+    $this->assertRaw('<h2>' . t('Empty section') . '</h2>');
+    $this->assertRaw('<p>' . t('This description should appear.'), '</p>');
+    $this->assertText(t('There is currently nothing in this section.'));
+
+    // Make sure links are properly added for modules implementing hook_help().
+    foreach ($this->getModuleList() as $module => $name) {
+      $this->assertLink($name, 0, format_string('Link properly added to @name (admin/help/@module)', array('@module' => $module, '@name' => $name)));
+    }
+
+    // Ensure that module which does not provide an module overview page is
+    // handled correctly.
+    $this->clickLink(\Drupal::moduleHandler()->getName('help_test'));
+    $this->assertRaw(t('No help is available for module %module.', array('%module' => \Drupal::moduleHandler()->getName('help_test'))));
+
+    // Verify that the order of topics is alphabetical by displayed module
+    // name, by checking the order of some modules, including some that would
+    // have a different order if it was done by machine name instead.
+    $this->drupalGet('admin/help');
+    $page_text = $this->getTextContent();
+    $start = strpos($page_text, 'Module overviews');
+    $pos = $start;
+    $list = ['Block', 'Color', 'Custom Block', 'History', 'Text Editor'];
+    foreach ($list as $name) {
+      $this->assertLink($name);
+      $new_pos = strpos($page_text, $name, $start);
+      $this->assertTrue($new_pos > $pos, 'Order of ' . $name . ' is correct on page');
+      $pos = $new_pos;
+    }
+  }
+
+  /**
+   * Verifies the logged in user has access to the various help pages.
+   *
+   * @param int $response
+   *   (optional) An HTTP response code. Defaults to 200.
+   */
+  protected function verifyHelp($response = 200) {
+    $this->drupalGet('admin/index');
+    $this->assertResponse($response);
+    if ($response == 200) {
+      $this->assertText('This page shows you all available administration tasks for each module.');
+    }
+    else {
+      $this->assertNoText('This page shows you all available administration tasks for each module.');
+    }
+
+    foreach ($this->getModuleList() as $module => $name) {
+      // View module help page.
+      $this->drupalGet('admin/help/' . $module);
+      $this->assertResponse($response);
+      if ($response == 200) {
+        $this->assertTitle($name . ' | Drupal', format_string('%module title was displayed', array('%module' => $module)));
+        $this->assertEquals($name, $this->cssSelect('h1.page-title')[0]->getText(), "$module heading was displayed");
+        $admin_tasks = system_get_module_admin_tasks($module, system_get_info('module', $module));
+        if (!empty($admin_tasks)) {
+          $this->assertText(t('@module administration pages', array('@module' => $name)));
+        }
+        foreach ($admin_tasks as $task) {
+          $this->assertLink($task['title']);
+          // Ensure there are no double escaped '&' or '<' characters.
+          $this->assertNoEscaped('&amp;', 'The help text does not have double escaped &amp;.');
+          $this->assertNoEscaped('&lt;', 'The help text does not have double escaped &lt;.');
+          // Ensure there are no escaped '<' characters.
+          $this->assertNoEscaped('<', 'The help text does not have single escaped &lt;.');
+        }
+        // Ensure there are no double escaped '&' or '<' characters.
+        $this->assertNoEscaped('&amp;');
+        $this->assertNoEscaped('&lt;');
+        // Ensure there are no escaped '<' characters.
+        $this->assertNoEscaped('<');
+      }
+    }
+  }
+
+  /**
+   * Gets the list of enabled modules that implement hook_help().
+   *
+   * @return array
+   *   A list of enabled modules.
+   */
+  protected function getModuleList() {
+    $modules = array();
+    $module_data = system_rebuild_module_data();
+    foreach (\Drupal::moduleHandler()->getImplementations('help') as $module) {
+      $modules[$module] = $module_data[$module]->info['name'];
+    }
+    return $modules;
+  }
+
+}

web/core/modules/help/tests/src/Functional/NoHelpTest.php

@@ -0,0 +1,49 @@
+<?php
+
+namespace Drupal\Tests\help\Functional;
+
+use Drupal\Tests\BrowserTestBase;
+
+/**
+ * Verify no help is displayed for modules not providing any help.
+ *
+ * @group help
+ */
+class NoHelpTest extends BrowserTestBase {
+
+  /**
+   * Modules to enable.
+   *
+   * Use one of the test modules that do not implement hook_help().
+   *
+   * @var array.
+   */
+  public static $modules = array('help', 'menu_test');
+
+  /**
+   * The user who will be created.
+   */
+  protected $adminUser;
+
+  protected function setUp() {
+    parent::setUp();
+    $this->adminUser = $this->drupalCreateUser(array('access administration pages'));
+  }
+
+  /**
+   * Ensures modules not implementing help do not appear on admin/help.
+   */
+  public function testMainPageNoHelp() {
+    $this->drupalLogin($this->adminUser);
+
+    $this->drupalGet('admin/help');
+    $this->assertResponse(200);
+    $this->assertText('Module overviews are provided by modules');
+    $this->assertFalse(\Drupal::moduleHandler()->implementsHook('menu_test', 'help'), 'The menu_test module does not implement hook_help');
+    $this->assertNoText(\Drupal::moduleHandler()->getName('menu_test'), 'Making sure the test module menu_test does not display a help link on admin/help.');
+
+    $this->drupalGet('admin/help/menu_test');
+    $this->assertResponse(404, 'Getting a module overview help page for a module that does not implement hook_help() results in a 404.');
+  }
+
+}

web/core/modules/help/tests/src/Kernel/HelpEmptyPageTest.php

@@ -0,0 +1,52 @@
+<?php
+
+namespace Drupal\Tests\help\Kernel;
+
+use Drupal\Core\DependencyInjection\ContainerBuilder;
+use Drupal\Core\Routing\RouteMatch;
+use Drupal\help_test\SupernovaGenerator;
+use Drupal\KernelTests\KernelTestBase;
+
+/**
+ * Tests the empty HTML page.
+ *
+ * @group help
+ */
+class HelpEmptyPageTest extends KernelTestBase {
+
+  /**
+   * {@inheritdoc}
+   */
+  public static $modules = ['system', 'help_test', 'user'];
+
+  /**
+   * {@inheritdoc}
+   */
+  public function register(ContainerBuilder $container) {
+    parent::register($container);
+
+    $container->set('url_generator', new SupernovaGenerator());
+  }
+
+  /**
+   * Ensures that no URL generator is called on a page without hook_help().
+   */
+  public function testEmptyHookHelp() {
+    $all_modules = system_rebuild_module_data();
+    $all_modules = array_filter($all_modules, function ($module) {
+      // Filter contrib, hidden, already enabled modules and modules in the
+      // Testing package.
+      if ($module->origin !== 'core' || !empty($module->info['hidden']) || $module->status == TRUE || $module->info['package'] == 'Testing') {
+        return FALSE;
+      }
+      return TRUE;
+    });
+
+    $this->enableModules(array_keys($all_modules));
+    $this->installEntitySchema('menu_link_content');
+
+    $route = \Drupal::service('router.route_provider')->getRouteByName('<front>');
+    \Drupal::service('module_handler')->invokeAll('help', ['<front>', new RouteMatch('<front>', $route)]);
+  }
+
+}