Drupal 8.0.0 beta 12. More info: https://www.drupal.org/node/2514176

core/modules/help/help.api.php

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+<?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
+ * 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 $route_match
+ *   The current route match. This can be used to generate different help
+ *   output for different pages that share the same route.
+ *
+ * @return string
+ *   A localized string containing the help text.
+ */
+function hook_help($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>';
+  }
+}
+
+/**
+ * @} End of "addtogroup hooks".
+ */

core/modules/help/help.info.yml

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+name: Help
+type: module
+description: 'Manages the display of online help.'
+package: Core
+version: VERSION
+core: 8.x

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

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

core/modules/help/help.module

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+<?php
+
+/**
+ * @file
+ * Manages displaying online help.
+ */
+
+use Drupal\Core\Routing\RouteMatchInterface;
+use Drupal\Core\Block\BlockPluginInterface;
+
+/**
+ * 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 subjects listed in the Help Topics section 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 $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 $output;
+  }
+}
+
+/**
+ * Implements hook_preprocess_HOOK() for block templates.
+ */
+function help_preprocess_block(&$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']);
+}

core/modules/help/help.routing.yml

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+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'

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

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+<?php
+
+/**
+ * @file
+ * Contains \Drupal\help\Controller\HelpController.
+ */
+
+namespace Drupal\help\Controller;
+
+use Drupal\Core\Controller\ControllerBase;
+use Drupal\Core\Routing\RouteMatchInterface;
+use Drupal\Core\Url;
+use Symfony\Component\DependencyInjection\ContainerInterface;
+use Symfony\Component\HttpKernel\Exception\NotFoundHttpException;
+use Drupal\Component\Utility\SafeMarkup;
+
+/**
+ * Controller routines for help routes.
+ */
+class HelpController extends ControllerBase {
+
+  /**
+   * The current route match.
+   *
+   * @var \Drupal\Core\Routing\RouteMatchInterface
+   */
+  protected $routeMatch;
+
+  /**
+   * Creates a new HelpController.
+   *
+   * @param \Drupal\Core\Routing\RouteMatchInterface $route_match
+   *   The current route match.
+   */
+  public function __construct(RouteMatchInterface $route_match) {
+    $this->routeMatch = $route_match;
+  }
+
+  /**
+   * {@inheritdoc}
+   */
+  public static function create(ContainerInterface $container) {
+    return new static(
+      $container->get('current_route_match')
+    );
+  }
+
+  /**
+   * Prints a page listing a glossary of Drupal terminology.
+   *
+   * @return string
+   *   An HTML string representing the contents of help page.
+   */
+  public function helpMain() {
+    $output = array(
+      '#markup' => '<h2>' . $this->t('Help topics') . '</h2><p>' . $this->t('Help is available on the following items:') . '</p>',
+      'links' => $this->helpLinksAsList(),
+    );
+    return $output;
+  }
+
+  /**
+   * Provides a formatted list of available help topics.
+   *
+   * @return string
+   *   A string containing the formatted list.
+   */
+  protected function helpLinksAsList() {
+    $modules = array();
+    foreach ($this->moduleHandler()->getImplementations('help') as $module) {
+      $modules[$module] = $this->moduleHandler->getName($module);
+    }
+    asort($modules);
+
+    // Output pretty four-column list.
+    $count = count($modules);
+    $break = ceil($count / 4);
+    $column = array(
+      '#type' => 'container',
+      'links' => array('#theme' => 'item_list'),
+      '#attributes' => array('class' => array('layout-column', 'quarter')),
+    );
+    $output = array(
+      '#prefix' => '<div class="clearfix">',
+      '#suffix' => '</div>',
+      0 => $column,
+    );
+
+    $i = 0;
+    $current_column = 0;
+    foreach ($modules as $module => $name) {
+      $output[$current_column]['links']['#items'][] = $this->l($name, new Url('help.page', array('name' => $module)));
+      if (($i + 1) % $break == 0 && ($i + 1) != $count) {
+        $current_column++;
+        $output[$current_column] = $column;
+      }
+      $i++;
+    }
+
+    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);
+      $build['#title'] = SafeMarkup::checkPlain($module_name);
+
+      $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 {
+        $build['top']['#markup'] = $temp;
+      }
+
+      // Only print list of administration pages if the module in question has
+      // any such pages associated to 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();
+    }
+  }
+
+}

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

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+<?php
+
+/**
+ * @file
+ * Contains \Drupal\help\Plugin\Block\HelpBlock.
+ */
+
+namespace Drupal\help\Plugin\Block;
+
+use Drupal\Core\Access\AccessResult;
+use Drupal\Core\Block\BlockBase;
+use Drupal\Core\Extension\ModuleHandlerInterface;
+use Drupal\Core\Plugin\ContainerFactoryPluginInterface;
+use Drupal\Core\Routing\RouteMatchInterface;
+use Drupal\Core\Session\AccountInterface;
+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 {
+
+  /**
+   * Stores the help text associated with the active menu item.
+   *
+   * @var string
+   */
+  protected $help;
+
+  /**
+   * 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}
+   */
+  protected function blockAccess(AccountInterface $account) {
+    $this->help = $this->getActiveHelp($this->request);
+    if ($this->help) {
+      return AccessResult::allowed();
+    }
+    else {
+      return AccessResult::forbidden();
+    }
+  }
+
+  /**
+   * Returns the help associated with the active menu item.
+   *
+   * @param \Symfony\Component\HttpFoundation\Request $request
+   *   The current request.
+   */
+  protected function getActiveHelp(Request $request) {
+    // Do not show on a 403 or 404 page.
+    if ($request->attributes->has('exception')) {
+      return '';
+    }
+
+    $help = $this->moduleHandler->invokeAll('help', array($this->routeMatch->getRouteName(), $this->routeMatch));
+    return $help ? implode("\n", $help) : '';
+  }
+
+  /**
+   * {@inheritdoc}
+   */
+  public function build() {
+    return array(
+      '#children' => $this->help,
+    );
+  }
+
+  /**
+   * {@inheritdoc}
+   */
+  public function getCacheContexts() {
+    // The "Help" block must be cached per URL: help is defined for a
+    // given path, and does not come with any access restrictions.
+    return array('url');
+  }
+
+}

core/modules/help/src/Tests/HelpEmptyPageTest.php

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+<?php
+
+/**
+ * @file
+ * Contains \Drupal\help\Tests\HelpEmptyPageTest.
+ */
+
+namespace Drupal\help\Tests;
+
+use Drupal\Core\DependencyInjection\ContainerBuilder;
+use Drupal\Core\Routing\RouteMatch;
+use Drupal\help_test\SupernovaGenerator;
+use Drupal\simpletest\KernelTestBase;
+
+/**
+ * Tests the empty HTML page.
+ *
+ * @group help
+ */
+class HelpEmptyPageTest extends KernelTestBase {
+
+  /**
+   * {@inheritdoc}
+   */
+  public static $modules = ['system', 'help_test', 'user'];
+
+  /**
+   * {@inheritdoc}
+   */
+  protected function setUp() {
+    parent::setUp();
+
+    $this->installSchema('system', 'router');
+  }
+
+  /**
+   * {@inheritdoc}
+   */
+  public function containerBuild(ContainerBuilder $container) {
+    parent::containerBuild($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 || $module->info['package'] == 'Testing') {
+        return FALSE;
+      }
+      return TRUE;
+    });
+
+    \Drupal::service('module_installer')->install(array_keys($all_modules));
+
+    $route = \Drupal::service('router.route_provider')->getRouteByName('<front>');
+    \Drupal::service('module_handler')->invokeAll('help', ['<front>', new RouteMatch('<front>', $route)]);
+  }
+
+}

core/modules/help/src/Tests/HelpTest.php

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+<?php
+
+/**
+ * @file
+ * Contains \Drupal\help\Tests\HelpTest.
+ */
+
+namespace Drupal\help\Tests;
+
+use Drupal\simpletest\WebTestBase;
+
+/**
+ * Verify help display and user access to help based on permissions.
+ *
+ * @group help
+ */
+class HelpTest extends WebTestBase {
+
+  /**
+   * Modules to enable.
+   *
+   * The help_test module implements hook_help() but does not provide a module
+   * overview page.
+   *
+   * @var array.
+   */
+  public static $modules = array('help_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();
+
+    $this->getModuleList();
+
+    // Create users.
+    $this->adminUser = $this->drupalCreateUser(array('access administration pages', 'view the administration theme', 'administer permissions'));
+    $this->anyUser = $this->drupalCreateUser(array());
+  }
+
+  /**
+   * Logs in users, creates dblog events, and tests dblog functionality.
+   */
+  public function testHelp() {
+    // Login the root user to ensure as many admin links appear as possible on
+    // the module overview pages.
+    $this->drupalLogin($this->rootUser);
+    $this->verifyHelp();
+
+    // Login 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 subjects listed in the Help Topics section 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')), 'Help intro text correctly appears.');
+
+    // Verify that help topics text appears.
+    $this->assertRaw('<h2>' . t('Help topics') . '</h2><p>' . t('Help is available on the following items:') . '</p>', 'Help topics text correctly appears.');
+
+    // Make sure links are properly added for modules implementing hook_help().
+    foreach ($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'))));
+  }
+
+  /**
+   * Verifies the logged in user has access to the various help nodes.
+   *
+   * @param integer $response
+   *   An HTTP response code.
+   */
+  protected function verifyHelp($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 node.
+      $this->drupalGet('admin/help/' . $module);
+      $this->assertResponse($response);
+      if ($response == 200) {
+        $this->assertTitle($name . ' | Drupal', format_string('%module title was displayed', array('%module' => $module)));
+        $this->assertRaw('<h1 class="page-title">' . t($name) . '</h1>', format_string('%module heading was displayed', array('%module' => $module)));
+        $admin_tasks = system_get_module_admin_tasks($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']);
+        }
+      }
+    }
+  }
+
+  /**
+   * 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;
+  }
+}

core/modules/help/src/Tests/NoHelpTest.php

@@ -0,0 +1,53 @@
+<?php
+
+/**
+ * @file
+ * Contains \Drupal\help\Tests\NoHelpTest.
+ */
+
+namespace Drupal\help\Tests;
+
+use Drupal\simpletest\WebTestBase;
+
+/**
+ * Verify no help is displayed for modules not providing any help.
+ *
+ * @group help
+ */
+class NoHelpTest extends WebTestBase {
+
+  /**
+   * 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('Help is available on the following items', 'Help page is found.');
+    $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.');
+  }
+}

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

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
+}

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

@@ -0,0 +1,74 @@
+<?php
+
+/**
+ * @file
+ * Contains \Drupal\help_test\SupernovaGenerator.
+ */
+
+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(), $referenceType = self::ABSOLUTE_PATH) {
+    throw new \Exception();
+  }
+
+  /**
+   * {@inheritdoc}
+   */
+  public function generateFromPath($path = NULL, $options = array(), $collect_cacheability_metadata = FALSE) {
+    throw new \Exception();
+  }
+
+  /**
+   * {@inheritdoc}
+   */
+  public function getPathFromRoute($name, $parameters = array()) {
+    throw new \Exception();
+  }
+
+  /**
+   * {@inheritdoc}
+   */
+  public function generateFromRoute($name, $parameters = array(), $options = array(), $collect_cacheability_metadata = FALSE) {
+    throw new \Exception();
+  }
+
+  /**
+   * {@inheritdoc}
+   */
+  public function supports($name) {
+    throw new \Exception();
+  }
+
+  /**
+   * {@inheritdoc}
+   */
+  public function getRouteDebugMessage($name, array $parameters = array()) {
+    throw new \Exception();
+  }
+
+}