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

core/modules/book/book.info.yml

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+name: Book
+type: module
+description: 'Allows users to create and organize related content in an outline.'
+package: Core
+version: VERSION
+core: 8.x
+dependencies:
+  - node
+configure: book.settings

core/modules/book/book.install

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+<?php
+
+/**
+ * @file
+ * Install, update and uninstall functions for the book module.
+ */
+
+/**
+ * Implements hook_uninstall().
+ */
+function book_uninstall() {
+  // Clear book data out of the cache.
+  \Drupal::cache('data')->deleteAll();
+}
+
+/**
+ * Implements hook_schema().
+ */
+function book_schema() {
+  $schema['book'] = array(
+  'description' => 'Stores book outline information. Uniquely defines the location of each node in the book outline',
+    'fields' => array(
+      'nid' => array(
+        'type' => 'int',
+        'unsigned' => TRUE,
+        'not null' => TRUE,
+        'default' => 0,
+        'description' => "The book page's {node}.nid.",
+      ),
+      'bid' => array(
+        'type' => 'int',
+        'unsigned' => TRUE,
+        'not null' => TRUE,
+        'default' => 0,
+        'description' => "The book ID is the {book}.nid of the top-level page.",
+      ),
+      'pid' => array(
+        'description' => 'The parent ID (pid) is the id of the node above in the hierarchy, or zero if the node is at the top level in its outline.',
+        'type' => 'int',
+        'unsigned' => TRUE,
+        'not null' => TRUE,
+        'default' => 0,
+      ),
+      'has_children' => array(
+        'description' => 'Flag indicating whether any nodes have this node as a parent (1 = children exist, 0 = no children).',
+        'type' => 'int',
+        'not null' => TRUE,
+        'default' => 0,
+        'size' => 'small',
+      ),
+      'weight' => array(
+        'description' => 'Weight among book entries in the same book at the same depth.',
+        'type' => 'int',
+        'not null' => TRUE,
+        'default' => 0,
+      ),
+      'depth' => array(
+        'description' => 'The depth relative to the top level. A link with pid == 0 will have depth == 1.',
+        'type' => 'int',
+        'not null' => TRUE,
+        'default' => 0,
+        'size' => 'small',
+      ),
+      'p1' => array(
+        'description' => 'The first nid in the materialized path. If N = depth, then pN must equal the nid. If depth > 1 then p(N-1) must equal the pid. All pX where X > depth must equal zero. The columns p1 .. p9 are also called the parents.',
+        'type' => 'int',
+        'unsigned' => TRUE,
+        'not null' => TRUE,
+        'default' => 0,
+      ),
+      'p2' => array(
+        'description' => 'The second nid in the materialized path. See p1.',
+        'type' => 'int',
+        'unsigned' => TRUE,
+        'not null' => TRUE,
+        'default' => 0,
+      ),
+      'p3' => array(
+        'description' => 'The third nid in the materialized path. See p1.',
+        'type' => 'int',
+        'unsigned' => TRUE,
+        'not null' => TRUE,
+        'default' => 0,
+      ),
+      'p4' => array(
+        'description' => 'The fourth nid in the materialized path. See p1.',
+        'type' => 'int',
+        'unsigned' => TRUE,
+        'not null' => TRUE,
+        'default' => 0,
+      ),
+      'p5' => array(
+        'description' => 'The fifth nid in the materialized path. See p1.',
+        'type' => 'int',
+        'unsigned' => TRUE,
+        'not null' => TRUE,
+        'default' => 0,
+      ),
+      'p6' => array(
+        'description' => 'The sixth nid in the materialized path. See p1.',
+        'type' => 'int',
+        'unsigned' => TRUE,
+        'not null' => TRUE,
+        'default' => 0,
+      ),
+      'p7' => array(
+        'description' => 'The seventh nid in the materialized path. See p1.',
+        'type' => 'int',
+        'unsigned' => TRUE,
+        'not null' => TRUE,
+        'default' => 0,
+      ),
+      'p8' => array(
+        'description' => 'The eighth nid in the materialized path. See p1.',
+        'type' => 'int',
+        'unsigned' => TRUE,
+        'not null' => TRUE,
+        'default' => 0,
+      ),
+      'p9' => array(
+        'description' => 'The ninth nid in the materialized path. See p1.',
+        'type' => 'int',
+        'unsigned' => TRUE,
+        'not null' => TRUE,
+        'default' => 0,
+      ),
+    ),
+    'primary key' => array('nid'),
+    'indexes' => array(
+      'book_parents' => array('bid', 'p1', 'p2', 'p3', 'p4', 'p5', 'p6', 'p7', 'p8', 'p9'),
+    ),
+  );
+
+  return $schema;
+}

core/modules/book/book.js

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+/**
+ * @file
+ * Javascript behaviors for the Book module.
+ */
+
+(function ($) {
+
+  "use strict";
+
+  /**
+   * @type {Drupal~behavior}
+   */
+  Drupal.behaviors.bookDetailsSummaries = {
+    attach: function (context) {
+      $(context).find('.book-outline-form').drupalSetSummary(function (context) {
+        var $select = $(context).find('.book-title-select');
+        var val = $select.val();
+
+        if (val === '0') {
+          return Drupal.t('Not in book');
+        }
+        else if (val === 'new') {
+          return Drupal.t('New book');
+        }
+        else {
+          return Drupal.checkPlain($select.find(':selected').text());
+        }
+      });
+    }
+  };
+
+})(jQuery);

core/modules/book/book.libraries.yml

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+drupal.book:
+  version: VERSION
+  js:
+    book.js: {}
+  dependencies:
+    - core/jquery
+    - core/drupal
+    - core/drupal.form
+

core/modules/book/book.links.menu.yml

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+book.admin:
+  title: Books
+  description: 'Manage your site''s book outlines.'
+  parent: system.admin_structure
+  route_name: book.admin
+book.render:
+  title: Books
+  route_name: book.render
+  enabled: 0

core/modules/book/book.links.task.yml

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+book.admin:
+  route_name: book.admin
+  title: 'List'
+  base_route: book.admin
+book.settings:
+  route_name: book.settings
+  title: 'Settings'
+  base_route: book.admin
+  weight: 100
+
+entity.node.book_outline_form:
+  route_name: entity.node.book_outline_form
+  base_route: entity.node.canonical
+  title: Outline
+  weight: 2

core/modules/book/book.module

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+<?php
+
+/**
+ * @file
+ * Allows users to create and organize related content in an outline.
+ */
+
+use Drupal\book\BookManager;
+use Drupal\book\BookManagerInterface;
+use Drupal\Component\Utility\SafeMarkup;
+use Drupal\Core\Entity\EntityInterface;
+use Drupal\Core\Form\FormStateInterface;
+use Drupal\Core\Render\Element;
+use Drupal\Core\Routing\RouteMatchInterface;
+use Drupal\Core\Url;
+use Drupal\node\NodeInterface;
+use Drupal\node\NodeTypeInterface;
+use Drupal\node\Entity\Node;
+use Drupal\Core\Language\LanguageInterface;
+use Drupal\Core\Entity\Display\EntityViewDisplayInterface;
+use Drupal\Core\Template\Attribute;
+
+/**
+ * Implements hook_help().
+ */
+function book_help($route_name, RouteMatchInterface $route_match) {
+  switch ($route_name) {
+    case 'help.page.book':
+      $output = '<h3>' . t('About') . '</h3>';
+      $output .= '<p>' . t('The Book module is used for creating structured, multi-page content, such as site resource guides, manuals, and wikis. It allows you to create content that has chapters, sections, subsections, or any similarly-tiered structure. Enabling the module creates a new content type <em>Book page</em>. For more information, see the <a href="!book">online documentation for the Book module</a>.', array('!book' => 'https://www.drupal.org/documentation/modules/book')) . '</p>';
+      $output .= '<h3>' . t('Uses') . '</h3>';
+      $output .= '<dl>';
+      $output .= '<dt>' . t('Adding and managing book content') . '</dt>';
+      $output .= '<dd>' . t('Books have a hierarchical structure, called a <em>book outline</em>. Each book outline can have nested pages up to nine levels deep. Multiple content types can be configured to behave as a book outline. From the content edit form, it is possible to add a page to a book outline or create a new book.') . '</dd>';
+      $output .= '<dd>' . t('You can assign separate permissions for <em>creating new books</em> as well as <em>creating</em>, <em>editing</em> and <em>deleting</em> book content. Users with the <em>Administer book outlines</em> permission can add <em>any</em> type of content to a book by selecting the appropriate book outline while editing the content. They can also view a list of all books, and edit and rearrange section titles on the <a href="!admin-book">Book list page</a>.', array('!admin-book' => \Drupal::url('book.admin'))) . '</dd>';
+      $output .= '<dt>' . t('Configuring content types for books') . '</dt>';
+      $output .= '<dd>' . t('The <em>Book page</em> content type is the initial content type enabled for book outlines. On the <a href="!admin-settings">Book settings page</a> you can configure content types that can used in book outlines.', array('!admin-settings' => \Drupal::url('book.settings'))) . '</dd>';
+      $output .= '<dd>' . t('Users with the <em>Add content and child pages to books</em> permission will see a link to <em>Add child page</em> when viewing a content item that is part of a book outline. This link will allow users to create a new content item of the content type you select on the <a href="!admin-settings">Book settings page</a>. By default this is the <em>Book page</em> content type.', array('!admin-settings' => \Drupal::url('book.settings'))) . '</dd>';
+      $output .= '<dt>' . t('Book navigation') . '</dt>';
+      $output .= '<dd>' . t("Book pages have a default book-specific navigation block. This navigation block contains links that lead to the previous and next pages in the book, and to the level above the current page in the book's structure. This block can be enabled on the <a href='!admin-block'>Blocks layout page</a>. For book pages to show up in the book navigation, they must be added to a book outline.", array('!admin-block' => (\Drupal::moduleHandler()->moduleExists('block')) ? \Drupal::url('block.admin_display') : '#')) . '</dd>';
+      $output .= '<dt>' . t('Collaboration') . '</dt>';
+      $output .= '<dd>' . t('Books can be created collaboratively, as they allow users with appropriate permissions to add pages into existing books, and add those pages to a custom table of contents.') . '</dd>';
+      $output .= '<dt>' . t('Printing books') . '</dt>';
+      $output .= '<dd>' . t("Users with the <em>View printer-friendly books</em> permission can select the <em>printer-friendly version</em> link visible at the bottom of a book page's content to generate a printer-friendly display of the page and all of its subsections.") . '</dd>';
+      $output .= '</dl>';
+      return $output;
+
+    case 'book.admin':
+      return '<p>' . t('The book module offers a means to organize a collection of related content pages, collectively known as a book. When viewed, this content automatically displays links to adjacent book pages, providing a simple navigation system for creating and reviewing structured content.') . '</p>';
+
+    case 'entity.node.book_outline_form':
+      return '<p>' . t('The outline feature allows you to include pages in the <a href="!book">Book hierarchy</a>, as well as move them within the hierarchy or to <a href="!book-admin">reorder an entire book</a>.', array('!book' => \Drupal::url('book.render'), '!book-admin' => \Drupal::url('book.admin'))) . '</p>';
+  }
+}
+
+/**
+ * Implements hook_theme().
+ */
+function book_theme() {
+  return array(
+    'book_navigation' => array(
+      'variables' => array('book_link' => NULL),
+    ),
+    'book_tree' => array(
+      'variables' => array('items' => array(), 'attributes' => array()),
+    ),
+    'book_export_html' => array(
+      'variables' => array('title' => NULL, 'contents' => NULL, 'depth' => NULL),
+    ),
+    'book_all_books_block' => array(
+      'render element' => 'book_menus',
+    ),
+    'book_node_export_html' => array(
+      'variables' => array('node' => NULL, 'content' => NULL, 'children' => NULL),
+    ),
+  );
+}
+
+/**
+ * Implements hook_entity_type_build().
+ */
+function book_entity_type_build(array &$entity_types) {
+  /** @var $entity_types \Drupal\Core\Entity\EntityTypeInterface[] */
+  $entity_types['node']
+    ->setFormClass('book_outline', 'Drupal\book\Form\BookOutlineForm')
+    ->setLinkTemplate('book-outline-form', '/node/{node}/outline')
+    ->setLinkTemplate('book-remove-form', '/node/{node}/outline/remove');
+}
+
+/**
+ * Implements hook_node_links_alter().
+ */
+function book_node_links_alter(array &$node_links, NodeInterface $node, array &$context) {
+  if ($context['view_mode'] != 'rss') {
+    $account = \Drupal::currentUser();
+
+    if (isset($node->book['depth'])) {
+      if ($context['view_mode'] == 'full' && node_is_page($node)) {
+        $child_type = \Drupal::config('book.settings')->get('child_type');
+        $access_control_handler = \Drupal::entityManager()->getAccessControlHandler('node');
+        if (($account->hasPermission('add content to books') || $account->hasPermission('administer book outlines')) && $access_control_handler->createAccess($child_type) && $node->isPublished() && $node->book['depth'] < BookManager::BOOK_MAX_DEPTH) {
+          $links['book_add_child'] = array(
+            'title' => t('Add child page'),
+            'url' => Url::fromRoute('node.add', ['node_type' => $child_type], ['query' => ['parent' => $node->id()]]),
+          );
+        }
+
+        if ($account->hasPermission('access printer-friendly version')) {
+          $links['book_printer'] = array(
+            'title' => t('Printer-friendly version'),
+            'url' => Url::fromRoute('book.export', [
+              'type' => 'html',
+              'node' => $node->id(),
+            ]),
+            'attributes' => array('title' => t('Show a printer-friendly version of this book page and its sub-pages.'))
+          );
+        }
+      }
+    }
+
+    if (!empty($links)) {
+      $node_links['book'] = array(
+        '#theme' => 'links__node__book',
+        '#links' => $links,
+        '#attributes' => array('class' => array('links', 'inline')),
+      );
+    }
+  }
+}
+
+/**
+ * Implements hook_form_BASE_FORM_ID_alter() for node_form().
+ *
+ * Adds the book form element to the node form.
+ *
+ * @see book_pick_book_nojs_submit()
+ */
+function book_form_node_form_alter(&$form, FormStateInterface $form_state, $form_id) {
+  $node = $form_state->getFormObject()->getEntity();
+  $account = \Drupal::currentUser();
+  $access = $account->hasPermission('administer book outlines');
+  if (!$access) {
+    if ($account->hasPermission('add content to books') && ((!empty($node->book['bid']) && !$node->isNew()) || book_type_is_allowed($node->getType()))) {
+      // Already in the book hierarchy, or this node type is allowed.
+      $access = TRUE;
+    }
+  }
+
+  if ($access) {
+    $collapsed = !($node->isNew() && !empty($node->book['pid']));
+    $form = \Drupal::service('book.manager')->addFormElements($form, $form_state, $node, $account, $collapsed);
+    // The "js-hide" class hides submit button when Javascript is enabled.
+    $form['book']['pick-book'] = array(
+      '#type' => 'submit',
+      '#value' => t('Change book (update list of parents)'),
+      '#submit' => array('book_pick_book_nojs_submit'),
+      '#weight' => 20,
+      '#attributes' => array(
+        'class' => array(
+          'js-hide',
+        ),
+      ),
+    );
+    $form['#entity_builders'][] = 'book_node_builder';
+  }
+}
+
+/**
+ * Entity form builder to add the book information to the node.
+ *
+ * @todo: Remove this in favor of an entity field.
+ */
+function book_node_builder($entity_type, NodeInterface $entity, &$form, FormStateInterface $form_state) {
+  $entity->book = $form_state->getValue('book');
+
+  // Always save a revision for non-administrators.
+  if (!empty($entity->book['bid']) && !\Drupal::currentUser()->hasPermission('administer nodes')) {
+    $entity->setNewRevision();
+  }
+}
+
+/**
+ * Form submission handler for node_form().
+ *
+ * This handler is run when JavaScript is disabled. It triggers the form to
+ * rebuild so that the "Parent item" options are changed to reflect the newly
+ * selected book. When JavaScript is enabled, the submit button that triggers
+ * this handler is hidden, and the "Book" dropdown directly triggers the
+ * book_form_update() Ajax callback instead.
+ *
+ * @see book_form_update()
+ * @see book_form_node_form_alter()
+ */
+function book_pick_book_nojs_submit($form, FormStateInterface $form_state) {
+  $node = $form_state->getFormObject()->getEntity();
+  $node->book = $form_state->getValue('book');
+  $form_state->setRebuild();
+}
+
+/**
+ * Renders a new parent page select element when the book selection changes.
+ *
+ * This function is called via Ajax when the selected book is changed on a node
+ * or book outline form.
+ *
+ * @return
+ *   The rendered parent page select element.
+ */
+function book_form_update($form, FormStateInterface $form_state) {
+  return $form['book']['pid'];
+}
+
+/**
+ * Implements hook_ENTITY_TYPE_load() for node entities.
+ */
+function book_node_load($nodes) {
+  /** @var \Drupal\book\BookManagerInterface $book_manager */
+  $book_manager = \Drupal::service('book.manager');
+  $links = $book_manager->loadBookLinks(array_keys($nodes), FALSE);
+  foreach ($links as $record) {
+    $nodes[$record['nid']]->book = $record;
+    $nodes[$record['nid']]->book['link_path'] = 'node/' . $record['nid'];
+    $nodes[$record['nid']]->book['link_title'] = $nodes[$record['nid']]->label();
+  }
+}
+
+/**
+ * Implements hook_ENTITY_TYPE_view() for node entities.
+ */
+function book_node_view(array &$build, EntityInterface $node, EntityViewDisplayInterface $display, $view_mode) {
+  if ($view_mode == 'full') {
+    if (!empty($node->book['bid']) && empty($node->in_preview)) {
+      $book_node = Node::load($node->book['bid']);
+      if (!$book_node->access()) {
+        return;
+      }
+      $build['book_navigation'] = array(
+        '#theme' => 'book_navigation',
+        '#book_link' => $node->book,
+        '#weight' => 100,
+        // The book navigation is a listing of Node entities, so associate its
+        // list cache tag for correct invalidation.
+        '#cache' => [
+          'tags' => $node->getEntityType()->getListCacheTags(),
+        ],
+      );
+    }
+  }
+}
+
+/**
+ * Implements hook_ENTITY_TYPE_presave() for node entities.
+ */
+function book_node_presave(EntityInterface $node) {
+  // Make sure a new node gets a new menu link.
+  if ($node->isNew()) {
+    $node->book['nid'] = NULL;
+  }
+}
+
+/**
+ * Implements hook_ENTITY_TYPE_insert() for node entities.
+ */
+function book_node_insert(EntityInterface $node) {
+  /** @var \Drupal\book\BookManagerInterface $book_manager */
+  $book_manager = \Drupal::service('book.manager');
+  $book_manager->updateOutline($node);
+}
+
+/**
+ * Implements hook_ENTITY_TYPE_update() for node entities.
+ */
+function book_node_update(EntityInterface $node) {
+  /** @var \Drupal\book\BookManagerInterface $book_manager */
+  $book_manager = \Drupal::service('book.manager');
+  $book_manager->updateOutline($node);
+}
+
+/**
+ * Implements hook_ENTITY_TYPE_predelete() for node entities.
+ */
+function book_node_predelete(EntityInterface $node) {
+  if (!empty($node->book['bid'])) {
+    /** @var \Drupal\book\BookManagerInterface $book_manager */
+    $book_manager = \Drupal::service('book.manager');
+    $book_manager->deleteFromBook($node->book['nid']);
+  }
+}
+
+/**
+ * Implements hook_ENTITY_TYPE_prepare_form() for node entities.
+ */
+function book_node_prepare_form(NodeInterface $node, $operation, FormStateInterface $form_state) {
+  /** @var \Drupal\book\BookManagerInterface $book_manager */
+  $book_manager = \Drupal::service('book.manager');
+
+  // Prepare defaults for the add/edit form.
+  $account = \Drupal::currentUser();
+  if (empty($node->book) && ($account->hasPermission('add content to books') || $account->hasPermission('administer book outlines'))) {
+    $node->book = array();
+
+    $query = \Drupal::request()->query;
+    if ($node->isNew() && !is_null($query->get('parent')) && is_numeric($query->get('parent'))) {
+      // Handle "Add child page" links:
+      $parent = $book_manager->loadBookLink($query->get('parent'), TRUE);
+
+      if ($parent && $parent['access']) {
+        $node->book['bid'] = $parent['bid'];
+        $node->book['pid'] = $parent['nid'];
+      }
+    }
+    // Set defaults.
+    $node_ref = !$node->isNew() ? $node->id() : 'new';
+    $node->book += $book_manager->getLinkDefaults($node_ref);
+  }
+  else {
+    if (isset($node->book['bid']) && !isset($node->book['original_bid'])) {
+      $node->book['original_bid'] = $node->book['bid'];
+    }
+  }
+  // Find the depth limit for the parent select.
+  if (isset($node->book['bid']) && !isset($node->book['parent_depth_limit'])) {
+    $node->book['parent_depth_limit'] = $book_manager->getParentDepthLimit($node->book);
+  }
+}
+
+/**
+ * Implements hook_form_FORM_ID_alter() for node_delete_confirm().
+ *
+ * Alters the confirm form for a single node deletion.
+ *
+ * @see node_delete_confirm()
+ */
+function book_form_node_delete_confirm_alter(&$form, FormStateInterface $form_state) {
+  $node = Node::load($form['nid']['#value']);
+
+  if (isset($node->book) && $node->book['has_children']) {
+    $form['book_warning'] = array(
+      '#markup' => '<p>' . t('%title is part of a book outline, and has associated child pages. If you proceed with deletion, the child pages will be relocated automatically.', array('%title' => $node->label())) . '</p>',
+      '#weight' => -10,
+    );
+  }
+}
+
+/**
+ * Prepares variables for book listing block templates.
+ *
+ * Default template: book-all-books-block.html.twig.
+ *
+ * All non-renderable elements are removed so that the template has full access
+ * to the structured data but can also simply iterate over all elements and
+ * render them (as in the default template).
+ *
+ * @param array $variables
+ *   An associative array containing the following key:
+ *   - book_menus: An associative array containing renderable menu links for all
+ *     book menus.
+ */
+function template_preprocess_book_all_books_block(&$variables) {
+  // Remove all non-renderable elements.
+  $elements = $variables['book_menus'];
+  $variables['book_menus'] = array();
+  foreach (Element::children($elements) as $index) {
+    $variables['book_menus'][] = array(
+      'id' => $index,
+      'menu' => $elements[$index],
+      'title' => $elements[$index]['#book_title'],
+    );
+  }
+}
+
+/**
+ * Prepares variables for book navigation templates.
+ *
+ * Default template: book-navigation.html.twig.
+ *
+ * @param array $variables
+ *   An associative array containing the following key:
+ *   - book_link: An associative array of book link properties.
+ *     Properties used: bid, link_title, depth, pid, nid.
+ */
+function template_preprocess_book_navigation(&$variables) {
+  $book_link = $variables['book_link'];
+
+  // Provide extra variables for themers. Not needed by default.
+  $variables['book_id'] = $book_link['bid'];
+  $variables['book_title'] = SafeMarkup::checkPlain($book_link['link_title']);
+  $variables['book_url'] = \Drupal::url('entity.node.canonical', array('node' => $book_link['bid']));
+  $variables['current_depth'] = $book_link['depth'];
+  $variables['tree'] = '';
+
+  /** @var \Drupal\book\BookOutline $book_outline */
+  $book_outline = \Drupal::service('book.outline');
+
+  if ($book_link['nid']) {
+    $variables['tree'] = $book_outline->childrenLinks($book_link);
+
+    $build = array();
+
+    if ($prev = $book_outline->prevLink($book_link)) {
+      $prev_href = \Drupal::url('entity.node.canonical', array('node' => $prev['nid']));
+      $build['#attached']['html_head_link'][][] = array(
+        'rel' => 'prev',
+        'href' => $prev_href,
+      );
+      $variables['prev_url'] = $prev_href;
+      $variables['prev_title'] = SafeMarkup::checkPlain($prev['title']);
+    }
+
+    /** @var \Drupal\book\BookManagerInterface $book_manager */
+    $book_manager = \Drupal::service('book.manager');
+    if ($book_link['pid'] && $parent = $book_manager->loadBookLink($book_link['pid'])) {
+      $parent_href = \Drupal::url('entity.node.canonical', array('node' => $book_link['pid']));
+      $build['#attached']['html_head_link'][][] = array(
+        'rel' => 'up',
+        'href' => $parent_href,
+      );
+      $variables['parent_url'] = $parent_href;
+      $variables['parent_title'] = SafeMarkup::checkPlain($parent['title']);
+    }
+
+    if ($next = $book_outline->nextLink($book_link)) {
+      $next_href = \Drupal::url('entity.node.canonical', array('node' => $next['nid']));
+      $build['#attached']['html_head_link'][][] = array(
+        'rel' => 'next',
+        'href' => $next_href,
+      );
+      $variables['next_url'] = $next_href;
+      $variables['next_title'] = SafeMarkup::checkPlain($next['title']);
+    }
+  }
+
+  if (!empty($build)) {
+    drupal_render($build);
+  }
+
+  $variables['has_links'] = FALSE;
+  // Link variables to filter for values and set state of the flag variable.
+  $links = array('prev_url', 'prev_title', 'parent_url', 'parent_title', 'next_url', 'next_title');
+  foreach ($links as $link) {
+    if (isset($variables[$link])) {
+      // Flag when there is a value.
+      $variables['has_links'] = TRUE;
+    }
+    else {
+      // Set empty to prevent notices.
+      $variables[$link] = '';
+    }
+  }
+}
+
+/**
+ * Prepares variables for book export templates.
+ *
+ * Default template: book-export-html.html.twig.
+ *
+ * @param array $variables
+ *   An associative array containing:
+ *   - title: The title of the book.
+ *   - contents: Output of each book page.
+ *   - depth: The max depth of the book.
+ */
+function template_preprocess_book_export_html(&$variables) {
+  global $base_url;
+  $language_interface = \Drupal::languageManager()->getCurrentLanguage();
+
+  $variables['title'] = SafeMarkup::checkPlain($variables['title']);
+  $variables['base_url'] = $base_url;
+  $variables['language'] = $language_interface;
+  $variables['language_rtl'] = ($language_interface->getDirection() == LanguageInterface::DIRECTION_RTL);
+  $variables['head'] = drupal_get_html_head();
+
+  // HTML element attributes.
+  $attributes = array();
+  $attributes['lang'] = $language_interface->getId();
+  $attributes['dir'] = $language_interface->getDirection();
+  $variables['html_attributes'] = new Attribute($attributes);
+}
+
+/**
+ * Prepares variables for single node export templates.
+ *
+ * Default template: book-node-export-html.html.twig.
+ *
+ * @param array $variables
+ *   An associative array containing the following keys:
+ *   - node: The node that will be output.
+ *   - children: All the rendered child nodes within the current node. Defaults
+ *     to an empty string.
+ */
+function template_preprocess_book_node_export_html(&$variables) {
+  $variables['depth'] = $variables['node']->book['depth'];
+  $variables['title'] = SafeMarkup::checkPlain($variables['node']->label());
+}
+
+/**
+ * Determines if a given node type is in the list of types allowed for books.
+ *
+ * @param string $type
+ *   A node type.
+ *
+ * @return bool
+ *   A Boolean TRUE if the node type can be included in books; otherwise, FALSE.
+ */
+function book_type_is_allowed($type) {
+  return in_array($type, \Drupal::config('book.settings')->get('allowed_types'));
+}
+
+/**
+ * Implements hook_ENTITY_TYPE_update() for node_type entities.
+ *
+ * Updates book.settings configuration object if the machine-readable name of a
+ * node type is changed.
+ */
+function book_node_type_update(NodeTypeInterface $type) {
+  if ($type->getOriginalId() != $type->id()) {
+    $config = \Drupal::configFactory()->getEditable('book.settings');
+    // Update the list of node types that are allowed to be added to books.
+    $allowed_types = $config->get('allowed_types');
+    $old_key = array_search($type->getOriginalId(), $allowed_types);
+
+    if ($old_key !== FALSE) {
+      $allowed_types[$old_key] = $type->id();
+      // Ensure that the allowed_types array is sorted consistently.
+      // @see BookSettingsForm::submitForm()
+      sort($allowed_types);
+      $config->set('allowed_types', $allowed_types);
+    }
+
+    // Update the setting for the "Add child page" link.
+    if ($config->get('child_type') == $type->getOriginalId()) {
+      $config->set('child_type', $type->id());
+    }
+    $config->save();
+  }
+}

core/modules/book/book.permissions.yml

@@ -0,0 +1,9 @@
+administer book outlines:
+  title: 'Administer book outlines'
+create new books:
+  title: 'Create new books'
+add content to books:
+  title: 'Add content and child pages to books'
+access printer-friendly version:
+  title: 'View printer-friendly books'
+  description: 'View a book page and all of its sub-pages as a single document for ease of printing. Can be performance heavy.'

core/modules/book/book.routing.yml

@@ -0,0 +1,64 @@
+book.render:
+  path: '/book'
+  defaults:
+    _controller: '\Drupal\book\Controller\BookController::bookRender'
+    _title: 'Books'
+  requirements:
+    _permission: 'access content'
+
+book.admin:
+  path: '/admin/structure/book'
+  defaults:
+    _controller: '\Drupal\book\Controller\BookController::adminOverview'
+    _title: 'Books'
+  requirements:
+    _permission: 'administer book outlines'
+
+book.settings:
+  path: '/admin/structure/book/settings'
+  defaults:
+    _form: '\Drupal\book\Form\BookSettingsForm'
+    _title: 'Books'
+  requirements:
+    _permission: 'administer site configuration'
+
+book.export:
+  path: '/book/export/{type}/{node}'
+  defaults:
+    _controller: '\Drupal\book\Controller\BookController::bookExport'
+  requirements:
+    _permission: 'access printer-friendly version'
+    _entity_access: 'node.view'
+
+entity.node.book_outline_form:
+  path: '/node/{node}/outline'
+  defaults:
+    _entity_form: 'node.book_outline'
+    _title: 'Outline'
+  requirements:
+    _permission: 'administer book outlines'
+    _entity_access: 'node.view'
+  options:
+    _node_operation_route: TRUE
+
+book.admin_edit:
+  path: '/admin/structure/book/{node}'
+  defaults:
+    _form: 'Drupal\book\Form\BookAdminEditForm'
+    _title: 'Re-order book pages and change titles'
+  requirements:
+    _permission: 'administer book outlines'
+    _entity_access: 'node.view'
+    node: \d+
+
+entity.node.book_remove_form:
+  path: '/node/{node}/outline/remove'
+  defaults:
+    _form: '\Drupal\book\Form\BookRemoveForm'
+    _title: 'Remove from outline'
+  options:
+    _node_operation_route: TRUE
+  requirements:
+    _permission: 'administer book outlines'
+    _entity_access: 'node.view'
+    _access_book_removable: 'TRUE'

core/modules/book/book.services.yml

@@ -0,0 +1,37 @@
+services:
+  book.breadcrumb:
+    class: Drupal\book\BookBreadcrumbBuilder
+    arguments: ['@entity.manager', '@access_manager', '@current_user']
+    tags:
+      - { name: breadcrumb_builder, priority: 701 }
+  book.manager:
+    class: Drupal\book\BookManager
+    arguments: ['@entity.manager', '@string_translation', '@config.factory', '@book.outline_storage', '@renderer']
+  book.outline:
+    class: Drupal\book\BookOutline
+    arguments: ['@book.manager']
+  book.export:
+    class: Drupal\book\BookExport
+    arguments: ['@entity.manager', '@book.manager', '@renderer']
+  book.outline_storage:
+    class: Drupal\book\BookOutlineStorage
+    arguments: ['@database']
+    tags:
+      - { name: backend_overridable }
+  access_check.book.removable:
+    class: Drupal\book\Access\BookNodeIsRemovableAccessCheck
+    arguments: ['@book.manager']
+    tags:
+      - { name: access_check, applies_to: _access_book_removable }
+  cache_context.route.book_navigation:
+    class: Drupal\book\Cache\BookNavigationCacheContext
+    arguments: ['@request_stack']
+    tags:
+      - { name: cache.context}
+
+  book.uninstall_validator:
+    class: Drupal\book\BookUninstallValidator
+    tags:
+      - { name: module_install.uninstall_validator }
+    arguments: ['@book.outline_storage', '@entity.query', '@string_translation']
+    lazy: true

core/modules/book/config/install/book.settings.yml

@@ -0,0 +1,6 @@
+allowed_types:
+  - book
+block:
+  navigation:
+    mode: 'all pages'
+child_type: book

core/modules/book/config/install/core.base_field_override.node.book.promote.yml

@@ -0,0 +1,20 @@
+langcode: en
+status: true
+dependencies:
+  config:
+    - node.type.book
+id: node.book.promote
+field_name: promote
+entity_type: node
+bundle: book
+label: Promoted to front page
+description: ''
+required: false
+translatable: true
+default_value:
+  -
+    value: 0
+default_value_callback: ''
+settings: {  }
+third_party_settings: {  }
+field_type: boolean

core/modules/book/config/install/core.entity_form_display.node.book.default.yml

@@ -0,0 +1,56 @@
+langcode: en
+status: true
+dependencies:
+  config:
+    - field.field.node.book.body
+    - node.type.book
+  module:
+    - entity_reference
+    - text
+id: node.book.default
+targetEntityType: node
+bundle: book
+mode: default
+content:
+  title:
+    type: string_textfield
+    weight: -5
+    settings:
+      size: 60
+      placeholder: ''
+    third_party_settings: {  }
+  uid:
+    type: entity_reference_autocomplete
+    weight: 5
+    settings:
+      match_operator: CONTAINS
+      size: 60
+      placeholder: ''
+    third_party_settings: {  }
+  created:
+    type: datetime_timestamp
+    weight: 10
+    settings: {  }
+    third_party_settings: {  }
+  promote:
+    type: boolean_checkbox
+    settings:
+      display_label: true
+    weight: 15
+    third_party_settings: {  }
+  sticky:
+    type: boolean_checkbox
+    settings:
+      display_label: true
+    weight: 16
+    third_party_settings: {  }
+  body:
+    type: text_textarea_with_summary
+    weight: 26
+    settings:
+      rows: 9
+      summary_rows: 3
+      placeholder: ''
+    third_party_settings: {  }
+hidden: {  }
+third_party_settings: {  }

core/modules/book/config/install/core.entity_view_display.node.book.default.yml

@@ -0,0 +1,25 @@
+langcode: en
+status: true
+dependencies:
+  config:
+    - field.field.node.book.body
+    - node.type.book
+  module:
+    - text
+    - user
+id: node.book.default
+targetEntityType: node
+bundle: book
+mode: default
+content:
+  body:
+    label: hidden
+    type: text_default
+    weight: 100
+    settings: {  }
+    third_party_settings: {  }
+  links:
+    weight: 101
+hidden:
+  langcode: true
+third_party_settings: {  }

core/modules/book/config/install/core.entity_view_display.node.book.teaser.yml

@@ -0,0 +1,27 @@
+langcode: en
+status: true
+dependencies:
+  config:
+    - core.entity_view_mode.node.teaser
+    - field.field.node.book.body
+    - node.type.book
+  module:
+    - text
+    - user
+id: node.book.teaser
+targetEntityType: node
+bundle: book
+mode: teaser
+content:
+  body:
+    label: hidden
+    type: text_summary_or_trimmed
+    weight: 100
+    settings:
+      trim_length: 600
+    third_party_settings: {  }
+  links:
+    weight: 101
+hidden:
+  langcode: true
+third_party_settings: {  }

core/modules/book/config/install/core.entity_view_mode.node.print.yml

@@ -0,0 +1,12 @@
+id: node.print
+label: Print
+status: false
+cache: true
+targetEntityType: node
+dependencies:
+  module:
+    - book
+    - node
+  enforced:
+    module:
+      - book

core/modules/book/config/install/field.field.node.book.body.yml

@@ -0,0 +1,22 @@
+langcode: en
+status: true
+dependencies:
+  config:
+    - field.storage.node.body
+    - node.type.book
+  module:
+    - text
+id: node.book.body
+field_name: body
+entity_type: node
+bundle: book
+label: Body
+description: ''
+required: false
+translatable: true
+default_value: {  }
+default_value_callback: ''
+settings:
+  display_summary: true
+third_party_settings: {  }
+field_type: text_with_summary

core/modules/book/config/install/node.type.book.yml

@@ -0,0 +1,17 @@
+langcode: en
+status: true
+dependencies:
+  module:
+    - book
+  enforced:
+    module:
+      - book
+name: 'Book page'
+type: book
+description: '<em>Books</em> have a built-in hierarchical navigation. Use for handbooks or tutorials.'
+help: ''
+new_revision: false
+display_submitted: true
+preview_mode: 1
+display_submitted: true
+third_party_settings: {  }

core/modules/book/config/schema/book.schema.yml

@@ -0,0 +1,34 @@
+# Schema for the configuration files of the book module.
+
+book.settings:
+  type: config_object
+  label: 'Book settings'
+  mapping:
+    allowed_types:
+      type: sequence
+      label: 'Content types allowed in book outlines'
+      sequence:
+        type: string
+        label: 'Content type'
+    block:
+      type: mapping
+      label: 'Block'
+      mapping:
+        navigation:
+          type: mapping
+          label: 'Navigation'
+          mapping:
+            mode:
+              type: string
+              label: 'Mode'
+    child_type:
+      type: string
+      label: 'Content type for child pages'
+
+block.settings.book_navigation:
+  type: block_settings
+  label: 'Book navigation block'
+  mapping:
+    block_mode:
+      type: string
+      label: 'Block display mode'

core/modules/book/src/Access/BookNodeIsRemovableAccessCheck.php

@@ -0,0 +1,50 @@
+<?php
+
+/**
+ * @file
+ * Contains \Drupal\book\Access\BookNodeIsRemovableAccessCheck.
+ */
+
+namespace Drupal\book\Access;
+
+use Drupal\book\BookManagerInterface;
+use Drupal\Core\Access\AccessResult;
+use Drupal\Core\Routing\Access\AccessInterface;
+use Drupal\node\NodeInterface;
+
+/**
+ * Determines whether the requested node can be removed from its book.
+ */
+class BookNodeIsRemovableAccessCheck implements AccessInterface{
+
+  /**
+   * Book Manager Service.
+   *
+   * @var \Drupal\book\BookManagerInterface
+   */
+  protected $bookManager;
+
+  /**
+   * Constructs a BookNodeIsRemovableAccessCheck object.
+   *
+   * @param \Drupal\book\BookManagerInterface $book_manager
+   *   Book Manager Service.
+   */
+  public function __construct(BookManagerInterface $book_manager) {
+    $this->bookManager = $book_manager;
+  }
+
+  /**
+   * Checks access for removing the node from its book.
+   *
+   * @param \Drupal\node\NodeInterface $node
+   *   The node requested to be removed from its book.
+   *
+   * @return \Drupal\Core\Access\AccessResultInterface
+   *   The access result.
+   */
+  public function access(NodeInterface $node) {
+    return AccessResult::allowedIf($this->bookManager->checkNodeIsRemovable($node))->cacheUntilEntityChanges($node);
+  }
+
+}

core/modules/book/src/BookBreadcrumbBuilder.php

@@ -0,0 +1,98 @@
+<?php
+
+/**
+ * @file
+ * Contains \Drupal\book\BookBreadcrumbBuilder.
+ */
+
+namespace Drupal\book;
+
+use Drupal\Core\Access\AccessManagerInterface;
+use Drupal\Core\Breadcrumb\BreadcrumbBuilderInterface;
+use Drupal\Core\Entity\EntityManagerInterface;
+use Drupal\Core\Link;
+use Drupal\Core\Routing\RouteMatchInterface;
+use Drupal\Core\Session\AccountInterface;
+use Drupal\Core\StringTranslation\StringTranslationTrait;
+use Drupal\node\NodeInterface;
+
+/**
+ * Provides a breadcrumb builder for nodes in a book.
+ */
+class BookBreadcrumbBuilder implements BreadcrumbBuilderInterface {
+  use StringTranslationTrait;
+
+  /**
+   * The node storage.
+   *
+   * @var \Drupal\Core\Entity\EntityStorageInterface
+   */
+  protected $nodeStorage;
+
+  /**
+   * The access manager.
+   *
+   * @var \Drupal\Core\Access\AccessManagerInterface
+   */
+  protected $accessManager;
+
+  /**
+   * The current user account.
+   *
+   * @var \Drupal\Core\Session\AccountInterface
+   */
+  protected $account;
+
+  /**
+   * Constructs the BookBreadcrumbBuilder.
+   *
+   * @param \Drupal\Core\Entity\EntityManagerInterface $entity_manager
+   *   The entity manager service.
+   * @param \Drupal\Core\Access\AccessManagerInterface $access_manager
+   *   The access manager.
+   * @param \Drupal\Core\Session\AccountInterface $account
+   *   The current user account.
+   */
+  public function __construct(EntityManagerInterface $entity_manager, AccessManagerInterface $access_manager, AccountInterface $account) {
+    $this->nodeStorage = $entity_manager->getStorage('node');
+    $this->accessManager = $access_manager;
+    $this->account = $account;
+  }
+
+  /**
+   * {@inheritdoc}
+   */
+  public function applies(RouteMatchInterface $route_match) {
+    $node = $route_match->getParameter('node');
+    return $node instanceof NodeInterface && !empty($node->book);
+  }
+
+  /**
+   * {@inheritdoc}
+   */
+  public function build(RouteMatchInterface $route_match) {
+    $book_nids = array();
+    $links = array(Link::createFromRoute($this->t('Home'), '<front>'));
+    $book = $route_match->getParameter('node')->book;
+    $depth = 1;
+    // We skip the current node.
+    while (!empty($book['p' . ($depth + 1)])) {
+      $book_nids[] = $book['p' . $depth];
+      $depth++;
+    }
+    $parent_books = $this->nodeStorage->loadMultiple($book_nids);
+    if (count($parent_books) > 0) {
+      $depth = 1;
+      while (!empty($book['p' . ($depth + 1)])) {
+        if (!empty($parent_books[$book['p' . $depth]]) && ($parent_book = $parent_books[$book['p' . $depth]])) {
+          if ($parent_book->access('view', $this->account)) {
+            $links[] = Link::createFromRoute($parent_book->label(), 'entity.node.canonical', array('node' => $parent_book->id()));
+          }
+        }
+        $depth++;
+      }
+    }
+    return $links;
+  }
+
+}

core/modules/book/src/BookExport.php

@@ -0,0 +1,151 @@
+<?php
+
+/**
+ * @file
+ * Contains \Drupal\book\BookExport.
+ */
+
+namespace Drupal\book;
+
+use Drupal\Core\Entity\EntityManagerInterface;
+use Drupal\Core\Render\RendererInterface;
+use Drupal\node\Entity\Node;
+use Drupal\node\NodeInterface;
+
+/**
+ * Provides methods for exporting book to different formats.
+ *
+ * If you would like to add another format, swap this class in container.
+ */
+class BookExport {
+
+  /**
+   * The node storage.
+   *
+   * @var \Drupal\Core\Entity\EntityStorageInterface
+   */
+  protected $nodeStorage;
+
+  /**
+   * The node view builder.
+   *
+   * @var \Drupal\Core\Entity\EntityViewBuilderInterface
+   */
+  protected $viewBuilder;
+
+  /**
+   * The book manager.
+   *
+   * @var \Drupal\book\BookManagerInterface
+   */
+  protected $bookManager;
+
+  /**
+   * Constructs a BookExport object.
+   *
+   * @param \Drupal\Core\Entity\EntityManagerInterface $entityManager
+   *   The entity manager.
+   * @param \Drupal\book\BookManagerInterface $book_manager
+   *   The book manager.
+   */
+  public function __construct(EntityManagerInterface $entityManager, BookManagerInterface $book_manager) {
+    $this->nodeStorage = $entityManager->getStorage('node');
+    $this->viewBuilder = $entityManager->getViewBuilder('node');
+    $this->bookManager = $book_manager;
+  }
+
+  /**
+   * Generates HTML for export when invoked by book_export().
+   *
+   * The given node is embedded to its absolute depth in a top level section. For
+   * example, a child node with depth 2 in the hierarchy is contained in
+   * (otherwise empty) <div> elements corresponding to depth 0 and depth 1.
+   * This is intended to support WYSIWYG output - e.g., level 3 sections always
+   * look like level 3 sections, no matter their depth relative to the node
+   * selected to be exported as printer-friendly HTML.
+   *
+   * @param \Drupal\node\NodeInterface $node
+   *   The node to export.
+   *
+   * @throws \Exception
+   *   Thrown when the node was not attached to a book.
+   *
+   * @return array
+   *   A render array representing the HTML for a node and its children in the
+   *   book hierarchy.
+   */
+  public function bookExportHtml(NodeInterface $node) {
+    if (!isset($node->book)) {
+      throw new \Exception();
+    }
+
+    $tree = $this->bookManager->bookSubtreeData($node->book);
+    $contents = $this->exportTraverse($tree, array($this, 'bookNodeExport'));
+    return array(
+      '#theme' => 'book_export_html',
+      '#title' => $node->label(),
+      '#contents' => $contents,
+      '#depth' => $node->book['depth'],
+      '#cache' => [
+        'tags' => $node->getEntityType()->getListCacheTags(),
+      ],
+    );
+  }
+
+  /**
+   * Traverses the book tree to build printable or exportable output.
+   *
+   * During the traversal, the callback is applied to each node and is called
+   * recursively for each child of the node (in weight, title order).
+   *
+   * @param array $tree
+   *   A subtree of the book menu hierarchy, rooted at the current page.
+   * @param callable $callable
+   *   A callback to be called upon visiting a node in the tree.
+   *
+   * @return string
+   *   The output generated in visiting each node.
+   */
+  protected function exportTraverse(array $tree, $callable) {
+    // If there is no valid callable, use the default callback.
+    $callable = !empty($callable) ? $callable : array($this, 'bookNodeExport');
+
+    $build = array();
+    foreach ($tree as $data) {
+      // Note- access checking is already performed when building the tree.
+      if ($node = $this->nodeStorage->load($data['link']['nid'])) {
+        $children = $data['below'] ? $this->exportTraverse($data['below'], $callable) : '';
+        $build[] = call_user_func($callable, $node, $children);
+      }
+    }
+
+    return $build;
+  }
+
+  /**
+   * Generates printer-friendly HTML for a node.
+   *
+   * @param \Drupal\node\NodeInterface $node
+   *   The node that will be output.
+   * @param string $children
+   *   (optional) All the rendered child nodes within the current node. Defaults
+   *   to an empty string.
+   *
+   * @return array
+   *   A render array for the exported HTML of a given node.
+   *
+   * @see \Drupal\book\BookExport::exportTraverse()
+   */
+  protected function bookNodeExport(NodeInterface $node, $children = '') {
+    $build = $this->viewBuilder->view($node, 'print', NULL);
+    unset($build['#theme']);
+
+    return array(
+      '#theme' => 'book_node_export_html',
+      '#content' => $build,
+      '#node' => $node,
+      '#children' => $children,
+    );
+  }
+
+}

core/modules/book/src/BookManagerInterface.php

@@ -0,0 +1,302 @@
+<?php
+
+/**
+ * @file
+ * Contains \Drupal\book\BookManagerInterface.
+ */
+
+namespace Drupal\book;
+
+use Drupal\Core\Form\FormStateInterface;
+use Drupal\Core\Session\AccountInterface;
+use Drupal\node\NodeInterface;
+
+
+/**
+ * Provides an interface defining a book manager.
+ */
+interface BookManagerInterface {
+
+  /**
+   * Gets the data structure representing a named menu tree.
+   *
+   * Since this can be the full tree including hidden items, the data returned
+   * may be used for generating an an admin interface or a select.
+   *
+   * @param int $bid
+   *   The Book ID to find links for.
+   * @param array|null $link
+   *   (optional) A fully loaded menu link, or NULL. If a link is supplied, only
+   *   the path to root will be included in the returned tree - as if this link
+   *   represented the current page in a visible menu.
+   * @param int|null $max_depth
+   *   (optional) Maximum depth of links to retrieve. Typically useful if only
+   *   one or two levels of a sub tree are needed in conjunction with a non-NULL
+   *   $link, in which case $max_depth should be greater than $link['depth'].
+   *
+   * @return array
+   *   An tree of menu links in an array, in the order they should be rendered.
+   *
+   * Note: based on menu_tree_all_data().
+   */
+  public function bookTreeAllData($bid, $link = NULL, $max_depth = NULL);
+
+  /**
+   * Gets the active trail IDs for the specified book at the provided path.
+   *
+   * @param string $bid
+   *   The Book ID to find links for.
+   * @param array $link
+   *   A fully loaded menu link.
+   *
+   * @return array
+   *   An array containing the active trail: a list of mlids.
+   */
+  public function getActiveTrailIds($bid, $link);
+
+  /**
+   * Loads a single book entry.
+   *
+   * The entries of a book entry is documented in
+   * \Drupal\book\BookOutlineStorageInterface::loadMultiple.
+   *
+   * If $translate is TRUE, it also checks access ('access' key) and
+   * loads the title from the node itself.
+   *
+   * @param int $nid
+   *   The node ID of the book.
+   * @param bool $translate
+   *   If TRUE, set access, title, and other elements.
+   *
+   * @return array
+   *   The book data of that node.
+   *
+   * @see \Drupal\book\BookOutlineStorageInterface::loadMultiple
+   */
+  public function loadBookLink($nid, $translate = TRUE);
+
+  /**
+   * Loads multiple book entries.
+   *
+   * The entries of a book entry is documented in
+   * \Drupal\book\BookOutlineStorageInterface::loadMultiple.
+   *
+   * If $translate is TRUE, it also checks access ('access' key) and
+   * loads the title from the node itself.
+   *
+   * @param int[] $nids
+   *   An array of nids to load.
+   *
+   * @param bool $translate
+   *   If TRUE, set access, title, and other elements.
+   *
+   * @return array[]
+   *   The book data of each node keyed by NID.
+   *
+   * @see \Drupal\book\BookOutlineStorageInterface::loadMultiple
+   */
+  public function loadBookLinks($nids, $translate = TRUE);
+
+  /**
+   * Returns an array of book pages in table of contents order.
+   *
+   * @param int $bid
+   *   The ID of the book whose pages are to be listed.
+   * @param int $depth_limit
+   *   Any link deeper than this value will be excluded (along with its
+   *   children).
+   * @param array $exclude
+   *   (optional) An array of menu link ID values. Any link whose menu link ID
+   *   is in this array will be excluded (along with its children). Defaults to
+   *   an empty array.
+   *
+   * @return array
+   *   An array of (menu link ID, title) pairs for use as options for selecting
+   *   a book page.
+   */
+  public function getTableOfContents($bid, $depth_limit, array $exclude = array());
+
+  /**
+   * Finds the depth limit for items in the parent select.
+   *
+   * @param array $book_link
+   *   A fully loaded menu link that is part of the book hierarchy.
+   *
+   * @return int
+   *   The depth limit for items in the parent select.
+   */
+  public function getParentDepthLimit(array $book_link);
+
+  /**
+   * Collects node links from a given menu tree recursively.
+   *
+   * @param array $tree
+   *   The menu tree you wish to collect node links from.
+   * @param array $node_links
+   *   An array in which to store the collected node links.
+   */
+  public function bookTreeCollectNodeLinks(&$tree, &$node_links);
+
+  /**
+   * Provides book loading, access control and translation.
+   *
+   * @param array $link
+   *   A book link.
+   *
+   * Note: copied from _menu_link_translate() in menu.inc, but reduced to the
+   * minimal code that's used.
+   */
+  public function bookLinkTranslate(&$link);
+
+  /**
+   * Gets the book for a page and returns it as a linear array.
+   *
+   * @param array $book_link
+   *   A fully loaded book link that is part of the book hierarchy.
+   *
+   * @return array
+   *   A linear array of book links in the order that the links are shown in the
+   *   book, so the previous and next pages are the elements before and after the
+   *   element corresponding to the current node. The children of the current node
+   *   (if any) will come immediately after it in the array, and links will only
+   *   be fetched as deep as one level deeper than $book_link.
+   */
+  public function bookTreeGetFlat(array $book_link);
+
+  /**
+   * Returns an array of all books.
+   *
+   * This list may be used for generating a list of all the books, or for
+   * building the options for a form select.
+   *
+   * @return array
+   *   An array of all books.
+   */
+  public function getAllBooks();
+
+  /**
+   * Handles additions and updates to the book outline.
+   *
+   * This common helper function performs all additions and updates to the book
+   * outline through node addition, node editing, node deletion, or the outline
+   * tab.
+   *
+   * @param \Drupal\node\NodeInterface $node
+   *   The node that is being saved, added, deleted, or moved.
+   *
+   * @return bool
+   *   TRUE if the book link was saved; FALSE otherwise.
+   */
+  public function updateOutline(NodeInterface $node);
+
+  /**
+   * Saves a single book entry.
+   *
+   * @param array $link
+   *   The link data to save.
+   * @param bool $new
+   *   Is this a new book.
+   *
+   * @return array
+   *   The book data of that node.
+   */
+  public function saveBookLink(array $link, $new);
+
+  /**
+   * Returns an array with default values for a book page's menu link.
+   *
+   * @param string|int $nid
+   *   The ID of the node whose menu link is being created.
+   *
+   * @return array
+   *   The default values for the menu link.
+   */
+  public function getLinkDefaults($nid);
+
+  public function getBookParents(array $item, array $parent = array());
+
+  /**
+   * Builds the common elements of the book form for the node and outline forms.
+   *
+   * @param array $form
+   *   An associative array containing the structure of the form.
+   * @param \Drupal\Core\Form\FormStateInterface $form_state
+   *   The current state of the form.
+   * @param \Drupal\node\NodeInterface $node
+   *   The node whose form is being viewed.
+   * @param \Drupal\Core\Session\AccountInterface $account
+   *   The account viewing the form.
+   * @param bool $collapsed
+   *   If TRUE, the fieldset starts out collapsed.
+   *
+   * @return array
+   *   The form structure, with the book elements added.
+   */
+  public function addFormElements(array $form, FormStateInterface $form_state, NodeInterface $node, AccountInterface $account, $collapsed = TRUE);
+
+  /**
+   * Deletes node's entry from book table.
+   *
+   * @param int $nid
+   *   The nid to delete.
+   */
+  public function deleteFromBook($nid);
+
+  /**
+   * Returns a rendered menu tree.
+   *
+   * The menu item's LI element is given one of the following classes:
+   * - expanded: The menu item is showing its submenu.
+   * - collapsed: The menu item has a submenu which is not shown.
+   *
+   * @param array $tree
+   *   A data structure representing the tree as returned from buildBookOutlineData.
+   *
+   * @return array
+   *   A structured array to be rendered by drupal_render().
+   *
+   * @see \Drupal\Core\Menu\MenuLinkTree::build
+   */
+  public function bookTreeOutput(array $tree);
+
+  /**
+   * Checks access and performs dynamic operations for each link in the tree.
+   *
+   * @param array $tree
+   *   The book tree you wish to operate on.
+   * @param array $node_links
+   *   A collection of node link references generated from $tree by
+   *   menu_tree_collect_node_links().
+   */
+  public function bookTreeCheckAccess(&$tree, $node_links = array());
+
+  /**
+   * Gets the data representing a subtree of the book hierarchy.
+   *
+   * The root of the subtree will be the link passed as a parameter, so the
+   * returned tree will contain this item and all its descendants in the menu
+   * tree.
+   *
+   * @param array $link
+   *   A fully loaded book link.
+   *
+   * @return
+   *   A subtree of book links in an array, in the order they should be rendered.
+   */
+  public function bookSubtreeData($link);
+
+  /**
+   * Determines if a node can be removed from the book.
+   *
+   * A node can be removed from a book if it is actually in a book and it either
+   * is not a top-level page or is a top-level page with no children.
+   *
+   * @param \Drupal\node\NodeInterface $node
+   *   The node to remove from the outline.
+   *
+   * @return bool
+   *   TRUE if a node can be removed from the book, FALSE otherwise.
+   */
+  public function checkNodeIsRemovable(NodeInterface $node);
+
+}

core/modules/book/src/BookOutline.php

@@ -0,0 +1,134 @@
+<?php
+
+/**
+ * @file
+ * Contains \Drupal\book\BookOutline.
+ */
+
+namespace Drupal\book;
+
+/**
+ * Provides handling to render the book outline.
+ */
+class BookOutline {
+
+  /**
+   * The book manager.
+   *
+   * @var \Drupal\book\BookManagerInterface
+   */
+  protected $bookManager;
+
+  /**
+   * Constructs a new BookOutline.
+   *
+   * @param \Drupal\book\BookManagerInterface $book_manager
+   *   The book manager.
+   */
+  public function __construct(BookManagerInterface $book_manager) {
+    $this->bookManager = $book_manager;
+  }
+
+  /**
+   * Fetches the book link for the previous page of the book.
+   *
+   * @param array $book_link
+   *   A fully loaded book link that is part of the book hierarchy.
+   *
+   * @return array
+   *   A fully loaded book link for the page before the one represented in
+   *   $book_link.
+   */
+  public function prevLink(array $book_link) {
+    // If the parent is zero, we are at the start of a book.
+    if ($book_link['pid'] == 0) {
+      return NULL;
+    }
+    // Assigning the array to $flat resets the array pointer for use with each().
+    $flat = $this->bookManager->bookTreeGetFlat($book_link);
+    $curr = NULL;
+    do {
+      $prev = $curr;
+      list($key, $curr) = each($flat);
+    } while ($key && $key != $book_link['nid']);
+
+    if ($key == $book_link['nid']) {
+      // The previous page in the book may be a child of the previous visible link.
+      if ($prev['depth'] == $book_link['depth']) {
+        // The subtree will have only one link at the top level - get its data.
+        $tree = $this->bookManager->bookSubtreeData($prev);
+        $data = array_shift($tree);
+        // The link of interest is the last child - iterate to find the deepest one.
+        while ($data['below']) {
+          $data = end($data['below']);
+        }
+        $this->bookManager->bookLinkTranslate($data['link']);
+        return $data['link'];
+      }
+      else {
+        $this->bookManager->bookLinkTranslate($prev);
+        return $prev;
+      }
+    }
+  }
+
+  /**
+   * Fetches the book link for the next page of the book.
+   *
+   * @param array $book_link
+   *   A fully loaded book link that is part of the book hierarchy.
+   *
+   * @return array
+   *   A fully loaded book link for the page after the one represented in
+   *   $book_link.
+   */
+  public function nextLink(array $book_link) {
+    // Assigning the array to $flat resets the array pointer for use with each().
+    $flat = $this->bookManager->bookTreeGetFlat($book_link);
+    do {
+      list($key,) = each($flat);
+    } while ($key && $key != $book_link['nid']);
+
+    if ($key == $book_link['nid']) {
+      $next = current($flat);
+      if ($next) {
+        $this->bookManager->bookLinkTranslate($next);
+      }
+      return $next;
+    }
+  }
+
+  /**
+   * Formats the book links for the child pages of the current page.
+   *
+   * @param array $book_link
+   *   A fully loaded book link that is part of the book hierarchy.
+   *
+   * @return array
+   *   HTML for the links to the child pages of the current page.
+   */
+  public function childrenLinks(array $book_link) {
+    $flat = $this->bookManager->bookTreeGetFlat($book_link);
+
+    $children = array();
+
+    if ($book_link['has_children']) {
+      // Walk through the array until we find the current page.
+      do {
+        $link = array_shift($flat);
+      } while ($link && ($link['nid'] != $book_link['nid']));
+      // Continue though the array and collect the links whose parent is this page.
+      while (($link = array_shift($flat)) && $link['pid'] == $book_link['nid']) {
+        $data['link'] = $link;
+        $data['below'] = '';
+        $children[] = $data;
+      }
+    }
+
+    if ($children) {
+      return $this->bookManager->bookTreeOutput($children);
+    }
+    return '';
+  }
+
+}

core/modules/book/src/BookOutlineStorage.php

@@ -0,0 +1,206 @@
+<?php
+
+/**
+ * @file
+ * Contains \Drupal\book\BookOutlineStorage.
+ */
+
+namespace Drupal\book;
+
+use Drupal\Core\Database\Connection;
+
+/**
+ * Defines a storage class for books outline.
+ */
+class BookOutlineStorage implements BookOutlineStorageInterface {
+
+  /**
+   * Database Service Object.
+   *
+   * @var \Drupal\Core\Database\Connection
+   */
+  protected $connection;
+
+  /**
+   * Constructs a BookOutlineStorage object.
+   */
+  public function __construct(Connection $connection) {
+    $this->connection = $connection;
+  }
+
+  /**
+   * {@inheritdoc}
+   */
+  public function getBooks() {
+    return $this->connection->query("SELECT DISTINCT(bid) FROM {book}")->fetchCol();
+  }
+
+  /**
+   * {@inheritdoc}
+   */
+  public function hasBooks() {
+    return (bool) $this->connection
+      ->query('SELECT count(bid) FROM {book}')
+      ->fetchField();
+  }
+
+  /**
+   * {@inheritdoc}
+   */
+  public function loadMultiple($nids, $access = TRUE) {
+    $query = $this->connection->select('book', 'b', array('fetch' => \PDO::FETCH_ASSOC));
+    $query->fields('b');
+    $query->condition('b.nid', $nids, 'IN');
+
+    if ($access) {
+      $query->addTag('node_access');
+      $query->addMetaData('base_table', 'book');
+    }
+
+    return $query->execute();
+  }
+
+  /**
+   * {@inheritdoc}
+   */
+  public function getChildRelativeDepth($book_link, $max_depth) {
+    $query = $this->connection->select('book');
+    $query->addField('book', 'depth');
+    $query->condition('bid', $book_link['bid']);
+    $query->orderBy('depth', 'DESC');
+    $query->range(0, 1);
+
+    $i = 1;
+    $p = 'p1';
+    while ($i <= $max_depth && $book_link[$p]) {
+      $query->condition($p, $book_link[$p]);
+      $p = 'p' . ++$i;
+    }
+
+    return $query->execute()->fetchField();
+  }
+
+  /**
+   * {@inheritdoc}
+   */
+  public function delete($nid) {
+    return $this->connection->delete('book')
+      ->condition('nid', $nid)
+      ->execute();
+  }
+
+  /**
+   * {@inheritdoc}
+   */
+  public function loadBookChildren($pid) {
+    return $this->connection
+      ->query("SELECT * FROM {book} WHERE pid = :pid", array(':pid' => $pid))
+      ->fetchAllAssoc('nid', \PDO::FETCH_ASSOC);
+  }
+
+  /**
+   * {@inheritdoc}
+   */
+  public function getBookMenuTree($bid, $parameters, $min_depth, $max_depth) {
+    $query = $this->connection->select('book');
+    $query->fields('book');
+    for ($i = 1; $i <= $max_depth; $i++) {
+      $query->orderBy('p' . $i, 'ASC');
+    }
+    $query->condition('bid', $bid);
+    if (!empty($parameters['expanded'])) {
+      $query->condition('pid', $parameters['expanded'], 'IN');
+    }
+    if ($min_depth != 1) {
+      $query->condition('depth', $min_depth, '>=');
+    }
+    if (isset($parameters['max_depth'])) {
+      $query->condition('depth', $parameters['max_depth'], '<=');
+    }
+    // Add custom query conditions, if any were passed.
+    if (isset($parameters['conditions'])) {
+      foreach ($parameters['conditions'] as $column => $value) {
+        $query->condition($column, $value);
+      }
+    }
+
+    return $query->execute();
+  }
+
+  /**
+   * {@inheritdoc}
+   */
+  public function insert($link, $parents) {
+    return $this->connection
+      ->insert('book')
+      ->fields(array(
+        'nid' => $link['nid'],
+        'bid' => $link['bid'],
+        'pid' => $link['pid'],
+        'weight' => $link['weight'],
+        ) + $parents
+      )
+      ->execute();
+  }
+
+  /**
+   * {@inheritdoc}
+   */
+  public function update($nid, $fields) {
+    return $this->connection
+      ->update('book')
+      ->fields($fields)
+      ->condition('nid', $nid)
+      ->execute();
+  }
+
+  /**
+   * {@inheritdoc}
+   */
+  public function updateMovedChildren($bid, $original, $expressions, $shift) {
+    $query = $this->connection->update('book');
+    $query->fields(array('bid' => $bid));
+
+    foreach ($expressions as $expression) {
+      $query->expression($expression[0], $expression[1], $expression[2]);
+    }
+
+    $query->expression('depth', 'depth + :depth', array(':depth' => $shift));
+    $query->condition('bid', $original['bid']);
+    $p = 'p1';
+    for ($i = 1; !empty($original[$p]); $p = 'p' . ++$i) {
+      $query->condition($p, $original[$p]);
+    }
+
+    return $query->execute();
+  }
+
+  /**
+   * {@inheritdoc}
+   */
+  public function countOriginalLinkChildren($original) {
+    return $this->connection->select('book', 'b')
+      ->condition('bid', $original['bid'])
+      ->condition('pid', $original['pid'])
+      ->condition('nid', $original['nid'], '<>')
+      ->countQuery()
+      ->execute()->fetchField();
+  }
+
+  /**
+   * {@inheritdoc}
+   */
+  public function getBookSubtree($link, $max_depth) {
+    $query = db_select('book', 'b', array('fetch' => \PDO::FETCH_ASSOC));
+    $query->fields('b');
+    $query->condition('b.bid', $link['bid']);
+
+    for ($i = 1; $i <= $max_depth && $link["p$i"]; ++$i) {
+      $query->condition("p$i", $link["p$i"]);
+    }
+    for ($i = 1; $i <= $max_depth; ++$i) {
+      $query->orderBy("p$i");
+    }
+    return $query->execute();
+  }
+}

core/modules/book/src/BookOutlineStorageInterface.php

@@ -0,0 +1,174 @@
+<?php
+
+/**
+ * @file
+ * Contains \Drupal\book\BookOutlineStorageInterface.
+*/
+
+namespace Drupal\book;
+
+/**
+ * Defines a common interface for book outline storage classes.
+ */
+interface BookOutlineStorageInterface {
+
+  /**
+   * Gets books (the highest positioned book links).
+   *
+   * @return array
+   *   An array of book IDs.
+   */
+  public function getBooks();
+
+  /**
+   * Checks if there are any books.
+   *
+   * @return bool
+   *   TRUE if there are books, FALSE if not.
+   */
+  public function hasBooks();
+
+  /**
+   * Loads books.
+   *
+   * Each book entry consists of the following keys:
+   *   - bid: The node ID of the main book.
+   *   - nid: The node ID of the book entry itself.
+   *   - pid: The parent node ID of the book.
+   *   - has_children: A boolean to indicate whether the book has children.
+   *   - weight: The weight of the book entry to order siblings.
+   *   - depth: The depth in the menu hierarchy the entry is placed into.
+   *
+   * @param array $nids
+   *   An array of node IDs.
+   * @param bool $access
+   *   Whether access checking should be taken into account.
+   *
+   * @return array
+   *   Array of loaded book items.
+   */
+  public function loadMultiple($nids, $access = TRUE);
+
+  /**
+   * Gets child relative depth.
+   *
+   * @param array $book_link
+   *   The book link.
+   *
+   * @param int $max_depth
+   *   The maximum supported depth of the book tree.
+   *
+   * @return int
+   *   The depth of the searched book.
+   */
+  public function getChildRelativeDepth($book_link, $max_depth);
+
+  /**
+   * Deletes a book entry.
+   *
+   * @param int $nid
+   *   Deletes a book entry.
+   *
+   * @return mixed
+   *   Number of deleted book entries.
+   */
+  public function delete($nid);
+
+  /**
+   * Loads book's children using it's parent ID.
+   *
+   * @param int $pid
+   *   The book's parent ID.
+   *
+   * @return array
+   *   Array of loaded book items.
+   */
+  public function loadBookChildren($pid);
+
+  /**
+   * Builds tree data used for the menu tree.
+   *
+   * @param int $bid
+   *   The ID of the book that we are building the tree for.
+   * @param array $parameters
+   *   An associative array of build parameters. For info about individual
+   *   parameters see BookManager::bookTreeBuild().
+   * @param int $min_depth
+   *   The minimum depth of book links in the resulting tree.
+   * @param int $max_depth
+   *   The maximum supported depth of the book tree.
+   *
+   * @return array
+   *   Array of loaded book links.
+   */
+  public function getBookMenuTree($bid, $parameters, $min_depth, $max_depth);
+
+  /**
+   * Inserts a book link.
+   *
+   * @param array $link
+   *   The link array to be inserted in the database.
+   * @param array $parents
+   *   The array of parent ids for the link to be inserted.
+   *
+   * @return mixed
+   *   The last insert ID of the query, if one exists.
+   */
+  public function insert($link, $parents);
+
+
+  /**
+   * Updates book reference for links that were moved between books.
+   *
+   * @param int $nid
+   *   The nid of the book entry to be updated.
+   * @param array $fields
+   *   The array of fields to be updated.
+   *
+   * @return mixed
+   *   The number of rows matched by the update query.
+   */
+  public function update($nid, $fields);
+
+  /**
+   * Update the book ID of the book link that it's being moved.
+   *
+   * @param int $bid
+   *   The ID of the book whose children we move.
+   * @param array $original
+   *   The original parent of the book link.
+   * @param array $expressions
+   *   Array of expressions to be added to the query.
+   * @param int $shift
+   *   The difference in depth between the old and the new position of the
+   *   element being moved.
+   *
+   * @return mixed
+   *   The number of rows matched by the update query.
+   */
+  public function updateMovedChildren($bid, $original, $expressions, $shift);
+
+  /**
+   * Count the number of original link children.
+   *
+   * @param array $original
+   *   The book link array.
+   *
+   * @return int
+   *   Number of children.
+   */
+  public function countOriginalLinkChildren($original);
+
+  /**
+   * Get book subtree.
+   *
+   * @param array $link
+   *   A fully loaded book link.
+   * @param int $max_depth
+   *   The maximum supported depth of the book tree.
+   *
+   * @return array
+   *   Array of unordered subtree book items.
+   */
+  public function getBookSubtree($link, $max_depth);
+}

core/modules/book/src/BookUninstallValidator.php

@@ -0,0 +1,98 @@
+<?php
+
+/**
+ * @file
+ * Contains \Drupal\book\BookUninstallValidator.
+ */
+
+namespace Drupal\book;
+
+use Drupal\Core\Entity\Query\QueryFactory;
+use Drupal\Core\Extension\ModuleUninstallValidatorInterface;
+use Drupal\Core\StringTranslation\StringTranslationTrait;
+use Drupal\Core\StringTranslation\TranslationInterface;
+
+/**
+ * Prevents book module from being uninstalled whilst any book nodes exist or
+ * there are any book outline stored.
+ */
+class BookUninstallValidator implements ModuleUninstallValidatorInterface {
+
+  use StringTranslationTrait;
+
+  /**
+   * The book outline storage.
+   *
+   * @var \Drupal\book\BookOutlineStorageInterface
+   */
+  protected $bookOutlineStorage;
+
+  /**
+   * The entity query for node.
+   *
+   * @var \Drupal\Core\Entity\Query\QueryInterface
+   */
+  protected $entityQuery;
+
+  /**
+   * Constructs a new BookUninstallValidator.
+   *
+   * @param \Drupal\book\BookOutlineStorageInterface $book_outline_storage
+   *   The book outline storage.
+   * @param \Drupal\Core\Entity\Query\QueryFactory $query_factory
+   *   The entity query factory.
+   * @param \Drupal\Core\StringTranslation\TranslationInterface $string_translation
+   *   The string translation service.
+   */
+  public function __construct(BookOutlineStorageInterface $book_outline_storage, QueryFactory $query_factory, TranslationInterface $string_translation) {
+    $this->bookOutlineStorage = $book_outline_storage;
+    $this->entityQuery = $query_factory->get('node');
+    $this->stringTranslation = $string_translation;
+  }
+
+  /**
+   * {@inheritdoc}
+   */
+  public function validate($module) {
+    $reasons = [];
+    if ($module == 'book') {
+      if ($this->hasBookOutlines()) {
+        $reasons[] = $this->t('To uninstall Book, delete all content that is part of a book');
+      }
+      else {
+        // The book node type is provided by the Book module. Prevent uninstall
+        // if there are any nodes of that type.
+        if ($this->hasBookNodes()) {
+          $reasons[] = $this->t('To uninstall Book, delete all content that has the Book content type');
+        }
+      }
+    }
+    return $reasons;
+  }
+
+  /**
+   * Checks if there are any books in an outline.
+   *
+   * @return bool
+   *   TRUE if there are books, FALSE if not.
+   */
+  protected function hasBookOutlines() {
+    return $this->bookOutlineStorage->hasBooks();
+  }
+
+  /**
+   * Determines if there is any book nodes or not.
+   *
+   * @return bool
+   *   TRUE if there are book nodes, FALSE otherwise.
+   */
+  protected function hasBookNodes() {
+    $nodes = $this->entityQuery
+      ->condition('type', 'book')
+      ->accessCheck(FALSE)
+      ->range(0, 1)
+      ->execute();
+    return !empty($nodes);
+  }
+
+}

core/modules/book/src/Cache/BookNavigationCacheContext.php

@@ -0,0 +1,71 @@
+<?php
+
+/**
+ * @file
+ * Contains \Drupal\book\Cache\BookNavigationCacheContext.
+ */
+
+namespace Drupal\book\Cache;
+
+use Drupal\Core\Cache\Context\CacheContextInterface;
+use Symfony\Component\DependencyInjection\ContainerAware;
+use Symfony\Component\HttpFoundation\RequestStack;
+
+/**
+ * Defines the book navigation cache context service.
+ *
+ * This allows for book navigation location-aware caching. It depends on:
+ * - whether the current route represents a book node at all
+ * - and if so, where in the book hierarchy we are
+ *
+ * This class is container-aware to avoid initializing the 'book.manager'
+ * service when it is not necessary.
+ */
+class BookNavigationCacheContext extends ContainerAware implements CacheContextInterface {
+
+  /**
+   * The request stack.
+   *
+   * @var \Symfony\Component\HttpFoundation\RequestStack
+   */
+  protected $requestStack;
+
+  /**
+   * Constructs a new BookNavigationCacheContext service.
+   *
+   * @param \Symfony\Component\HttpFoundation\RequestStack $request_stack
+   *   The request stack.
+   */
+  public function __construct(RequestStack $request_stack) {
+    $this->requestStack = $request_stack;
+  }
+
+  /**
+   * {@inheritdoc}
+   */
+  public static function getLabel() {
+    return t("Book navigation");
+  }
+
+  /**
+   * {@inheritdoc}
+   */
+  public function getContext() {
+    // Find the current book's ID.
+    $current_bid = 0;
+    if ($node = $this->requestStack->getCurrentRequest()->get('node')) {
+      $current_bid = empty($node->book['bid']) ? 0 : $node->book['bid'];
+    }
+
+    // If we're not looking at a book node, then we're not navigating a book.
+    if ($current_bid === 0) {
+      return 'book.none';
+    }
+
+    // If we're looking at a book node, get the trail for that node.
+    $active_trail = $this->container->get('book.manager')
+      ->getActiveTrailIds($node->book['bid'], $node->book);
+    return 'book.' . implode('|', $active_trail);
+  }
+
+}

core/modules/book/src/Controller/BookController.php

@@ -0,0 +1,172 @@
+<?php
+
+/**
+ * @file
+ * Contains \Drupal\book\Controller\BookController.
+ */
+
+namespace Drupal\book\Controller;
+
+use Drupal\book\BookExport;
+use Drupal\book\BookManagerInterface;
+use Drupal\Core\Controller\ControllerBase;
+use Drupal\Core\Render\RendererInterface;
+use Drupal\Core\Url;
+use Drupal\node\Entity\Node;
+use Drupal\node\NodeInterface;
+use Symfony\Component\DependencyInjection\Container;
+use Symfony\Component\DependencyInjection\ContainerInterface;
+use Symfony\Component\HttpFoundation\Response;
+use Symfony\Component\HttpKernel\Exception\NotFoundHttpException;
+
+/**
+ * Controller routines for book routes.
+ */
+class BookController extends ControllerBase {
+
+  /**
+   * The book manager.
+   *
+   * @var \Drupal\book\BookManagerInterface
+   */
+  protected $bookManager;
+
+  /**
+   * The book export service.
+   *
+   * @var \Drupal\book\BookExport
+   */
+  protected $bookExport;
+
+  /**
+   * The renderer.
+   *
+   * @var \Drupal\Core\Render\RendererInterface
+   */
+  protected $renderer;
+
+  /**
+   * Constructs a BookController object.
+   *
+   * @param \Drupal\book\BookManagerInterface $bookManager
+   *   The book manager.
+   * @param \Drupal\book\BookExport $bookExport
+   *   The book export service.
+   * @param \Drupal\Core\Render\RendererInterface $renderer
+   *   The renderer.
+   */
+  public function __construct(BookManagerInterface $bookManager, BookExport $bookExport, RendererInterface $renderer) {
+    $this->bookManager = $bookManager;
+    $this->bookExport = $bookExport;
+    $this->renderer = $renderer;
+  }
+
+  /**
+   * {@inheritdoc}
+   */
+  public static function create(ContainerInterface $container) {
+    return new static(
+      $container->get('book.manager'),
+      $container->get('book.export'),
+      $container->get('renderer')
+    );
+  }
+
+  /**
+   * Returns an administrative overview of all books.
+   *
+   * @return array
+   *   A render array representing the administrative page content.
+   *
+   */
+  public function adminOverview() {
+    $rows = array();
+
+    $headers = array(t('Book'), t('Operations'));
+    // Add any recognized books to the table list.
+    foreach ($this->bookManager->getAllBooks() as $book) {
+      /** @var \Drupal\Core\Url $url */
+      $url = $book['url'];
+      if (isset($book['options'])) {
+        $url->setOptions($book['options']);
+      }
+      $row = array(
+        $this->l($book['title'], $url),
+      );
+      $links = array();
+      $links['edit'] = array(
+        'title' => t('Edit order and titles'),
+        'url' => Url::fromRoute('book.admin_edit', ['node' => $book['nid']]),
+      );
+      $row[] = array(
+        'data' => array(
+          '#type' => 'operations',
+          '#links' => $links,
+        ),
+      );
+      $rows[] = $row;
+    }
+    return array(
+      '#type' => 'table',
+      '#header' => $headers,
+      '#rows' => $rows,
+      '#empty' => t('No books available.'),
+    );
+  }
+
+  /**
+   * Prints a listing of all books.
+   *
+   * @return array
+   *   A render array representing the listing of all books content.
+   */
+  public function bookRender() {
+    $book_list = array();
+    foreach ($this->bookManager->getAllBooks() as $book) {
+      $book_list[] = $this->l($book['title'], $book['url']);
+    }
+    return array(
+      '#theme' => 'item_list',
+      '#items' => $book_list,
+      '#cache' => [
+        'tags' => \Drupal::entityManager()->getDefinition('node')->getListCacheTags(),
+      ],
+    );
+  }
+
+  /**
+   * Generates representations of a book page and its children.
+   *
+   * The method delegates the generation of output to helper methods. The method
+   * name is derived by prepending 'bookExport' to the camelized form of given
+   * output type. For example, a type of 'html' results in a call to the method
+   * bookExportHtml().
+   *
+   * @param string $type
+   *   A string encoding the type of output requested. The following types are
+   *   currently supported in book module:
+   *   - html: Printer-friendly HTML.
+   *   Other types may be supported in contributed modules.
+   * @param \Drupal\node\NodeInterface $node
+   *   The node to export.
+   *
+   * @return array
+   *   A render array representing the node and its children in the book
+   *   hierarchy in a format determined by the $type parameter.
+   *
+   * @throws \Symfony\Component\HttpKernel\Exception\NotFoundHttpException
+   */
+  public function bookExport($type, NodeInterface $node) {
+    $method = 'bookExport' . Container::camelize($type);
+
+    // @todo Convert the custom export functionality to serializer.
+    if (!method_exists($this->bookExport, $method)) {
+      drupal_set_message(t('Unknown export format.'));
+      throw new NotFoundHttpException();
+    }
+
+    $exported_book = $this->bookExport->{$method}($node);
+    return new Response($this->renderer->renderRoot($exported_book));
+  }
+
+}

core/modules/book/src/Form/BookAdminEditForm.php

@@ -0,0 +1,300 @@
+<?php
+
+/**
+ * @file
+ * Contains \Drupal\book\Form\BookAdminEditForm.
+ */
+
+namespace Drupal\book\Form;
+
+use Drupal\book\BookManager;
+use Drupal\book\BookManagerInterface;
+use Drupal\Component\Utility\Crypt;
+use Drupal\Core\Entity\EntityStorageInterface;
+use Drupal\Core\Form\FormBase;
+use Drupal\Core\Form\FormStateInterface;
+use Drupal\Core\Render\Element;
+use Drupal\Core\Url;
+use Drupal\node\NodeInterface;
+use Symfony\Component\DependencyInjection\ContainerInterface;
+
+/**
+ * Provides a form for administering a single book's hierarchy.
+ */
+class BookAdminEditForm extends FormBase {
+
+  /**
+   * The node storage.
+   *
+   * @var \Drupal\Core\Entity\EntityStorageInterface
+   */
+  protected $nodeStorage;
+
+  /**
+   * The book manager.
+   *
+   * @var \Drupal\book\BookManagerInterface
+   */
+  protected $bookManager;
+
+  /**
+   * Constructs a new BookAdminEditForm.
+   *
+   * @param \Drupal\Core\Entity\EntityStorageInterface $node_storage
+   *   The custom block storage.
+   * @param \Drupal\book\BookManagerInterface $book_manager
+   *   The book manager.
+   */
+  public function __construct(EntityStorageInterface $node_storage, BookManagerInterface $book_manager) {
+    $this->nodeStorage = $node_storage;
+    $this->bookManager = $book_manager;
+  }
+
+  /**
+   * {@inheritdoc}
+   */
+  public static function create(ContainerInterface $container) {
+    $entity_manager = $container->get('entity.manager');
+    return new static(
+      $entity_manager->getStorage('node'),
+      $container->get('book.manager')
+    );
+  }
+
+  /**
+   * {@inheritdoc}
+   */
+  public function getFormId() {
+    return 'book_admin_edit';
+  }
+
+  /**
+   * {@inheritdoc}
+   */
+  public function buildForm(array $form, FormStateInterface $form_state, NodeInterface $node = NULL) {
+    $form['#title'] = $node->label();
+    $form['#node'] = $node;
+    $this->bookAdminTable($node, $form);
+    $form['save'] = array(
+      '#type' => 'submit',
+      '#value' => $this->t('Save book pages'),
+    );
+
+    return $form;
+  }
+
+  /**
+   * {@inheritdoc}
+   */
+  public function validateForm(array &$form, FormStateInterface $form_state) {
+    if ($form_state->getValue('tree_hash') != $form_state->getValue('tree_current_hash')) {
+      $form_state->setErrorByName('', $this->t('This book has been modified by another user, the changes could not be saved.'));
+    }
+  }
+
+  /**
+   * {@inheritdoc}
+   */
+  public function submitForm(array &$form, FormStateInterface $form_state) {
+    // Save elements in the same order as defined in post rather than the form.
+    // This ensures parents are updated before their children, preventing orphans.
+    $user_input = $form_state->getUserInput();
+    if (isset($user_input['table'])) {
+      $order = array_flip(array_keys($user_input['table']));
+      $form['table'] = array_merge($order, $form['table']);
+
+      foreach (Element::children($form['table']) as $key) {
+        if ($form['table'][$key]['#item']) {
+          $row = $form['table'][$key];
+          $values = $form_state->getValue(array('table', $key));
+
+          // Update menu item if moved.
+          if ($row['parent']['pid']['#default_value'] != $values['pid'] || $row['weight']['#default_value'] != $values['weight']) {
+            $link = $this->bookManager->loadBookLink($values['nid'], FALSE);
+            $link['weight'] = $values['weight'];
+            $link['pid'] = $values['pid'];
+            $this->bookManager->saveBookLink($link, FALSE);
+          }
+
+          // Update the title if changed.
+          if ($row['title']['#default_value'] != $values['title']) {
+            $node = $this->nodeStorage->load($values['nid']);
+            $node->revision_log = $this->t('Title changed from %original to %current.', array('%original' => $node->label(), '%current' => $values['title']));
+            $node->title = $values['title'];
+            $node->book['link_title'] = $values['title'];
+            $node->setNewRevision();
+            $node->save();
+            $this->logger('content')->notice('book: updated %title.', array('%title' => $node->label(), 'link' => $node->link($this->t('View'))));
+          }
+        }
+      }
+    }
+
+    drupal_set_message($this->t('Updated book %title.', array('%title' => $form['#node']->label())));
+  }
+
+  /**
+   * Builds the table portion of the form for the book administration page.
+   *
+   * @param \Drupal\node\NodeInterface $node
+   *   The node of the top-level page in the book.
+   * @param array $form
+   *   The form that is being modified, passed by reference.
+   *
+   * @see self::buildForm()
+   */
+  protected function bookAdminTable(NodeInterface $node, array &$form) {
+    $form['table'] = array(
+      '#type' => 'table',
+      '#header' => [
+        $this->t('Title'),
+        $this->t('Weight'),
+        $this->t('Parent'),
+        $this->t('Operations'),
+      ],
+      '#empty' => $this->t('No book content available.'),
+      '#tabledrag' => [
+        [
+          'action' => 'match',
+          'relationship' => 'parent',
+          'group' => 'book-pid',
+          'subgroup' => 'book-pid',
+          'source' => 'book-nid',
+          'hidden' => TRUE,
+          'limit' => BookManager::BOOK_MAX_DEPTH - 2,
+        ],
+        [
+          'action' => 'order',
+          'relationship' => 'sibling',
+          'group' => 'book-weight',
+        ],
+      ],
+    );
+
+    $tree = $this->bookManager->bookSubtreeData($node->book);
+    // Do not include the book item itself.
+    $tree = array_shift($tree);
+    if ($tree['below']) {
+      $hash = Crypt::hashBase64(serialize($tree['below']));
+      // Store the hash value as a hidden form element so that we can detect
+      // if another user changed the book hierarchy.
+      $form['tree_hash'] = array(
+        '#type' => 'hidden',
+        '#default_value' => $hash,
+      );
+      $form['tree_current_hash'] = array(
+        '#type' => 'value',
+        '#value' => $hash,
+      );
+      $this->bookAdminTableTree($tree['below'], $form['table']);
+    }
+  }
+
+  /**
+   * Helps build the main table in the book administration page form.
+   *
+   * @param array $tree
+   *   A subtree of the book menu hierarchy.
+   * @param array $form
+   *   The form that is being modified, passed by reference.
+   *
+   * @see self::buildForm()
+   */
+  protected function bookAdminTableTree(array $tree, array &$form) {
+    // The delta must be big enough to give each node a distinct value.
+    $count = count($tree);
+    $delta = ($count < 30) ? 15 : intval($count / 2) + 1;
+
+    $access = \Drupal::currentUser()->hasPermission('administer nodes');
+    $destination = $this->getDestinationArray();
+
+    foreach ($tree as $data) {
+      $nid = $data['link']['nid'];
+      $id = 'book-admin-' . $nid;
+
+      $form[$id]['#item'] = $data['link'];
+      $form[$id]['#nid'] = $nid;
+      $form[$id]['#attributes']['class'][] = 'draggable';
+      $form[$id]['#weight'] = $data['link']['weight'];
+
+      if (isset($data['link']['depth']) && $data['link']['depth'] > 2) {
+        $indentation = [
+          '#theme' => 'indentation',
+          '#size' => $data['link']['depth'] - 2,
+        ];
+      }
+
+      $form[$id]['title'] = [
+        '#prefix' => !empty($indentation) ? drupal_render($indentation) : '',
+        '#type' => 'textfield',
+        '#default_value' => $data['link']['title'],
+        '#maxlength' => 255,
+        '#size' => 40,
+      ];
+
+      $form[$id]['weight'] = [
+        '#type' => 'weight',
+        '#default_value' => $data['link']['weight'],
+        '#delta' => max($delta, abs($data['link']['weight'])),
+        '#title' => $this->t('Weight for @title', ['@title' => $data['link']['title']]),
+        '#title_display' => 'invisible',
+        '#attributes' => [
+          'class' => ['book-weight'],
+        ],
+      ];
+
+      $form[$id]['parent']['nid'] = [
+        '#parents' => ['table', $id, 'nid'],
+        '#type' => 'hidden',
+        '#value' => $nid,
+        '#attributes' => [
+          'class' => ['book-nid'],
+        ],
+      ];
+
+      $form[$id]['parent']['pid'] = [
+        '#parents' => ['table', $id, 'pid'],
+        '#type' => 'hidden',
+        '#default_value' => $data['link']['pid'],
+        '#attributes' => [
+          'class' => ['book-pid'],
+        ],
+      ];
+
+      $form[$id]['parent']['bid'] = [
+        '#parents' => ['table', $id, 'bid'],
+        '#type' => 'hidden',
+        '#default_value' => $data['link']['bid'],
+        '#attributes' => [
+          'class' => ['book-bid'],
+        ],
+      ];
+
+      $form[$id]['operations'] = [
+        '#type' => 'operations',
+      ];
+      $form[$id]['operations']['#links']['view'] = [
+        'title' => $this->t('View'),
+        'url' => new Url('entity.node.canonical', ['node' => $nid]),
+      ];
+
+      if ($access) {
+        $form[$id]['operations']['#links']['edit'] = [
+          'title' => $this->t('Edit'),
+          'url' => new Url('entity.node.edit_form', ['node' => $nid]),
+          'query' => $destination,
+        ];
+        $form[$id]['operations']['#links']['delete'] = [
+          'title' => $this->t('Delete'),
+          'url' => new Url('entity.node.delete_form', ['node' => $nid]),
+          'query' => $destination,
+        ];
+      }
+
+      if ($data['below']) {
+        $this->bookAdminTableTree($data['below'], $form);
+      }
+    }
+  }
+
+}

core/modules/book/src/Form/BookOutlineForm.php

@@ -0,0 +1,136 @@
+<?php
+
+/**
+ * @file
+ * Contains \Drupal\book\Form\BookOutlineForm.
+ */
+
+namespace Drupal\book\Form;
+
+use Drupal\book\BookManagerInterface;
+use Drupal\Core\Entity\ContentEntityForm;
+use Drupal\Core\Entity\EntityManagerInterface;
+use Drupal\Core\Form\FormStateInterface;
+use Symfony\Component\DependencyInjection\ContainerInterface;
+
+/**
+ * Displays the book outline form.
+ */
+class BookOutlineForm extends ContentEntityForm {
+
+  /**
+   * The book being displayed.
+   *
+   * @var \Drupal\node\NodeInterface
+   */
+  protected $entity;
+
+  /**
+   * BookManager service.
+   *
+   * @var \Drupal\book\BookManagerInterface
+   */
+  protected $bookManager;
+
+  /**
+   * Constructs a BookOutlineForm object.
+   *
+   * @param \Drupal\Core\Entity\EntityManagerInterface $entity_manager
+   *   The entity manager.
+   * @param \Drupal\book\BookManagerInterface $book_manager
+   *   The BookManager service.
+   */
+  public function __construct(EntityManagerInterface $entity_manager, BookManagerInterface $book_manager) {
+    parent::__construct($entity_manager);
+    $this->bookManager = $book_manager;
+  }
+
+  /**
+   * {@inheritdoc}
+   */
+  public static function create(ContainerInterface $container) {
+    return new static(
+      $container->get('entity.manager'),
+      $container->get('book.manager')
+    );
+  }
+
+  /**
+   * {@inheritdoc}
+   */
+  public function getBaseFormId() {
+    return NULL;
+  }
+
+  /**
+   * {@inheritdoc}
+   */
+  public function form(array $form, FormStateInterface $form_state) {
+    $form['#title'] = $this->entity->label();
+
+    if (!isset($this->entity->book)) {
+      // The node is not part of any book yet - set default options.
+      $this->entity->book = $this->bookManager->getLinkDefaults($this->entity->id());
+    }
+    else {
+      $this->entity->book['original_bid'] = $this->entity->book['bid'];
+    }
+
+    // Find the depth limit for the parent select.
+    if (!isset($this->entity->book['parent_depth_limit'])) {
+      $this->entity->book['parent_depth_limit'] = $this->bookManager->getParentDepthLimit($this->entity->book);
+    }
+    $form = $this->bookManager->addFormElements($form, $form_state, $this->entity, $this->currentUser(), FALSE);
+
+    return $form;
+  }
+
+  /**
+   * {@inheritdoc}
+   */
+  protected function actions(array $form, FormStateInterface $form_state) {
+    $actions = parent::actions($form, $form_state);
+    $actions['submit']['#value'] = $this->entity->book['original_bid'] ? $this->t('Update book outline') : $this->t('Add to book outline');
+    $actions['delete']['#value'] = $this->t('Remove from book outline');
+    $actions['delete']['#access'] = $this->bookManager->checkNodeIsRemovable($this->entity);
+    return $actions;
+  }
+
+  /**
+   * {@inheritdoc}
+   */
+  public function save(array $form, FormStateInterface $form_state) {
+    $form_state->setRedirect(
+      'entity.node.canonical',
+      array('node' => $this->entity->id())
+    );
+    $book_link = $form_state->getValue('book');
+    if (!$book_link['bid']) {
+      drupal_set_message($this->t('No changes were made'));
+      return;
+    }
+
+    $this->entity->book = $book_link;
+    if ($this->bookManager->updateOutline($this->entity)) {
+      if (isset($this->entity->book['parent_mismatch']) && $this->entity->book['parent_mismatch']) {
+        // This will usually only happen when JS is disabled.
+        drupal_set_message($this->t('The post has been added to the selected book. You may now position it relative to other pages.'));
+        $form_state->setRedirectUrl($this->entity->urlInfo('book-outline-form'));
+      }
+      else {
+        drupal_set_message($this->t('The book outline has been updated.'));
+      }
+    }
+    else {
+      drupal_set_message($this->t('There was an error adding the post to the book.'), 'error');
+    }
+  }
+
+  /**
+   * {@inheritdoc}
+   */
+  public function delete(array $form, FormStateInterface $form_state) {
+    $form_state->setRedirectUrl($this->entity->urlInfo('book-remove-form'));
+  }
+
+}

core/modules/book/src/Form/BookRemoveForm.php

@@ -0,0 +1,115 @@
+<?php
+
+/**
+ * @file
+ * Contains \Drupal\book\Form\BookRemoveForm.
+ */
+
+namespace Drupal\book\Form;
+
+use Drupal\book\BookManagerInterface;
+use Drupal\Core\Form\ConfirmFormBase;
+use Drupal\Core\Form\FormStateInterface;
+use Drupal\Core\Url;
+use Drupal\node\NodeInterface;
+use Symfony\Component\DependencyInjection\ContainerInterface;
+
+/**
+ * Remove form for book module.
+ */
+class BookRemoveForm extends ConfirmFormBase {
+
+  /**
+   * The book manager.
+   *
+   * @var \Drupal\book\BookManagerInterface
+   */
+  protected $bookManager;
+
+  /**
+   * The node representing the book.
+   *
+   * @var \Drupal\node\NodeInterface
+   */
+  protected $node;
+
+  /**
+   * Constructs a BookRemoveForm object.
+   *
+   * @param \Drupal\book\BookManagerInterface $book_manager
+   *   The book manager.
+   */
+  public function __construct(BookManagerInterface $book_manager) {
+    $this->bookManager = $book_manager;
+  }
+
+  /**
+   * {@inheritdoc}
+   */
+  public static function create(ContainerInterface $container) {
+    return new static(
+      $container->get('book.manager')
+    );
+  }
+
+  /**
+   * {@inheritdoc}
+   */
+  public function getFormId() {
+    return 'book_remove_form';
+  }
+
+  /**
+   * {@inheritdoc}
+   */
+  public function buildForm(array $form, FormStateInterface $form_state, NodeInterface $node = NULL) {
+    $this->node = $node;
+    return parent::buildForm($form, $form_state);
+  }
+
+  /**
+   * {@inheritdoc}
+   */
+  public function getDescription() {
+    $title = array('%title' => $this->node->label());
+    if ($this->node->book['has_children']) {
+      return $this->t('%title has associated child pages, which will be relocated automatically to maintain their connection to the book. To recreate the hierarchy (as it was before removing this page), %title may be added again using the Outline tab, and each of its former child pages will need to be relocated manually.', $title);
+    }
+    else {
+      return $this->t('%title may be added to hierarchy again using the Outline tab.', $title);
+    }
+  }
+
+  /**
+   * {@inheritdoc}
+   */
+  public function getConfirmText() {
+    return $this->t('Remove');
+  }
+
+  /**
+   * {@inheritdoc}
+   */
+  public function getQuestion() {
+    return $this->t('Are you sure you want to remove %title from the book hierarchy?', array('%title' => $this->node->label()));
+  }
+
+  /**
+   * {@inheritdoc}
+   */
+  public function getCancelUrl() {
+    return $this->node->urlInfo();
+  }
+
+  /**
+   * {@inheritdoc}
+   */
+  public function submitForm(array &$form, FormStateInterface $form_state) {
+    if ($this->bookManager->checkNodeIsRemovable($this->node)) {
+      $this->bookManager->deleteFromBook($this->node->id());
+      drupal_set_message($this->t('The post has been removed from the book.'));
+    }
+    $form_state->setRedirectUrl($this->getCancelUrl());
+  }
+
+}

core/modules/book/src/Form/BookSettingsForm.php

@@ -0,0 +1,89 @@
+<?php
+
+/**
+ * @file
+ * Contains \Drupal\book\Form\BookSettingsForm.
+ */
+
+namespace Drupal\book\Form;
+
+use Drupal\Core\Form\ConfigFormBase;
+use Drupal\Core\Form\FormStateInterface;
+
+/**
+ * Configure book settings for this site.
+ */
+class BookSettingsForm extends ConfigFormBase {
+
+  /**
+   * {@inheritdoc}
+   */
+  public function getFormId() {
+    return 'book_admin_settings';
+  }
+
+  /**
+   * {@inheritdoc}
+   */
+  protected function getEditableConfigNames() {
+    return ['book.settings'];
+  }
+
+  /**
+   * {@inheritdoc}
+   */
+  public function buildForm(array $form, FormStateInterface $form_state) {
+    $types = node_type_get_names();
+    $config = $this->config('book.settings');
+    $form['book_allowed_types'] = array(
+      '#type' => 'checkboxes',
+      '#title' => $this->t('Content types allowed in book outlines'),
+      '#default_value' => $config->get('allowed_types'),
+      '#options' => $types,
+      '#description' => $this->t('Users with the %outline-perm permission can add all content types.', array('%outline-perm' => $this->t('Administer book outlines'))),
+      '#required' => TRUE,
+    );
+    $form['book_child_type'] = array(
+      '#type' => 'radios',
+      '#title' => $this->t('Content type for the <em>Add child page</em> link'),
+      '#default_value' => $config->get('child_type'),
+      '#options' => $types,
+      '#required' => TRUE,
+    );
+    $form['array_filter'] = array('#type' => 'value', '#value' => TRUE);
+
+    return parent::buildForm($form, $form_state);
+  }
+
+  /**
+   * {@inheritdoc}
+   */
+  public function validateForm(array &$form, FormStateInterface $form_state) {
+    $child_type = $form_state->getValue('book_child_type');
+    if ($form_state->isValueEmpty(array('book_allowed_types', $child_type))) {
+      $form_state->setErrorByName('book_child_type', $this->t('The content type for the %add-child link must be one of those selected as an allowed book outline type.', array('%add-child' => $this->t('Add child page'))));
+    }
+
+    parent::validateForm($form, $form_state);
+  }
+
+  /**
+   * {@inheritdoc}
+   */
+  public function submitForm(array &$form, FormStateInterface $form_state) {
+    $allowed_types = array_filter($form_state->getValue('book_allowed_types'));
+    // We need to save the allowed types in an array ordered by machine_name so
+    // that we can save them in the correct order if node type changes.
+    // @see book_node_type_update().
+    sort($allowed_types);
+    $this->config('book.settings')
+    // Remove unchecked types.
+      ->set('allowed_types', $allowed_types)
+      ->set('child_type', $form_state->getValue('book_child_type'))
+      ->save();
+
+    parent::submitForm($form, $form_state);
+  }
+
+}
+

core/modules/book/src/Plugin/Block/BookNavigationBlock.php

@@ -0,0 +1,202 @@
+<?php
+
+/**
+ * @file
+ * Contains \Drupal\book\Plugin\Block\BookNavigationBlock.
+ */
+
+namespace Drupal\book\Plugin\Block;
+
+use Drupal\Core\Block\BlockBase;
+use Drupal\book\BookManagerInterface;
+use Drupal\Core\Form\FormStateInterface;
+use Drupal\Core\Plugin\ContainerFactoryPluginInterface;
+use Symfony\Component\DependencyInjection\ContainerInterface;
+use Symfony\Component\HttpFoundation\RequestStack;
+use Drupal\Core\Entity\EntityStorageInterface;
+
+/**
+ * Provides a 'Book navigation' block.
+ *
+ * @Block(
+ *   id = "book_navigation",
+ *   admin_label = @Translation("Book navigation"),
+ *   category = @Translation("Menus")
+ * )
+ */
+class BookNavigationBlock extends BlockBase implements ContainerFactoryPluginInterface {
+
+  /**
+   * The request object.
+   *
+   * @var \Symfony\Component\HttpFoundation\RequestStack
+   */
+  protected $requestStack;
+
+  /**
+   * The book manager.
+   *
+   * @var \Drupal\book\BookManagerInterface
+   */
+  protected $bookManager;
+
+  /**
+   * The node storage.
+   *
+   * @var \Drupal\Core\Entity\EntityStorageInterface
+   */
+  protected $nodeStorage;
+
+  /**
+   * Constructs a new BookNavigationBlock 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\RequestStack $request_stack
+   *   The request stack object.
+   * @param \Drupal\book\BookManagerInterface $book_manager
+   *   The book manager.
+   * @param \Drupal\Core\Entity\EntityStorageInterface $node_storage
+   *   The node storage.
+   */
+  public function __construct(array $configuration, $plugin_id, $plugin_definition, RequestStack $request_stack, BookManagerInterface $book_manager, EntityStorageInterface $node_storage) {
+    parent::__construct($configuration, $plugin_id, $plugin_definition);
+
+    $this->requestStack = $request_stack;
+    $this->bookManager = $book_manager;
+    $this->nodeStorage = $node_storage;
+  }
+
+  /**
+   * {@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'),
+      $container->get('book.manager'),
+      $container->get('entity.manager')->getStorage('node')
+    );
+  }
+
+  /**
+   * {@inheritdoc}
+   */
+  public function defaultConfiguration() {
+    return array(
+      'block_mode' => "all pages",
+    );
+  }
+
+  /**
+   * {@inheritdoc}
+   */
+  function blockForm($form, FormStateInterface $form_state) {
+    $options = array(
+      'all pages' => $this->t('Show block on all pages'),
+      'book pages' => $this->t('Show block only on book pages'),
+    );
+    $form['book_block_mode'] = array(
+      '#type' => 'radios',
+      '#title' => $this->t('Book navigation block display'),
+      '#options' => $options,
+      '#default_value' => $this->configuration['block_mode'],
+      '#description' => $this->t("If <em>Show block on all pages</em> is selected, the block will contain the automatically generated menus for all of the site's books. If <em>Show block only on book pages</em> is selected, the block will contain only the one menu corresponding to the current page's book. In this case, if the current page is not in a book, no block will be displayed. The <em>Page specific visibility settings</em> or other visibility settings can be used in addition to selectively display this block."),
+      );
+
+    return $form;
+  }
+
+  /**
+   * {@inheritdoc}
+   */
+  public function blockSubmit($form, FormStateInterface $form_state) {
+    $this->configuration['block_mode'] = $form_state->getValue('book_block_mode');
+  }
+
+  /**
+   * {@inheritdoc}
+   */
+  public function build() {
+    $current_bid = 0;
+
+    if ($node = $this->requestStack->getCurrentRequest()->get('node')) {
+      $current_bid = empty($node->book['bid']) ? 0 : $node->book['bid'];
+    }
+    if ($this->configuration['block_mode'] == 'all pages') {
+      $book_menus = array();
+      $pseudo_tree = array(0 => array('below' => FALSE));
+      foreach ($this->bookManager->getAllBooks() as $book_id => $book) {
+        if ($book['bid'] == $current_bid) {
+          // If the current page is a node associated with a book, the menu
+          // needs to be retrieved.
+          $data = $this->bookManager->bookTreeAllData($node->book['bid'], $node->book);
+          $book_menus[$book_id] = $this->bookManager->bookTreeOutput($data);
+        }
+        else {
+          // Since we know we will only display a link to the top node, there
+          // is no reason to run an additional menu tree query for each book.
+          $book['in_active_trail'] = FALSE;
+          // Check whether user can access the book link.
+          $book_node = $this->nodeStorage->load($book['nid']);
+          $book['access'] = $book_node->access('view');
+          $pseudo_tree[0]['link'] = $book;
+          $book_menus[$book_id] = $this->bookManager->bookTreeOutput($pseudo_tree);
+        }
+        $book_menus[$book_id] += array(
+          '#book_title' => $book['title'],
+        );
+      }
+      if ($book_menus) {
+        return array(
+          '#theme' => 'book_all_books_block',
+        ) + $book_menus;
+      }
+    }
+    elseif ($current_bid) {
+      // Only display this block when the user is browsing a book.
+      $query = \Drupal::entityQuery('node');
+      $nid = $query->condition('nid', $node->book['bid'], '=')->execute();
+
+      // Only show the block if the user has view access for the top-level node.
+      if ($nid) {
+        $tree = $this->bookManager->bookTreeAllData($node->book['bid'], $node->book);
+        // There should only be one element at the top level.
+        $data = array_shift($tree);
+        $below = $this->bookManager->bookTreeOutput($data['below']);
+        if (!empty($below)) {
+          return $below;
+        }
+      }
+    }
+    return array();
+  }
+
+  /**
+   * {@inheritdoc}
+   */
+  public function getCacheContexts() {
+    // The "Book navigation" block must be cached per role and book navigation
+    // context.
+    return [
+      'user.roles',
+      'route.book_navigation',
+    ];
+  }
+
+  /**
+   * {@inheritdoc}
+   *
+   * @todo Make cacheable in https://www.drupal.org/node/2483181
+   */
+  public function getCacheMaxAge() {
+    return 0;
+  }
+
+}

core/modules/book/src/Tests/BookTest.php

@@ -0,0 +1,730 @@
+<?php
+
+/**
+ * @file
+ * Contains \Drupal\book\Tests\BookTest.
+ */
+
+namespace Drupal\book\Tests;
+
+use Drupal\Component\Utility\SafeMarkup;
+use Drupal\Core\Entity\EntityInterface;
+use Drupal\simpletest\WebTestBase;
+use Drupal\user\RoleInterface;
+
+/**
+ * Create a book, add pages, and test book interface.
+ *
+ * @group book
+ */
+class BookTest extends WebTestBase {
+
+  /**
+   * Modules to install.
+   *
+   * @var array
+   */
+  public static $modules = array('book', 'block', 'node_access_test');
+
+  /**
+   * A book node.
+   *
+   * @var object
+   */
+  protected $book;
+
+  /**
+   * A user with permission to create and edit books.
+   *
+   * @var object
+   */
+  protected $bookAuthor;
+
+  /**
+   * A user with permission to view a book and access printer-friendly version.
+   *
+   * @var object
+   */
+  protected $webUser;
+
+  /**
+   * A user with permission to create and edit books and to administer blocks.
+   *
+   * @var object
+   */
+  protected $adminUser;
+
+  /**
+   * A user without the 'node test view' permission.
+   *
+   * @var \Drupal\user\UserInterface
+   */
+  protected $webUserWithoutNodeAccess;
+
+  /**
+   * {@inheritdoc}
+   */
+  protected function setUp() {
+    parent::setUp();
+    $this->drupalPlaceBlock('system_breadcrumb_block');
+
+    // node_access_test requires a node_access_rebuild().
+    node_access_rebuild();
+
+    // Create users.
+    $this->bookAuthor = $this->drupalCreateUser(array('create new books', 'create book content', 'edit own book content', 'add content to books'));
+    $this->webUser = $this->drupalCreateUser(array('access printer-friendly version', 'node test view'));
+    $this->webUserWithoutNodeAccess = $this->drupalCreateUser(array('access printer-friendly version'));
+    $this->adminUser = $this->drupalCreateUser(array('create new books', 'create book content', 'edit own book content', 'add content to books', 'administer blocks', 'administer permissions', 'administer book outlines', 'node test view', 'administer content types', 'administer site configuration'));
+  }
+
+  /**
+   * Creates a new book with a page hierarchy.
+   */
+  function createBook() {
+    // Create new book.
+    $this->drupalLogin($this->bookAuthor);
+
+    $this->book = $this->createBookNode('new');
+    $book = $this->book;
+
+    /*
+     * Add page hierarchy to book.
+     * Book
+     *  |- Node 0
+     *   |- Node 1
+     *   |- Node 2
+     *  |- Node 3
+     *  |- Node 4
+     */
+    $nodes = array();
+    $nodes[] = $this->createBookNode($book->id()); // Node 0.
+    $nodes[] = $this->createBookNode($book->id(), $nodes[0]->book['nid']); // Node 1.
+    $nodes[] = $this->createBookNode($book->id(), $nodes[0]->book['nid']); // Node 2.
+    $nodes[] = $this->createBookNode($book->id()); // Node 3.
+    $nodes[] = $this->createBookNode($book->id()); // Node 4.
+
+    $this->drupalLogout();
+
+    return $nodes;
+  }
+
+  /**
+   * Tests saving the book outline on an empty book.
+   */
+  function testEmptyBook() {
+    // Create a new empty book.
+    $this->drupalLogin($this->bookAuthor);
+    $book = $this->createBookNode('new');
+    $this->drupalLogout();
+
+    // Log in as a user with access to the book outline and save the form.
+    $this->drupalLogin($this->adminUser);
+    $this->drupalPostForm('admin/structure/book/' . $book->id(), array(), t('Save book pages'));
+    $this->assertText(t('Updated book @book.', array('@book' => $book->label())));
+  }
+
+  /**
+   * Tests book functionality through node interfaces.
+   */
+  function testBook() {
+    // Create new book.
+    $nodes = $this->createBook();
+    $book = $this->book;
+
+    $this->drupalLogin($this->webUser);
+
+    // Check that book pages display along with the correct outlines and
+    // previous/next links.
+    $this->checkBookNode($book, array($nodes[0], $nodes[3], $nodes[4]), FALSE, FALSE, $nodes[0], array());
+    $this->checkBookNode($nodes[0], array($nodes[1], $nodes[2]), $book, $book, $nodes[1], array($book));
+    $this->checkBookNode($nodes[1], NULL, $nodes[0], $nodes[0], $nodes[2], array($book, $nodes[0]));
+    $this->checkBookNode($nodes[2], NULL, $nodes[1], $nodes[0], $nodes[3], array($book, $nodes[0]));
+    $this->checkBookNode($nodes[3], NULL, $nodes[2], $book, $nodes[4], array($book));
+    $this->checkBookNode($nodes[4], NULL, $nodes[3], $book, FALSE, array($book));
+
+    $this->drupalLogout();
+    $this->drupalLogin($this->bookAuthor);
+
+    // Check the presence of expected cache tags.
+    $this->drupalGet('node/add/book');
+    $this->assertCacheTag('config:book.settings');
+
+    /*
+     * Add Node 5 under Node 3.
+     * Book
+     *  |- Node 0
+     *   |- Node 1
+     *   |- Node 2
+     *  |- Node 3
+     *   |- Node 5
+     *  |- Node 4
+     */
+    $nodes[] = $this->createBookNode($book->id(), $nodes[3]->book['nid']); // Node 5.
+    $this->drupalLogout();
+    $this->drupalLogin($this->webUser);
+    // Verify the new outline - make sure we don't get stale cached data.
+    $this->checkBookNode($nodes[3], array($nodes[5]), $nodes[2], $book, $nodes[5], array($book));
+    $this->checkBookNode($nodes[4], NULL, $nodes[5], $book, FALSE, array($book));
+    $this->drupalLogout();
+    // Create a second book, and move an existing book page into it.
+    $this->drupalLogin($this->bookAuthor);
+    $other_book = $this->createBookNode('new');
+    $node = $this->createBookNode($book->id());
+    $edit = array('book[bid]' => $other_book->id());
+    $this->drupalPostForm('node/' . $node->id() . '/edit', $edit, t('Save'));
+
+    $this->drupalLogout();
+    $this->drupalLogin($this->webUser);
+
+    // Check that the nodes in the second book are displayed correctly.
+    // First we must set $this->book to the second book, so that the
+    // correct regex will be generated for testing the outline.
+    $this->book = $other_book;
+    $this->checkBookNode($other_book, array($node), FALSE, FALSE, $node, array());
+    $this->checkBookNode($node, NULL, $other_book, $other_book, FALSE, array($other_book));
+
+    // Test that we can save a book programatically.
+    $this->drupalLogin($this->bookAuthor);
+    $book = $this->createBookNode('new');
+    $book->save();
+  }
+
+  /**
+   * Checks the outline of sub-pages; previous, up, and next.
+   *
+   * Also checks the printer friendly version of the outline.
+   *
+   * @param \Drupal\Core\Entity\EntityInterface $node
+   *   Node to check.
+   * @param $nodes
+   *   Nodes that should be in outline.
+   * @param $previous
+   *   (optional) Previous link node. Defaults to FALSE.
+   * @param $up
+   *   (optional) Up link node. Defaults to FALSE.
+   * @param $next
+   *   (optional) Next link node. Defaults to FALSE.
+   * @param array $breadcrumb
+   *   The nodes that should be displayed in the breadcrumb.
+   */
+  function checkBookNode(EntityInterface $node, $nodes, $previous = FALSE, $up = FALSE, $next = FALSE, array $breadcrumb) {
+    // $number does not use drupal_static as it should not be reset
+    // since it uniquely identifies each call to checkBookNode().
+    static $number = 0;
+    $this->drupalGet('node/' . $node->id());
+
+    // Check outline structure.
+    if ($nodes !== NULL) {
+      $this->assertPattern($this->generateOutlinePattern($nodes), format_string('Node @number outline confirmed.', array('@number' => $number)));
+    }
+    else {
+      $this->pass(format_string('Node %number does not have outline.', array('%number' => $number)));
+    }
+
+    // Check previous, up, and next links.
+    if ($previous) {
+      /** @var \Drupal\Core\Url $url */
+      $url = $previous->urlInfo();
+      $url->setOptions(array('attributes' => array('rel' => array('prev'), 'title' => t('Go to previous page'))));
+      $text = SafeMarkup::format('<b>‹</b> @label', array('@label' => $previous->label()));
+      $this->assertRaw(\Drupal::l($text, $url), 'Previous page link found.');
+    }
+
+    if ($up) {
+      /** @var \Drupal\Core\Url $url */
+      $url = $up->urlInfo();
+      $url->setOptions(array('attributes' => array('title' => t('Go to parent page'))));
+      $this->assertRaw(\Drupal::l('Up', $url), 'Up page link found.');
+    }
+
+    if ($next) {
+      /** @var \Drupal\Core\Url $url */
+      $url = $next->urlInfo();
+      $url->setOptions(array('attributes' => array('rel' => array('next'), 'title' => t('Go to next page'))));
+      $text = SafeMarkup::format('@label <b>›</b>', array('@label' => $next->label()));
+      $this->assertRaw(\Drupal::l($text, $url), 'Next page link found.');
+    }
+
+    // Compute the expected breadcrumb.
+    $expected_breadcrumb = array();
+    $expected_breadcrumb[] = \Drupal::url('<front>');
+    foreach ($breadcrumb as $a_node) {
+      $expected_breadcrumb[] = $a_node->url();
+    }
+
+    // Fetch links in the current breadcrumb.
+    $links = $this->xpath('//nav[@class="breadcrumb"]/ol/li/a');
+    $got_breadcrumb = array();
+    foreach ($links as $link) {
+      $got_breadcrumb[] = (string) $link['href'];
+    }
+
+    // Compare expected and got breadcrumbs.
+    $this->assertIdentical($expected_breadcrumb, $got_breadcrumb, 'The breadcrumb is correctly displayed on the page.');
+
+    // Check printer friendly version.
+    $this->drupalGet('book/export/html/' . $node->id());
+    $this->assertText($node->label(), 'Printer friendly title found.');
+    $this->assertRaw($node->body->processed, 'Printer friendly body found.');
+
+    $number++;
+  }
+
+  /**
+   * Creates a regular expression to check for the sub-nodes in the outline.
+   *
+   * @param array $nodes
+   *   An array of nodes to check in outline.
+   *
+   * @return string
+   *   A regular expression that locates sub-nodes of the outline.
+   */
+  function generateOutlinePattern($nodes) {
+    $outline = '';
+    foreach ($nodes as $node) {
+      $outline .= '(node\/' . $node->id() . ')(.*?)(' . $node->label() . ')(.*?)';
+    }
+
+    return '/<nav id="book-navigation-' . $this->book->id() . '"(.*?)<ul(.*?)' . $outline . '<\/ul>/s';
+  }
+
+  /**
+   * Creates a book node.
+   *
+   * @param int|string $book_nid
+   *   A book node ID or set to 'new' to create a new book.
+   * @param int|null $parent
+   *   (optional) Parent book reference ID. Defaults to NULL.
+   */
+  function createBookNode($book_nid, $parent = NULL) {
+    // $number does not use drupal_static as it should not be reset
+    // since it uniquely identifies each call to createBookNode().
+    static $number = 0; // Used to ensure that when sorted nodes stay in same order.
+
+    $edit = array();
+    $edit['title[0][value]'] = $number . ' - SimpleTest test node ' . $this->randomMachineName(10);
+    $edit['body[0][value]'] = 'SimpleTest test body ' . $this->randomMachineName(32) . ' ' . $this->randomMachineName(32);
+    $edit['book[bid]'] = $book_nid;
+
+    if ($parent !== NULL) {
+      $this->drupalPostForm('node/add/book', $edit, t('Change book (update list of parents)'));
+
+      $edit['book[pid]'] = $parent;
+      $this->drupalPostForm(NULL, $edit, t('Save'));
+      // Make sure the parent was flagged as having children.
+      $parent_node = \Drupal::entityManager()->getStorage('node')->loadUnchanged($parent);
+      $this->assertFalse(empty($parent_node->book['has_children']), 'Parent node is marked as having children');
+    }
+    else {
+      $this->drupalPostForm('node/add/book', $edit, t('Save'));
+    }
+
+    // Check to make sure the book node was created.
+    $node = $this->drupalGetNodeByTitle($edit['title[0][value]']);
+    $this->assertNotNull(($node === FALSE ? NULL : $node), 'Book node found in database.');
+    $number++;
+
+    return $node;
+  }
+
+  /**
+   * Tests book export ("printer-friendly version") functionality.
+   */
+  function testBookExport() {
+    // Create a book.
+    $nodes = $this->createBook();
+
+    // Login as web user and view printer-friendly version.
+    $this->drupalLogin($this->webUser);
+    $this->drupalGet('node/' . $this->book->id());
+    $this->clickLink(t('Printer-friendly version'));
+
+    // Make sure each part of the book is there.
+    foreach ($nodes as $node) {
+      $this->assertText($node->label(), 'Node title found in printer friendly version.');
+      $this->assertRaw($node->body->processed, 'Node body found in printer friendly version.');
+    }
+
+    // Make sure we can't export an unsupported format.
+    $this->drupalGet('book/export/foobar/' . $this->book->id());
+    $this->assertResponse('404', 'Unsupported export format returned "not found".');
+
+    // Make sure we get a 404 on a not existing book node.
+    $this->drupalGet('book/export/html/123');
+    $this->assertResponse('404', 'Not existing book node returned "not found".');
+
+    // Make sure an anonymous user cannot view printer-friendly version.
+    $this->drupalLogout();
+
+    // Load the book and verify there is no printer-friendly version link.
+    $this->drupalGet('node/' . $this->book->id());
+    $this->assertNoLink(t('Printer-friendly version'), 'Anonymous user is not shown link to printer-friendly version.');
+
+    // Try getting the URL directly, and verify it fails.
+    $this->drupalGet('book/export/html/' . $this->book->id());
+    $this->assertResponse('403', 'Anonymous user properly forbidden.');
+
+    // Now grant anonymous users permission to view the printer-friendly
+    // version and verify that node access restrictions still prevent them from
+    // seeing it.
+    user_role_grant_permissions(RoleInterface::ANONYMOUS_ID, array('access printer-friendly version'));
+    $this->drupalGet('book/export/html/' . $this->book->id());
+    $this->assertResponse('403', 'Anonymous user properly forbidden from seeing the printer-friendly version when denied by node access.');
+  }
+
+  /**
+   * Tests the functionality of the book navigation block.
+   */
+  function testBookNavigationBlock() {
+    $this->drupalLogin($this->adminUser);
+
+    // Enable the block.
+    $block = $this->drupalPlaceBlock('book_navigation');
+
+    // Give anonymous users the permission 'node test view'.
+    $edit = array();
+    $edit[RoleInterface::ANONYMOUS_ID . '[node test view]'] = TRUE;
+    $this->drupalPostForm('admin/people/permissions/' . RoleInterface::ANONYMOUS_ID, $edit, t('Save permissions'));
+    $this->assertText(t('The changes have been saved.'), "Permission 'node test view' successfully assigned to anonymous users.");
+
+    // Test correct display of the block.
+    $nodes = $this->createBook();
+    $this->drupalGet('<front>');
+    $this->assertText($block->label(), 'Book navigation block is displayed.');
+    $this->assertText($this->book->label(), format_string('Link to book root (@title) is displayed.', array('@title' => $nodes[0]->label())));
+    $this->assertNoText($nodes[0]->label(), 'No links to individual book pages are displayed.');
+  }
+
+  /**
+   * Tests the book navigation block when an access module is installed.
+   */
+  function testNavigationBlockOnAccessModuleInstalled() {
+    $this->drupalLogin($this->adminUser);
+    $block = $this->drupalPlaceBlock('book_navigation', array('block_mode' => 'book pages'));
+
+    // Give anonymous users the permission 'node test view'.
+    $edit = array();
+    $edit[RoleInterface::ANONYMOUS_ID . '[node test view]'] = TRUE;
+    $this->drupalPostForm('admin/people/permissions/' . RoleInterface::ANONYMOUS_ID, $edit, t('Save permissions'));
+    $this->assertText(t('The changes have been saved.'), "Permission 'node test view' successfully assigned to anonymous users.");
+
+    // Create a book.
+    $this->createBook();
+
+    // Test correct display of the block to registered users.
+    $this->drupalLogin($this->webUser);
+    $this->drupalGet('node/' . $this->book->id());
+    $this->assertText($block->label(), 'Book navigation block is displayed to registered users.');
+    $this->drupalLogout();
+
+    // Test correct display of the block to anonymous users.
+    $this->drupalGet('node/' . $this->book->id());
+    $this->assertText($block->label(), 'Book navigation block is displayed to anonymous users.');
+
+    // Test the 'book pages' block_mode setting.
+    $this->drupalGet('<front>');
+    $this->assertNoText($block->label(), 'Book navigation block is not shown on non-book pages.');
+  }
+
+  /**
+   * Tests the access for deleting top-level book nodes.
+   */
+   function testBookDelete() {
+     $node_storage = $this->container->get('entity.manager')->getStorage('node');
+     $nodes = $this->createBook();
+     $this->drupalLogin($this->adminUser);
+     $edit = array();
+
+     // Test access to delete top-level and child book nodes.
+     $this->drupalGet('node/' . $this->book->id() . '/outline/remove');
+     $this->assertResponse('403', 'Deleting top-level book node properly forbidden.');
+     $this->drupalPostForm('node/' . $nodes[4]->id() . '/outline/remove', $edit, t('Remove'));
+     $node_storage->resetCache(array($nodes[4]->id()));
+     $node4 = $node_storage->load($nodes[4]->id());
+     $this->assertTrue(empty($node4->book), 'Deleting child book node properly allowed.');
+
+     // Delete all child book nodes and retest top-level node deletion.
+     foreach ($nodes as $node) {
+       $nids[] = $node->id();
+     }
+     entity_delete_multiple('node', $nids);
+     $this->drupalPostForm('node/' . $this->book->id() . '/outline/remove', $edit, t('Remove'));
+     $node_storage->resetCache(array($this->book->id()));
+     $node = $node_storage->load($this->book->id());
+     $this->assertTrue(empty($node->book), 'Deleting childless top-level book node properly allowed.');
+   }
+
+  /*
+   * Tests node type changing machine name when type is a book allowed type.
+   */
+  function testBookNodeTypeChange() {
+    $this->drupalLogin($this->adminUser);
+    // Change the name, machine name and description.
+    $edit = array(
+      'name' => 'Bar',
+      'type' => 'bar',
+    );
+    $this->drupalPostForm('admin/structure/types/manage/book', $edit, t('Save content type'));
+
+    // Ensure that the config book.settings:allowed_types has been updated with
+    // the new machine and the old one has been removed.
+    $this->assertTrue(book_type_is_allowed('bar'), 'Config book.settings:allowed_types contains the updated node type machine name "bar".');
+    $this->assertFalse(book_type_is_allowed('book'), 'Config book.settings:allowed_types does not contain the old node type machine name "book".');
+
+    $edit = array(
+      'name' => 'Basic page',
+      'title_label' => 'Title for basic page',
+      'type' => 'page',
+    );
+    $this->drupalPostForm('admin/structure/types/add', $edit, t('Save content type'));
+
+    // Add page to the allowed node types.
+    $edit = array(
+      'book_allowed_types[page]' => 'page',
+      'book_allowed_types[bar]' => 'bar',
+    );
+
+    $this->drupalPostForm('admin/structure/book/settings', $edit, t('Save configuration'));
+    $this->assertTrue(book_type_is_allowed('bar'), 'Config book.settings:allowed_types contains the bar node type.');
+    $this->assertTrue(book_type_is_allowed('page'), 'Config book.settings:allowed_types contains the page node type.');
+
+    // Test the order of the book.settings::allowed_types configuration is as
+    // expected. The point of this test is to prove that after changing a node
+    // type going to admin/structure/book/settings and pressing save without
+    // changing anything should not alter the book.settings configuration. The
+    // order will be:
+    // @code
+    // array(
+    //   'bar',
+    //   'page',
+    // );
+    // @endcode
+    $current_config = $this->config('book.settings')->get();
+    $this->drupalPostForm('admin/structure/book/settings', array(), t('Save configuration'));
+    $this->assertIdentical($current_config, $this->config('book.settings')->get());
+
+    // Change the name, machine name and description.
+    $edit = array(
+      'name' => 'Zebra book',
+      'type' => 'zebra',
+    );
+    $this->drupalPostForm('admin/structure/types/manage/bar', $edit, t('Save content type'));
+    $this->assertTrue(book_type_is_allowed('zebra'), 'Config book.settings:allowed_types contains the zebra node type.');
+    $this->assertTrue(book_type_is_allowed('page'), 'Config book.settings:allowed_types contains the page node type.');
+
+    // Test the order of the book.settings::allowed_types configuration is as
+    // expected. The order should be:
+    // @code
+    // array(
+    //   'page',
+    //   'zebra',
+    // );
+    // @endcode
+    $current_config = $this->config('book.settings')->get();
+    $this->drupalPostForm('admin/structure/book/settings', array(), t('Save configuration'));
+    $this->assertIdentical($current_config, $this->config('book.settings')->get());
+
+    $edit = array(
+      'name' => 'Animal book',
+      'type' => 'zebra',
+    );
+    $this->drupalPostForm('admin/structure/types/manage/zebra', $edit, t('Save content type'));
+
+    // Test the order of the book.settings::allowed_types configuration is as
+    // expected. The order should be:
+    // @code
+    // array(
+    //   'page',
+    //   'zebra',
+    // );
+    // @endcode
+    $current_config = $this->config('book.settings')->get();
+    $this->drupalPostForm('admin/structure/book/settings', array(), t('Save configuration'));
+    $this->assertIdentical($current_config, $this->config('book.settings')->get());
+
+    // Ensure that after all the node type changes book.settings:child_type has
+    // the expected value.
+    $this->assertEqual($this->config('book.settings')->get('child_type'), 'zebra');
+  }
+
+  /**
+   * Tests re-ordering of books.
+   */
+  public function testBookOrdering() {
+    // Create new book.
+    $this->createBook();
+    $book = $this->book;
+
+    $this->drupalLogin($this->adminUser);
+    $node1 = $this->createBookNode($book->id());
+    $node2 = $this->createBookNode($book->id());
+    $pid = $node1->book['nid'];
+
+    // Head to admin screen and attempt to re-order.
+    $this->drupalGet('admin/structure/book/' . $book->id());
+    $edit = array(
+      "table[book-admin-{$node1->id()}][weight]" => 1,
+      "table[book-admin-{$node2->id()}][weight]" => 2,
+      // Put node 2 under node 1.
+      "table[book-admin-{$node2->id()}][pid]" => $pid,
+    );
+    $this->drupalPostForm(NULL, $edit, t('Save book pages'));
+    // Verify weight was updated.
+    $this->assertFieldByName("table[book-admin-{$node1->id()}][weight]", 1);
+    $this->assertFieldByName("table[book-admin-{$node2->id()}][weight]", 2);
+    $this->assertFieldByName("table[book-admin-{$node2->id()}][pid]", $pid);
+  }
+
+  /**
+   * Tests outline of a book.
+   */
+  public function testBookOutline() {
+    $this->drupalLogin($this->bookAuthor);
+
+    // Create new node not yet a book.
+    $empty_book = $this->drupalCreateNode(array('type' => 'book'));
+    $this->drupalGet('node/' . $empty_book->id() . '/outline');
+    $this->assertNoLink(t('Book outline'), 'Book Author is not allowed to outline');
+
+    $this->drupalLogin($this->adminUser);
+    $this->drupalGet('node/' . $empty_book->id() . '/outline');
+    $this->assertRaw(t('Book outline'));
+    $this->assertOptionSelected('edit-book-bid', 0, 'Node does not belong to a book');
+
+    $edit = array();
+    $edit['book[bid]'] = '1';
+    $this->drupalPostForm('node/' . $empty_book->id() . '/outline', $edit, t('Add to book outline'));
+    $node = \Drupal::entityManager()->getStorage('node')->load($empty_book->id());
+    // Test the book array.
+    $this->assertEqual($node->book['nid'], $empty_book->id());
+    $this->assertEqual($node->book['bid'], $empty_book->id());
+    $this->assertEqual($node->book['depth'], 1);
+    $this->assertEqual($node->book['p1'], $empty_book->id());
+    $this->assertEqual($node->book['pid'], '0');
+
+    // Create new book.
+    $this->drupalLogin($this->bookAuthor);
+    $book = $this->createBookNode('new');
+
+    $this->drupalLogin($this->adminUser);
+    $this->drupalGet('node/' . $book->id() . '/outline');
+    $this->assertRaw(t('Book outline'));
+
+    // Create a new node and set the book after the node was created.
+    $node = $this->drupalCreateNode(array('type' => 'book'));
+    $edit = array();
+    $edit['book[bid]'] = $node->id();
+    $this->drupalPostForm('node/' . $node->id() . '/edit', $edit, t('Save'));
+    $node = \Drupal::entityManager()->getStorage('node')->load($node->id());
+
+    // Test the book array.
+    $this->assertEqual($node->book['nid'], $node->id());
+    $this->assertEqual($node->book['bid'], $node->id());
+    $this->assertEqual($node->book['depth'], 1);
+    $this->assertEqual($node->book['p1'], $node->id());
+    $this->assertEqual($node->book['pid'], '0');
+
+    // Test the form itself.
+    $this->drupalGet('node/' . $node->id() . '/edit');
+    $this->assertOptionSelected('edit-book-bid', $node->id());
+  }
+
+  /**
+   * Tests that saveBookLink() returns something.
+   */
+  public function testSaveBookLink() {
+    $book_manager = \Drupal::service('book.manager');
+
+    // Mock a link for a new book.
+    $link = array('nid' => 1, 'has_children' => 0, 'original_bid' => 0, 'parent_depth_limit' => 8, 'pid' => 0, 'weight' => 0, 'bid' => 1);
+    $new = TRUE;
+
+    // Save the link.
+    $return = $book_manager->saveBookLink($link, $new);
+
+    // Add the link defaults to $link so we have something to compare to the return from saveBookLink().
+    $link += $book_manager->getLinkDefaults($link['nid']);
+
+    // Test the return from saveBookLink.
+    $this->assertEqual($return, $link);
+  }
+
+  /**
+   * Tests the listing of all books.
+   */
+  public function testBookListing() {
+    // Create a new book.
+    $this->createBook();
+
+    // Must be a user with 'node test view' permission since node_access_test is installed.
+    $this->drupalLogin($this->webUser);
+
+    // Load the book page and assert the created book title is displayed.
+    $this->drupalGet('book');
+
+    $this->assertText($this->book->label(), 'The book title is displayed on the book listing page.');
+  }
+
+  /**
+   * Tests the administrative listing of all books.
+   */
+  public function testAdminBookListing() {
+    // Create a new book.
+    $this->createBook();
+
+    // Load the book page and assert the created book title is displayed.
+    $this->drupalLogin($this->adminUser);
+    $this->drupalGet('admin/structure/book');
+    $this->assertText($this->book->label(), 'The book title is displayed on the administrative book listing page.');
+  }
+
+  /**
+   * Tests the administrative listing of all book pages in a book.
+   */
+  public function testAdminBookNodeListing() {
+    // Create a new book.
+    $this->createBook();
+    $this->drupalLogin($this->adminUser);
+
+    // Load the book page list and assert the created book title is displayed
+    // and action links are shown on list items.
+    $this->drupalGet('admin/structure/book/' . $this->book->id());
+    $this->assertText($this->book->label(), 'The book title is displayed on the administrative book listing page.');
+
+    $elements = $this->xpath('//table//ul[@class="dropbutton"]/li/a');
+    $this->assertEqual((string) $elements[0], 'View', 'View link is found from the list.');
+  }
+
+  /**
+   * Ensure the loaded book in hook_node_load() does not depend on the user.
+   */
+  public function testHookNodeLoadAccess() {
+    \Drupal::service('module_installer')->install(['node_access_test']);
+
+    // Ensure that the loaded book in hook_node_load() does NOT depend on the
+    // current user.
+    $this->drupalLogin($this->bookAuthor);
+    $this->book = $this->createBookNode('new');
+    // Reset any internal static caching.
+    $node_storage = \Drupal::entityManager()->getStorage('node');
+    $node_storage->resetCache();
+
+    // Login as user without access to the book node, so no 'node test view'
+    // permission.
+    // @see node_access_test_node_grants().
+    $this->drupalLogin($this->webUserWithoutNodeAccess);
+    $book_node = $node_storage->load($this->book->id());
+    $this->assertTrue(!empty($book_node->book));
+    $this->assertEqual($book_node->book['bid'], $this->book->id());
+
+    // Reset the internal cache to retrigger the hook_node_load() call.
+    $node_storage->resetCache();
+
+    $this->drupalLogin($this->webUser);
+    $book_node = $node_storage->load($this->book->id());
+    $this->assertTrue(!empty($book_node->book));
+    $this->assertEqual($book_node->book['bid'], $this->book->id());
+  }
+
+}

core/modules/book/src/Tests/BookUninstallTest.php

@@ -0,0 +1,99 @@
+<?php
+
+/**
+ * @file
+ * Contains \Drupal\book\Tests\BookUninstallTest.
+ */
+
+namespace Drupal\book\Tests;
+
+use Drupal\node\Entity\Node;
+use Drupal\node\Entity\NodeType;
+use Drupal\simpletest\KernelTestBase;
+
+/**
+ * Tests that the Book module cannot be uninstalled if books exist.
+ *
+ * @group book
+ */
+class BookUninstallTest extends KernelTestBase {
+
+  /**
+   * Modules to enable.
+   *
+   * @var array
+   */
+  public static $modules = array('system', 'user', 'field', 'filter', 'text', 'entity_reference', 'node', 'book');
+
+  /**
+   * {@inheritdoc}
+   */
+  protected function setUp() {
+    parent::setUp();
+    $this->installEntitySchema('user');
+    $this->installEntitySchema('node');
+    $this->installSchema('book', array('book'));
+    $this->installSchema('node', array('node_access'));
+    $this->installConfig(array('node', 'book', 'field'));
+    // For uninstall to work.
+    $this->installSchema('user', array('users_data'));
+  }
+
+  /**
+   * Tests the book_system_info_alter() method.
+   */
+  public function testBookUninstall() {
+    // No nodes exist.
+    $validation_reasons = \Drupal::service('module_installer')->validateUninstall(['book']);
+    $this->assertEqual([], $validation_reasons, 'The book module is not required.');
+
+    $content_type = NodeType::create(array(
+      'type' => $this->randomMachineName(),
+      'name' => $this->randomString(),
+    ));
+    $content_type->save();
+    $book_config = $this->config('book.settings');
+    $allowed_types = $book_config->get('allowed_types');
+    $allowed_types[] = $content_type->id();
+    $book_config->set('allowed_types', $allowed_types)->save();
+
+    $node = Node::create(array('type' => $content_type->id()));
+    $node->book['bid'] = 'new';
+    $node->save();
+
+    // One node in a book but not of type book.
+    $validation_reasons = \Drupal::service('module_installer')->validateUninstall(['book']);
+    $this->assertEqual(['To uninstall Book, delete all content that is part of a book'], $validation_reasons['book']);
+
+    $book_node = Node::create(array('type' => 'book'));
+    $book_node->book['bid'] = FALSE;
+    $book_node->save();
+
+    // Two nodes, one in a book but not of type book and one book node (which is
+    // not in a book).
+    $validation_reasons = \Drupal::service('module_installer')->validateUninstall(['book']);
+    $this->assertEqual(['To uninstall Book, delete all content that is part of a book'], $validation_reasons['book']);
+
+    $node->delete();
+    // One node of type book but not actually part of a book.
+    $validation_reasons = \Drupal::service('module_installer')->validateUninstall(['book']);
+    $this->assertEqual(['To uninstall Book, delete all content that has the Book content type'], $validation_reasons['book']);
+
+    $book_node->delete();
+    // No nodes exist therefore the book module is not required.
+    $module_data = _system_rebuild_module_data();
+    $this->assertFalse(isset($module_data['book']->info['required']), 'The book module is not required.');
+
+    $node = Node::create(array('type' => $content_type->id()));
+    $node->save();
+    // One node exists but is not part of a book therefore the book module is
+    // not required.
+    $validation_reasons = \Drupal::service('module_installer')->validateUninstall(['book']);
+    $this->assertEqual([], $validation_reasons, 'The book module is not required.');
+
+    // Uninstall the Book module and check the node type is deleted.
+    \Drupal::service('module_installer')->uninstall(array('book'));
+    $this->assertNull(NodeType::load('book'), "The book node type does not exist.");
+  }
+
+}

core/modules/book/templates/book-all-books-block.html.twig

@@ -0,0 +1,24 @@
+{#
+/**
+ * @file
+ * Default theme implementation for rendering book outlines within a block.
+ *
+ * This template is used only when the block is configured to "show block on all
+ * pages", which presents multiple independent books on all pages.
+ *
+ * Available variables:
+ * - book_menus: Book outlines.
+ *   - id: The parent book ID.
+ *   - title: The parent book title.
+ *   - menu: The top-level book links.
+ *
+ * @see template_preprocess_book_all_books_block()
+ *
+ * @ingroup themeable
+ */
+#}
+{% for book in book_menus %}
+  <nav role="navigation" aria-label="{% trans %}Book outline for {{ book.title }}{% endtrans %}">
+    {{ book.menu }}
+  </nav>
+{% endfor %}

core/modules/book/templates/book-export-html.html.twig

@@ -0,0 +1,47 @@
+{#
+/**
+ * @file
+ * Default theme implementation for printed version of book outline.
+ *
+ * Available variables:
+ * - title: Top level node title.
+ * - head: Header tags.
+ * - language: Language object.
+ * - language_rtl: A flag indicating whether the current display language is a
+ *   right to left language.
+ * - base_url: URL to the home page.
+ * - contents: Nodes within the current outline rendered through
+ *   book-node-export-html.html.twig.
+ *
+ * @see template_preprocess_book_export_html()
+ *
+ * @ingroup themeable
+ */
+#}
+<!DOCTYPE html>
+<html{{ html_attributes }}>
+  <head>
+    <title>{{ title }}</title>
+    {{ page.head }}
+    <base href="{{ base_url }}" />
+    <link type="text/css" rel="stylesheet" href="misc/print.css" />
+  </head>
+  <body>
+    {#
+      The given node is embedded to its absolute depth in a top level section.
+      For example, a child node with depth 2 in the hierarchy is contained in
+      (otherwise empty) div elements corresponding to depth 0 and depth 1. This
+      is intended to support WYSIWYG output - e.g., level 3 sections always look
+      like level 3 sections, no matter their depth relative to the node selected
+      to be exported as printer-friendly HTML.
+    #}
+
+  {% for i in 1..depth-1 if depth > 1 %}
+    <div>
+  {% endfor %}
+  {{ contents }}
+  {% for i in 1..depth-1 if depth > 1 %}
+    </div>
+  {% endfor %}
+  </body>
+</html>

core/modules/book/templates/book-navigation.html.twig

@@ -0,0 +1,57 @@
+{#
+/**
+ * @file
+ * Default theme implementation to navigate books.
+ *
+ * Presented under nodes that are a part of book outlines.
+ *
+ * Available variables:
+ * - tree: The immediate children of the current node rendered as an unordered
+ *   list.
+ * - current_depth: Depth of the current node within the book outline. Provided
+ *   for context.
+ * - prev_url: URL to the previous node.
+ * - prev_title: Title of the previous node.
+ * - parent_url: URL to the parent node.
+ * - parent_title: Title of the parent node. Not printed by default. Provided
+ *   as an option.
+ * - next_url: URL to the next node.
+ * - next_title: Title of the next node.
+ * - has_links: Flags TRUE whenever the previous, parent or next data has a
+ *   value.
+ * - book_id: The book ID of the current outline being viewed. Same as the node
+ *   ID containing the entire outline. Provided for context.
+ * - book_url: The book/node URL of the current outline being viewed. Provided
+ *   as an option. Not used by default.
+ * - book_title: The book/node title of the current outline being viewed.
+ *
+ * @see template_preprocess_book_navigation()
+ *
+ * @ingroup themeable
+ */
+#}
+{% if tree or has_links %}
+  <nav role="navigation" aria-labelledby="book-label-{{ book_id }}">
+    {{ tree }}
+    {% if has_links %}
+      <h2>{{ 'Book traversal links for'|t }} {{ book_title }}</h2>
+      <ul>
+      {% if prev_url %}
+        <li>
+          <a href="{{ prev_url }}" rel="prev" title="{{ 'Go to previous page'|t }}"><b>{{ '‹'|t }}</b> {{ prev_title }}</a>
+        </li>
+      {% endif %}
+      {% if parent_url %}
+        <li>
+          <a href="{{ parent_url }}" title="{{ 'Go to parent page'|t }}">{{ 'Up'|t }}</a>
+        </li>
+      {% endif %}
+      {% if next_url %}
+        <li>
+          <a href="{{ next_url }}" rel="next" title="{{ 'Go to next page'|t }}">{{ next_title }} <b>{{ '›'|t }}</b></a>
+        </li>
+      {% endif %}
+    </ul>
+    {% endif %}
+  </nav>
+{% endif %}

core/modules/book/templates/book-node-export-html.html.twig

@@ -0,0 +1,22 @@
+{#
+/**
+ * @file
+ * Default theme implementation for a single node in a printer-friendly outline.
+ *
+ * Available variables:
+ * - node: Fully loaded node.
+ * - depth: Depth of the current node inside the outline.
+ * - title: Node title.
+ * - content: Node content.
+ * - children: All the child nodes recursively rendered through this file.
+ *
+ * @see template_preprocess_book_node_export_html()
+ *
+ * @ingroup themeable
+ */
+#}
+<article>
+  <h1>{{ title }}</h1>
+  {{ content }}
+  {{ children }}
+</article>

core/modules/book/templates/book-tree.html.twig

@@ -0,0 +1,44 @@
+{#
+/**
+ * @file
+ * Default theme implementation to display a book tree.
+ *
+ * Returns HTML for a wrapper for a book sub-tree.
+ *
+ * Available variables:
+ * - items: A nested list of book items. Each book item contains:
+ *   - attributes: HTML attributes for the book item.
+ *   - below: The book item child items.
+ *   - title: The book link title.
+ *   - url: The book link URL, instance of \Drupal\Core\Url.
+ *
+ * @ingroup themeable
+ */
+#}
+{% import _self as book_tree %}
+
+{#
+  We call a macro which calls itself to render the full tree.
+  @see http://twig.sensiolabs.org/doc/tags/macro.html
+#}
+{{ book_tree.book_links(items, attributes, 0) }}
+
+{% macro book_links(items, attributes, menu_level) %}
+  {% import _self as book_tree %}
+  {% if items %}
+    {% if menu_level == 0 %}
+      <ul{{ attributes }}>
+    {% else %}
+      <ul>
+    {% endif %}
+      {% for item in items %}
+        <li{{ item.attributes }}>
+          {{ link(item.title, item.url) }}
+          {% if item.below %}
+            {{ book_tree.book_links(item.below, attributes, menu_level + 1) }}
+          {% endif %}
+        </li>
+      {% endfor %}
+    </ul>
+  {% endif %}
+{% endmacro %}

core/modules/book/tests/src/Unit/BookManagerTest.php

@@ -0,0 +1,122 @@
+<?php
+
+/**
+ * @file
+ * Contains \Drupal\Tests\book\Unit\BookManagerTest.
+ */
+
+namespace Drupal\Tests\book\Unit;
+
+use Drupal\book\BookManager;
+use Drupal\Tests\UnitTestCase;
+
+/**
+ * @coversDefaultClass \Drupal\book\BookManager
+ * @group book
+ */
+class BookManagerTest extends UnitTestCase {
+
+  /**
+   * The mocked entity manager.
+   *
+   * @var \Drupal\Core\Entity\EntityManager|\PHPUnit_Framework_MockObject_MockObject
+   */
+  protected $entityManager;
+
+  /**
+   * The mocked config factory.
+   *
+   * @var \Drupal\Core\Config\ConfigFactory|\PHPUnit_Framework_MockObject_MockObject
+   */
+  protected $configFactory;
+
+  /**
+   * The mocked translation manager.
+   *
+   * @var \Drupal\Core\StringTranslation\TranslationInterface|\PHPUnit_Framework_MockObject_MockObject
+   */
+  protected $translation;
+
+  /**
+   * The mocked renderer.
+   *
+   * @var \Drupal\Core\Render\RendererInterface|\PHPUnit_Framework_MockObject_MockObject
+   */
+  protected $renderer;
+
+  /**
+   * The tested book manager.
+   *
+   * @var \Drupal\book\BookManager
+   */
+  protected $bookManager;
+
+  /**
+   * Book outline storage.
+   *
+   * @var \Drupal\book\BookOutlineStorageInterface
+   */
+  protected $bookOutlineStorage;
+
+  /**
+   * {@inheritdoc}
+   */
+  protected function setUp() {
+    $this->entityManager = $this->getMock('Drupal\Core\Entity\EntityManagerInterface');
+    $this->translation = $this->getStringTranslationStub();
+    $this->configFactory = $this->getConfigFactoryStub(array());
+    $this->bookOutlineStorage = $this->getMock('Drupal\book\BookOutlineStorageInterface');
+    $this->renderer = $this->getMock('\Drupal\Core\Render\RendererInterface');
+    $this->bookManager = new BookManager($this->entityManager, $this->translation, $this->configFactory, $this->bookOutlineStorage, $this->renderer);
+  }
+
+  /**
+   * Tests the getBookParents() method.
+   *
+   * @dataProvider providerTestGetBookParents
+   */
+  public function testGetBookParents($book, $parent, $expected) {
+    $this->assertEquals($expected, $this->bookManager->getBookParents($book, $parent));
+  }
+
+  /**
+   * Provides test data for testGetBookParents.
+   *
+   * @return array
+   *   The test data.
+   */
+  public function providerTestGetBookParents() {
+    $empty = array(
+      'p1' => 0,
+      'p2' => 0,
+      'p3' => 0,
+      'p4' => 0,
+      'p5' => 0,
+      'p6' => 0,
+      'p7' => 0,
+      'p8' => 0,
+      'p9' => 0,
+    );
+    return array(
+      // Provides a book without an existing parent.
+      array(
+        array('pid' => 0, 'nid' => 12),
+        array(),
+        array('depth' => 1, 'p1' => 12) + $empty,
+      ),
+      // Provides a book with an existing parent.
+      array(
+        array('pid' => 11, 'nid' => 12),
+        array('nid' => 11, 'depth' => 1, 'p1' => 11,),
+        array('depth' => 2, 'p1' => 11, 'p2' => 12) + $empty,
+      ),
+      // Provides a book with two existing parents.
+      array(
+        array('pid' => 11, 'nid' => 12),
+        array('nid' => 11, 'depth' => 2, 'p1' => 10, 'p2' => 11),
+        array('depth' => 3, 'p1' => 10, 'p2' => 11, 'p3' => 12) + $empty,
+      ),
+    );
+  }
+
+}

core/modules/book/tests/src/Unit/BookUninstallValidatorTest.php

@@ -0,0 +1,100 @@
+<?php
+
+/**
+ * @file
+ * Contains \Drupal\Tests\book\Unit\BookUninstallValidatorTest.
+ */
+
+namespace Drupal\Tests\book\Unit;
+
+use Drupal\Tests\UnitTestCase;
+
+/**
+ * @coversDefaultClass \Drupal\book\BookUninstallValidator
+ * @group book
+ */
+class BookUninstallValidatorTest extends UnitTestCase {
+
+  /**
+   * @var \Drupal\book\BookUninstallValidator|\PHPUnit_Framework_MockObject_MockObject
+   */
+  protected $bookUninstallValidator;
+
+  /**
+   * {@inheritdoc}
+   */
+  protected function setUp() {
+    parent::setUp();
+    $this->bookUninstallValidator = $this->getMockBuilder('Drupal\book\BookUninstallValidator')
+      ->disableOriginalConstructor()
+      ->setMethods(['hasBookOutlines', 'hasBookNodes'])
+      ->getMock();
+    $this->bookUninstallValidator->setStringTranslation($this->getStringTranslationStub());
+  }
+
+  /**
+   * @covers ::validate
+   */
+  public function testValidateNotBook() {
+    $this->bookUninstallValidator->expects($this->never())
+      ->method('hasBookOutlines');
+    $this->bookUninstallValidator->expects($this->never())
+      ->method('hasBookNodes');
+
+    $module = 'not_book';
+    $expected = [];
+    $reasons = $this->bookUninstallValidator->validate($module);
+    $this->assertSame($expected, $reasons);
+  }
+
+  /**
+   * @covers ::validate
+   */
+  public function testValidateEntityQueryWithoutResults() {
+    $this->bookUninstallValidator->expects($this->once())
+      ->method('hasBookOutlines')
+      ->willReturn(FALSE);
+    $this->bookUninstallValidator->expects($this->once())
+      ->method('hasBookNodes')
+      ->willReturn(FALSE);
+
+    $module = 'book';
+    $expected = [];
+    $reasons = $this->bookUninstallValidator->validate($module);
+    $this->assertSame($expected, $reasons);
+  }
+
+  /**
+   * @covers ::validate
+   */
+  public function testValidateEntityQueryWithResults() {
+    $this->bookUninstallValidator->expects($this->once())
+      ->method('hasBookOutlines')
+      ->willReturn(FALSE);
+    $this->bookUninstallValidator->expects($this->once())
+      ->method('hasBookNodes')
+      ->willReturn(TRUE);
+
+    $module = 'book';
+    $expected = ['To uninstall Book, delete all content that has the Book content type'];
+    $reasons = $this->bookUninstallValidator->validate($module);
+    $this->assertSame($expected, $reasons);
+  }
+
+  /**
+   * @covers ::validate
+   */
+  public function testValidateOutlineStorage() {
+    $this->bookUninstallValidator->expects($this->once())
+      ->method('hasBookOutlines')
+      ->willReturn(TRUE);
+    $this->bookUninstallValidator->expects($this->never())
+      ->method('hasBookNodes');
+
+    $module = 'book';
+    $expected = ['To uninstall Book, delete all content that is part of a book'];
+    $reasons = $this->bookUninstallValidator->validate($module);
+    $this->assertSame($expected, $reasons);
+  }
+
+}

core/modules/book/tests/src/Unit/Menu/BookLocalTasksTest.php

@@ -0,0 +1,70 @@
+<?php
+
+/**
+ * @file
+ * Contains \Drupal\Tests\book\Unit\Menu\BookLocalTasksTest.
+ */
+
+namespace Drupal\Tests\book\Unit\Menu;
+
+use Drupal\Tests\Core\Menu\LocalTaskIntegrationTestBase;
+
+/**
+ * Tests existence of book local tasks.
+ *
+ * @group book
+ */
+class BookLocalTasksTest extends LocalTaskIntegrationTestBase {
+
+  protected function setUp() {
+    $this->directoryList = array(
+      'book' => 'core/modules/book',
+      'node' => 'core/modules/node',
+    );
+    parent::setUp();
+  }
+
+  /**
+   * Tests local task existence.
+   *
+   * @dataProvider getBookAdminRoutes
+   */
+  public function testBookAdminLocalTasks($route) {
+
+    $this->assertLocalTasks($route, array(
+      0 => array('book.admin', 'book.settings'),
+    ));
+  }
+
+  /**
+   * Provides a list of routes to test.
+   */
+  public function getBookAdminRoutes() {
+    return array(
+      array('book.admin'),
+      array('book.settings'),
+    );
+  }
+
+  /**
+   * Tests local task existence.
+   *
+   * @dataProvider getBookNodeRoutes
+   */
+  public function testBookNodeLocalTasks($route) {
+    $this->assertLocalTasks($route, array(
+      0 => array('entity.node.book_outline_form', 'entity.node.canonical', 'entity.node.edit_form', 'entity.node.delete_form', 'entity.node.version_history',),
+    ));
+  }
+
+  /**
+   * Provides a list of routes to test.
+   */
+  public function getBookNodeRoutes() {
+    return array(
+      array('entity.node.canonical'),
+      array('entity.node.book_outline_form'),
+    );
+  }
+
+}