drupal/core/modules/taxonomy/taxonomy.module

<?php

/**
 * @file
 * Enables the organization of content into categories.
 */

use Drupal\Component\Utility\Tags;
use Drupal\Component\Utility\Unicode;
use Drupal\Core\Entity\Sql\SqlContentEntityStorage;
use Drupal\Core\Entity\EntityInterface;
use Drupal\Core\Render\Element;
use Drupal\Core\Routing\RouteMatchInterface;
use Drupal\Core\Url;
use Drupal\taxonomy\Entity\Term;
use Drupal\taxonomy\Entity\Vocabulary;
use Drupal\taxonomy\TermInterface;
use Drupal\taxonomy\VocabularyInterface;

/**
 * Denotes that no term in the vocabulary has a parent.
 */
const TAXONOMY_HIERARCHY_DISABLED = 0;

/**
 * Denotes that one or more terms in the vocabulary has a single parent.
 */
const TAXONOMY_HIERARCHY_SINGLE = 1;

/**
 * Denotes that one or more terms in the vocabulary have multiple parents.
 */
const TAXONOMY_HIERARCHY_MULTIPLE = 2;

/**
 * Implements hook_help().
 */
function taxonomy_help($route_name, RouteMatchInterface $route_match) {
  switch ($route_name) {
    case 'help.page.taxonomy':
      $field_ui_url = \Drupal::moduleHandler()->moduleExists('field_ui') ? \Drupal::url('help.page', array('name' => 'field_ui')) : '#';
      $output = '';
      $output .= '<h3>' . t('About') . '</h3>';
      $output .= '<p>' . t('The Taxonomy module allows users who have permission to create and edit content to categorize (tag) content of that type. Users who have the <em>Administer vocabularies and terms</em> <a href=":permissions" title="Taxonomy module permissions">permission</a> can add <em>vocabularies</em> that contain a set of related <em>terms</em>. The terms in a vocabulary can either be pre-set by an administrator or built gradually as content is added and edited. Terms may be organized hierarchically if desired.', array(':permissions' => \Drupal::url('user.admin_permissions', array(), array('fragment' => 'module-taxonomy')))) . '</p>';
      $output .= '<p>' . t('For more information, see the <a href=":taxonomy">online documentation for the Taxonomy module</a>.', array(':taxonomy' => 'https://www.drupal.org/documentation/modules/taxonomy/')) . '</p>';
      $output .= '<h3>' . t('Uses') . '</h3>';
      $output .= '<dl>';
      $output .= '<dt>' . t('Managing vocabularies') . '</dt>';
      $output .= '<dd>' . t('Users who have the <em>Administer vocabularies and terms</em> permission can add and edit vocabularies from the <a href=":taxonomy_admin">Taxonomy administration page</a>. Vocabularies can be deleted from their <em>Edit vocabulary</em> page. Users with the <em>Taxonomy term: Administer fields</em> permission may add additional fields for terms in that vocabulary using the <a href=":field_ui">Field UI module</a>.', array(':taxonomy_admin' => \Drupal::url('entity.taxonomy_vocabulary.collection'), ':field_ui' => $field_ui_url)) . '</dd>';
      $output .= '<dt>' . t('Managing terms') . '</dt>';
      $output .= '<dd>' . t('Users who have the <em>Administer vocabularies and terms</em> permission or the <em>Edit terms</em> permission for a particular vocabulary can add, edit, and organize the terms in a vocabulary from a vocabulary\'s term listing page, which can be accessed by going to the <a href=":taxonomy_admin">Taxonomy administration page</a> and clicking <em>List terms</em> in the <em>Operations</em> column. Users must have the <em>Administer vocabularies and terms</em> permission or the <em>Delete terms</em> permission for a particular vocabulary to delete terms.', array(':taxonomy_admin' => \Drupal::url('entity.taxonomy_vocabulary.collection'))) . ' </dd>';
      $output .= '<dt>' . t('Classifying entity content') . '</dt>';
      $output .= '<dd>' . t('A user with the <em>Administer fields</em> permission for a certain entity type may add <em>Taxonomy term</em> reference fields to the entity type, which will allow entities to be classified using taxonomy terms. See the <a href=":entity_reference">Entity Reference help</a> for more information about reference fields. See the <a href=":field">Field module help</a> and the <a href=":field_ui">Field UI help</a> pages for general information on fields and how to create and manage them.', array(':field_ui' => $field_ui_url, ':field' => \Drupal::url('help.page', array('name' => 'field')), ':entity_reference' => \Drupal::url('help.page', array('name' => 'entity_reference')))) . '</dd>';
      $output .= '<dt>' . t('Adding new terms during content creation') . '</dt>';
      $output .= '<dd>' . t('Allowing users to add new terms gradually builds a vocabulary as content is added and edited. Users can add new terms if either of the two <em>Autocomplete</em> widgets is chosen for the Taxonomy term reference field in the <em>Manage form display</em> page for the field. You will also need to enable the <em>Create referenced entities if they don\'t already exist</em> option, and restrict the field to one vocabulary.') . '</dd>';
      $output .= '<dt>' . t('Configuring displays and form displays') . '</dt>';
      $output .= '<dd>' . t('See the <a href=":entity_reference">Entity Reference help</a> page for the field widgets and formatters that can be configured for any reference field on the <em>Manage display</em> and <em>Manage form display</em> pages. Taxonomy additionally provides an <em>RSS category</em> formatter that displays nothing when the entity item is displayed as HTML, but displays an RSS category instead of a list when the entity item is displayed in an RSS feed.', array(':entity_reference' => \Drupal::url('help.page', array('name' => 'entity_reference')))) . '</li>';
      $output .= '</ul>';
      $output .= '</dd>';
      $output .= '</dl>';
      return $output;

    case 'entity.taxonomy_vocabulary.collection':
      $output = '<p>' . t('Taxonomy is for categorizing content. Terms are grouped into vocabularies. For example, a vocabulary called "Fruit" would contain the terms "Apple" and "Banana".') . '</p>';
      return $output;

    case 'entity.taxonomy_vocabulary.overview_form':
      $vocabulary = $route_match->getParameter('taxonomy_vocabulary');
      switch ($vocabulary->getHierarchy()) {
        case TAXONOMY_HIERARCHY_DISABLED:
          return '<p>' . t('You can reorganize the terms in %capital_name using their drag-and-drop handles, and group terms under a parent term by sliding them under and to the right of the parent.', array('%capital_name' => Unicode::ucfirst($vocabulary->label()), '%name' => $vocabulary->label())) . '</p>';
        case TAXONOMY_HIERARCHY_SINGLE:
          return '<p>' . t('%capital_name contains terms grouped under parent terms. You can reorganize the terms in %capital_name using their drag-and-drop handles.', array('%capital_name' => Unicode::ucfirst($vocabulary->label()), '%name' => $vocabulary->label())) . '</p>';
        case TAXONOMY_HIERARCHY_MULTIPLE:
          return '<p>' . t('%capital_name contains terms with multiple parents. Drag and drop of terms with multiple parents is not supported, but you can re-enable drag-and-drop support by editing each term to include only a single parent.', array('%capital_name' => Unicode::ucfirst($vocabulary->label()))) . '</p>';
      }
  }
}

/**
 * Entity URI callback.
 */
function taxonomy_term_uri($term) {
  return new Url('entity.taxonomy_term.canonical', array(
    'taxonomy_term' => $term->id(),
  ));
}

/**
 * Implements hook_page_attachments_alter().
 */
function taxonomy_page_attachments_alter(array &$page) {
  $route_match = \Drupal::routeMatch();
  if ($route_match->getRouteName() == 'entity.taxonomy_term.canonical' && ($term = $route_match->getParameter('taxonomy_term')) && $term instanceof TermInterface) {
    foreach ($term->uriRelationships() as $rel) {
      // Set the URI relationships, like canonical.
      $page['#attached']['html_head_link'][] = array(
        array(
          'rel' => $rel,
          'href' => $term->url($rel),
        ),
        TRUE,
      );

      // Set the term path as the canonical URL to prevent duplicate content.
      if ($rel == 'canonical') {
        // Set the non-aliased canonical path as a default shortlink.
        $page['#attached']['html_head_link'][] = array(
          array(
            'rel' => 'shortlink',
            'href' => $term->url($rel, array('alias' => TRUE)),
          ),
          TRUE,
        );
      }
    }
  }
}

/**
 * Implements hook_theme().
 */
function taxonomy_theme() {
  return array(
    'taxonomy_term' => array(
      'render element' => 'elements',
    ),
  );
}

/**
 * Checks and updates the hierarchy flag of a vocabulary.
 *
 * Checks the current parents of all terms in a vocabulary and updates the
 * vocabulary's hierarchy setting to the lowest possible level. If no term
 * has parent terms then the vocabulary will be given a hierarchy of
 * TAXONOMY_HIERARCHY_DISABLED. If any term has a single parent then the
 * vocabulary will be given a hierarchy of TAXONOMY_HIERARCHY_SINGLE. If any
 * term has multiple parents then the vocabulary will be given a hierarchy of
 * TAXONOMY_HIERARCHY_MULTIPLE.
 *
 * @param \Drupal\taxonomy\VocabularyInterface $vocabulary
 *   A taxonomy vocabulary entity.
 * @param $changed_term
 *   An array of the term structure that was updated.
 *
 * @return
 *   An integer that represents the level of the vocabulary's hierarchy.
 */
function taxonomy_check_vocabulary_hierarchy(VocabularyInterface $vocabulary, $changed_term) {
  $tree = \Drupal::entityManager()->getStorage('taxonomy_term')->loadTree($vocabulary->id());
  $hierarchy = TAXONOMY_HIERARCHY_DISABLED;
  foreach ($tree as $term) {
    // Update the changed term with the new parent value before comparison.
    if ($term->tid == $changed_term['tid']) {
      $term = (object) $changed_term;
      $term->parents = $term->parent;
    }
    // Check this term's parent count.
    if (count($term->parents) > 1) {
      $hierarchy = TAXONOMY_HIERARCHY_MULTIPLE;
      break;
    }
    elseif (count($term->parents) == 1 && !isset($term->parents[0])) {
      $hierarchy = TAXONOMY_HIERARCHY_SINGLE;
    }
  }
  if ($hierarchy != $vocabulary->getHierarchy()) {
    $vocabulary->setHierarchy($hierarchy);
    $vocabulary->save();
  }

  return $hierarchy;
}

/**
 * Generates an array which displays a term detail page.
 *
 * @param \Drupal\taxonomy\Entity\Term $term
 *   A taxonomy term object.
 * @param string $view_mode
 *   View mode; e.g., 'full', 'teaser', etc.
 * @param string $langcode
 *   (optional) A language code to use for rendering. Defaults to the global
 *   content language of the current request.
 *
 * @return array
 *   A $page element suitable for use by drupal_render().
 */
function taxonomy_term_view(Term $term, $view_mode = 'full', $langcode = NULL) {
  return entity_view($term, $view_mode, $langcode);
}

/**
 * Constructs a drupal_render() style array from an array of loaded terms.
 *
 * @param array $terms
 *   An array of taxonomy terms as returned by Term::loadMultiple().
 * @param string $view_mode
 *   View mode; e.g., 'full', 'teaser', etc.
 * @param string $langcode
 *   (optional) A language code to use for rendering. Defaults to the global
 *   content language of the current request.
 *
 * @return array
 *   An array in the format expected by drupal_render().
 */
function taxonomy_term_view_multiple(array $terms, $view_mode = 'full', $langcode = NULL) {
  return entity_view_multiple($terms, $view_mode, $langcode);
}

/**
 * Implements hook_theme_suggestions_HOOK().
 */
function taxonomy_theme_suggestions_taxonomy_term(array $variables) {
  $suggestions = array();

  /** @var \Drupal\taxonomy\TermInterface $term */
  $term = $variables['elements']['#taxonomy_term'];

  $suggestions[] = 'taxonomy_term__' . $term->bundle();
  $suggestions[] = 'taxonomy_term__' . $term->id();

  return $suggestions;
}

/**
 * Prepares variables for taxonomy term templates.
 *
 * Default template: taxonomy-term.html.twig.
 *
 * @param array $variables
 *   An associative array containing:
 *   - elements: An associative array containing the taxonomy term and any
 *     fields attached to the term. Properties used:
 *     - #taxonomy_term: A \Drupal\taxonomy\TermInterface object.
 *     - #view_mode: The current view mode for this taxonomy term, e.g.
 *       'full' or 'teaser'.
 *   - attributes: HTML attributes for the containing element.
 */
function template_preprocess_taxonomy_term(&$variables) {
  $variables['view_mode'] = $variables['elements']['#view_mode'];
  $variables['term'] = $variables['elements']['#taxonomy_term'];
  /** @var \Drupal\taxonomy\TermInterface $term */
  $term = $variables['term'];

  $variables['url'] = $term->url();
  // We use name here because that is what appears in the UI.
  $variables['name'] = $variables['elements']['name'];
  unset($variables['elements']['name']);
  $variables['page'] = $variables['view_mode'] == 'full' && taxonomy_term_is_page($term);

  // Helpful $content variable for templates.
  $variables['content'] = array();
  foreach (Element::children($variables['elements']) as $key) {
    $variables['content'][$key] = $variables['elements'][$key];
  }
}

/**
 * Returns whether the current page is the page of the passed-in term.
 *
 * @param \Drupal\taxonomy\Entity\Term $term
 *   A taxonomy term entity.
 */
function taxonomy_term_is_page(Term $term) {
  if (\Drupal::routeMatch()->getRouteName() == 'entity.taxonomy_term.canonical' && $page_term_id = \Drupal::routeMatch()->getRawParameter('taxonomy_term')) {
    return $page_term_id == $term->id();
  }
  return FALSE;
}

/**
 * Clear all static cache variables for terms.
 */
function taxonomy_terms_static_reset() {
  \Drupal::entityManager()->getStorage('taxonomy_term')->resetCache();
}

/**
 * Clear all static cache variables for vocabularies.
 *
 * @param $ids
 *   An array of ids to reset in the entity cache.
 */
function taxonomy_vocabulary_static_reset(array $ids = NULL) {
  \Drupal::entityManager()->getStorage('taxonomy_vocabulary')->resetCache($ids);
}

/**
 * Get names for all taxonomy vocabularies.
 *
 * @return array
 *   A list of existing vocabulary IDs.
 */
function taxonomy_vocabulary_get_names() {
  $names = &drupal_static(__FUNCTION__);

  if (!isset($names)) {
    $names = array();
    $config_names = \Drupal::configFactory()->listAll('taxonomy.vocabulary.');
    foreach ($config_names as $config_name) {
      $id = substr($config_name, strlen('taxonomy.vocabulary.'));
      $names[$id] = $id;
    }
  }

  return $names;
}

/**
 * Try to map a string to an existing term, as for glossary use.
 *
 * Provides a case-insensitive and trimmed mapping, to maximize the
 * likelihood of a successful match.
 *
 * @param $name
 *   Name of the term to search for.
 * @param $vocabulary
 *   (optional) Vocabulary machine name to limit the search. Defaults to NULL.
 *
 * @return
 *   An array of matching term objects.
 */
function taxonomy_term_load_multiple_by_name($name, $vocabulary = NULL) {
  $values = array('name' => trim($name));
  if (isset($vocabulary)) {
    $vocabularies = taxonomy_vocabulary_get_names();
    if (isset($vocabularies[$vocabulary])) {
      $values['vid'] = $vocabulary;
    }
    else {
      // Return an empty array when filtering by a non-existing vocabulary.
      return array();
    }
  }
  return entity_load_multiple_by_properties('taxonomy_term', $values);
}

/**
 * Load multiple taxonomy terms based on certain conditions.
 *
 * This function should be used whenever you need to load more than one term
 * from the database. Terms are loaded into memory and will not require
 * database access if loaded again during the same page request.
 *
 * @see entity_load_multiple()
 * @see \Drupal\Core\Entity\Query\EntityQueryInterface
 *
 * @deprecated in Drupal 8.x, will be removed before Drupal 9.0.
 *   Use \Drupal\taxonomy\Entity\Term::loadMultiple().
 *
 * @param array $tids
 *   (optional) An array of entity IDs. If omitted, all entities are loaded.
 *
 * @return array
 *   An array of taxonomy term entities, indexed by tid. When no results are
 *   found, an empty array is returned.
 */
function taxonomy_term_load_multiple(array $tids = NULL) {
  return Term::loadMultiple($tids);
}

/**
 * Loads multiple taxonomy vocabularies based on certain conditions.
 *
 * This function should be used whenever you need to load more than one
 * vocabulary from the database. Terms are loaded into memory and will not
 * require database access if loaded again during the same page request.
 *
 * @see entity_load_multiple()
 *
 * @deprecated in Drupal 8.x, will be removed before Drupal 9.0.
 *   Use \Drupal\taxonomy\Entity\Vocabulary::loadMultiple().
 *
 * @param array $vids
 *   (optional) An array of entity IDs. If omitted, all entities are loaded.
 *
 * @return array
 *   An array of vocabulary objects, indexed by vid.
 */
function taxonomy_vocabulary_load_multiple(array $vids = NULL) {
  return Vocabulary::loadMultiple($vids);
}

/**
 * Return the taxonomy vocabulary entity matching a vocabulary ID.
 *
 * @deprecated in Drupal 8.x, will be removed before Drupal 9.0.
 *   Use \Drupal\taxonomy\Entity\Vocabulary::load().
 *
 * @param int $vid
 *   The vocabulary's ID.
 *
 * @return \Drupal\taxonomy\Entity\Vocabulary|null
 *   The taxonomy vocabulary entity, if exists, NULL otherwise. Results are
 *   statically cached.
 */
function taxonomy_vocabulary_load($vid) {
  return Vocabulary::load($vid);
}

/**
 * Return the taxonomy term entity matching a term ID.
 *
 * @deprecated in Drupal 8.x, will be removed before Drupal 9.0.
 *   Use \Drupal\taxonomy\Entity\Term::load().
 *
 * @param $tid
 *   A term's ID
 *
 * @return \Drupal\taxonomy\Entity\Term|null
 *   A taxonomy term entity, or NULL if the term was not found. Results are
 *   statically cached.
 */
function taxonomy_term_load($tid) {
  if (!is_numeric($tid)) {
    return NULL;
  }
  return Term::load($tid);
}

/**
 * Implodes a list of tags of a certain vocabulary into a string.
 *
 * @see \Drupal\Component\Utility\Tags::explode()
 */
function taxonomy_implode_tags($tags, $vid = NULL) {
  $typed_tags = array();
  foreach ($tags as $tag) {
    // Extract terms belonging to the vocabulary in question.
    if (!isset($vid) || $tag->bundle() == $vid) {
      // Make sure we have a completed loaded taxonomy term.
      if ($tag instanceof EntityInterface && $label = $tag->label()) {
        // Commas and quotes in tag names are special cases, so encode 'em.
        $typed_tags[] = Tags::encode($label);
      }
    }
  }
  return implode(', ', $typed_tags);
}

/**
 * Title callback for term pages.
 *
 * @param \Drupal\taxonomy\Entity\Term $term
 *   A taxonomy term entity.
 *
 * @return
 *   The term name to be used as the page title.
 */
function taxonomy_term_title(Term $term) {
  return $term->getName();
}

/**
 * @defgroup taxonomy_index Taxonomy indexing
 * @{
 * Functions to maintain taxonomy indexing.
 *
 * Taxonomy uses default field storage to store canonical relationships
 * between terms and fieldable entities. However its most common use case
 * requires listing all content associated with a term or group of terms
 * sorted by creation date. To avoid slow queries due to joining across
 * multiple node and field tables with various conditions and order by criteria,
 * we maintain a denormalized table with all relationships between terms,
 * published nodes and common sort criteria such as status, sticky and created.
 * When using other field storage engines or alternative methods of
 * denormalizing this data you should set the
 * taxonomy.settings:maintain_index_table to '0' to avoid unnecessary writes in
 * SQL.
 */

/**
 * Implements hook_ENTITY_TYPE_insert() for node entities.
 */
function taxonomy_node_insert(EntityInterface $node) {
  // Add taxonomy index entries for the node.
  taxonomy_build_node_index($node);
}

/**
 * Builds and inserts taxonomy index entries for a given node.
 *
 * The index lists all terms that are related to a given node entity, and is
 * therefore maintained at the entity level.
 *
 * @param \Drupal\node\Entity\Node $node
 *   The node entity.
 */
function taxonomy_build_node_index($node) {
  // We maintain a denormalized table of term/node relationships, containing
  // only data for current, published nodes.
  if (!\Drupal::config('taxonomy.settings')->get('maintain_index_table') || !(\Drupal::entityManager()->getStorage('node') instanceof SqlContentEntityStorage)) {
    return;
  }

  $status = $node->isPublished();
  $sticky = (int) $node->isSticky();
  // We only maintain the taxonomy index for published nodes.
  if ($status && $node->isDefaultRevision()) {
    // Collect a unique list of all the term IDs from all node fields.
    $tid_all = array();
    $entity_reference_class = 'Drupal\Core\Field\Plugin\Field\FieldType\EntityReferenceItem';
    foreach ($node->getFieldDefinitions() as $field) {
      $field_name = $field->getName();
      $class = $field->getItemDefinition()->getClass();
      $is_entity_reference_class = ($class === $entity_reference_class) || is_subclass_of($class, $entity_reference_class);
      if ($is_entity_reference_class && $field->getSetting('target_type') == 'taxonomy_term') {
        foreach ($node->getTranslationLanguages() as $language) {
          foreach ($node->getTranslation($language->getId())->$field_name as $item) {
            if (!$item->isEmpty()) {
              $tid_all[$item->target_id] = $item->target_id;
            }
          }
        }
      }
    }
    // Insert index entries for all the node's terms.
    if (!empty($tid_all)) {
      foreach ($tid_all as $tid) {
        db_merge('taxonomy_index')
          ->key(array('nid' => $node->id(), 'tid' => $tid, 'status' => $node->isPublished()))
          ->fields(array('sticky' => $sticky, 'created' => $node->getCreatedTime()))
          ->execute();
      }
    }
  }
}

/**
 * Implements hook_ENTITY_TYPE_update() for node entities.
 */
function taxonomy_node_update(EntityInterface $node) {
  // If we're not dealing with the default revision of the node, do not make any
  // change to the taxonomy index.
  if (!$node->isDefaultRevision()) {
    return;
  }
  taxonomy_delete_node_index($node);
  taxonomy_build_node_index($node);
}

/**
 * Implements hook_ENTITY_TYPE_predelete() for node entities.
 */
function taxonomy_node_predelete(EntityInterface $node) {
  // Clean up the {taxonomy_index} table when nodes are deleted.
  taxonomy_delete_node_index($node);
}

/**
 * Deletes taxonomy index entries for a given node.
 *
 * @param \Drupal\Core\Entity\EntityInterface $node
 *   The node entity.
 */
function taxonomy_delete_node_index(EntityInterface $node) {
  if (\Drupal::config('taxonomy.settings')->get('maintain_index_table')) {
    db_delete('taxonomy_index')->condition('nid', $node->id())->execute();
  }
}

/**
 * Implements hook_ENTITY_TYPE_delete() for taxonomy_term entities.
 */
function taxonomy_taxonomy_term_delete(Term $term) {
  if (\Drupal::config('taxonomy.settings')->get('maintain_index_table')) {
    // Clean up the {taxonomy_index} table when terms are deleted.
    db_delete('taxonomy_index')->condition('tid', $term->id())->execute();
  }
}

/**
 * @} End of "defgroup taxonomy_index".
 */