drupal/core/modules/layout_builder/layout_builder.module

<?php

/**
 * @file
 * Provides hook implementations for Layout Builder.
 */

use Drupal\Core\Entity\EntityInterface;
use Drupal\Core\Form\FormStateInterface;
use Drupal\Core\Routing\RouteMatchInterface;
use Drupal\Core\Url;
use Drupal\field\FieldConfigInterface;
use Drupal\layout_builder\Entity\LayoutBuilderEntityViewDisplay;
use Drupal\layout_builder\Entity\LayoutBuilderEntityViewDisplayStorage;
use Drupal\layout_builder\Form\LayoutBuilderEntityViewDisplayForm;
use Drupal\Core\Entity\Display\EntityViewDisplayInterface;
use Drupal\layout_builder\Entity\LayoutEntityDisplayInterface;
use Drupal\layout_builder\Plugin\Block\ExtraFieldBlock;
use Drupal\layout_builder\InlineBlockEntityOperations;
use Drupal\Core\Session\AccountInterface;
use Drupal\Core\Access\AccessResult;
use Drupal\layout_builder\Plugin\SectionStorage\OverridesSectionStorage;

/**
 * Implements hook_help().
 */
function layout_builder_help($route_name, RouteMatchInterface $route_match) {
  // Add help text to the Layout Builder UI.
  if ($route_match->getRouteObject()->getOption('_layout_builder')) {
    $output = '<p>' . t('This layout builder tool allows you to configure the layout of the main content area.') . '</p>';
    if (\Drupal::currentUser()->hasPermission('administer blocks')) {
      $output .= '<p>' . t('To manage other areas of the page, use the <a href="@block-ui">block administration page</a>.', ['@block-ui' => Url::fromRoute('block.admin_display')->toString()]) . '</p>';
    }
    else {
      $output .= '<p>' . t('To manage other areas of the page, use the block administration page.') . '</p>';
    }
    return $output;
  }

  switch ($route_name) {
    case 'help.page.layout_builder':
      $output = '<h3>' . t('About') . '</h3>';
      $output .= '<p>' . t('Layout Builder provides layout building utility.') . '</p>';
      $output .= '<p>' . t('For more information, see the <a href=":layout-builder-documentation">online documentation for the Layout Builder module</a>.', [':layout-builder-documentation' => 'https://www.drupal.org/docs/8/core/modules/layout_builder']) . '</p>';
      return $output;
  }
}

/**
 * Implements hook_entity_type_alter().
 */
function layout_builder_entity_type_alter(array &$entity_types) {
  /** @var \Drupal\Core\Entity\EntityTypeInterface[] $entity_types */
  $entity_types['entity_view_display']
    ->setClass(LayoutBuilderEntityViewDisplay::class)
    ->setStorageClass(LayoutBuilderEntityViewDisplayStorage::class)
    ->setFormClass('edit', LayoutBuilderEntityViewDisplayForm::class);
}

/**
 * Implements hook_form_FORM_ID_alter() for \Drupal\field_ui\Form\EntityFormDisplayEditForm.
 */
function layout_builder_form_entity_form_display_edit_form_alter(&$form, FormStateInterface $form_state) {
  // Hides the Layout Builder field. It is rendered directly in
  // \Drupal\layout_builder\Entity\LayoutBuilderEntityViewDisplay::buildMultiple().
  unset($form['fields'][OverridesSectionStorage::FIELD_NAME]);
  $key = array_search(OverridesSectionStorage::FIELD_NAME, $form['#fields']);
  if ($key !== FALSE) {
    unset($form['#fields'][$key]);
  }
}

/**
 * Implements hook_field_config_insert().
 */
function layout_builder_field_config_insert(FieldConfigInterface $field_config) {
  // Clear the sample entity for this entity type and bundle.
  $sample_entity_generator = \Drupal::service('layout_builder.sample_entity_generator');
  $sample_entity_generator->delete($field_config->getTargetEntityTypeId(), $field_config->getTargetBundle());
  \Drupal::service('plugin.manager.block')->clearCachedDefinitions();
}

/**
 * Implements hook_field_config_delete().
 */
function layout_builder_field_config_delete(FieldConfigInterface $field_config) {
  // Clear the sample entity for this entity type and bundle.
  $sample_entity_generator = \Drupal::service('layout_builder.sample_entity_generator');
  $sample_entity_generator->delete($field_config->getTargetEntityTypeId(), $field_config->getTargetBundle());
  \Drupal::service('plugin.manager.block')->clearCachedDefinitions();
}

/**
 * Implements hook_entity_view_alter().
 *
 * ExtraFieldBlock block plugins add placeholders for each extra field which is
 * configured to be displayed. Those placeholders are replaced by this hook.
 * Modules that implement hook_entity_extra_field_info() use their
 * implementations of hook_entity_view_alter() to add the rendered output of
 * the extra fields they provide, so we cannot get the rendered output of extra
 * fields before this point in the view process.
 * layout_builder_module_implements_alter() moves this implementation of
 * hook_entity_view_alter() to the end of the list.
 *
 * @see \Drupal\layout_builder\Plugin\Block\ExtraFieldBlock::build()
 * @see layout_builder_module_implements_alter()
 */
function layout_builder_entity_view_alter(array &$build, EntityInterface $entity, EntityViewDisplayInterface $display) {
  if ($display instanceof LayoutEntityDisplayInterface) {
    /** @var \Drupal\Core\Entity\EntityFieldManagerInterface $field_manager */
    $field_manager = \Drupal::service('entity_field.manager');
    $extra_fields = $field_manager->getExtraFields($entity->getEntityTypeId(), $entity->bundle());
    if (!empty($extra_fields['display'])) {
      foreach ($extra_fields['display'] as $field_name => $extra_field) {
        // If the extra field is not set replace with an empty array to avoid
        // the placeholder text from being rendered.
        $replacement = isset($build[$field_name]) ? $build[$field_name] : [];
        ExtraFieldBlock::replaceFieldPlaceholder($build, $replacement, $field_name);
        // After the rendered field in $build has been copied over to the
        // ExtraFieldBlock block we must remove it from its original location or
        // else it will be rendered twice.
        unset($build[$field_name]);
      }
    }
  }
}

/**
 * Implements hook_builder_module_implements_alter().
 */
function layout_builder_module_implements_alter(&$implementations, $hook) {
  if ($hook === 'entity_view_alter') {
    // Ensure that this module's implementation of hook_entity_view_alter() runs
    // last so that other modules that use this hook to render extra fields will
    // run before it.
    $group = $implementations['layout_builder'];
    unset($implementations['layout_builder']);
    $implementations['layout_builder'] = $group;
  }
}

/**
 * Implements hook_entity_presave().
 */
function layout_builder_entity_presave(EntityInterface $entity) {
  if (\Drupal::moduleHandler()->moduleExists('block_content')) {
    /** @var \Drupal\layout_builder\InlineBlockEntityOperations $entity_operations */
    $entity_operations = \Drupal::classResolver(InlineBlockEntityOperations::class);
    $entity_operations->handlePreSave($entity);
  }
}

/**
 * Implements hook_entity_delete().
 */
function layout_builder_entity_delete(EntityInterface $entity) {
  if (\Drupal::moduleHandler()->moduleExists('block_content')) {
    /** @var \Drupal\layout_builder\InlineBlockEntityOperations $entity_operations */
    $entity_operations = \Drupal::classResolver(InlineBlockEntityOperations::class);
    $entity_operations->handleEntityDelete($entity);
  }
}

/**
 * Implements hook_cron().
 */
function layout_builder_cron() {
  if (\Drupal::moduleHandler()->moduleExists('block_content')) {
    /** @var \Drupal\layout_builder\InlineBlockEntityOperations $entity_operations */
    $entity_operations = \Drupal::classResolver(InlineBlockEntityOperations::class);
    $entity_operations->removeUnused();
  }
}

/**
 * Implements hook_plugin_filter_TYPE_alter().
 */
function layout_builder_plugin_filter_block_alter(array &$definitions, array $extra, $consumer) {
  // @todo Determine the 'inline_block' blocks should be allowed outside
  //   of layout_builder https://www.drupal.org/node/2979142.
  if ($consumer !== 'layout_builder' || !isset($extra['list']) || $extra['list'] !== 'inline_blocks') {
    foreach ($definitions as $id => $definition) {
      if ($definition['id'] === 'inline_block') {
        unset($definitions[$id]);
      }
    }
  }
}

/**
 * Implements hook_ENTITY_TYPE_access().
 */
function layout_builder_block_content_access(EntityInterface $entity, $operation, AccountInterface $account) {
  /** @var \Drupal\block_content\BlockContentInterface $entity */
  if ($operation === 'view' || $entity->isReusable() || empty(\Drupal::service('inline_block.usage')->getUsage($entity->id()))) {
    // If the operation is 'view' or this is reusable block or if this is
    // non-reusable that isn't used by this module then don't alter the access.
    return AccessResult::neutral();
  }

  if ($account->hasPermission('configure any layout')) {
    return AccessResult::allowed();
  }
  return AccessResult::forbidden();
}

/**
 * Implements hook_plugin_filter_TYPE__CONSUMER_alter().
 */
function layout_builder_plugin_filter_block__block_ui_alter(array &$definitions, array $extra) {
  foreach ($definitions as $id => $definition) {
    // Filter out any layout_builder definition with required contexts.
    if ($definition['provider'] === 'layout_builder' && !empty($definition['context'])) {
      /** @var \Drupal\Core\Plugin\Context\ContextDefinitionInterface $context */
      foreach ($definition['context'] as $context) {
        if ($context->isRequired()) {
          unset($definitions[$id]);
          break;
        }
      }
    }
  }
}

/**
 * Implements hook_layout_builder_section_storage_alter().
 */
function layout_builder_layout_builder_section_storage_alter(array &$definitions) {
  // @todo Until https://www.drupal.org/node/3016420 is resolved, context
  //   definition annotations cannot specify any constraints. Alter
  //   \Drupal\layout_builder\Plugin\SectionStorage\OverridesSectionStorage to
  //   add the constraint of having the required layout field.
  /** @var \Drupal\layout_builder\SectionStorage\SectionStorageDefinition[] $definitions */
  $definitions['overrides']->getContextDefinition('entity')
    ->addConstraint('EntityHasField', OverridesSectionStorage::FIELD_NAME);
}