Issue #2953656 by tedbow, tim.plunkett, diqidoq, phenaproxima, sarahjean, mglaman, xjm: No ability to control "extra fields" with Layout Builder

core/modules/layout_builder/layout_builder.module

@@ -12,6 +12,10 @@ 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\EntityInterface;
+use Drupal\Core\Entity\Display\EntityViewDisplayInterface;
+use Drupal\layout_builder\Entity\LayoutEntityDisplayInterface;
+use Drupal\layout_builder\Plugin\Block\ExtraFieldBlock;
 
 /**
  * Implements hook_help().
@@ -81,3 +85,52 @@ function layout_builder_field_config_delete(FieldConfigInterface $field_config)
   $sample_entity_generator->delete($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;
+  }
+}

core/modules/layout_builder/layout_builder.post_update.php

@@ -5,6 +5,9 @@
  * Post update functions for Layout Builder.
  */
 
+use Drupal\Core\Config\Entity\ConfigEntityUpdater;
+use Drupal\Core\Entity\Display\EntityViewDisplayInterface;
+
 /**
  * Rebuild plugin dependencies for all entity view displays.
  */
@@ -24,3 +27,30 @@ function layout_builder_post_update_rebuild_plugin_dependencies(&$sandbox = NULL
 
   $sandbox['#finished'] = empty($sandbox['ids']) ? 1 : ($sandbox['count'] - count($sandbox['ids'])) / $sandbox['count'];
 }
+
+/**
+ * Ensure all extra fields are properly stored on entity view displays.
+ *
+ * Previously
+ * \Drupal\layout_builder\Entity\LayoutBuilderEntityViewDisplay::setComponent()
+ * was not correctly setting the configuration for extra fields. This function
+ * calls setComponent() for all extra field components to ensure the updated
+ * logic is invoked on all extra fields to correct the settings.
+ */
+function layout_builder_post_update_add_extra_fields(&$sandbox = NULL) {
+  $entity_field_manager = \Drupal::service('entity_field.manager');
+  \Drupal::classResolver(ConfigEntityUpdater::class)->update($sandbox, 'entity_view_display', function (EntityViewDisplayInterface $display) use ($entity_field_manager) {
+    $extra_fields = $entity_field_manager->getExtraFields($display->getTargetEntityTypeId(), $display->getTargetBundle());
+    $components = $display->getComponents();
+    // Sort the components to avoid them being reordered by setComponent().
+    uasort($components, 'Drupal\Component\Utility\SortArray::sortByWeightElement');
+    $result = FALSE;
+    foreach ($components as $name => $component) {
+      if (isset($extra_fields['display'][$name])) {
+        $display->setComponent($name, $component);
+        $result = TRUE;
+      }
+    }
+    return $result;
+  });
+}

core/modules/layout_builder/src/Entity/LayoutBuilderEntityViewDisplay.php

@@ -25,6 +25,24 @@ class LayoutBuilderEntityViewDisplay extends BaseEntityViewDisplay implements La
 
   use SectionStorageTrait;
 
+  /**
+   * The entity field manager.
+   *
+   * @var \Drupal\Core\Entity\EntityFieldManagerInterface
+   */
+  protected $entityFieldManager;
+
+  /**
+   * {@inheritdoc}
+   */
+  public function __construct(array $values, $entity_type) {
+    // Set $entityFieldManager before calling the parent constructor because the
+    // constructor will call init() which then calls setComponent() which needs
+    // $entityFieldManager.
+    $this->entityFieldManager = \Drupal::service('entity_field.manager');
+    parent::__construct($values, $entity_type);
+  }
+
   /**
    * {@inheritdoc}
    */
@@ -258,13 +276,21 @@ class LayoutBuilderEntityViewDisplay extends BaseEntityViewDisplay implements La
     $options = $this->content[$name];
     // Provide backwards compatibility by converting to a section component.
     $field_definition = $this->getFieldDefinition($name);
-    if ($field_definition && $field_definition->isDisplayConfigurable('view') && isset($options['type'])) {
-      $configuration = [];
-      $configuration['id'] = 'field_block:' . $this->getTargetEntityTypeId() . ':' . $this->getTargetBundle() . ':' . $name;
-      $configuration['label_display'] = FALSE;
-      $keys = array_flip(['type', 'label', 'settings', 'third_party_settings']);
-      $configuration['formatter'] = array_intersect_key($options, $keys);
-      $configuration['context_mapping']['entity'] = 'layout_builder.entity';
+    $extra_fields = $this->entityFieldManager->getExtraFields($this->getTargetEntityTypeId(), $this->getTargetBundle());
+    $is_view_configurable_non_extra_field = $field_definition && $field_definition->isDisplayConfigurable('view') && isset($options['type']);
+    if ($is_view_configurable_non_extra_field || isset($extra_fields['display'][$name])) {
+      $configuration = [
+        'label_display' => '0',
+        'context_mapping' => ['entity' => 'layout_builder.entity'],
+      ];
+      if ($is_view_configurable_non_extra_field) {
+        $configuration['id'] = 'field_block:' . $this->getTargetEntityTypeId() . ':' . $this->getTargetBundle() . ':' . $name;
+        $keys = array_flip(['type', 'label', 'settings', 'third_party_settings']);
+        $configuration['formatter'] = array_intersect_key($options, $keys);
+      }
+      else {
+        $configuration['id'] = 'extra_field_block:' . $this->getTargetEntityTypeId() . ':' . $this->getTargetBundle() . ':' . $name;
+      }
 
       $section = $this->getDefaultSection();
       $region = isset($options['region']) ? $options['region'] : $section->getDefaultRegion();

core/modules/layout_builder/src/Plugin/Block/ExtraFieldBlock.php

@@ -0,0 +1,174 @@
+<?php
+
+namespace Drupal\layout_builder\Plugin\Block;
+
+use Drupal\Core\Block\BlockBase;
+use Drupal\Core\Cache\CacheableMetadata;
+use Drupal\Core\Entity\EntityFieldManagerInterface;
+use Drupal\Core\Entity\EntityTypeManagerInterface;
+use Drupal\Core\Plugin\ContainerFactoryPluginInterface;
+use Drupal\Core\Plugin\ContextAwarePluginInterface;
+use Drupal\Core\Render\Element;
+use Drupal\Core\Session\AccountInterface;
+use Drupal\Core\StringTranslation\TranslatableMarkup;
+use Symfony\Component\DependencyInjection\ContainerInterface;
+
+/**
+ * Provides a block that renders an extra field from an entity.
+ *
+ * This block handles fields that are provided by implementations of
+ * hook_entity_extra_field_info().
+ *
+ * @see \Drupal\layout_builder\Plugin\Block\FieldBlock
+ *   This block plugin handles all other field entities not provided by
+ *   hook_entity_extra_field_info().
+ *
+ * @Block(
+ *   id = "extra_field_block",
+ *   deriver = "\Drupal\layout_builder\Plugin\Derivative\ExtraFieldBlockDeriver",
+ * )
+ *
+ * @internal
+ *   Plugin classes are internal.
+ */
+class ExtraFieldBlock extends BlockBase implements ContextAwarePluginInterface, ContainerFactoryPluginInterface {
+
+  /**
+   * The entity field manager.
+   *
+   * @var \Drupal\Core\Entity\EntityFieldManagerInterface
+   */
+  protected $entityFieldManager;
+
+  /**
+   * The field name.
+   *
+   * @var string
+   */
+  protected $fieldName;
+
+  /**
+   * The entity type manager.
+   *
+   * @var \Drupal\Core\Entity\EntityTypeManagerInterface
+   */
+  protected $entityTypeManager;
+
+  /**
+   * Constructs a new ExtraFieldBlock.
+   *
+   * @param array $configuration
+   *   A configuration array containing information about the plugin instance.
+   * @param string $plugin_id
+   *   The plugin ID for the plugin instance.
+   * @param mixed $plugin_definition
+   *   The plugin implementation definition.
+   * @param \Drupal\Core\Entity\EntityTypeManagerInterface $entity_type_manager
+   *   The entity type manager.
+   * @param \Drupal\Core\Entity\EntityFieldManagerInterface $entity_field_manager
+   *   The entity field manager.
+   */
+  public function __construct(array $configuration, $plugin_id, $plugin_definition, EntityTypeManagerInterface $entity_type_manager, EntityFieldManagerInterface $entity_field_manager) {
+    $this->entityTypeManager = $entity_type_manager;
+    $this->entityFieldManager = $entity_field_manager;
+    // Get field name from the plugin ID.
+    list (, , , $field_name) = explode(static::DERIVATIVE_SEPARATOR, $plugin_id, 4);
+    assert(!empty($field_name));
+    $this->fieldName = $field_name;
+
+    parent::__construct($configuration, $plugin_id, $plugin_definition);
+  }
+
+  /**
+   * {@inheritdoc}
+   */
+  public function defaultConfiguration() {
+    return [
+      'label_display' => FALSE,
+    ];
+  }
+
+  /**
+   * {@inheritdoc}
+   */
+  public static function create(ContainerInterface $container, array $configuration, $plugin_id, $plugin_definition) {
+    return new static(
+      $configuration,
+      $plugin_id,
+      $plugin_definition,
+      $container->get('entity_type.manager'),
+      $container->get('entity_field.manager')
+    );
+  }
+
+  /**
+   * Gets the entity that has the field.
+   *
+   * @return \Drupal\Core\Entity\FieldableEntityInterface
+   *   The entity.
+   */
+  protected function getEntity() {
+    return $this->getContextValue('entity');
+  }
+
+  /**
+   * {@inheritdoc}
+   */
+  public function build() {
+    $entity = $this->getEntity();
+    // Add a placeholder to replace after the entity view is built.
+    // @see layout_builder_entity_view_alter().
+    $extra_fields = $this->entityFieldManager->getExtraFields($entity->getEntityTypeId(), $entity->bundle());
+    if (!isset($extra_fields['display'][$this->fieldName])) {
+      $build = [];
+    }
+    else {
+      $build = [
+        '#extra_field_placeholder_field_name' => $this->fieldName,
+        // Always provide a placeholder. The Layout Builder will NOT invoke
+        // hook_entity_view_alter() so extra fields will not be added to the
+        // render array. If the hook is invoked the placeholder will be
+        // replaced.
+        // @see ::replaceFieldPlaceholder()
+        '#markup' => new TranslatableMarkup('Placeholder for the "@field" field', ['@field' => $extra_fields['display'][$this->fieldName]['label']]),
+      ];
+    }
+    CacheableMetadata::createFromObject($this)->applyTo($build);
+    return $build;
+  }
+
+  /**
+   * Replaces all placeholders for a given field.
+   *
+   * @param array $build
+   *   The built render array for the elements.
+   * @param array $built_field
+   *   The render array to replace the placeholder.
+   * @param string $field_name
+   *   The field name.
+   *
+   * @see ::build()
+   */
+  public static function replaceFieldPlaceholder(array &$build, array $built_field, $field_name) {
+    foreach (Element::children($build) as $child) {
+      if (isset($build[$child]['#extra_field_placeholder_field_name']) && $build[$child]['#extra_field_placeholder_field_name'] === $field_name) {
+        $placeholder_cache = CacheableMetadata::createFromRenderArray($build[$child]);
+        $built_cache = CacheableMetadata::createFromRenderArray($built_field);
+        $merged_cache = $placeholder_cache->merge($built_cache);
+        $build[$child] = $built_field;
+        $merged_cache->applyTo($build);
+      }
+      else {
+        static::replaceFieldPlaceholder($build[$child], $built_field, $field_name);
+      }
+    }
+  }
+
+  /**
+   * {@inheritdoc}
+   */
+  protected function blockAccess(AccountInterface $account) {
+    return $this->getEntity()->access('view', $account, TRUE);
+  }
+
+}

core/modules/layout_builder/src/Plugin/Derivative/ExtraFieldBlockDeriver.php

@@ -0,0 +1,115 @@
+<?php
+
+namespace Drupal\layout_builder\Plugin\Derivative;
+
+use Drupal\Component\Plugin\Derivative\DeriverBase;
+use Drupal\Component\Plugin\PluginBase;
+use Drupal\Core\Entity\EntityFieldManagerInterface;
+use Drupal\Core\Entity\EntityTypeBundleInfoInterface;
+use Drupal\Core\Entity\EntityTypeManagerInterface;
+use Drupal\Core\Entity\FieldableEntityInterface;
+use Drupal\Core\Plugin\Context\EntityContextDefinition;
+use Drupal\Core\Plugin\Discovery\ContainerDeriverInterface;
+use Drupal\Core\StringTranslation\StringTranslationTrait;
+use Symfony\Component\DependencyInjection\ContainerInterface;
+
+/**
+ * Provides entity field block definitions for every field.
+ *
+ * @internal
+ *   Layout Builder is currently experimental and should only be leveraged by
+ *   experimental modules and development releases of contributed modules.
+ *   See https://www.drupal.org/core/experimental for more information.
+ */
+class ExtraFieldBlockDeriver extends DeriverBase implements ContainerDeriverInterface {
+
+  use StringTranslationTrait;
+
+  /**
+   * The entity field manager.
+   *
+   * @var \Drupal\Core\Entity\EntityFieldManagerInterface
+   */
+  protected $entityFieldManager;
+
+  /**
+   * The entity type manager.
+   *
+   * @var \Drupal\Core\Entity\EntityTypeManagerInterface
+   */
+  protected $entityTypeManager;
+
+  /**
+   * The entity type bundle info.
+   *
+   * @var \Drupal\Core\Entity\EntityTypeBundleInfoInterface
+   */
+  protected $entityTypeBundleInfo;
+
+  /**
+   * Constructs new FieldBlockDeriver.
+   *
+   * @param \Drupal\Core\Entity\EntityFieldManagerInterface $entity_field_manager
+   *   The entity field manager.
+   * @param \Drupal\Core\Entity\EntityTypeManagerInterface $entity_type_manager
+   *   The entity type manager.
+   * @param \Drupal\Core\Entity\EntityTypeBundleInfoInterface $entity_type_bundle_info
+   *   The entity type bundle info.
+   */
+  public function __construct(EntityFieldManagerInterface $entity_field_manager, EntityTypeManagerInterface $entity_type_manager, EntityTypeBundleInfoInterface $entity_type_bundle_info) {
+    $this->entityFieldManager = $entity_field_manager;
+    $this->entityTypeManager = $entity_type_manager;
+    $this->entityTypeBundleInfo = $entity_type_bundle_info;
+  }
+
+  /**
+   * {@inheritdoc}
+   */
+  public static function create(ContainerInterface $container, $base_plugin_id) {
+    return new static(
+      $container->get('entity_field.manager'),
+      $container->get('entity_type.manager'),
+      $container->get('entity_type.bundle.info')
+    );
+  }
+
+  /**
+   * {@inheritdoc}
+   */
+  public function getDerivativeDefinitions($base_plugin_definition) {
+    foreach ($this->entityTypeManager->getDefinitions() as $entity_type_id => $entity_type) {
+      // Only process fieldable entity types.
+      if (!$entity_type->entityClassImplements(FieldableEntityInterface::class)) {
+        continue;
+      }
+
+      $bundles = $this->entityTypeBundleInfo->getBundleInfo($entity_type_id);
+      foreach ($bundles as $bundle_id => $bundle) {
+        $extra_fields = $this->entityFieldManager->getExtraFields($entity_type_id, $bundle_id);
+        // Skip bundles without any extra fields.
+        if (empty($extra_fields['display'])) {
+          continue;
+        }
+
+        foreach ($extra_fields['display'] as $extra_field_id => $extra_field) {
+          $derivative = $base_plugin_definition;
+
+          $derivative['category'] = $entity_type->getLabel();
+
+          $derivative['admin_label'] = $extra_field['label'];
+
+          $context_definition = EntityContextDefinition::fromEntityType($entity_type)
+            ->addConstraint('Bundle', [$bundle_id]);
+          $derivative['context'] = [
+            'entity' => $context_definition,
+          ];
+
+          $derivative_id = $entity_type_id . PluginBase::DERIVATIVE_SEPARATOR . $bundle_id . PluginBase::DERIVATIVE_SEPARATOR . $extra_field_id;
+          $this->derivatives[$derivative_id] = $derivative;
+        }
+      }
+    }
+    return $this->derivatives;
+  }
+
+}

core/modules/layout_builder/tests/fixtures/update/layout-builder.php

@@ -0,0 +1,31 @@
+<?php
+
+/**
+ * @file
+ * Test fixture.
+ */
+
+use Drupal\Core\Database\Database;
+
+$connection = Database::getConnection();
+
+// Update core.extension.
+$extensions = $connection->select('config')
+  ->fields('config', ['data'])
+  ->condition('collection', '')
+  ->condition('name', 'core.extension')
+  ->execute()
+  ->fetchField();
+$extensions = unserialize($extensions);
+$extensions['module']['layout_builder'] = 0;
+$extensions['module']['layout_discovery'] = 0;
+$extensions['module']['layout_test'] = 0;
+$connection->update('config')
+  ->fields([
+    'data' => serialize($extensions),
+    'collection' => '',
+    'name' => 'core.extension',
+  ])
+  ->condition('collection', '')
+  ->condition('name', 'core.extension')
+  ->execute();

core/modules/layout_builder/tests/fixtures/update/section-dependencies.php

@@ -9,27 +9,6 @@ use Drupal\Core\Database\Database;
 
 $connection = Database::getConnection();
 
-// Update core.extension.
-$extensions = $connection->select('config')
-  ->fields('config', ['data'])
-  ->condition('collection', '')
-  ->condition('name', 'core.extension')
-  ->execute()
-  ->fetchField();
-$extensions = unserialize($extensions);
-$extensions['module']['layout_builder'] = 0;
-$extensions['module']['layout_discovery'] = 0;
-$extensions['module']['layout_test'] = 0;
-$connection->update('config')
-  ->fields([
-    'data' => serialize($extensions),
-    'collection' => '',
-    'name' => 'core.extension',
-  ])
-  ->condition('collection', '')
-  ->condition('name', 'core.extension')
-  ->execute();
-
 // Add a layout plugin with a dependency to an existing entity view display.
 $display = $connection->select('config')
   ->fields('config', ['data'])

core/modules/layout_builder/tests/modules/layout_builder_test/layout_builder_test.module

@@ -5,6 +5,9 @@
  * Provides hook implementations for Layout Builder tests.
  */
 
+use Drupal\Core\Entity\Display\EntityViewDisplayInterface;
+use Drupal\Core\Entity\EntityInterface;
+
 /**
  * Implements hook_plugin_filter_TYPE__CONSUMER_alter().
  */
@@ -32,3 +35,26 @@ function layout_builder_test_plugin_filter_block__layout_builder_alter(array &$d
     }
   }
 }
+
+/**
+ * Implements hook_entity_extra_field_info().
+ */
+function layout_builder_test_entity_extra_field_info() {
+  $extra['node']['bundle_with_section_field']['display']['layout_builder_test'] = [
+    'label' => t('Extra label'),
+    'description' => t('Extra description'),
+    'weight' => 0,
+  ];
+  return $extra;
+}
+
+/**
+ * Implements hook_entity_node_view().
+ */
+function layout_builder_test_node_view(array &$build, EntityInterface $entity, EntityViewDisplayInterface $display, $view_mode) {
+  if ($display->getComponent('layout_builder_test')) {
+    $build['layout_builder_test'] = [
+      '#markup' => 'Extra, Extra read all about it.',
+    ];
+  }
+}

core/modules/layout_builder/tests/src/Functional/LayoutBuilderTest.php

@@ -83,8 +83,25 @@ class LayoutBuilderTest extends BrowserTestBase {
     $assert_session->linkExists('Manage layout');
     $this->clickLink('Manage layout');
     $assert_session->addressEquals("$field_ui_prefix/display-layout/default");
-    // The body field is present.
-    $assert_session->elementExists('css', '.field--name-body');
+    // The body field is only present once.
+    $assert_session->elementsCount('css', '.field--name-body', 1);
+    // The extra field is only present once.
+    $this->assertTextAppearsOnce('Placeholder for the "Extra label" field');
+    // Save the defaults.
+    $assert_session->linkExists('Save Layout');
+    $this->clickLink('Save Layout');
+    $assert_session->addressEquals("$field_ui_prefix/display/default");
+
+    // Load the default layouts again after saving to confirm fields are only
+    // added on new layouts.
+    $this->drupalGet("$field_ui_prefix/display/default");
+    $assert_session->linkExists('Manage layout');
+    $this->clickLink('Manage layout');
+    $assert_session->addressEquals("$field_ui_prefix/display-layout/default");
+    // The body field is only present once.
+    $assert_session->elementsCount('css', '.field--name-body', 1);
+    // The extra field is only present once.
+    $this->assertTextAppearsOnce('Placeholder for the "Extra label" field');
 
     // Add a new block.
     $assert_session->linkExists('Add Block');
@@ -107,6 +124,8 @@ class LayoutBuilderTest extends BrowserTestBase {
     $this->drupalGet('node/1');
     $assert_session->pageTextContains('The first node body');
     $assert_session->pageTextContains('Powered by Drupal');
+    $assert_session->pageTextContains('Extra, Extra read all about it.');
+    $assert_session->pageTextNotContains('Placeholder for the "Extra label" field');
     $assert_session->linkNotExists('Layout');
 
     // Enable overrides.
@@ -116,6 +135,7 @@ class LayoutBuilderTest extends BrowserTestBase {
     // Remove the section from the defaults.
     $assert_session->linkExists('Layout');
     $this->clickLink('Layout');
+    $assert_session->pageTextContains('Placeholder for the "Extra label" field');
     $assert_session->linkExists('Remove section');
     $this->clickLink('Remove section');
     $page->pressButton('Remove');
@@ -128,6 +148,8 @@ class LayoutBuilderTest extends BrowserTestBase {
     $this->clickLink('Save Layout');
     $assert_session->pageTextNotContains('The first node body');
     $assert_session->pageTextNotContains('Powered by Drupal');
+    $assert_session->pageTextNotContains('Extra, Extra read all about it.');
+    $assert_session->pageTextNotContains('Placeholder for the "Extra label" field');
 
     // Assert that overrides cannot be turned off while overrides exist.
     $this->drupalGet("$field_ui_prefix/display/default");
@@ -149,12 +171,16 @@ class LayoutBuilderTest extends BrowserTestBase {
     $assert_session->pageTextContains('The second node title');
     $assert_session->pageTextContains('The second node body');
     $assert_session->pageTextContains('Powered by Drupal');
+    $assert_session->pageTextContains('Extra, Extra read all about it.');
+    $assert_session->pageTextNotContains('Placeholder for the "Extra label" field');
 
     // The overridden node does not pick up the changes to defaults.
     $this->drupalGet('node/1');
     $assert_session->elementNotExists('css', '.field--name-title');
     $assert_session->pageTextNotContains('The first node body');
     $assert_session->pageTextNotContains('Powered by Drupal');
+    $assert_session->pageTextNotContains('Extra, Extra read all about it.');
+    $assert_session->pageTextNotContains('Placeholder for the "Extra label" field');
     $assert_session->linkExists('Layout');
 
     // Reverting the override returns it to the defaults.
@@ -166,6 +192,7 @@ class LayoutBuilderTest extends BrowserTestBase {
     $assert_session->elementExists('css', '.field--name-title');
     $assert_session->pageTextContains('The first node body');
     $assert_session->pageTextContains('Powered by Drupal');
+    $assert_session->pageTextContains('Placeholder for the "Extra label" field');
 
     // Assert that overrides can be turned off now that all overrides are gone.
     $this->drupalPostForm("$field_ui_prefix/display/default", ['layout[allow_custom]' => FALSE], 'Save');
@@ -407,4 +434,14 @@ class LayoutBuilderTest extends BrowserTestBase {
     $assert_session->pageTextNotContains('Test Block View');
   }
 
+  /**
+   * Asserts that a text string only appears once on the page.
+   *
+   * @param string $needle
+   *   The string to look for.
+   */
+  protected function assertTextAppearsOnce($needle) {
+    $this->assertEquals(1, substr_count($this->getSession()->getPage()->getContent(), $needle), "'$needle' only appears once on the page.");
+  }
+
 }

core/modules/layout_builder/tests/src/Functional/Update/ExtraFieldUpdatePathTest.php

@@ -0,0 +1,41 @@
+<?php
+
+namespace Drupal\Tests\layout_builder\Functional\Update;
+
+use Drupal\Core\Entity\Entity\EntityViewDisplay;
+use Drupal\FunctionalTests\Update\UpdatePathTestBase;
+
+/**
+ * Tests the upgrade path for Layout Builder extra fields.
+ *
+ * @group layout_builder
+ * @group legacy
+ */
+class ExtraFieldUpdatePathTest extends UpdatePathTestBase {
+
+  /**
+   * {@inheritdoc}
+   */
+  protected function setDatabaseDumpFiles() {
+    $this->databaseDumpFiles = [
+      __DIR__ . '/../../../../../system/tests/fixtures/update/drupal-8.4.0.bare.standard.php.gz',
+      __DIR__ . '/../../../fixtures/update/layout-builder.php',
+    ];
+  }
+
+  /**
+   * Tests the upgrade path for Layout Builder extra fields.
+   */
+  public function testRunUpdates() {
+    $data = EntityViewDisplay::load('node.article.teaser')->toArray();
+    $this->assertArrayNotHasKey('third_party_settings', $data);
+
+    $this->runUpdates();
+
+    $data = EntityViewDisplay::load('node.article.teaser')->toArray();
+    $components = $data['third_party_settings']['layout_builder']['sections'][0]->getComponents();
+    $component = reset($components);
+    $this->assertSame('extra_field_block:node:article:links', $component->getPluginId());
+  }
+
+}

core/modules/layout_builder/tests/src/Functional/Update/SectionDependenciesUpdatePathTest.php

@@ -19,6 +19,7 @@ class SectionDependenciesUpdatePathTest extends UpdatePathTestBase {
   protected function setDatabaseDumpFiles() {
     $this->databaseDumpFiles = [
       __DIR__ . '/../../../../../system/tests/fixtures/update/drupal-8.4.0.bare.standard.php.gz',
+      __DIR__ . '/../../../fixtures/update/layout-builder.php',
       __DIR__ . '/../../../fixtures/update/section-dependencies.php',
     ];
   }