Layout builder for products cannot render extra fields

Problem/Motivation

If you attempt to add an extra field (pseudo field) or an EVA field to a product variation, Drupal crashes as soon as you add the field to the layout. The error is:

Notice: Undefined index: default_formatter in Drupal\layout_builder\Plugin\Block\FieldBlock->defaultConfiguration() (line 222 of /var/www/html/web/core/modules/layout_builder/src/Plugin/Block/FieldBlock.php).

Steps to reproduce

Create an extra field:

/**
 * Implements hook_entity_extra_field_info().
 */
function HOOK_entity_extra_field_info() {
  $extra = [];

  foreach (ProductVariationType::loadMultiple() as $bundle) {
    $extra['commerce_product_variation'][$bundle->id()]['display']['specifications'] = [
      'label' => t('Specifications'),
      'description' => t('Rendered table with all variation fields.'),
      'weight' => 0,
      'visible' => TRUE,
    ];
  }
  return $extra;
}

/**
 * Implements hook_ENTITY_TYPE_view_alter() for commerce_product_variation.
 */
function HOOK_commerce_product_variation_view_alter(array &$build, EntityInterface $entity, EntityViewDisplayInterface $display) {
  $view_mode = $display->getMode();

  if ($view_mode != 'default') {
    $build['specifications'] = [
      // Render specifications.
      '#markup' => 'foo',
    ];
  }
}

Configure a product display (not product variation) and enter layout builder.
Add the extra field that appears in the Product Variations list.
See the error.

Proposed resolution

Layout builder has two BlockPlugins; 'FieldBlock' and 'ExtraFieldBlock'. The relevant difference is that ExtraFieldBlock does not make use a view_mode. The problem comes from commerce_product_block_alter which incorrectly checks the base_plugin_id.

/**
 * Implements hook_block_alter().
 */
function commerce_product_block_alter(array &$info) {
  if (\Drupal::moduleHandler()->moduleExists('layout_builder')) {
    $base_plugin_id = 'field_block' . PluginBase::DERIVATIVE_SEPARATOR . 'commerce_product_variation' . PluginBase::DERIVATIVE_SEPARATOR;
    foreach ($info as $block_plugin_id => $block_definition) {
      if (strpos($block_plugin_id, $base_plugin_id) !== FALSE) {
        $info[$block_plugin_id]['class'] = VariationFieldBlock::class;
      }
    }
  }
}

For a field block the base form id is: field_block:commerce_product_variation:field_name. However for an extra field, the pattern is: extra_field_block:commerce_product_variation:field_name.

The following line causes the issue: if (strpos($block_plugin_id, $base_plugin_id) !== FALSE). That also triggers for extra fields, where it should not. Instead the if-statement should check if the base plugin id starts with field_block. The logic should be: if (strpos($block_plugin_id, $base_plugin_id) === 0)

Remaining tasks

1. Update the if-statement with above logic. This no longer triggers the error, but the fields are not getting replaced.
2. Find out what fields need to get replaced; possibly a commerce product variation variant of ExtraFieldBlock?

User interface changes

API changes

Data model changes