<?php

/**
 * Entity query helper.
 */
function migration_helpers_entity_query($entity_type, $bundle, $field = '') {

  /** @var \Drupal\Core\Entity\EntityTypeManagerInterface $entity_type_manager */
  $entity_type_manager = \Drupal::service('entity_type.manager');

  $entity_storage = $entity_type_manager->getStorage($entity_type);
  $bundle_key = $entity_storage->getEntityType()->getKey('bundle');

  $entity_query = $entity_storage->getQuery();
  $entity_query->condition($bundle_key, $bundle);

  if (!empty($field)) {
    // Check that field BOTH is present on entity bundle AND has a value saved.
    $entity_query->exists($field);
  }

  $entity_query->accessCheck(FALSE);

  $entity_ids = $entity_query->execute();

  return $entity_type_manager->getStorage($entity_type)->loadMultiple($entity_ids);

}


// The below almost serve more as examples that can be followed

function migration_helpers_text_list_to_boolean($old_field_name, $new_field_name, $bundle, $entity_type = 'node', $value_map = NULL) {

  $value_map = $value_map ?? [
    'Yes' => TRUE,
    'No' => FALSE,
  ];

  $nodes = migration_helpers_entity_query($entity_type, $bundle, $old_field_name);
  foreach ($nodes as $node) {
    /** @var \Drupal\node\NodeInterface $node */
    $orig_value = trim($node->$old_field_name->value);
    $new_value = $value_map[$orig_value] ?? (boolean) $orig_value;
    $node->set($new_field_name, $new_value);
    $node->save();
  }
}