Update settings on all existing block instances (of a certain plugin type) [BC]

For an entity_submenu_block issue, I had to write a little update hook to introduce a new setting with a value for existing installation to not make a breaking change [BC].

The following snippet helps to find existing instances of a block from a certain Block Plugin and set a certain setting on them:

<?php

/**
 * @file
 * Install / update for entity_submenu_block module.
 */

/**
 * Set new setting "show_if_empty"=TRUE for all existing entity_submenu_block
 * blocks to keep previous behaviour of showing empty entity_submenu_block
 * blocks.
 */
function entity_submenu_block_update_8001() {
  // Get all block instances of the type 'my_custom_block'.
  $block_storage = \Drupal::entityTypeManager()->getStorage('block');
  $block_ids = \Drupal::entityQuery('block')
    ->condition('plugin', 'entity_submenu_block:', 'STARTS_WITH')
    ->execute();

  $blocks = $block_storage->loadMultiple($block_ids);

  $count = 0;
  /** @var \Drupal\block\BlockInterface[] $blocks */
  foreach ($blocks as $block) {
    $configuration = $block->get('settings');
    // Set the new setting if it doesn't exist.
    if (!isset($configuration['show_if_empty'])) {
      $configuration['show_if_empty'] = TRUE;
      $block->set('settings', $configuration);
      $block->save();
      $count++;
    }
  }

  return t('Set "Show the block, even if empty" option TRUE on @count existing entity_submenu_block blocks. Adjust the setting if needed to hide these blocks entirely, if empty.', ['@count' => $count]);
}

For details see the commit: https://git.drupalcode.org/project/entity_submenu_block/-/commit/a031db…