Issue #3066801 by catch, WidgetsBurritos, alexpott, pobster, jungle, tedbow,...

        }

        drupal_set_installed_schema_version($module, $version);

        // Ensure that all post_update functions are registered already.

        // Ensure that all post_update functions are registered already. This

        // should include existing post-updates, as well as any specified as

        // having been previously removed, to ensure that newly installed and

        // updated sites have the same entries in the registry.

        /** @var \Drupal\Core\Update\UpdateRegistry $post_update_registry */

        $post_update_registry = \Drupal::service('update.post_update_registry');

        $post_update_registry->registerInvokedUpdates($post_update_registry->getModuleUpdateFunctions($module));

        $post_update_registry->registerInvokedUpdates(array_merge($post_update_registry->getModuleUpdateFunctions($module), array_keys($post_update_registry->getRemovedPostUpdates($module))));

        // Record the fact that it was installed.

        $modules_installed[] = $module;

 * @ingroup update_api

 *

 * @see hook_update_N()

 * @see hook_removed_post_updates()

 */

function hook_post_update_NAME(&$sandbox) {

  // Example of updating some content.

  return $result;

}

/**

 * Return an array of removed hook_post_update_NAME() function names.

 *

 * This should be used to indicate post-update functions that have existed in

 * some previous version of the module, but are no longer available.

 *

 * This implementation has to be placed in a MODULE.post_update.php file.

 *

 * @return string[]

 *   An array where the keys are removed post-update function names, and the

 *   values are the first stable version in which the update was removed.

 *

 * @ingroup update_api

 *

 * @see hook_post_update_NAME()

 */

function hook_removed_post_updates() {

  return [

    'mymodule_post_update_foo' => '8.x-2.0',

    'mymodule_post_update_bar' => '8.x-3.0',

    'mymodule_post_update_baz' => '8.x-3.0',

  ];

}

/**

 * Return an array of information about module update dependencies.

 *

<?php

namespace Drupal\Core\Update;

/**

 * An exception thrown for removed post-update functions.

 *

 * Occurs when a module defines hook_post_update_NAME() implementations

 * that are listed as removed in hook_removed_post_updates().

 */

class RemovedPostUpdateNameException extends \LogicException {

}

    $this->includeTests = $include_tests;

  }

  /**

   * Gets removed hook_post_update_NAME() implementations for a module.

   *

   * @return string[]

   *   A list of post-update functions that have been removed.

   */

  public function getRemovedPostUpdates($module) {

    $this->scanExtensionsAndLoadUpdateFiles();

    $function = "{$module}_removed_post_updates";

    if (function_exists($function)) {

      return $function();

    }

    return [];

  }

  /**

   * Gets all available update functions.

   *

      // module updates.

      if (preg_match($regexp, $function, $matches)) {

        if (in_array($matches['module'], $this->enabledModules)) {

          $updates[] = $matches['module'] . '_' . $this->updateType . '_' . $matches['name'];

          $function_name = $matches['module'] . '_' . $this->updateType . '_' . $matches['name'];

          if ($this->updateType === 'post_update') {

            $removed = array_keys($this->getRemovedPostUpdates($matches['module']));

            if (array_search($function_name, $removed) !== FALSE) {

              throw new RemovedPostUpdateNameException(sprintf('The following update is specified as removed in hook_removed_post_updates() but still exists in the code base: %s', $function_name));

            }

          }

          $updates[] = $function_name;

        }

      }

    }

    // Ensure that the update order is deterministic.

    sort($updates);

    return $updates;

use Drupal\Core\Site\Settings;

use Drupal\Core\StreamWrapper\PrivateStream;

use Drupal\Core\StreamWrapper\PublicStream;

use Drupal\Core\StringTranslation\PluralTranslatableMarkup;

use Drupal\Core\StringTranslation\TranslatableMarkup;

use Drupal\Core\Url;

use Symfony\Component\HttpFoundation\Request;

    }

  }

  // Check all the expected post-updates have been run.

  if ($phase === 'update') {

    $existing_updates = \Drupal::service('keyvalue')->get('post_update')->get('existing_updates', []);

    $post_update_registry = \Drupal::service('update.post_update_registry');

    $modules = \Drupal::moduleHandler()->getModuleList();

    $module_extension_list = \Drupal::service('extension.list.module');

    foreach ($modules as $module => $extension) {

      $module_info = $module_extension_list->get($module);

      $removed_post_updates = $post_update_registry->getRemovedPostUpdates($module);

      if ($missing_updates = array_diff(array_keys($removed_post_updates), $existing_updates)) {

        $versions = array_unique(array_intersect_key($removed_post_updates, array_flip($missing_updates)));

        $description = new PluralTranslatableMarkup(count($versions),

          'The installed version of the %module module is too old to update. Update to a version prior to @versions first (missing updates: @missing_updates).',

          'The installed version of the %module module is too old to update. Update first to a version prior to all of the following: @versions (missing updates: @missing_updates).',

          [

            '%module' => $module_info->info['name'],

            '@missing_updates' => implode(', ', $missing_updates),

            '@versions' => implode(', ', $versions),

          ]

        );

        $requirements[$module . '_post_update_removed'] = [

          'title' => t('Missing updates for: @module', ['@module' => $module_info->info['name']]),

          'description' => $description,

          'severity' => REQUIREMENT_ERROR,

        ];

      }

    }

  }

  return $requirements;

}