Issue #3436993 stager exceptions handling

Closes #3436993

automatic_updates_extensions/src/Validator/ForbidCoreChangesValidator.php

+<?php
+
+declare(strict_types=1);
+
+namespace Drupal\automatic_updates_extensions\Validator;
+
+use Drupal\Core\StringTranslation\StringTranslationTrait;
+use Drupal\Core\Url;
+use Drupal\package_manager\ComposerInspector;
+use Drupal\package_manager\Event\PreApplyEvent;
+use Drupal\package_manager\Event\StatusCheckEvent;
+use Drupal\package_manager\InstalledPackagesList;
+use Drupal\package_manager\PathLocator;
+use Symfony\Component\EventDispatcher\EventSubscriberInterface;
+
+/**
+ * Validates that no changes were made to Drupal Core packages.
+ *
+ * @internal
+ *   This is an internal part of Automatic Updates and may be changed or removed
+ *   at any time without warning. External code should not interact with this
+ *   class.
+ */
+final class ForbidCoreChangesValidator implements EventSubscriberInterface {
+
+  use StringTranslationTrait;
+
+  public function __construct(
+    private readonly PathLocator $pathLocator,
+    private readonly ComposerInspector $composerInspector,
+  ) {}
+
+  /**
+   * Validates the staged packages.
+   *
+   * @param \Drupal\package_manager\Event\StatusCheckEvent|\Drupal\package_manager\Event\PreApplyEvent $event
+   *   The event object.
+   */
+  public function validateStagedCorePackages(StatusCheckEvent|PreApplyEvent $event): void {
+    $stage = $event->stage;
+    // We only want to do this check if the stage belongs to Automatic Updates
+    // Extensions.
+    if ($stage->getType() !== 'automatic_updates_extensions:attended' || !$stage->stageDirectoryExists()) {
+      return;
+    }
+    $active_core_packages = $this->getInstalledCorePackages($this->pathLocator->getProjectRoot());
+    $stage_core_packages = $this->getInstalledCorePackages($stage->getStageDirectory());
+
+    $new_packages = $stage_core_packages->getPackagesNotIn($active_core_packages);
+    $removed_packages = $active_core_packages->getPackagesNotIn($stage_core_packages);
+    $changed_packages = $active_core_packages->getPackagesWithDifferentVersionsIn($stage_core_packages);
+
+    $error_messages = [];
+    foreach ($new_packages as $new_package) {
+      $error_messages[] = $this->t("'@name' installed.", ['@name' => $new_package->name]);
+    }
+    foreach ($removed_packages as $removed_package) {
+      $error_messages[] = $this->t("'@name' removed.", ['@name' => $removed_package->name]);
+    }
+    foreach ($changed_packages as $name => $updated_package) {
+      $error_messages[] = $this->t(
+        "'@name' version changed from @active_version to @staged_version.",
+        [
+          '@name' => $updated_package->name,
+          '@staged_version' => $stage_core_packages[$name]->version,
+          '@active_version' => $updated_package->version,
+        ]
+      );
+
+    }
+    if ($error_messages) {
+      $event->addError($error_messages, $this->t(
+        'Updating Drupal Core while updating extensions is currently not supported. Use <a href=":url">this form</a> to update Drupal core. The following changes were made to the Drupal core packages:',
+        [':url' => Url::fromRoute('update.report_update')->toString()]
+      ));
+    }
+  }
+
+  /**
+   * Gets all the installed core packages for a given project root.
+   *
+   * This method differs from
+   * \Drupal\package_manager\ComposerInspector::getInstalledPackagesList in that
+   * it ensures that the 'drupal/core' is included in the list if present.
+   *
+   * @param string $composer_root
+   *   The path to the composer root.
+   *
+   * @return \Drupal\package_manager\InstalledPackagesList
+   *   The installed core packages.
+   */
+  private function getInstalledCorePackages(string $composer_root): InstalledPackagesList {
+    $installed_package_list = $this->composerInspector->getInstalledPackagesList($composer_root);
+    $core_packages = $installed_package_list->getCorePackages();
+    if (isset($installed_package_list['drupal/core']) && !isset($core_packages['drupal/core'])) {
+      $core_packages = new InstalledPackagesList(array_merge($core_packages->getArrayCopy(), ['drupal/core' => $installed_package_list['drupal/core']]));
+    }
+    return $core_packages;
+  }
+
+  /**
+   * {@inheritdoc}
+   */
+  public static function getSubscribedEvents(): array {
+    $events[StatusCheckEvent::class][] = ['validateStagedCorePackages'];
+    $events[PreApplyEvent::class][] = ['validateStagedCorePackages'];
+    return $events;
+  }
+
+}