Issue #3311472 Set minimum stability for form

Closes #3311472

src/Validator/VersionPolicy/TargetVersionNotPreRelease.php

@@ -4,7 +4,8 @@ declare(strict_types = 1);
 
 namespace Drupal\automatic_updates\Validator\VersionPolicy;
 
-use Drupal\Core\StringTranslation\TranslatableMarkup;
+use Composer\Semver\VersionParser;
+use Drupal\Core\StringTranslation\StringTranslationTrait;
 
 /**
  * A policy rule requiring the target version to be a RC or higher.
@@ -14,20 +15,30 @@ use Drupal\Core\StringTranslation\TranslatableMarkup;
  *   Drupal core. It may be changed or removed at any time without warning.
  *   External code should not interact with this class.
  */
-final class TargetVersionNotPreRelease extends TargetVersionStabilityBase {
+final class TargetVersionNotPreRelease {
 
-  /**
-   * {@inheritdoc}
-   */
-  protected string $minimumStability = 'rc';
+  use StringTranslationTrait;
 
   /**
-   * {@inheritdoc}
+   * Checks that the target version of Drupal is a stable release.
+   *
+   * @param string $installed_version
+   *   The installed version of Drupal.
+   * @param string|null $target_version
+   *   The target version of Drupal, or NULL if not known.
+   *
+   * @return \Drupal\Core\StringTranslation\TranslatableMarkup[]
+   *   The error messages, if any.
    */
-  protected function getErrorMessage(string $target_version): TranslatableMarkup {
-    return $this->t('Drupal cannot be updated to the recommended version, @target_version, because it is pre-release version.', [
-      '@target_version' => $target_version,
-    ]);
+  public function validate(string $installed_version, ?string $target_version): array {
+    if (!in_array(VersionParser::parseStability($target_version), ['stable', 'RC'], TRUE)) {
+      return [
+        $this->t('Drupal cannot be automatically updated during cron to the recommended version, @target_version, because it is not a stable version.', [
+          '@target_version' => $target_version,
+        ]),
+      ];
+    }
+    return [];
   }
 
 }