Add a core-convert job

Closes #3414168

package_manager/tests/src/Build/TemplateProjectTestBase.php

@@ -8,7 +8,6 @@ use Composer\Autoload\ClassLoader;
 use Composer\InstalledVersions;
 use Drupal\BuildTests\QuickStart\QuickStartTestBase;
 use Drupal\Component\Serialization\Yaml;
-use Drupal\Composer\Composer;
 use Drupal\package_manager\Event\CollectPathsToExcludeEvent;
 use Drupal\package_manager_test_event_logger\EventSubscriber\EventLogSubscriber;
 use Drupal\Tests\package_manager\Traits\AssertPreconditionsTrait;
@@ -94,14 +93,15 @@ abstract class TemplateProjectTestBase extends QuickStartTestBase {
     // these are updated as well, despite `sites/default` being write-protected.
     // @see ::assertUpdateSuccessful()
     // @see ::createTestProject()
-    $workspace_dir = $this->getWorkspaceDirectory();
-    require_once "$workspace_dir/composer/Composer.php";
-    Composer::setDrupalVersion($workspace_dir, $version);
-    file_put_contents("$workspace_dir/core/README.txt", "Placeholder for Drupal core $version.");
+    // @see \Drupal\Composer\Composer::setDrupalVersion()
+    $core_dir = $this->getWorkspaceDrupalRoot() . '/core';
+    $drupal_static_path = "$core_dir/lib/Drupal.php";
+    $drupal_static_source = preg_replace('#const VERSION = [^;]*#', "const VERSION = '$version'", file_get_contents($drupal_static_path));
+    file_put_contents($drupal_static_path, $drupal_static_source);
+    file_put_contents("$core_dir/README.txt", "Placeholder for Drupal core $version.");
 
     foreach (['default.settings.php', 'default.services.yml'] as $file) {
-      $bytes_written = file_put_contents("$workspace_dir/core/assets/scaffold/files/$file", "# This is part of Drupal $version.\n", FILE_APPEND);
-      $this->assertIsInt($bytes_written);
+      file_put_contents("$core_dir/assets/scaffold/files/$file", "# This is part of Drupal $version.\n", FILE_APPEND);
     }
   }