Added replacement Drush cache:rebuild command to correctly handle app root so contrib modules don’t vanish.

Author: joachim-n

README.md

@@ -27,12 +27,6 @@ Once the installation is complete, you can install Drupal as normal, either with
 
 ## Limitations
 
-Most Drush commands work, but `drush cr` does *not*. To rebuild the Drupal
-container and clear caches, install Devel module and use its menu items instead.
-
-A fix is being worked on: see
-https://www.drupal.org/project/drupal/issues/1792310.
-
 During some Composer commands you may see multiple copies of this error message:
 
 > Could not scan for classes inside [Drupal class filename].
@@ -147,6 +141,9 @@ Several workarounds are necessary to make Drupal core work correctly when
 symlinked into the project. These are all taken care of by Composer scripts
 during installation. Details are below.
 
+Most if not all of these will no longer be needed once
+https://www.drupal.org/project/drupal/issues/1792310 is fixed.
+
 #### Vendor folder
 
 The vendor folder has to be symlinked into the Drupal core repository, because
@@ -176,6 +173,15 @@ cd web && patch -p1 <../scaffold/scaffold-patch-update-php.patch
 
 See https://www.drupal.org/project/drupal/issues/3188703 for more detail.
 
+#### Drush rebuild command
+
+The Drush cache:rebuild command does not work correctly if contrib modules are
+present, because it calls drupal_rebuild() which lets DrupalKernel guess the
+app root incorrectly.
+
+This project template contains a /drush folder which has a command class which
+replaces that command with custom code to correctly handle the app root.
+
 #### Simpletest folder
 
 When running browser tests, the initial setup of Drupal in

drush/Commands/core_development/DevelopmentProjectCommands.php

@@ -0,0 +1,108 @@
+<?php
+
+namespace Drush\Commands\core_development;
+
+use Consolidation\AnnotatedCommand\AnnotationData;
+use Drupal\Core\DrupalKernel;
+use Drupal\Core\Site\Settings;
+use Drush\Commands\core\CacheCommands;
+use Drush\Drush;
+use Symfony\Component\Console\Command\Command;
+use Symfony\Component\Console\Input\ArgvInput;
+use Symfony\Component\Console\Input\InputInterface;
+use Symfony\Component\HttpFoundation\Request;
+
+/**
+ * Replaces the cache:rebuild command to correctly work with symlinked Drupal.
+ *
+ * This prevents contrib modules from vanishing when the cache:rebuild command
+ * is run.
+ *
+ * For maintainability, changes from the original are marked 'CHANGE'.
+ */
+class DevelopmentProjectCommands extends CacheCommands {
+
+  /**
+   * @hook replace-command cache:rebuild
+   */
+  public function rebuild($options = ['cache-clear' => true]) {
+    if (!$options['cache-clear']) {
+      $this->logger()->info(dt("Skipping cache-clear operation due to --no-cache-clear option."));
+      return true;
+    }
+
+    // CHANGE: Get the app root ourselves instead of using DRUPAL_ROOT.
+    $app_root = $this->getAppRoot();
+    chdir($this->getAppRoot());
+
+    // We no longer clear APC and similar caches as they are useless on CLI.
+    // See https://github.com/drush-ops/drush/pull/2450
+
+    $autoloader = $this->loadDrupalAutoloader(DRUPAL_ROOT);
+    require_once DRUSH_DRUPAL_CORE . '/includes/utility.inc';
+
+    $request = Drush::bootstrap()->getRequest();
+    DrupalKernel::bootEnvironment();
+
+    // Avoid 'Only variables should be passed by reference'
+    // CHANGE: Don't use DRUPAL_ROOT.
+    $root = $app_root;
+    $site_path = DrupalKernel::findSitePath($request);
+    Settings::initialize($root, $site_path, $autoloader);
+
+    // drupal_rebuild() calls drupal_flush_all_caches() itself, so we don't do it manually.
+    // CHANGE: call our own version of drupal_rebuild().
+    $this->drupal_rebuild($autoloader, $request);
+    $this->logger()->success(dt('Cache rebuild complete.'));
+  }
+
+  /**
+   * Replacement for drupal_rebuild().
+   *
+   * This passes the app root to DrupalKernel.
+   */
+  function drupal_rebuild($class_loader, Request $request) {
+    // Remove Drupal's error and exception handlers; they rely on a working
+    // service container and other subsystems and will only cause a fatal error
+    // that hides the actual error.
+    restore_error_handler();
+    restore_exception_handler();
+
+    // Invalidate the container.
+    // Bootstrap up to where caches exist and clear them.
+    // CHANGE: Pass the correct app root to DrupalKernel.
+    $kernel = new DrupalKernel('prod', $class_loader, TRUE, $this->getAppRoot());
+    $kernel->setSitePath(DrupalKernel::findSitePath($request));
+    $kernel->invalidateContainer();
+    $kernel->boot();
+    $kernel->preHandle($request);
+    // Ensure our request includes the session if appropriate.
+    if (PHP_SAPI !== 'cli') {
+      $request->setSession($kernel->getContainer()->get('session'));
+    }
+
+    drupal_flush_all_caches($kernel);
+
+    // Disable recording of cached pages.
+    \Drupal::service('page_cache_kill_switch')->trigger();
+
+    // Restore Drupal's error and exception handlers.
+    // @see \Drupal\Core\DrupalKernel::boot()
+    set_error_handler('_drupal_error_handler');
+    set_exception_handler('_drupal_exception_handler');
+  }
+
+  /**
+   * Gets the app root.
+   *
+   * @return string
+   *   The app root.
+   */
+  protected function getAppRoot(): string {
+    // This core belongs to the project template, so we can hardcode the
+    // location of this file relative to the project root, and the scaffold
+    // location defined in the project's composer.json.
+    return dirname(__DIR__, 3) . '/web';
+  }
+
+}