Bolt: Workaround for issue with missing templates

composer.json

{
  "name": "stoco/config_cache_fix",
  "description": "Fixes a cache issue which results in missing templates.",
  "type": "bolt-extension",
  "require": {
    "bolt/bolt": ">=2.0.0,<3.0.0"
  },
  "license": "MIT",
  "authors": [
    {
      "name": "Hannes Lilljequist",
      "email": "hannes@sthlmconnection.se"
    }
  ],
  "autoload": {
    "files": [
      "init.php"
    ],
    "psr-4": {
      "Bolt\\Extension\\Stoco\\ConfigCacheFix\\": ""
    }
  }
}

Extension.php

<?php

// See https://github.com/bolt/bolt/issues/4290

namespace Bolt\Extension\Stoco\ConfigCacheFix;

use Bolt\Application;
use Bolt\BaseExtension;
use Symfony\Component\HttpFoundation\Request;

class Extension extends BaseExtension
{

  public function __construct(Application $app) {
    parent::__construct($app);
  }

  public function initialize() {
    $app = $this->app;
    $app->before(function (Request $request) use ($app) {
      // Check the theme config. It it is empty, save a semaphore file, delete
      // the config cache and reload.
      $themeconfig = $app['config']->get('theme');
      $semaphore = $app['paths']['cache'] . '/config-cache-fix-applied';
      if (empty($themeconfig) && !file_exists($semaphore)) {
        $this->app['logger.system']->info('Theme config is missing. Deleting the config cache file and reloading.', ['event' => 'config_cache_fix']);
        @unlink($app['paths']['cache'] . '/config_cache.php');
        @touch($semaphore);
        return $app->redirect($_SERVER['REQUEST_URI'], 302);
      }
      elseif (!empty($themeconfig) && file_exists($semaphore)) {
        @unlink($semaphore);
        $this->app['logger.system']->info('The config cache fix has been sucessfully applied.', ['event' => 'config_cache_fix']);
      }
    });
  }

  public function getName() {
    return "ConfigCacheFix";
  }
}

init.php

<?php

namespace Bolt\Extension\Stoco\ConfigCacheFix;

$app['extensions']->register(new Extension($app));