Magento 2 HTTP error 500 on categories after compilation

Question

I am working on a Magento 2.1 website for one of my clients. When running setup:di:compile, my Magento files are successfully compiled without errors.

When I open the frontend of my website, my homepages and other CMS pages work fine. But when I go to a category page, like /shop, I get a HTTP error 500.

The strange thing is, once I delete the var/di folder, this error disappears and I can visit all my pages and categories, but my website becomes extremely slow (like 11 seconds to load a simple page).

So what could cause the HTTP 500 error after compiling and what could be wrong with my var/di folder?

EDIT: after turning on PHP error reporting, the following error is shown when visiting category pages (not homepage and CMS pages):

Fatal error: Uncaught TypeError: Argument 1 passed to Plazathemes\LayeredNavigation\Controller\Category\View::__construct() must be an instance of Magento\Framework\App\Action\Context, instance of Magento\Framework\ObjectManager\ObjectManager given, called in vendor/magento/framework/ObjectManager/Factory/AbstractFactory.php on line 93 and defined in app/code/Plazathemes/Layerednavigation/Controller/Category/View.php:27
Stack trace: #0 vendor/magento/framework/ObjectManager/Factory/AbstractFactory.php(93): Plazathemes\LayeredNavigation\Controller\Category\View->__construct(Object(Magento\Framework\ObjectManager\ObjectManager))
#1 vendor/magento/framework/ObjectManager/Factory/Compiled.php(88): Magento\Framework\ObjectManager\Factory\AbstractFactory->createObject('Plazathemes\Lay...', Array)
#2 vendor/magento/framework/ObjectManager/ObjectManager.php(57): Magento\F in app/code/Plazathemes/Layerednavigation/Controller/Category/View.php on line 27

The file app/code/Plazathemes/Layerednavigation/Controller/Category/View.phplooks like this:

    namespace Plazathemes\LayeredNavigation\Controller\Category;

use Magento\Catalog\Api\CategoryRepositoryInterface;
use Magento\Catalog\Model\Layer\Resolver;
use Magento\Framework\Exception\NoSuchEntityException;
use Magento\Framework\View\Result\PageFactory;

/**
 * @SuppressWarnings(PHPMD.CouplingBetweenObjects)
 */
class View extends \Magento\Catalog\Controller\Category\View
{
    /**
     * Catalog Layer Resolver
     *
     * @var Resolver
     */
    private $layerResolver;

    public function __construct(
        \Magento\Framework\App\Action\Context $context,
        \Magento\Catalog\Model\Design $catalogDesign,
        \Magento\Catalog\Model\Session $catalogSession,
        \Magento\Framework\Registry $coreRegistry,
        \Magento\Store\Model\StoreManagerInterface $storeManager,
        \Magento\CatalogUrlRewrite\Model\CategoryUrlPathGenerator $categoryUrlPathGenerator,
        PageFactory $resultPageFactory,
        \Magento\Framework\Controller\Result\ForwardFactory $resultForwardFactory,
        Resolver $layerResolver,
        CategoryRepositoryInterface $categoryRepository
    )
    {
        parent::__construct($context, $catalogDesign, $catalogSession, $coreRegistry, $storeManager, $categoryUrlPathGenerator, $resultPageFactory, $resultForwardFactory, $layerResolver, $categoryRepository);
        $this->layerResolver = $layerResolver;
    }

    public function execute()
    {
        $layer_action = $this->getRequest()->getParam('layer_action');
        if($layer_action == 1) {
            if ($this->_request->getParam(\Magento\Framework\App\ActionInterface::PARAM_NAME_URL_ENCODED)) {
                return $this->resultRedirectFactory->create()->setUrl($this->_redirect->getRedirectUrl());
            }

            $category = $this->_initCategory();

            if ($category) {
                $this->layerResolver->create(Resolver::CATALOG_LAYER_CATEGORY);
                $settings = $this->_catalogDesign->getDesignSettings($category);

                if ($settings->getCustomDesign()) {
                    $this->_catalogDesign->applyCustomDesign($settings->getCustomDesign());
                }

                $this->_catalogSession->setLastViewedCategoryId($category->getId());

                $page = $this->resultPageFactory->create();

                if ($settings->getPageLayout()) {
                    $page->getConfig()->setPageLayout($settings->getPageLayout());
                }
                if ($category->getIsAnchor()) {
                    $type = $category->hasChildren() ? 'layered' : 'layered_without_children';
                } else {
                    $type = $category->hasChildren() ? 'default' : 'default_without_children';
                }

                if (!$category->hasChildren()) {

                    $parentType = strtok($type, '_');
                    $page->addPageLayoutHandles(['type' => $parentType]);
                }
                $page->addPageLayoutHandles(['type' => $type, 'id' => $category->getId()]);

                $layoutUpdates = $settings->getLayoutUpdates();
                if ($layoutUpdates && is_array($layoutUpdates)) {
                    foreach ($layoutUpdates as $layoutUpdate) {
                        $page->addUpdate($layoutUpdate);
                    }
                }

                $product_list = $page->getLayout()->getBlock('category.products.list')->toHtml();
                if($page->getLayout()->getBlock('catalog.leftnav')) {
                    $leftLayer = $page->getLayout()->getBlock('catalog.leftnav')->toHtml();
                } else {
                    $leftLayer = false;
                }


                $data['leftLayer'] = $leftLayer;
                $data['productlist'] = $product_list;

                $this->getResponse()->representJson(
                    $this->_objectManager->get('Magento\Framework\Json\Helper\Data')->jsonEncode($data)
                );
            } elseif (!$this->getResponse()->isRedirect()) {
                return $this->resultForwardFactory->create()->forward('noroute');
            }
        } else {
            return parent::execute();
        }
    }
}

I have found this issue on GitHub (https://github.com/magento/magento2/issues/4896) which is very similar to mine, but I cannot find how to adapt my code.

Answer 1

Just in case someone else comes across this, I finally got it to work.

There seemed to be a problem with two files inside the var/di folder: frontend.ser and global.ser. Once these files were deleted, everything works just fine and the internal server error disappears.

I am still not sure what caused these files to become a problem, but at least just deleting them got me going again and fixed the issue.

Hopefully this solution will work for others experiencing this same problem.

Answer 2

1) You should check your current application mode:

php bin/magento deploy:mode:show

If the current mode is developer mode. You shouldn't run di compile. Di compile is used for production mode.

2) 500 Error is a server error. You should enable Display Errors in app/bootstrap.php or index.php file to see the error.

ini_set('display_errors', -1); // Remember to set -1

NOTE: should enable cache and check the permission properly.