Magento 2.4 syntax error, unexpected token "readonly", expecting identifier#0

Question

We are using Magento 2.4.5-p1 and php 8.1 version, upgrade command is working fine but when we try to run the di-compile command getting an error of

Repositories code generation... 1/9 [===>------------------------]  11% < 1 sec 139.0 MiBsyntax error, unexpected token "readonly", expecting identifier#0 /var/www/html/project_name/setup/src/Magento/Setup/Module/Di/Code/Reader/ClassesScanner.php(117): Magento\Setup\Module\Di\Code\Reader\ClassesScanner->includeClass()
#1 /var/www/html/project_name/setup/src/Magento/Setup/Module/Di/Code/Reader/ClassesScanner.php(87): Magento\Setup\Module\Di\Code\Reader\ClassesScanner->extract()
#2 /var/www/html/project_name/setup/src/Magento/Setup/Module/Di/App/Task/Operation/RepositoryGenerator.php(61): Magento\Setup\Module\Di\Code\Reader\ClassesScanner->getList()
#3 /var/www/html/project_name/setup/src/Magento/Setup/Module/Di/App/Task/Manager.php(56): Magento\Setup\Module\Di\App\Task\Operation\RepositoryGenerator->doOperation()
#4 /var/www/html/project_name/setup/src/Magento/Setup/Console/Command/DiCompileCommand.php(216): Magento\Setup\Module\Di\App\Task\Manager->process()
#5 /var/www/html/project_name/vendor/symfony/console/Command/Command.php(255): Magento\Setup\Console\Command\DiCompileCommand->execute()
#6 /var/www/html/project_name/vendor/symfony/console/Application.php(1021): Symfony\Component\Console\Command\Command->run()
#7 /var/www/html/project_name/vendor/symfony/console/Application.php(275): Symfony\Component\Console\Application->doRunCommand()
#8 /var/www/html/project_name/vendor/magento/framework/Console/Cli.php(116): Symfony\Component\Console\Application->doRun()
#9 /var/www/html/project_name/vendor/symfony/console/Application.php(149): Magento\Framework\Console\Cli->doRun()
#10 /var/www/html/project_name/bin/magento(23): Symfony\Component\Console\Application->run()
#11 {main}

Also, this issue is also in GitHub but the not fully proper response - https://github.com/magento/magento2/issues/36521

Does anyone know how to resolve this?

Answer 1

As you can see, the original poster of the issue in the Github issue mentioned a custom module causing his issue.

PHP 8.1 introduces readonly as a reserved PHP keyword.
So find in your custom code or 3rd-party extensions to see if any file using readonly is invalid then fix it. Run this command: grep -r --include \*.php --exclude-dir=vendor/magento readonly app vendor

Answer 2

Issue belongs to vendor file. Please remove and update vendor files by composer. Backup current vendor folder first then remove by using below steps:

1. rm -rf vendor/*
2. composer update/install. It will download latest files and the try after give all required permissions.

It may help you!

Thankyou.

Answer 3

You can detect the problematic module easily by adding a little bit of debug code to the vendor/composer/ClassLoader.php file. In the findFile class, arround line 447, add a var_dump($class); like so:

public function findFile($class)
{
    // class map lookup
    var_dump($class);

Then run bin/magento setup:di:compile. the last class printed before the fatal error is your problem.