To reproduce this bug, create a new database (I use MariaDB) and add a .env.local file containing

#APP_ENV=prod
DATABASE_URL=mysql://autowirebug:[email protected]:3306/autowirebug?serverVersion=mariadb-10.5.5

Change DATABASE_URL according to your setup.

Now run

composer install
bin/console app:migrations:migrate myproject

Visit the root directory, e.g. http://autowiring-bug. If everything went well, an empty page with title "Welcome!" and the profile toolbar will appear.

Now remove the comment hash before APP_ENV=prod in .env.local and reload the page. A 500 error will occur.

Within the real application, I also got the following error in var/log/prod.log:

request.CRITICAL: Uncaught PHP Exception Doctrine\Persistence\Mapping\MappingException: "The class 'App\Entity\MyProject\TheEntity' was not found in the chain configured namespaces " at /srv/http/myproject/vendor/doctrine/persistence/lib/Doctrine/Persistence/Mapping/MappingException.php line 23 {"exception":"[object] (Doctrine\\Persistence\\Mapping\\MappingException(code: 0): The class 'App\\Entity\\MyProject\\TheEntity' was not found in the chain configured namespaces  at /srv/http/myproject/vendor/doctrine/persistence/lib/Doctrine/Persistence/Mapping/MappingException.php:23)"}

This error is about the line

        $this->repository = $em->getRepository(TheEntity::class);

in src/Service/TheService.php.

With this example, this message is not written, I'm not sure why not (trying to use a repository method also does not write the line; also, in dev mode, this also functions as expected).