Symfony version(s) affected: confirmed on 4.4.4+, but possibly 4.1.1+ (see related issues in additional context)

Description
Private non-shared services are removed from the test container.

IF private non-shared service x is injected into service y AND the service definition of x is replaced by a service reference through a compiler pass THEN the following error occurs in the test environment: The service "y" has a dependency on a non-existent service "x".

How to reproduce

• Check out reproducer
• Run composer install
• Run bin/console ca:cl -e test

The following error occurs: The service "App\Twig\FooRuntime" has a dependency on a non-existent service "App\Services\FooService".

This error only triggers in the test environment (dev and prod produce [OK])

IMPORTANT: Note that App\Twig\FooRuntime goes through compiler pass Symfony\Bundle\TwigBundle\DependencyInjection\Compiler\RuntimeLoaderPassdue to the class implementing RuntimeExtensionInterface. Either removing implements RuntimeExtensionInterface or deleting App\Controller\DefaultController resolves the issue.

Possible Solution
Disabling Symfony\Bundle\FrameworkBundle\DependencyInjection\Compiler\TestServiceContainerWeakRefPass resolves the issue; a solution might be found inside that class.

The following lines in Symfony\Component\DependencyInjection\Compiler\InlineServiceDefinitionsPass also seem related.

if (!$definition->isShared() && !$definition->isPublic()) {
    $container->removeDefinition($id);
}

Additional context
Related issues:

• test.service_container doesn't work with private shared:false services #27488
• AbstractController and non-shared service break in test environment #29628