Definine a synthetic service in Symfony 4.1 doesn't work from within a bundle

Question

I am creating a Symfony Bundle that defines a synthetic service:

my_alias:
    public: true
    synthetic: true

After installing the bundle, the application's console command cache:clear always fails with the error:

[Symfony\Component\DependencyInjection\Exception\RuntimeException] Invalid service "my_alias": class "" does not exist.

If I create the same alias inside the actual framework, this error does not turn up.

Is this a bug, or am I doing something wrong?

Answer 1

清除缓存后，将重新编译内核，并且容器将不会找出未注入到容器中的服务，这就是为什么需要将其注入到您的Kernel类下：

if (!$container->hasDefinition('my_alias')) {
    $container->set('my_alias', new SyntheticService());
}