When installing a service using provides():

ServiceName name = ServiceName.parse("my.service.name");
ServiceName alias = ServiceName.parse("my.service.alias");

ServiceBuilder builder = ServiceTarget.addService();
builder.provides(name, alias);
builder.setInstance(new UnaryService(....));

this results in a ServiceBuilder with the following attributes:

serviceId = null
Set<ServiceName> provides = {name, alias}
Set<ServiceName> aliases = {}

When using the management console to dump services, the listing looks like this:

/core-service=service-container:dump-services()
Service \"null\" (class org.wildfly.service.Installer$UnaryService) (aliases: []) mode PASSIVE state UP (parent: jboss.as.server-controller)
sivation)

In the documentation for the MSC, I remember reading that if you configure service names using provides only, the first service name will become the serviceId and any subsequent service names will become aliases, but this does not seem to be happening.