Not sure if Needle is still active...we will probably fix this on our own and would be happy to contribute back.

Consider the following situation:

* Namespaces represent customers:

  customer_a
  customer_b
  # ...
  customer_z # 26 customers

* Most customers use the default implementation of most services, i.e. exceptions are rare.

# (In config.rb, or similar)
# 24 customers use the default mailer, only two need something else
registry.register(:mailer) {DefaultMailer.new} # The default
registry.customer_a.register(:mailer) {SpecialMailer.new}
registry.customer_m.register(:mailer) {SpecialMailer.new}

# (In some application code)
def send_bulk_mails(customer)
  mailer = registry[customer][:mailer]
  # ...

The problem is that I still have to register the namespaces for the 24 customers that don't need custom service
implementations, e.g. the following code will fail:

customer = :customer_b
registry[customer][:mailer] # Fails with ServiceNotFound for :customer_b

We actually have several levels of namespaces, e.g customer/project/...  It seems like wasted effort to describe the
entire namespace 'tree' when only a few 'nodes' are actual service implementations.

Am I missing something?

It seems to me like Needle::Container.get could be changed to react differently on ServiceNotFoundException, i.e. checking
the parent.  However, that might be naive...I'll try it and see.