Services overriding LagomApplicationLoader.describeService are not discovered by ConductR

Reported by @aruj244 in Gitter: https://gitter.im/lagom/lagom?at=59495f9b746f1fd66322662c

override def describeServices = List(
    readDescriptor[HelloService]
  )

The describeServices: Seq[Descriptor] method is deprecated per the Scaladoc, and describeService: Option[Descriptor] is recommended. When I try to load the hello lagom bundle to ConductR using describeService: Option[Descriptor], it doesn’t work. conduct info shows that the bundle is running, but conduct service-names does not show it running. This problem goes away if I use the deprecated method instead.

[TimMoore]

Actually, let’s go ahead and close this issue (since it was originally about the specific problem reported by @aruj244 and fixed in #830) and I’ll raise new issues for follow up work.

[TimMoore]

I discovered another unfortunate surprise while working on this: scalac does not seem to warn when you override a deprecated method, only when you call one.

There’s also no way to silence a deprecation warning, so all the @deprecated annotation does is increase the number of warning in the Lagom build itself (where we still call the deprecated API for backward compatibility reasons). It does not actually display a warning when building Lagom services that override the deprecated method.

We will want to add a runtime warning of some kind before removing the deprecated functionality.