So in our lightning code base we usually refer to labels from js helpers and controllers as the following (it's static reference, not dynamic one):
Everything works fine. The problem appeared when we packaged all our stuff into managed package and installed it on client orgs. As it turns out, all labels referred from lightning helpers and controllers were not included into the package.
The funny think - there is no way to directly add specific label to the managed package, it relies on dependency auto-detection mechanism, which doesn't work for some reason in regards to js helpers and controllers.
The only workaround we've come up so far - add some comments/invisible sections to component's markup and mention all those labels explicitly there. But it's dozens of components and hard to maintain in the future.
Is there any better suggestions? Are we doing something wrong?