If we use the target indirection scheme, and someone wanted a jar_library to be used as

provided

for libraries and as

runtime

for junit tests, for example, you’d need a structure like

jar_library(foo-library) <- target(foo-library-provided) <- java_library()
jar_library(foo-library) <- target(foo-library-runtime) <- junit_tests()

or:

jar_library(foo-library-provided) <- java_library()
jar_library(foo-library-runtime) <- junit_tests()