Am 07.03.2018 um 13:05 schrieb Timoses:

I can't seem to be able to set up dub so that I can build subpackages.

(...)
./dep/dub.json:

(...)

     "dependencies": {
         "test:dep2": "*"
     },

     "targetType": "library"
}

The dependency above must be "test:dep2": {"path": ".."}, because a
sub package, apart from inheriting the prefix from its parent package,
behaves just like a normal package. In particular, when building from
the sub package directory, there is no knowledge about the parent package.

It may make sense to make some improvements in this area, though.