Of course, but we break that rule. Solder is one example, there's multiple utility classes in the implementation that are required to compile other modules.

I consider that a bug (or a work in progress, depending on how you look at it).

Also, by making the implementation runtime-only, the user is forced to declare two dependencies for their project, one for the API and one for the implementation. If the implementation was compile-scoped, they could just declare the implementation dependency and the API would then be pulled in automatically. This is the kind of stuff we need to discuss and come to a resolution on.

Again, I don't think one dependency is a holy grail. We are making an optimization that I don't find necessary. Making an implementation compile-scoped could be classified as careless programming (by some strict architects, let's say).

If it's setup correctly, depending on seam-faces (the impl) should make it a runtime dep, make the api compile time, make any dependent api compile time and make any dependency impl runtime. If Maven can't accommodate that, then it's just a pita (even then, the worse thing that happens is that the user has two dependencies).