So far I don't really see a solution for how I can use a library to extend my Package.swift file while also declaring the library within that file.
The API complexity and model complexity is increased quite a bit. Core concepts went from packages, targets, products, and dependencies to packages, targets, products, dependencies, package extensions, custom rules, and tools. And that's keeping the fringe stuff like pkg-config for system libraries, package providers, modulemaps, testing, etc, off the table.
It's a lot. As the Package spec gets more and more specific, it feels like maybe we're fighting a losing battle against the complexity of the problem, hence the desire on my side to expand the scope of the conversation to include a different approach that may enable more flexibility more simply, by combining both the workspace concept and the extensibility concept into one (kinda major) shift in direction.
Maybe a new proposal is in order. Either way, I've voiced my objections.