Package.swift

private enum Plugins {
    case rswiftGenerateInternalResources

    private var definition: (name: String, package: ExternalPackage) {
        switch self {
        case .rswiftGenerateInternalResources: (name: "RswiftGenerateInternalResources", package: .rswift)
        }
    }

    var name: String { definition.name }
    var package: ExternalPackage { definition.package }
}

extension PackageDescription.Target.PluginUsage {
    fileprivate static func plugin(_ plugin: Plugins) -> Self {
        .plugin(name: plugin.name, package: plugin.package.name)
    }
}