Add support for empty source packages

Author: aciidgh

Sources/Transmute/transmute().swift

@@ -10,14 +10,25 @@
 
 import PackageType
 import Utility
+import func libc.exit
 
-public func transmute(packages: [Package]) throws -> ([Module], [Product]) {
+public func transmute(packages: [Package], rootdir: String) throws -> ([Module], [Product]) {
 
     var products: [Product] = []
     var map: [Package: [Module]] = [:]
 
     for package in packages {
-        let modules = try package.modules()
+
+        let modules: [Module]
+        do {
+            modules = try package.modules()
+        } catch Package.ModuleError.NoModules(let pkg) where pkg.path == rootdir {
+            //Ignore and print warning if root package doesn't contain any sources
+            print("warning: root package '\(pkg)' does not contain any sources")
+            if packages.count == 1 { exit(0) } //Exit now if there is no more packages 
+            modules = []
+        }
+
         let testModules = try package.testModules()
         products += try package.products(modules, tests: testModules)
 

Sources/swift-build/main.swift

@@ -44,7 +44,7 @@ do {
         case .Build(let conf):
             let dirs = try directories()
             let packages = try fetch(dirs.root)
-            let (modules, products) = try transmute(packages)
+            let (modules, products) = try transmute(packages, rootdir: dirs.root)
             let yaml = try describe(dirs.build, conf, modules, products, Xcc: opts.Xcc, Xld: opts.Xld, Xswiftc: opts.Xswiftc)
             try build(YAMLPath: yaml, target: "default")