pass fd to PackageDescription while parsing manifests instead of using SWIFT_DUMP_PACKAGE

Sources/ManifestParser/Manifest+parse.swift

@@ -12,6 +12,10 @@ import struct PackageType.Manifest
 import func POSIX.realpath
 import PackageDescription
 import Utility
+import func POSIX.fopen
+import func libc.fileno
+import func libc.unlink
+import func libc.fclose
 
 extension Manifest {
     public init(path pathComponents: String..., baseURL: String) throws {
@@ -49,16 +53,10 @@ extension Manifest {
 
 private func parse(manifestPath: String) throws -> String? {
 
-    // For now, we load the manifest by having Swift interpret it directly
-    // and using a special environment variable to trigger the PackageDescription
-    // library to dump the package (as TOML) at exit.  Eventually, we should
-    // have two loading processes, one that loads only the the declarative
-    // package specification using the Swift compiler directly and validates
-    // it.
-    //
-    // FIXME: We also should make the mechanism for communicating the
-    // package between the PackageDescription module more robust, for example by passing
-    // in the id of another file descriptor to write the output onto.
+    // For now, we load the manifest by having Swift interpret it directly.
+    // Eventually, we should have two loading processes, one that loads only
+    // the the declarative package specification using the Swift compiler
+    // directly and validates it.
 
     let libdir = Resources.runtimeLibPath
 
@@ -71,5 +69,17 @@ private func parse(manifestPath: String) throws -> String? {
 #endif
     cmd += [manifestPath]
 
-    return try popen(cmd, environment: ["SWIFT_DUMP_PACKAGE": "1"]).chuzzle()
+    //Create and open a temporary file to write toml to
+    let filePath = Path.join(manifestPath.parentDirectory, ".Package.toml")
+    let fp = try fopen(filePath, mode: .Write)
+    defer { fclose(fp) }
+
+    //Pass the fd in arguments
+    cmd += ["-fileno", "\(fileno(fp))"]
+    try system(cmd)
+
+    let toml = try File(path: filePath).enumerate().reduce("") { $0 + "\n" + $1 }
+    unlink(filePath) //Delete the temp file after reading it
+
+    return toml != "" ? toml : nil
 }

Sources/PackageDescription/Package.swift

@@ -14,7 +14,6 @@ import Glibc
 import Darwin.C
 #endif
 
-
 /// The description for a complete package.
 public final class Package {
     /// The description for a package dependency.
@@ -69,8 +68,10 @@ public final class Package {
         // FIXME: This doesn't belong here, but for now is the mechanism we use
         // to get the interpreter to dump the package when attempting to load a
         // manifest.
-        if getenv("SWIFT_DUMP_PACKAGE") != nil {
-            dumpPackageAtExit(self)
+
+        if let fileNoOptIndex = Process.arguments.indexOf("-fileno"),
+               fileNo = Int32(Process.arguments[fileNoOptIndex + 1]) {
+            dumpPackageAtExit(self, fileNo: fileNo)
         }
     }
 }
@@ -128,16 +129,21 @@ public func ==(lhs: Package.Dependency, rhs: Package.Dependency) -> Bool {
 
 // MARK: Package Dumping
 
-private var thePackageToDump: Package? = nil
-private func dumpPackageAtExit(package: Package) {
+private var dumpInfo: (package: Package, fileNo: Int32)? = nil
+private func dumpPackageAtExit(package: Package, fileNo: Int32) {
     func dump() {
-        print(thePackageToDump!.toTOML())
+        guard let dumpInfo = dumpInfo else { return }
+        let fd = fdopen(dumpInfo.fileNo, "w")
+        guard fd != nil else { return }
+        fputs(dumpInfo.package.toTOML(), fd)
         for product in products {
-            print("[[products]]")
-            print(product.toTOML())
-            print()
+            fputs("[[products]]", fd)
+            fputs("\n", fd)
+            fputs(product.toTOML(), fd)
+            fputs("\n", fd)
         }
+        fclose(fd)
     }
-    thePackageToDump = package
+    dumpInfo = (package, fileNo)
     atexit(dump)
 }