fenced netrc feature for macOS 10.13+

Author: sstadelman

Sources/Commands/Options.swift

@@ -112,8 +112,10 @@ public class ToolOptions {
         archs.count > 1 ? .xcode : _buildSystem
     }
 
+    #if os(macOS)
     /// The location of the netrc file which should be use for authentication when downloading binary target artifacts
     public var netrcFilePath: AbsolutePath?
+    #endif
 
     public var _buildSystem: BuildSystemKind = .native
 

Sources/Commands/SwiftTool.swift

@@ -474,11 +474,16 @@ public class SwiftTool<Options: ToolOptions> {
             option: parser.add(option: "--build-system", kind: BuildSystemKind.self, usage: nil),
             to: { $0._buildSystem = $1 })
 
-        binder.bind(
-            option: parser.add(
-                option: "--netrc-file", kind: PathArgument.self,
-                usage: "Absolute path to netrc file for downloading binary target artifacts"),
-            to: { $0.netrcFilePath = $1.path })
+        #if os(macOS)
+        if #available(macOS 10.13, *) {
+            // implementation of the netrc reader depends upon macOS 10.13
+            binder.bind(
+                option: parser.add(
+                    option: "--netrc-file", kind: PathArgument.self,
+                    usage: "Absolute path to netrc file for downloading binary target artifacts"),
+                to: { $0.netrcFilePath = $1.path })
+        }
+        #endif
 
         // Let subclasses bind arguments.
         type(of: self).defineArguments(parser: parser, binder: binder)
@@ -610,7 +615,13 @@ public class SwiftTool<Options: ToolOptions> {
     }()
 
     func resolvedNetrcFilePath() -> AbsolutePath? {
-        return options.netrcFilePath ?? AbsolutePath("\(NSHomeDirectory())/.netrc")
+        // Netrc feature depends upon macOS 10.13
+        #if os(macOS)
+        if #available(macOS 10.13, *) {
+            return options.netrcFilePath
+        }
+        #endif
+        return nil
     }
 
     /// Holds the currently active workspace.

Sources/Workspace/Workspace.swift

@@ -1403,9 +1403,15 @@ extension Workspace {
     private func download(_ artifacts: [ManagedArtifact], diagnostics: DiagnosticsEngine) {
         let group = DispatchGroup()
         let tempDiagnostics = DiagnosticsEngine()
-
-        let netrc = try? Netrc.load(fromFileAtPath: netrcFilePath).get()
 
+        var authProvider: AuthorizationProviding? = nil
+        #if os(macOS)
+        // Netrc feature currently only supported on macOS 10.13+ due to dependency
+        // on NSTextCheckingResult.range(with:)
+        if #available(macOS 10.13, *) {
+            authProvider = try? Netrc.load(fromFileAtPath: netrcFilePath).get()
+        }
+        #endif
         for artifact in artifacts {
             group.enter()
 
@@ -1429,7 +1435,7 @@ extension Workspace {
             downloader.downloadFile(
                 at: parsedURL,
                 to: archivePath,
-                withAuthorizationProvider: netrc,
+                withAuthorizationProvider: authProvider,
                 progress: { bytesDownloaded, totalBytesToDownload in
                     self.delegate?.downloadingBinaryArtifact(
                         from: url,