Handle -version argument

Author: cltnschlosser

Sources/SwiftDriver/Driver/Driver.swift

@@ -566,6 +566,17 @@ extension Driver {
       return
     }
 
+    if parsedOptions.hasArgument(.version) || parsedOptions.hasArgument(.version_) {
+      // Follow gcc/clang behavior and use stdout for --version and stderr for -v.
+      printVersion(outputStream: &stdoutStream)
+      stdoutStream.flush()
+      return
+    }
+    if parsedOptions.hasArgument(.v) {
+      printVersion(outputStream: &stderrStream)
+//      SuppressNoInputFilesError = true;
+    }
+
     // Plan the build.
     let jobs = try planBuild()
     if jobs.isEmpty { return }
@@ -634,6 +645,18 @@ extension Driver {
 
     return try exec(path: tool, args: arguments)
   }
+
+  private func printVersion<S: TextOutputStream>(outputStream: inout S) {
+//    OS << version::getSwiftFullVersion(version::Version::getCurrentLanguageVersion()) << '\n';
+//    OS << "Target: " << TC.getTriple().str() << '\n';
+
+    // TODO: don't hardcode
+    outputStream.write("Apple Swift version 5.1.2 (swiftlang-1100.0.278 clang-1100.0.33.9)")
+    outputStream.write("\n")
+    outputStream.write("Target: ")
+    outputStream.write(targetTriple.triple)
+    outputStream.write("\n")
+  }
 }
 
 extension Diagnostic.Message {