Forward -print-target-info to the frontend, begin refactoring planning for simple driver invocations

Sources/SwiftDriver/Driver/Driver.swift

@@ -553,6 +553,7 @@ extension Driver {
 
   /// Run the driver.
   public mutating func run(
+    jobs: [Job],
     resolver: ArgsResolver,
     executorDelegate: JobExecutorDelegate? = nil,
     processSet: ProcessSet? = nil
@@ -567,17 +568,10 @@ extension Driver {
       return
     }
 
-    if parsedOptions.hasArgument(.version) || parsedOptions.hasArgument(.version_) {
-      // Follow gcc/clang behavior and use stdout for --version and stderr for -v.
-      try printVersion(outputStream: &stdoutStream)
-      return
-    }
     if parsedOptions.hasArgument(.v) {
       try printVersion(outputStream: &stderrStream)
     }
 
-    // Plan the build.
-    let jobs = try planBuild()
     if jobs.isEmpty { return }
 
     // If we're only supposed to print the jobs, do so now.

Sources/SwiftDriver/Jobs/Job.swift

@@ -27,6 +27,8 @@ public struct Job: Codable, Equatable {
     case interpret
     case repl
     case verifyDebugInfo = "verify-debug-info"
+    case printTargetInfo = "print-target-info"
+    case versionRequest = "version-request"
   }
 
   public enum ArgTemplate: Equatable {

Sources/SwiftDriver/Jobs/Planning.swift

@@ -165,8 +165,42 @@ extension Driver {
     return jobs
   }
 
+  /// Create a job if needed for simple requests that can be immediately
+  /// forwarded to the frontend.
+  public mutating func immediateForwardingJob() throws -> Job? {
+    if parsedOptions.hasArgument(.printTargetInfo) {
+      var commandLine: [Job.ArgTemplate] = [.flag("-frontend"),
+                                            .flag("-print-target-info")]
+      try commandLine.appendLast(.target, from: &parsedOptions)
+      try commandLine.appendLast(.sdk, from: &parsedOptions)
+      try commandLine.appendLast(.resourceDir, from: &parsedOptions)
+      return Job(kind: .printTargetInfo,
+                 tool: .absolute(try toolchain.getToolPath(.swiftCompiler)),
+                 commandLine: commandLine,
+                 inputs: [],
+                 outputs: [],
+                 requiresInPlaceExecution: true)
+    }
+
+    if parsedOptions.hasArgument(.version) || parsedOptions.hasArgument(.version_) {
+      return Job(kind: .versionRequest,
+                 tool: .absolute(try toolchain.getToolPath(.swiftCompiler)),
+                 commandLine: [.flag("--version")],
+                 inputs: [],
+                 outputs: [],
+                 requiresInPlaceExecution: true)
+    }
+
+    return nil
+  }
+
   /// Plan a build by producing a set of jobs to complete the build.
   public mutating func planBuild() throws -> [Job] {
+
+    if let job = try immediateForwardingJob() {
+      return [job]
+    }
+
     // Plan the build.
     switch compilerMode {
     case .repl:

Sources/swift-driver/main.swift

@@ -41,8 +41,9 @@ do {
   }
 
   var driver = try Driver(args: arguments, diagnosticsEngine: diagnosticsEngine)
+  let jobs = try driver.planBuild()
   let resolver = try ArgsResolver()
-  try driver.run(resolver: resolver, processSet: processSet)
+  try driver.run(jobs: jobs, resolver: resolver, processSet: processSet)
 
   if driver.diagnosticEngine.hasErrors {
     exit(EXIT_FAILURE)

Tests/SwiftDriverTests/SwiftDriverTests.swift

@@ -1203,6 +1203,29 @@ final class SwiftDriverTests: XCTestCase {
     XCTAssertNoThrow(try driver2.toolchain.getToolPath(.dsymutil))
   }
 
+  func testVersionRequest() throws {
+    for arg in ["-version", "--version"] {
+      var driver = try Driver(args: ["swift"] + [arg])
+      let plannedJobs = try driver.planBuild()
+      XCTAssertTrue(plannedJobs.count == 1)
+      let job = plannedJobs[0]
+      XCTAssertEqual(job.kind, .versionRequest)
+      XCTAssertEqual(job.commandLine, [.flag("--version")])
+    }
+  }
+
+  func testPrintTargetInfo() throws {
+    var driver = try Driver(args: ["swift", "-print-target-info", "-target", "arm64-apple-ios12.0", "-sdk", "bar", "-resource-dir", "baz"])
+    let plannedJobs = try driver.planBuild()
+    XCTAssertTrue(plannedJobs.count == 1)
+    let job = plannedJobs[0]
+    XCTAssertEqual(job.kind, .printTargetInfo)
+    XCTAssertTrue(job.commandLine.contains(.flag("-print-target-info")))
+    XCTAssertTrue(job.commandLine.contains(.flag("-target")))
+    XCTAssertTrue(job.commandLine.contains(.flag("-sdk")))
+    XCTAssertTrue(job.commandLine.contains(.flag("-resource-dir")))
+  }
+
   func testPCHGeneration() throws {
     do {
       var driver = try Driver(args: ["swiftc", "-typecheck", "-import-objc-header", "TestInputHeader.h", "foo.swift"])