Support -print-target-info flag

Author: owenv

Sources/SwiftDriver/Driver/Driver.swift

@@ -551,6 +551,35 @@ extension Driver {
     }
   }
 
+  /// 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
+  }
+
   /// Run the driver.
   public mutating func run(
     resolver: ArgsResolver,
@@ -567,17 +596,18 @@ 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()
+    let jobs: [Job]
+    if let job = try immediateForwardingJob() {
+      jobs = [job]
+    } else {
+      // Plan the build.
+      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 {