Support Scala Native build target (#2898)

This allows to build static and dynamic libraries other than binaries.

Pull Request: #2898

scalanativelib/src/mill/scalanativelib/ScalaNativeModule.scala

@@ -210,30 +210,35 @@ trait ScalaNativeModule extends ScalaModule { outer =>
 
   def nativeOptimize: Target[Boolean] = T { nativeOptimizeInput().getOrElse(true) }
 
+  /** Build target for current compilation */
+  def nativeBuildTarget: Target[BuildTarget] = T { BuildTarget.Application }
+
   private def nativeConfig: Task[NativeConfig] = T.task {
     val classpath = runClasspath().map(_.path).filter(_.toIO.exists).toList
 
-    NativeConfig(
-      scalaNativeBridge().config(
-        finalMainClass(),
-        classpath.map(_.toIO),
-        nativeWorkdir().toIO,
-        nativeClang().toIO,
-        nativeClangPP().toIO,
-        nativeTarget(),
-        nativeCompileOptions(),
-        nativeLinkingOptions(),
-        nativeGC(),
-        nativeLinkStubs(),
-        nativeLTO().value,
-        releaseMode().value,
-        nativeOptimize(),
-        nativeEmbedResources(),
-        nativeIncrementalCompilation(),
-        nativeDump(),
-        toWorkerApi(logLevel())
-      )
-    )
+    scalaNativeBridge().config(
+      finalMainClassOpt(),
+      classpath.map(_.toIO),
+      nativeWorkdir().toIO,
+      nativeClang().toIO,
+      nativeClangPP().toIO,
+      nativeTarget(),
+      nativeCompileOptions(),
+      nativeLinkingOptions(),
+      nativeGC(),
+      nativeLinkStubs(),
+      nativeLTO().value,
+      releaseMode().value,
+      nativeOptimize(),
+      nativeEmbedResources(),
+      nativeIncrementalCompilation(),
+      nativeDump(),
+      toWorkerApi(logLevel()),
+      toWorkerApi(nativeBuildTarget())
+    ) match {
+      case Right(config) => Result.Success(NativeConfig(config))
+      case Left(error) => Result.Failure(error)
+    }
   }
 
   private[scalanativelib] def toWorkerApi(logLevel: api.NativeLogLevel): workerApi.NativeLogLevel =
@@ -245,11 +250,18 @@ trait ScalaNativeModule extends ScalaModule { outer =>
       case api.NativeLogLevel.Trace => workerApi.NativeLogLevel.Trace
     }
 
+  private[scalanativelib] def toWorkerApi(buildTarget: api.BuildTarget): workerApi.BuildTarget =
+    buildTarget match {
+      case api.BuildTarget.Application => workerApi.BuildTarget.Application
+      case api.BuildTarget.LibraryDynamic => workerApi.BuildTarget.LibraryDynamic
+      case api.BuildTarget.LibraryStatic => workerApi.BuildTarget.LibraryStatic
+    }
+
   // Generates native binary
   def nativeLink = T {
     os.Path(scalaNativeBridge().nativeLink(
       nativeConfig().config,
-      (T.dest / "out").toIO
+      T.dest.toIO
     ))
   }
 

scalanativelib/src/mill/scalanativelib/api/ScalaNativeApi.scala

@@ -60,3 +60,21 @@ object NativeConfig {
   def apply(config: Object): NativeConfig =
     new NativeConfig(config)
 }
+
+sealed trait BuildTarget
+object BuildTarget {
+
+  /** Link code as application */
+  case object Application extends BuildTarget
+
+  /** Link code as shared/dynamic library */
+  case object LibraryDynamic extends BuildTarget
+
+  /** Link code as static library */
+  case object LibraryStatic extends BuildTarget
+
+  implicit val rwApplication: ReadWriter[Application.type] = macroRW[Application.type]
+  implicit val rwLibraryDynamic: ReadWriter[LibraryDynamic.type] = macroRW[LibraryDynamic.type]
+  implicit val rwLibraryStatic: ReadWriter[LibraryStatic.type] = macroRW[LibraryStatic.type]
+  implicit val rw: ReadWriter[BuildTarget] = macroRW[BuildTarget]
+}

scalanativelib/worker-api/src/mill/scalanativelib/worker/api/ScalaNativeWorkerApi.scala

@@ -11,7 +11,7 @@ private[scalanativelib] trait ScalaNativeWorkerApi {
   def defaultGarbageCollector(): String
 
   def config(
-      mainClass: String,
+      mainClass: Either[String, String],
       classpath: Seq[File],
       nativeWorkdir: File,
       nativeClang: File,
@@ -27,8 +27,9 @@ private[scalanativelib] trait ScalaNativeWorkerApi {
       nativeEmbedResources: Boolean,
       nativeIncrementalCompilation: Boolean,
       nativeDump: Boolean,
-      logLevel: NativeLogLevel
-  ): Object
+      logLevel: NativeLogLevel,
+      buildTarget: BuildTarget
+  ): Either[String, Object]
 
   def nativeLink(nativeConfig: Object, outPath: File): File
 
@@ -48,3 +49,10 @@ private[scalanativelib] object NativeLogLevel {
   case object Debug extends NativeLogLevel(500)
   case object Trace extends NativeLogLevel(600)
 }
+
+private[scalanativelib] sealed trait BuildTarget
+private[scalanativelib] object BuildTarget {
+  case object Application extends BuildTarget
+  case object LibraryDynamic extends BuildTarget
+  case object LibraryStatic extends BuildTarget
+}

scalanativelib/worker/0.4/src/mill/scalanativelib/worker/ScalaNativeWorkerImpl.scala

@@ -7,13 +7,15 @@ import mill.scalanativelib.worker.api._
 import scala.scalanative.util.Scope
 import scala.scalanative.build.{
   Build,
+  BuildTarget => ScalaNativeBuildTarget,
   Config,
   Discover,
   GC,
   Logger,
   LTO,
   Mode,
-  NativeConfig => ScalaNativeNativeConfig
+  NativeConfig => ScalaNativeNativeConfig,
+  MillUtils
 }
 import scala.scalanative.nir.Versions
 import scala.scalanative.testinterface.adapter.TestAdapter
@@ -45,7 +47,7 @@ class ScalaNativeWorkerImpl extends mill.scalanativelib.worker.api.ScalaNativeWo
   def defaultGarbageCollector(): String = GC.default.name
 
   def config(
-      mainClass: String,
+      mainClass: Either[String, String],
       classpath: Seq[File],
       nativeWorkdir: File,
       nativeClang: File,
@@ -61,9 +63,9 @@ class ScalaNativeWorkerImpl extends mill.scalanativelib.worker.api.ScalaNativeWo
       nativeEmbedResources: Boolean,
       nativeIncrementalCompilation: Boolean,
       nativeDump: Boolean,
-      logLevel: NativeLogLevel
-  ): Object = {
-    val entry = if (patchIsGreaterThanOrEqual(3)) mainClass else mainClass + "$"
+      logLevel: NativeLogLevel,
+      buildTarget: BuildTarget
+  ): Either[String, Config] = {
     var nativeConfig =
       ScalaNativeNativeConfig.empty
         .withClang(nativeClang.toPath)
@@ -77,24 +79,71 @@ class ScalaNativeWorkerImpl extends mill.scalanativelib.worker.api.ScalaNativeWo
         .withOptimize(nativeOptimize)
         .withLTO(LTO(nativeLTO))
         .withDump(nativeDump)
+    if (patchIsGreaterThanOrEqual(8)) {
+      val nativeBuildTarget = buildTarget match {
+        case BuildTarget.Application => ScalaNativeBuildTarget.application
+        case BuildTarget.LibraryDynamic => ScalaNativeBuildTarget.libraryDynamic
+        case BuildTarget.LibraryStatic => ScalaNativeBuildTarget.libraryStatic
+      }
+      nativeConfig = nativeConfig.withBuildTarget(nativeBuildTarget)
+    } else {
+      if (buildTarget != BuildTarget.Application) {
+        return Left("nativeBuildTarget not supported. Please update to Scala Native 0.4.8+")
+      }
+    }
     if (patchIsGreaterThanOrEqual(4)) {
       nativeConfig = nativeConfig.withEmbedResources(nativeEmbedResources)
     }
     if (patchIsGreaterThanOrEqual(9)) {
       nativeConfig = nativeConfig.withIncrementalCompilation(nativeIncrementalCompilation)
     }
-    val config =
-      Config.empty
-        .withMainClass(entry)
-        .withClassPath(classpath.map(_.toPath))
-        .withWorkdir(nativeWorkdir.toPath)
-        .withCompilerConfig(nativeConfig)
-        .withLogger(logger(logLevel))
-    config
+    var config = Config.empty
+      .withClassPath(classpath.map(_.toPath))
+      .withWorkdir(nativeWorkdir.toPath)
+      .withCompilerConfig(nativeConfig)
+      .withLogger(logger(logLevel))
+
+    if (buildTarget == BuildTarget.Application) {
+      mainClass match {
+        case Left(error) => return Left(error)
+        case Right(mainClass) =>
+          val entry = if (patchIsGreaterThanOrEqual(3)) mainClass else mainClass + "$"
+          config = config.withMainClass(entry)
+      }
+    }
+
+    Right(config)
   }
 
-  def nativeLink(nativeConfig: Object, outPath: File): File = {
+  def nativeLink(nativeConfig: Object, outDirectory: File): File = {
     val config = nativeConfig.asInstanceOf[Config]
+    val compilerConfig = config.compilerConfig
+
+    val name = if (patchIsGreaterThanOrEqual(8)) {
+      val isWindows = MillUtils.targetsWindows(config)
+      val isMac = MillUtils.targetsMac(config)
+
+      val ext = if (compilerConfig.buildTarget == ScalaNativeBuildTarget.application) {
+        if (MillUtils.targetsWindows(config)) ".exe" else ""
+      } else if (compilerConfig.buildTarget == ScalaNativeBuildTarget.libraryDynamic) {
+        if (isWindows) ".dll"
+        else if (isMac) ".dylib"
+        else ".so"
+      } else if (compilerConfig.buildTarget == ScalaNativeBuildTarget.libraryStatic) {
+        if (isWindows) ".lib"
+        else ".a"
+      } else {
+        throw new RuntimeException(s"Unknown buildTarget ${compilerConfig.buildTarget}")
+      }
+
+      val namePrefix = if (compilerConfig.buildTarget == ScalaNativeBuildTarget.application) ""
+      else {
+        if (isWindows) "" else "lib"
+      }
+      s"${namePrefix}out${ext}"
+    } else "out"
+
+    val outPath = new File(outDirectory, name)
     Build.build(config, outPath.toPath)(Scope.unsafe())
     outPath
   }

scalanativelib/worker/0.4/src/mill/scalanativelib/worker/scala/scalanative/Utils.scala

@@ -0,0 +1,6 @@
+package scala.scalanative.build
+
+object MillUtils {
+  def targetsWindows(config: Config): Boolean = config.targetsWindows
+  def targetsMac(config: Config): Boolean = config.targetsMac
+}