Add export command

modules/build/src/main/scala/scala/build/preprocessing/ScalaPreprocessor.scala

@@ -8,7 +8,14 @@ import java.util.Locale
 
 import scala.build.{Inputs, Os, Sources}
 import scala.build.internal.AmmUtil
-import scala.build.options.{BuildOptions, BuildRequirements, ClassPathOptions, ScalaOptions}
+import scala.build.options.{
+  BuildOptions,
+  BuildRequirements,
+  ClassPathOptions,
+  ScalaJsOptions,
+  ScalaNativeOptions,
+  ScalaOptions
+}
 import scala.collection.JavaConverters._
 
 case object ScalaPreprocessor extends Preprocessor {
@@ -105,8 +112,33 @@ case object ScalaPreprocessor extends Preprocessor {
                 scalaVersion = Some(scalaVer)
               )
             )
-          case _ =>
-            sys.error(s"Unrecognized using directive: ${dir.values.mkString(" ")}")
+          case Seq("repository", repo) if repo.nonEmpty =>
+            BuildOptions(
+              classPathOptions = ClassPathOptions(
+                extraRepositories = Seq(repo)
+              )
+            )
+          case other =>
+            val maybeOptions =
+              // TODO Accept several platforms for cross-compilation
+              if (other.lengthCompare(1) == 0)
+                isPlatform(normalizePlatform(other.head)).map {
+                  case BuildRequirements.Platform.JVM =>
+                    BuildOptions()
+                  case BuildRequirements.Platform.JS =>
+                    BuildOptions(
+                      scalaJsOptions = ScalaJsOptions(enable = true)
+                    )
+                  case BuildRequirements.Platform.Native =>
+                    BuildOptions(
+                      scalaNativeOptions = ScalaNativeOptions(enable = true)
+                    )
+                }
+              else
+                None
+            maybeOptions.getOrElse {
+              sys.error(s"Unrecognized using directive: ${other.mkString(" ")}")
+            }
         }
       }
       .foldLeft(BuildOptions())(_ orElse _)

modules/cli/src/main/scala/scala/cli/ScalaCli.scala

@@ -20,6 +20,7 @@ object ScalaCli extends CommandsEntryPoint {
     Clean,
     Compile,
     Directories,
+    Export,
     InstallCompletions,
     Metabrowse,
     Repl,

modules/cli/src/main/scala/scala/cli/commands/Export.scala

@@ -0,0 +1,69 @@
+package scala.cli.commands
+
+import caseapp._
+
+import scala.build.{BloopBuildClient, Build, CrossSources, Inputs, Logger, Sources}
+import scala.build.internal.CustomCodeWrapper
+import scala.build.options.BuildOptions
+import scala.build.GeneratedSource
+
+import scala.cli.export._
+
+object Export extends ScalaCommand[ExportOptions] {
+
+  private def prepareBuild(
+    inputs: Inputs,
+    buildOptions: BuildOptions,
+    logger: Logger,
+    verbosity: Int
+  ): (Sources, BuildOptions) = {
+
+    logger.log("Preparing build")
+
+    val crossSources = CrossSources.forInputs(
+      inputs,
+      Sources.defaultPreprocessors(
+        buildOptions.scriptOptions.codeWrapper.getOrElse(CustomCodeWrapper)
+      )
+    )
+    val sources = crossSources.sources(buildOptions)
+
+    if (verbosity >= 3)
+      pprint.better.log(sources)
+
+    val options0 = buildOptions.orElse(sources.buildOptions)
+
+    (sources, options0)
+  }
+
+  def sbtBuildTool     = Sbt("1.5.5")
+  def defaultBuildTool = sbtBuildTool
+
+  def run(options: ExportOptions, args: RemainingArgs): Unit = {
+
+    val logger      = options.shared.logger
+    val inputs      = options.shared.inputsOrExit(args)
+    val baseOptions = options.buildOptions
+
+    val (sources, options0) =
+      prepareBuild(inputs, baseOptions, logger, options.shared.logging.verbosity)
+
+    val buildTool =
+      if (options.sbt.getOrElse(true))
+        sbtBuildTool
+      else
+        defaultBuildTool
+
+    val project = buildTool.export(options0, sources)
+
+    val output = options.output.getOrElse("dest")
+    val dest   = os.Path(output, os.pwd)
+    if (os.exists(dest)) {
+      System.err.println(s"Error: $output already exists.")
+      sys.exit(1)
+    }
+
+    os.makeDir.all(dest)
+    project.writeTo(dest)
+  }
+}

modules/cli/src/main/scala/scala/cli/commands/ExportOptions.scala

@@ -0,0 +1,28 @@
+package scala.cli.commands
+
+import caseapp._
+
+import scala.build.options.BuildOptions
+
+// format: off
+final case class ExportOptions(
+  // FIXME There might be too many options for 'scala-cli export' there
+  @Recurse
+    shared: SharedOptions = SharedOptions(),
+  @Recurse
+    mainClass: MainClassOptions = MainClassOptions(),
+
+  sbt: Option[Boolean] = None,
+
+  @Name("o")
+    output: Option[String] = None
+) {
+  // format: on
+
+  def buildOptions: BuildOptions = {
+    val baseOptions = shared.buildOptions(enableJmh = false, None, ignoreErrors = false)
+    baseOptions.copy(
+      mainClass = mainClass.mainClass.filter(_.nonEmpty)
+    )
+  }
+}

modules/cli/src/main/scala/scala/cli/commands/MainClassOptions.scala

@@ -0,0 +1,18 @@
+package scala.cli.commands
+
+import caseapp._
+
+// format: off
+final case class MainClassOptions(
+  @Group("Entrypoint")
+  @HelpMessage("Specify which main class to run")
+  @ValueDescription("main-class")
+  @Name("M")
+    mainClass: Option[String] = None
+)
+// format: on
+
+object MainClassOptions {
+  implicit val parser = Parser[MainClassOptions]
+  implicit val help   = Help[MainClassOptions]
+}

modules/cli/src/main/scala/scala/cli/commands/PackageOptions.scala

@@ -15,6 +15,8 @@ final case class PackageOptions(
     watch: SharedWatchOptions = SharedWatchOptions(),
   @Recurse
     compileCross: CompileCrossOptions = CompileCrossOptions(),
+  @Recurse
+    mainClass: MainClassOptions = MainClassOptions(),
 
   @Group("Package")
   @HelpMessage("Set destination path")
@@ -32,11 +34,6 @@ final case class PackageOptions(
   @HelpMessage("Generate an assembly JAR")
     assembly: Boolean = false,
 
-  @Group("Package")
-  @HelpMessage("Specify which main class to run")
-  @ValueDescription("main-class")
-  @Name("M")
-    mainClass: Option[String] = None,
   @Recurse
     packager: PackagerOptions = PackagerOptions(),
   @Group("Package")
@@ -72,7 +69,7 @@ final case class PackageOptions(
   def buildOptions: BuildOptions = {
     val baseOptions = shared.buildOptions(enableJmh = false, jmhVersion = None)
     baseOptions.copy(
-      mainClass = mainClass.filter(_.nonEmpty),
+      mainClass = mainClass.mainClass.filter(_.nonEmpty),
       packageOptions = baseOptions.packageOptions.copy(
         version = Some(packager.version),
         launcherApp = packager.launcherApp,

modules/cli/src/main/scala/scala/cli/commands/RunOptions.scala

@@ -22,12 +22,8 @@ final case class RunOptions(
     watch: SharedWatchOptions = SharedWatchOptions(),
   @Recurse
     compileCross: CompileCrossOptions = CompileCrossOptions(),
-
-  @Group("Runner")
-  @HelpMessage("Specify which main class to run")
-  @ValueDescription("main-class")
-  @Name("M")
-    mainClass: Option[String] = None
+  @Recurse
+    mainClass: MainClassOptions = MainClassOptions()
 ) {
   // format: on
 
@@ -37,7 +33,7 @@ final case class RunOptions(
       jmhVersion = benchmarking.jmhVersion
     )
     baseOptions.copy(
-      mainClass = mainClass,
+      mainClass = mainClass.mainClass,
       javaOptions = baseOptions.javaOptions.copy(
         javaOpts = baseOptions.javaOptions.javaOpts ++ sharedJava.allJavaOpts
       )

modules/cli/src/main/scala/scala/cli/export/BuildTool.scala

@@ -0,0 +1,8 @@
+package scala.cli.export
+
+import scala.build.options.BuildOptions
+import scala.build.Sources
+
+sealed abstract class BuildTool extends Product with Serializable {
+  def export(options: BuildOptions, sources: Sources): Project
+}

modules/cli/src/main/scala/scala/cli/export/Project.scala

@@ -0,0 +1,5 @@
+package scala.cli.export
+
+abstract class Project extends Product with Serializable {
+  def writeTo(dir: os.Path): Unit
+}