Link Scala.JS with scala-js-cli

So that we don't have to embed the whole scala-js linker in the Scala
CLI native image.

build.sc

@@ -208,7 +208,6 @@ class Build(val crossScalaVersion: String)
     Deps.osLib,
     Deps.pprint,
     Deps.scalaJsEnvNodeJs,
-    Deps.scalaJsLinkerInterface,
     Deps.scalaJsTestAdapter,
     Deps.scalametaTrees,
     Deps.scalaparse,
@@ -248,9 +247,11 @@ class Build(val crossScalaVersion: String)
          |  def version = "${publishVersion()}"
          |  def detailedVersion: Option[String] = $detailedVersionValue
          |
-         |  def scalaJsVersion = "${Deps.scalaJsLinker.dep.version}"
+         |  def scalaJsVersion = "${Scala.scalaJs}"
          |  def scalaNativeVersion = "${Deps.nativeTools.dep.version}"
          |
+         |  def scalaJsCliVersion = "${InternalDeps.Versions.scalaJsCli}"
+         |
          |  def stubsOrganization = "${stubs.pomSettings().organization}"
          |  def stubsModuleName = "${stubs.artifactName()}"
          |  def stubsVersion = "${stubs.publishVersion()}"
@@ -361,7 +362,6 @@ trait Cli extends SbtModule with CliLaunchers with ScalaCliPublishModule with Fo
     Deps.jimfs, // scalaJsEnvNodeJs pulls jimfs:1.1, whose class path seems borked (bin compat issue with the guava version it depends on)
     Deps.jniUtils,
     Deps.jsoniterCore,
-    Deps.scalaJsLinker,
     Deps.scalaPackager,
     Deps.metaconfigTypesafe
   )

modules/build/src/main/scala/scala/build/Artifacts.scala

@@ -28,6 +28,7 @@ final case class Artifacts(
   extraJavacPlugins: Seq[os.Path],
   userDependencies: Seq[AnyDependency],
   internalDependencies: Seq[AnyDependency],
+  scalaJsCli: Seq[os.Path],
   scalaNativeCli: Seq[os.Path],
   detailedArtifacts: Seq[(CsDependency, csCore.Publication, csUtil.Artifact, os.Path)],
   extraClassPath: Seq[os.Path],
@@ -79,6 +80,7 @@ object Artifacts {
     addJsTestBridge: Option[String],
     addNativeTestInterface: Option[String],
     addJmhDependencies: Option[String],
+    scalaJsCliVersion: Option[String],
     scalaNativeCliVersion: Option[String],
     extraRepositories: Seq[String],
     cache: FileCache[Task],
@@ -133,6 +135,15 @@ object Artifacts {
         Nil
     }
 
+    val scalaJsCliDependency =
+      scalaJsCliVersion.map { version =>
+        import coursier.moduleString
+        val mod =
+          if (version.contains("-sc-")) mod"org.scala-js:scalajs-cli_2.13"
+          else mod"io.github.alexarchambault.tmp:scalajs-cli_2.13"
+        Seq(coursier.Dependency(mod, version))
+      }
+
     val scalaNativeCliDependency =
       scalaNativeCliVersion.map { version =>
         import coursier.moduleString
@@ -201,6 +212,7 @@ object Artifacts {
               Positioned.none(dependency),
               allExtraRepositories,
               None,
+              Nil,
               logger,
               cache.withMessage("Downloading Scala Native CLI"),
               None
@@ -217,6 +229,35 @@ object Artifacts {
       }
     }
 
+    val fetchedScalaJsCli = scalaJsCliDependency match {
+      case Some(dependency) =>
+        import coursier.moduleString
+        val forcedVersions = Seq(
+          mod"org.scala-js:scalajs-linker_2.13" -> scalaJsVersion
+        )
+        Some(
+          value {
+            fetch0(
+              Positioned.none(dependency),
+              allExtraRepositories,
+              None,
+              forcedVersions,
+              logger,
+              cache.withMessage("Downloading Scala.JS CLI"),
+              None
+            )
+          }
+        )
+      case None =>
+        None
+    }
+
+    val scalaJsCli = fetchedScalaJsCli.toSeq.flatMap { fetched =>
+      fetched.fullDetailedArtifacts.collect { case (_, _, _, Some(f)) =>
+        os.Path(f, Os.pwd)
+      }
+    }
+
     val extraStubsJars =
       if (addStubs)
         value {
@@ -269,6 +310,7 @@ object Artifacts {
       extraJavacPlugins,
       dependencies.map(_.value),
       internalDependencies.map(_.value),
+      scalaJsCli,
       scalaNativeCli,
       fetchRes.fullDetailedArtifacts.collect { case (d, p, a, Some(f)) =>
         (d, p, a, os.Path(f, Os.pwd))
@@ -315,6 +357,7 @@ object Artifacts {
       dependencies.map(_.map(_.toCs(params))),
       extraRepositories,
       Some(params.scalaVersion),
+      Nil,
       logger,
       cache,
       classifiersOpt
@@ -324,6 +367,7 @@ object Artifacts {
     dependencies: Positioned[Seq[coursier.Dependency]],
     extraRepositories: Seq[String],
     forceScalaVersionOpt: Option[String],
+    forcedVersions: Seq[(coursier.Module, String)],
     logger: Logger,
     cache: FileCache[Task],
     classifiersOpt: Option[Set[String]]
@@ -339,7 +383,7 @@ object Artifacts {
         .left.map(errors => new RepositoryFormatError(errors))
     }
 
-    val forceVersions = forceScalaVersionOpt match {
+    val forceScalaVersions = forceScalaVersionOpt match {
       case None => Nil
       case Some(sv) =>
         import coursier.moduleString
@@ -367,7 +411,8 @@ object Artifacts {
       .addRepositories(extraRepositories0: _*)
       .addDependencies(dependencies.value: _*)
       .mapResolutionParams { params =>
-        params.addForceVersion(forceVersions: _*)
+        params
+          .addForceVersion(forceScalaVersions ++ forcedVersions: _*)
       }
     for (classifiers <- classifiersOpt) {
       if (classifiers("_"))

modules/build/src/main/scala/scala/build/errors/ScalaJsLinkingError.scala

@@ -0,0 +1,3 @@
+package scala.build.errors
+
+final class ScalaJsLinkingError extends BuildException("Error linking Scala.JS")

modules/build/src/main/scala/scala/build/internal/ScalaJsLinkerConfig.scala

@@ -0,0 +1,55 @@
+package scala.build.internal
+
+final case class ScalaJsLinkerConfig(
+  // trying to have the same defaults as org.scalajs.linker.interface.StandardConfig here
+  moduleKind: String = ScalaJsLinkerConfig.ModuleKind.NoModule,
+  checkIR: Boolean = false,
+  sourceMap: Boolean = true,
+  moduleSplitStyle: String = ScalaJsLinkerConfig.ModuleSplitStyle.FewestModules,
+  esFeatures: ScalaJsLinkerConfig.ESFeatures = ScalaJsLinkerConfig.ESFeatures(),
+  jsHeader: Option[String] = None,
+  prettyPrint: Boolean = false,
+  relativizeSourceMapBase: Option[String] = None,
+  semantics: ScalaJsLinkerConfig.Semantics = ScalaJsLinkerConfig.Semantics()
+)
+
+object ScalaJsLinkerConfig {
+  object ModuleKind {
+    val NoModule       = "NoModule"
+    val ESModule       = "ESModule"
+    val CommonJSModule = "CommonJSModule"
+  }
+
+  object ModuleSplitStyle {
+    val FewestModules   = "FewestModules"
+    val SmallestModules = "SmallestModules"
+  }
+
+  final case class ESFeatures(
+    allowBigIntsForLongs: Boolean = false,
+    avoidClasses: Boolean = true,
+    avoidLetsAndConsts: Boolean = true,
+    esVersion: String = ESVersion.default
+  )
+
+  object ESVersion {
+    val ES5_1  = "ES5_1"
+    val ES2015 = "ES2015"
+    val ES2016 = "ES2016"
+    val ES2017 = "ES2017"
+    val ES2018 = "ES2018"
+    val ES2019 = "ES2019"
+    val ES2020 = "ES2020"
+    val ES2021 = "ES2021"
+
+    def default = ES2015
+  }
+
+  final case class Semantics(
+    asInstanceOfs: String = CheckedBehavior.Compliant
+  )
+
+  object CheckedBehavior {
+    val Compliant = "Compliant"
+  }
+}

modules/build/src/main/scala/scala/build/options/BuildOptions.scala

@@ -613,6 +613,8 @@ final case class BuildOptions(
       extraJavacPlugins = javaOptions.javacPlugins.map(_.value),
       dependencies = value(dependencies),
       extraClassPath = allExtraJars,
+      scalaJsCliVersion =
+        if (platform.value == Platform.JS) Some(scalaJsCliVersion) else None,
       scalaNativeCliVersion =
         if (platform.value == Platform.Native) Some(scalaNativeOptions.finalVersion) else None,
       extraCompileOnlyJars = allExtraCompileOnlyJars,