refactor/simplify scalaJs plugin and example

- Restructure code as 1 library case class and 1 Build mixin trait. A library is generally easier to understand and could be re-used independently. 1 trait seems simpler than several here.
- Let not the plugin create the multi-project build, but the user project manually. I think while this adds some minor code overhead it is much simpler to understand. Fewer tasks and other moving parts needed.
- Remove verbose nested sbt-style folder structure. It's simpler without it :).

17 files changed, 122 insertions, 145 deletions

diff --git a/examples/build-scalajs/build/build/build.scala b/examples/build-scalajs/build/build/build.scala
deleted file mode 100644
index 19593f9..0000000
--- a/examples/build-scalajs/build/build/build.scala
+++ /dev/null
@@ -1,7 +0,0 @@
-import cbt._
-class Build(val context: Context) extends BuildBuild{
-
-  override def dependencies =
-    super.dependencies :+
-      DirectoryDependency(new File(context.cbtHome + "/plugins/scalajs"))
-}
diff --git a/examples/build-scalajs/README.md b/examples/scalajs-react-example/README.md
index 74e015a..74e015a 100644
--- a/examples/build-scalajs/README.md
+++ b/examples/scalajs-react-example/README.md
diff --git a/examples/build-scalajs/js/src/main/scala/App.scala b/examples/scalajs-react-example/js/App.scala
index 2682936..0cd170e 100644
--- a/examples/build-scalajs/js/src/main/scala/App.scala
+++ b/examples/scalajs-react-example/js/App.scala
@@ -3,19 +3,12 @@ package prototype
 import japgolly.scalajs.react.ReactDOM
 import org.scalajs.dom
 
-import scala.scalajs.js
 import scala.scalajs.js.JSApp
 import scala.scalajs.js.annotation.JSExport
-import scalajs.js.Dynamic.{global => g}
 
-/**
- * Created by katrin on 2016-04-10.
- */
 @JSExport("App")
 object App extends JSApp {
-
   def main(): Unit = {
-
     val doc = dom.document
     ReactDOM.render(Pictures.PictureComponent(), doc.getElementById("main"))
   }
diff --git a/examples/build-scalajs/js/src/main/scala/Pictures.scala b/examples/scalajs-react-example/js/Pictures.scala
index 88329ee..db1d7ef 100644
--- a/examples/build-scalajs/js/src/main/scala/Pictures.scala
+++ b/examples/scalajs-react-example/js/Pictures.scala
@@ -8,9 +8,6 @@ import japgolly.scalajs.react.vdom.all._
 
 import scala.scalajs.js.JSON
 
-/**
- * Created by katrin on 2016-04-10.
- */
 object Pictures {
 
   case class State(pictures: List[Picture], favourites: List[Picture])
diff --git a/examples/build-scalajs/build/build.scala b/examples/scalajs-react-example/js/build/build.scala
index 89ad030..29f1c73 100644
--- a/examples/build-scalajs/build/build.scala
+++ b/examples/scalajs-react-example/js/build/build.scala
@@ -1,9 +1,11 @@
 import cbt._
-import java.io.File
-class Build( val context: Context ) extends ScalaJsBuild {
-
+class Build(val context: Context) extends ScalaJsBuild{
   override val projectName = "my-project"
 
+  override def sources = super.sources ++ Seq(
+    projectDirectory.getParentFile ++ "/shared"
+  )
+
   override def dependencies = (
     super.dependencies ++
       Resolver( mavenCentral ).bind(
@@ -14,11 +16,7 @@ class Build( val context: Context ) extends ScalaJsBuild {
       )
   )
 
-  /* ++ some JVM only dependencies */
-  override def jvmDependencies = Seq.empty
-
-  override def fastOptOutput = {
-    projectDirectory.getAbsolutePath + "/server/public/" + new File(super.fastOptOutput).getName
+  override protected def fastOptJSFile = {
+    projectDirectory.getParentFile ++ "/server/public" ++ ("/"++super.fastOptJSFile.getName)
   }
 }
-
diff --git a/examples/scalajs-react-example/js/build/build/build.scala b/examples/scalajs-react-example/js/build/build/build.scala
new file mode 100644
index 0000000..b30e005
--- /dev/null
+++ b/examples/scalajs-react-example/js/build/build/build.scala
@@ -0,0 +1,4 @@
+import cbt._
+class Build(val context: Context) extends BuildBuild{
+  override def dependencies = super.dependencies :+ plugins.scalaJs
+}
diff --git a/examples/scalajs-react-example/jvm/build/build.scala b/examples/scalajs-react-example/jvm/build/build.scala
new file mode 100644
index 0000000..327d705
--- /dev/null
+++ b/examples/scalajs-react-example/jvm/build/build.scala
@@ -0,0 +1,6 @@
+import cbt._
+class Build(val context: Context) extends BaseBuild{
+  override def sources = super.sources ++ Seq(
+    projectDirectory.getParentFile ++ "/shared"
+  )
+}
diff --git a/examples/build-scalajs/server/app.js b/examples/scalajs-react-example/server/app.js
index 620c26a..620c26a 100644
--- a/examples/build-scalajs/server/app.js
+++ b/examples/scalajs-react-example/server/app.js
diff --git a/examples/build-scalajs/server/package.json b/examples/scalajs-react-example/server/package.json
index d20ec98..d20ec98 100644
--- a/examples/build-scalajs/server/package.json
+++ b/examples/scalajs-react-example/server/package.json
diff --git a/examples/build-scalajs/server/public/index.html b/examples/scalajs-react-example/server/public/index.html
index 08de20d..08de20d 100644
--- a/examples/build-scalajs/server/public/index.html
+++ b/examples/scalajs-react-example/server/public/index.html
diff --git a/examples/build-scalajs/shared/src/main/scala/prototype/Picture.scala b/examples/scalajs-react-example/shared/Picture.scala
index dbb985a..dbb985a 100644
--- a/examples/build-scalajs/shared/src/main/scala/prototype/Picture.scala
+++ b/examples/scalajs-react-example/shared/Picture.scala
diff --git a/plugins/scalajs/ScalaJs.scala b/plugins/scalajs/ScalaJs.scala
deleted file mode 100644
index 8b55044..0000000
--- a/plugins/scalajs/ScalaJs.scala
+++ /dev/null
@@ -1,93 +0,0 @@
-import java.io.File
-
-import cbt._
-
-
-trait ScalaJsSbtDependencyDsl extends SbtDependencyDsl { self: ScalaJsBuild =>
-
-  //Note: We make same assumption about scala version.
-  //In order to be able to choose different scala version, one has to use %.
-  implicit class ScalaJsDependencyBuilder(groupId: String){
-    def %%%(artifactId: String) = new DependencyBuilder2(
-      groupId, artifactId + artifactIdSuffix, Some(scalaMajorVersion))
-  }
-}
-
-trait ScalaJsBuild extends BaseBuild with ScalaJsSbtDependencyDsl with ScalaJsInformation { outer =>
-
-  def sharedFolder = projectDirectory ++ "/shared"
-  def jvmFolder = projectDirectory ++ "/jvm"
-  def jsFolder = projectDirectory ++ "/js"
-
-  private lazy val jvmBuild = new BasicBuild(outer.context){
-    override def sources = Seq(sharedFolder ++ "/src/main/scala", jvmFolder ++ "/src/main/scala")
-    override def target = jvmFolder ++ "/target"
-    override def dependencies = outer.dependencies ++ jvmDependencies
-  }
-  private lazy val jsBuild = new BasicBuild(outer.context){
-    override def sources = Seq(sharedFolder ++ "/src/main/scala", jsFolder ++ "/src/main/scala")
-    override def target = jsFolder ++ "/target"
-    override def dependencies = outer.dependencies :+ scalaJsLibDep
-    override def scalacOptions = super.scalacOptions ++
-      Seq(s"-Xplugin:${scalaJsCompilerDep.jar.getAbsolutePath}", "-Xplugin-require:scalajs")
-  }
-
-  override def triggerLoopFiles = super.triggerLoopFiles ++ (jvmBuild.sources ++ jsBuild.sources).distinct
-
-  def jvmDependencies = Seq.empty[Dependency]
-  //TODO: implement
-  def jsDependencies = Seq.empty[Dependency]
-  def jvmCompile: Option[File] = jvmBuild.compile
-  def jsCompile: Option[File] = jsBuild.compile
-  override def compile = {
-    jvmCompile
-    jsCompile
-  }
-
-  trait JsOutputMode {
-    def option: String
-    def fileSuffix: String
-  }
-  case object FastOptJS extends JsOutputMode{
-    override val option = "--fastOpt"
-    override val fileSuffix = "fastopt"
-  }
-  case object FullOptJS extends JsOutputMode{
-    override val option = "--fullOpt"
-    override val fileSuffix = "fullopt"
-  }
-
-  private def output(mode: JsOutputMode) = s"${jsBuild.target.getAbsolutePath}/$projectName-${mode.fileSuffix}.js"
-
-  private def link(mode: JsOutputMode, outputPath: String) = {
-    lib.runMain(
-      "org.scalajs.cli.Scalajsld",
-      Seq(
-        mode.option,
-        "--sourceMap",
-        "--stdlib", s"${scalaJsLibDep.jar.getAbsolutePath}",
-        "--output", outputPath
-      ) ++ scalaJsOptions ++ Seq(
-        jsBuild.target.getAbsolutePath) ++
-        jsBuild.dependencies.collect{case d: BoundMavenDependency => d.jar.getAbsolutePath},
-      scalaJsCliDep.classLoader(jsBuild.context.classLoaderCache)
-    )
-  }
-
-  def scalaJsOptions: Seq[String] = Seq()
-
-  def fastOptJS = {
-    compile
-    link(FastOptJS, fastOptOutput, scalaJsOptions)
-  }
-  def fullOptJS = {
-    compile
-    link(FullOptJS, fastOptOutput, scalaJsOptions)
-  }
-  def fastOptOutput: String = output(FastOptJS)
-  def fullOptOutput: String = output(FullOptJS)
-}
-
-
-
-
diff --git a/plugins/scalajs/ScalaJsBuild.scala b/plugins/scalajs/ScalaJsBuild.scala
new file mode 100644
index 0000000..9374f66
--- /dev/null
+++ b/plugins/scalajs/ScalaJsBuild.scala
@@ -0,0 +1,52 @@
+package cbt
+import java.io.File
+import java.net.URL
+
+trait ScalaJsBuild extends BaseBuild {
+  final protected val scalaJsLib = ScalaJsLib(
+    scalaJsVersion,
+    scalaVersion,
+    context.cbtHasChanged,
+    context.classLoaderCache,
+    context.paths.mavenCache
+  )
+  import scalaJsLib.{link => _,_}
+
+  def scalaJsVersion = "0.6.8"
+  final protected val scalaJsMajorVersion: String = lib.libMajorVersion(scalaJsVersion)
+  final protected val artifactIdSuffix = s"_sjs$scalaJsMajorVersion"
+
+  override def dependencies = super.dependencies :+ scalaJsLibraryDependency
+  override def scalacOptions = super.scalacOptions ++ scalaJsLib.scalacOptions
+
+  /** Note: We make same assumption about scala version.
+      In order to be able to choose different scala version, one has to use %. */
+  implicit class ScalaJsDependencyBuilder(groupId: String){
+    def %%%(artifactId: String) = new DependencyBuilder2(
+      groupId, artifactId + artifactIdSuffix, Some(scalaMajorVersion))
+  }
+  
+  private def link(mode: ScalaJsOutputMode, outputPath: File) = scalaJsLib.link(
+    mode, outputPath, scalaJsOptions,
+    target +: dependencies.collect{case d: BoundMavenDependency => d.jar}
+  )
+
+  def scalaJsOptions: Seq[String] = Seq()
+  def scalaJsOptionsFastOpt: Seq[String] = scalaJsOptions
+  def scalaJsOptionsFullOpt: Seq[String] = scalaJsOptions
+
+  private def output(mode: ScalaJsOutputMode) = target ++ s"/$projectName-${mode.fileSuffix}.js"
+  protected def fastOptJSFile: File = output(FastOptJS)
+  protected def fullOptJSFile: File = output(FullOptJS)
+
+  def fastOptJS = {
+    compile
+    link(FastOptJS, fastOptJSFile)
+    fastOptJSFile
+  }
+  def fullOptJS = {
+    compile
+    link(FullOptJS, fullOptJSFile)
+    fullOptJSFile
+  }
+}
diff --git a/plugins/scalajs/ScalaJsInformation.scala b/plugins/scalajs/ScalaJsInformation.scala
deleted file mode 100644
index ada3baf..0000000
--- a/plugins/scalajs/ScalaJsInformation.scala
+++ /dev/null
@@ -1,25 +0,0 @@
-import cbt._
-
-trait ScalaJsInformation extends BaseBuild { outer =>
-
-  val sjsVersion = "0.6.8"
-  final private val sjsMajorVersion: String = lib.libMajorVersion(sjsVersion)
-  final protected val artifactIdSuffix = s"_sjs$sjsMajorVersion"
-
-  final protected val scalaJsCompilerDep =
-    Resolver( mavenCentral ).bindOne(
-      // Has to be full Scala version because the compiler is incompatible between versions
-      MavenDependency("org.scala-js", "scalajs-compiler_2.11.8", sjsVersion)
-    )
-
-  final protected val scalaJsLibDep =
-    Resolver( mavenCentral ).bindOne(
-      ScalaDependency("org.scala-js", "scalajs-library", sjsVersion)
-    )
-
-  final protected val scalaJsCliDep =
-    Resolver( mavenCentral ).bindOne(
-      ScalaDependency("org.scala-js", "scalajs-cli", sjsVersion)
-    )
-}
-
diff --git a/plugins/scalajs/ScalaJsLib.scala b/plugins/scalajs/ScalaJsLib.scala
new file mode 100644
index 0000000..0355850
--- /dev/null
+++ b/plugins/scalajs/ScalaJsLib.scala
@@ -0,0 +1,51 @@
+package cbt
+import java.io.File
+
+case class ScalaJsLib(
+  scalaJsVersion: String, scalaVersion: String,
+  cbtHasChanged: Boolean, classLoaderCache: ClassLoaderCache, mavenCache: File
+)(implicit logger: Logger){
+  sealed trait ScalaJsOutputMode {
+    def option: String
+    def fileSuffix: String
+  }
+  case object FastOptJS extends ScalaJsOutputMode{
+    override val option = "--fastOpt"
+    override val fileSuffix = "fastopt"
+  }
+  case object FullOptJS extends ScalaJsOutputMode{
+    override val option = "--fullOpt"
+    override val fileSuffix = "fullopt"
+  }
+
+  val lib = new Lib(logger)
+  def dep(artifactId: String) = MavenResolver( cbtHasChanged, mavenCache, mavenCentral ).bindOne(
+    MavenDependency("org.scala-js", artifactId, scalaJsVersion)
+  )
+
+  def link(
+    mode: ScalaJsOutputMode, outputPath: File,
+    scalaJsOptions: Seq[String], entriesToLink: Seq[File]
+  ) = {
+    val scalaJsCliDep = dep( "scalajs-cli_"++lib.libMajorVersion(scalaVersion) )
+    lib.runMain(
+      "org.scalajs.cli.Scalajsld",
+      Seq(
+        mode.option,
+        "--sourceMap",
+        "--stdlib", s"${scalaJsLibraryDependency.jar.getAbsolutePath}",
+        "--output", outputPath.string
+      ) ++ scalaJsOptions ++ entriesToLink.map(_.getAbsolutePath),
+      scalaJsCliDep.classLoader(classLoaderCache)
+    )
+  }
+
+  val scalaJsLibraryDependency = dep( "scalajs-library_"++lib.libMajorVersion(scalaVersion) )
+
+  // Has to be full Scala version because the compiler is incompatible between versions
+  val scalaJsCompilerDependency = dep( "scalajs-compiler_"++scalaVersion )  
+  val scalacOptions = Seq(
+    "-Xplugin:" ++ scalaJsCompilerDependency.jar.string,
+    "-Xplugin-require:scalajs"
+  )
+}
diff --git a/stage1/cbt.scala b/stage1/cbt.scala
index 78015b6..8564695 100644
--- a/stage1/cbt.scala
+++ b/stage1/cbt.scala
@@ -16,7 +16,7 @@ object `package`{
   implicit class FileExtensionMethods( file: File ){
     def ++( s: String ): File = {
       if(s endsWith "/") throw new Exception(
-        """Trying to append a String that ends in "/" to a File would loose it. Use .stripSuffix("/") if you need to."""
+        """Trying to append a String that ends in "/" to a File would loose the trailing "/". Use .stripSuffix("/") if you need to."""
       )
       new File( file.toString ++ s )
     }
diff --git a/stage2/BuildBuild.scala b/stage2/BuildBuild.scala
index db5374c..4d9c869 100644
--- a/stage2/BuildBuild.scala
+++ b/stage2/BuildBuild.scala
@@ -10,6 +10,7 @@ trait BuildBuild extends BaseBuild{
   object plugins{
     final val scalaTest = DirectoryDependency( managedContext.cbtHome ++ "/plugins/scalatest" )
     final val sbtLayout = DirectoryDependency( managedContext.cbtHome ++ "/plugins/sbt_layout" )
+    final val scalaJs   = DirectoryDependency( managedContext.cbtHome ++ "/plugins/scalajs" )
   }
 
   override def dependencies =