japgolly · October 1, 2019 12:22 · Oct 1, 2019 · Oct 1, 2019
diff --git a/dev-prod-settings.sbt b/dev-prod-settings.sbt
@@ -0,0 +1,20 @@
+// SBT doesn't have a standard concept of dev/prod builds so however you decide to
+// specify that, you can use settings similar to below.
+// The `scalaJSLinkedFile in Compile` setting referenced in the snippet above will
+// choose fast/full opt via the `scalaJSStage` below.
+
+  def jsDevSettings: Project => Project =
+    _.settings(emitSourceMaps := true)
+
+  def jsProdSettings: Project => Project =
+    _.settings(
+      emitSourceMaps := false,
+      scalaJSStage := FullOptStage,
+      scalaJSSemantics in fullOptJS ~= (_
+        .withProductionMode(true)
+        .withRuntimeClassNameMapper(Semantics.RuntimeClassNameMapper.discardAll())
+        .withArrayIndexOutOfBounds(CheckedBehavior.Unchecked)
+        .withAsInstanceOfs(CheckedBehavior.Unchecked)))
+      scalaJSOptimizerOptions ~= (_
+        .withBatchMode(true)
+        .withCheckScalaJSIR(true)))
diff --git a/copy.sbt b/copy.sbt
@@ -0,0 +1,44 @@
+// Assumptions:
+// 1. You have one or more Scala.JS modules named jsModule1, jsModule2, ...
+// 2. You have a web-serving (or otherwise JVM) module that will serve the JS assets
+
+// The only "webby"/JS plugin I use apart from Scala.JS itself, is xsbt-web-plugin,
+// and even that, only on my pre-http4s projects.
+// xsbt-web-plugin allows me to quickly stop/start a servlet container from SBT.
+// The snippet below is for "webappPostProcess" which is an xsbt-web-plugin task but
+// if you aren't using it, you can just create a task with the same content and make
+// "package" depend on it.
+
+webappPostProcess := {
+  implicit val log      = streams.value.log
+  val outputOfJsModule1 = (scalaJSLinkedFile in Compile in jsModule1).value
+  val outputOfJsModule2 = (scalaJSLinkedFile in Compile in jsModule2).value
+  // ...
+
+  (target: File) => {
+
+    // Copy Scala.JS assets
+    def copyScalaJs(jsf: VirtualJSFile, to: String): Unit =
+      jsf match {
+        case f: FileVirtualJSFile => fileSync(f.file, target / to, mandatory = true)
+        case other                => sys.error("Unsupported virtual file type: " + other)
+      }
+    copyScalaJs(outputOfJsModule1, targetForJsModule1)
+    copyScalaJs(outputOfJsModule2, targetForJsModule2)
+    // ...
+
+    // <copy other assets here too>
+  }
+}
+
+// Little helper. Is it still needed in SBT 1.3.x? Who knows?? It was definately helpful in the 0.13.x days.
+def fileSync(from: File, to: File, mandatory: Boolean)(implicit log: Logger): Unit =
+  if (from.exists()) {
+    log.info(s"Copying $from → $to")
+    IO.copyFile(from, to, preserveLastModified = true)
+  } else if (mandatory)
+    sys.error("File not found: " + from.absolutePath)
+  else if (to.exists()) {
+    log.info(s"Deleting $to")
+    IO.delete(to)
+  }