sscalaJSModuleKind := ModuleKind.CommonJSModule - cannot invoke main method anymore :( - scala.js

Question

I am trying to build a new facade that uses a lot of JSImport statements. I wanted to put it in a subfolder of a project I am currently working on, to improve it while at it.
Before my root build.sbt looked like this for the scala.js part:
lazy val client = (project in file("modules/client"))
.enablePlugins(ScalaJSPlugin, ScalaJSWeb)
.settings(generalSettings: _*)
.settings(
name := "client",
libraryDependencies += CrossDependencies.scalaTags,
persistLauncher := true
)
now I added this: scalaJSModuleKind := ModuleKind.CommonJSModule, which is incompatible with the persistLauncher setting, so I removed persistLauncher := true
Of course in my view I could no longer just add client-launcher.js. So I tried to wrap the main-method call manually, like this:
<script type="text/javascript">
tld.test.Test().main()
</script>
Now, this does NOT work IF scalaJSModuleKind := ModuleKind.CommonJSModule is added to my build.sbt. If I remove that setting everything works just fine.
This is my Test
package tld.test
import org.scalajs.dom
import scala.scalajs.js.JSApp
object Test extends JSApp
{
import scalatags.JsDom.all._
def main(): Unit =
{
// Add js script dynamically
val s = script(
"alert('Hello World!')"
)
dom.document.getElementsByTagName("head")(0).appendChild(s.render)
}
}
Now, if I remove that ModuleKind-setting an alert pops up with 'Hello World', but if it's there nope. What is causing this and how can I prevent it?
edit
After answer from #sjrd I tried the following:
plugins.sbt:
addSbtPlugin("ch.epfl.scala" % "sbt-scalajs-bundler" % "0.5.0")
addSbtPlugin("ch.epfl.scala" % "sbt-web-scalajs-bundler" % "0.5.0")
build.sbt:
lazy val client = (project in file("modules/client"))
.enablePlugins(ScalaJSBundlerPlugin, ScalaJSWeb) // ScalaJSBundlerPlugin automatically enables ScalaJSPlugin
.settings(generalSettings: _*)
.settings(
name := "client"
, libraryDependencies += CrossDependencies.scalaTags
//, scalaJSModuleKind := ModuleKind.CommonJSModule // ScalaJSBundlerPlugin implicitly sets moduleKind to CommonJSModule enables ScalaJSPlugin
)
lazy val server = (project in file("modules/server"))
.enablePlugins(PlayScala, WebScalaJSBundlerPlugin)
.settings(generalSettings: _*)
.settings(
name := "server"
,libraryDependencies ++= Seq(
CrossDependencies.scalaTest,
CrossDependencies.scalactic,
CrossDependencies.scalaTags,
"com.typesafe.play" %% "play-json" % "2.6.0-M1")
,scalaJSProjects := Seq(client)
,pipelineStages in Assets := Seq(scalaJSPipeline)
//,pipelineStages := Seq(digest, gzip)
,compile in Compile := ((compile in Compile) dependsOn scalaJSPipeline).value
)
But during compilation I get:
ERROR in ./fastopt-launcher.js
[info] Module not found: Error: Cannot resolve 'file' or 'directory' /home/sorona/scalajstestbed/modules/client/target/scala-2.12/scalajs-bundler/main/client-fastopt.js in /home/sorona/scalajstestbed/modules/client/target/scala-2.12/scalajs-bundler/main
edit: Solution is to then include client-fastopt-bundle.js et voila

Answer 1

Changing the module kind significantly changes the shape of the output file, include its external "specification". In particular, it is not a script that can be embedded in Web page anymore. Instead, it is a CommonJS module.
To be able to include it in a Web page, you will need to bundle it. The best way to do so is too use scalajs-bundler.