Building separate JS files

[dpinn]

My Play Framework app delivers a number of separate HTML pages to the browser. Rather than download elmMain.js into each of those pages, I would prefer each HTML page to download only the Elm-generated JavaScript that it needs. For example, my ConfigPage.html wants to embed elmConfigPage.js; and my ProjectAdmin.html wants to embed elmProjectAdmin.js.

Can you imagine how I might be able to achieve that with sbt-elm?
Would it require a very significant change to sbt-elm?

[krzemin]

If all of your sources are under single elm project (elm-package.json or elm.json), it's relatively easy to do so.

lazy val `frontend-app1` = project.in(file(".elm/app1"))
  .enablePlugins(SbtWeb, SbtElm)
  .settings(
    name := "frontend-app1",
    inConfig(Assets)(Seq(
      sourceDirectories in elmMake := Seq(new File("elm/App1")),
      elmOutput in elmMake := (resourceManaged in elmMake).value / "js" / "App1.js"
    )),
    (managedClasspath in Runtime) += (packageBin in Assets).value,
    publishArtifact in (Compile, packageDoc) := false,
    publishArtifact in packageDoc := false,
    sources in (Compile,doc) := Seq.empty
  )

lazy val `frontend-app2` = project.in(file(".elm/app2"))
  .enablePlugins(SbtWeb, SbtElm)
  .settings(
    name := "frontend-app2",
    inConfig(Assets)(Seq(
      sourceDirectories in elmMake := Seq(new File("elm/App2")),
      elmOutput in elmMake := (resourceManaged in elmMake).value / "js" / "App2.js"
    )),
    (managedClasspath in Runtime) += (packageBin in Assets).value,
    publishArtifact in (Compile, packageDoc) := false,
    publishArtifact in packageDoc := false,
    sources in (Compile,doc) := Seq.empty
  )

Idea is to keep elm.json (elm-package.json in case of 0.18) in root directory, sources in elm/ directory, but also have all AppX application sources (including Main module) contained in elm/AppX directory.

It's a bit worse, when you have multiple, independent elm projects (separate elm-package.jsons) as it seems sbt-web doesn't support such case.