How to invoke npm via sbt in a multi-module project - sbt

Question

I am using sbt to build a multi-module project. One of the modules is a JavaScript application which builds with npm. I would like to simply execute npm via a shell script as part of the package task, and use the resulting output file as the artifact for that module. I am able to run a shell command as part of the package task, but for some reason this task is ignored when I run publish or publishLocal.
Attached is my Build.scala.
It is the accounts-ui project which should build using npm. Right now the actual npm build is represented by a simple script.
import sbt._
import Keys._
import play.Play.autoImport._
import PlayKeys._
import play.PlayScala
import sbtassembly._
import AssemblyKeys._
import net.virtualvoid.sbt.graph.Plugin.graphSettings
import ohnosequences.sbt.SbtS3Resolver.autoImport._
object Build extends Build {
lazy val commonSettings = Seq(
organization := "myorg",
scalaVersion := "2.11.5"
)
lazy val publishSettings = Seq(
publishTo := {
val prefix = if (isSnapshot.value) "snapshots" else "releases"
Some(s3resolver.value("MyOrg " + prefix + " S3 bucket", s3(prefix+".repo.myorg.com")))
}
)
lazy val root = Project(id = "root", base = file(".")).settings(commonSettings).settings(
name := "accounts-root"
).settings(publishSettings).aggregate(api, ui)
val _apiName = "accounts-api"
lazy val api = Project(id = "api", base = file("./api")).settings(commonSettings).settings(
name := "accounts-api",
libraryDependencies ++= Seq(
specs2
)
).settings(publishSettings).settings(graphSettings).settings(
mainClass in assembly := Some("play.core.server.NettyServer"),
fullClasspath in assembly += Attributed.blank(PlayKeys.playPackageAssets.value),
test in assembly := {},
assemblyExcludedJars in assembly := {
val cp = (fullClasspath in assembly).value
cp filter { (el) => {
val name = el.data.getName
name.contains("mockito") || name.contains("commons-logging") || name.contains("specs2")
}
}
}
).settings(addArtifact(Artifact(_apiName, "assembly"), assembly)
).enablePlugins(PlayScala)
val npmBuildTask = taskKey[Unit]("some custom task")
lazy val ui = Project(id = "ui", base = file("./ui")).settings(commonSettings).settings(
name := "accounts-ui",
npmBuildTask := {
val processBuilder = Process("npm-build.sh")
val process = processBuilder.run()
if(process.exitValue() != 0)
throw new Error(s"custom task failed with exit value ${process.exitValue()}")
},
Keys.`package` <<= (Keys.`package` in Compile) dependsOn npmBuildTask
).settings(publishSettings)
}

Answer 1

I was able to solve it as follows:
val npmPackageTask = taskKey[File]("npm package task")
lazy val ui = Project(id = "ui", base = file("./ui")).settings(commonSettings).settings(
name := "accounts-ui",
npmPackageTask := {
val processBuilder = Process("npm-build.sh")
val process = processBuilder.run()
if(process.exitValue() != 0)
throw new Error(s"custom task failed with exit value ${process.exitValue()}")
file(".")
},
packageBin in Compile <<= npmPackageTask
).settings(publishSettings)
The key was to create the key as taskKey[File], use the packageBin key, and replace the task with the <<= operator.