SBT Resolvers work in build.sbt, not working in Build.scala

Question

Once upon a time, in a far off land, there existed a project with a little project/build.sbt file that looks like this:

resolvers += Resolver.url("scala-js-snapshots",
  url("http://repo.scala-js.org/repo/snapshots/")
)(Resolver.ivyStylePatterns)

addSbtPlugin("org.scala-lang.modules.scalajs" % "scalajs-sbt-plugin" % "0.2-SNAPSHOT")

At project load time, things looked great, and there was peace in the land:

[info] Resolving org.fusesource.jansi#jansi;1.4 ...
[info] downloading http://repo.scalajs.org/repo/snapshots/org.scalalang.modules.scalajs/scalajs-sbtplugin/scala_2.10/sbt_0.13/0.2-SNAPSHOT/jars/scalajs-sbt-plugin.jar ...
[info]  [SUCCESSFUL ] org.scala-lang.modules.scalajs#scalajs-sbt-plugin;0.2SNAPSHOT!scalajs-sbt-plugin.jar (1936ms)
[info] Done updating.

One day, another project was created. Unlike the first project, this project was big and complicated, and so it has a project/project/Build.scala which looks like this:

import sbt._
import Keys._
object Build extends sbt.Build {
  import sbt._

  override lazy val projects = Seq(root)
  lazy val root =
    Project("plugins", file("."))
      .settings(
        resolvers += Resolver.url("scala-js-snapshots",
          url("http://repo.scala-js.org/repo/snapshots/")
        )(Resolver.ivyStylePatterns),
        addSbtPlugin("org.scala-lang.modules.scalajs" % "scalajs-sbt-plugin" % "0.2-SNAPSHOT")
      )
      .dependsOn(uri("../../scala-js-resource/plugin"))
      .dependsOn(uri("../../scala-js-workbench"))
}

It seemed to me that this should set up the SBT plugin in an identical way to the earlier arrangement. After all, what is a build.sbt but a bunch of settings? The only difference was that it depended on some other local projects and thus couldn't be a plain .sbt file.

But at load time, something terrible happened:

[warn]  module not found: org.scala-lang.modules.scalajs#scalajs-sbt-plugin;0.2-SNAPSHOT
[warn] ==== typesafe-ivy-releases: tried
[warn]   http://repo.typesafe.com/typesafe/ivy-releases/org.scalalang.modules.scalajs/scalajs-sbt-plugin/scala_2.10/sbt_0.13/0.2-SNAPSHOT/ivys/ivy.xml
[warn] ==== sbt-plugin-releases: tried
[warn]   http://repo.scala-sbt.org/scalasbt/sbt-plugin-releases/org.scalalang.modules.scalajs/scalajs-sbt-plugin/scala_2.10/sbt_0.13/0.2-SNAPSHOT/ivys/ivy.xml
[warn] ==== local: tried
[warn]   C:\Users\Haoyi\.ivy2\local\org.scala-lang.modules.scalajs\scalajs-sbt-plugin\scala_2.10\sbt_0.13\0.2-SNAPSHOT\ivys\ivy.xml
[warn] ==== public: tried
[warn]   http://repo1.maven.org/maven2/org/scala-lang/modules/scalajs/scalajs-sbt-plugin_2.10_0.13/0.2-SNAPSHOT/scalajs-sbt-plugin-0.2-SNAPSHOT.pom

Stupid Build.scala, you didn't even try the resolver I gave you! I even told you where to look for the damn module, why did you give up without even trying? Your little brother the build.sbt found it perfectly fine.

Anyone know what gives, and how I can make the Build.scala work like I want it to?

Answer 1

project/build.sbt is not the little brother of project/Build.scala. The former defines sbt plugins, whereas the latter is the actual build file. Its little brother, if you want, would be <root-dir>/build.sbt.

You should leave the plugin definitions in project/build.sbt. There is nothing wrong with having both files.

Your project definition (along with the dependsOn) should either be in project/Build.scala, or you use <root-dir>/build.sbt where in sbt 0.13 you can basically do everything that was formerly restricted to Build.scala, so my advise is to only use .sbt files these days.

---

So leave project/build.sbt, or better rename it to project/plugins.sbt so there is less confusion, and use this as ./build.sbt:

lazy val root = Project("plugins", file("."))
  .dependsOn(uri("../scala-js-resource/plugin"))
  .dependsOn(uri("../scala-js-workbench"))