Why is the error Conflicting cross-version suffixes?

Question

I'm getting this error when I try to compile a Scala project in sbt.

Modules were resolved with conflicting cross-version suffixes in {file:/home/seven3n/caja/Flujo_de_caja/}flujo_de_caja:
[error]    com.typesafe.akka:akka-actor _2.11, _2.10
[error]    org.scalaz:scalaz-effect _2.10, _2.11
[error]    org.scalaz:scalaz-core _2.10, _2.11
[trace] Stack trace suppressed: run last *:update for the full output.
[error] (*:update) Conflicting cross-version suffixes in: com.typesafe.akka:akka-actor, org.scalaz:scalaz-effect, org.scalaz:scalaz-core

This is my build.sbt file:

scalaVersion := "2.11.0"

resolvers ++= Seq(
  "Sonatype snapshots repository" at "https://oss.sonatype.org/content/repositories/snapshots/",
  "Spray repository" at "http://repo.spray.io/",
  "Typesafe repository" at "http://repo.typesafe.com/typesafe/releases/"
)

libraryDependencies ++= {
  val akkaVersion = "2.3.2"
  val sprayVersion = "1.3.1-20140423"
  val sprayJsonVersion = "1.2.6"
  val reactiveMongoVersion = "0.11.0-SNAPSHOT"
  val scalaTestVersion = "2.1.5"
  val specs2Version = "2.3.11"
  val foloneVersion = "0.12-SNAPSHOT"
  Seq(
    "com.typesafe.akka" %% "akka-actor"        % akkaVersion,
    "com.typesafe.akka" %% "akka-testkit"      % akkaVersion,
    "io.spray"          %% "spray-can"         % sprayVersion,
    "io.spray"          %% "spray-routing"     % sprayVersion,
    "io.spray"          %% "spray-testkit"     % sprayVersion,
    "io.spray"          %% "spray-json"        % sprayJsonVersion,
    "org.reactivemongo" % "reactivemongo_2.10" % reactiveMongoVersion,
    "org.scalatest"     %% "scalatest"         % scalaTestVersion % "test",
    "org.specs2"        %% "specs2"            % specs2Version % "test",
    "info.folone"       % "poi-scala_2.10"     % foloneVersion
  )
}

Any suggestions?

Answer 1

The conflicts appear because:

1. you've specified your Scala version to be 2.11
2. you've explicitly specified the Scala version (2.10) for the reactivemongo and poi-scala libraries.

The fix is to use the %% operator for those two libraries as well.

"org.reactivemongo" %% "reactivemongo" % reactiveMongoVersion,
"info.folone"       %% "poi-scala"     % foloneVersion

That's the purpose of the %% operator. To append the declared Scala version (2.11 in your case) to the artifact name.