为什么将 ScalaVersion 设置为 2.11 的 sbt 项目也加载 2.10

Question

以下是 scalatra/spark 项目的 project/build.sbt 的核心：

  val ScalaVersion = "2.11.6"
  val ScalatraVersion = "2.4.0-RC2-2"

//   ivyScala := ivyScala.value map { _.copy(overrideScalaVersion = true)}
  lazy val project = Project (
    "keywordsservlet",
    file("."),
    settings = ScalatraPlugin.scalatraSettings ++ scalateSettings ++ Seq(
      organization := Organization,
      name := Name,
      version := Version,
      scalaVersion := ScalaVersion,
      resolvers += Classpaths.typesafeReleases,
      resolvers += "Scalaz Bintray Repo" at "http://dl.bintray.com/scalaz/releases",
      libraryDependencies ++= Seq(
//        "org.scala-lang" % "scala-reflect" % ScalaVersion,
        "org.apache.spark" % "spark-core_2.11" % "1.4.1",
        "org.scalatra" %% "scalatra" % ScalatraVersion,
        "org.scalatra" %% "scalatra-scalate" % ScalatraVersion,
        "org.scalatra" %% "scalatra-specs2" % ScalatraVersion % "test",
        "ch.qos.logback" % "logback-classic" % "1.1.2" % "runtime",
        "org.eclipse.jetty" % "jetty-webapp" % "9.2.10.v20150310" % "container",
        "javax.servlet" % "javax.servlet-api" % "3.1.0" % "provided"
      ),

这是 sbt 输出：注意它正在加载 2.10 目标！

$ sbt   

[info] Loading project definition from /shared/keywords/project
[info] Updating {file:/shared/keywords/project/}keywords-build...
[info] Resolving org.fusesource.jansi#jansi;1.4 ...
[info] Done updating.
[info] Compiling 1 Scala source to /shared/keywords/project/target/scala-2.10/sbt-0.13/classes...
[info] Set current project to KeywordsServlet (in build file:/shared/keywords/)

那么这里发生了什么？

Answer 1

您用于项目的 Scala 版本与 sbt 本身使用的 Scala 版本之间存在差异。

sbt 0.13 可以编译 2.9、2.10 和 2.11（以及 2.12）。然而，当它编译你的 build.sbt 或 Build.scala 文件时，sbt 0.13 使用 Scala 2.10。

同样，sbt 使用的所有插件都是用 2.10 编译的。

另一方面，sbt 0.12 使用 Scala 2.9。