Adding SBT as a dependency in SBT file - scala

Question

I am writing few sbt tasks in a scala file. These SBT tasks will be imported into many other projects.
lazy val root = (project in file(".")).
settings(
inThisBuild(List(
organization := "com.example",
scalaVersion := "2.11.8",
version := "1.0.0"
)),
name := "sbttasks",
libraryDependencies ++= Seq(
"org.scala-sbt" % "sbt" % "1.0.0" % "provided"
)
)
I get a compilation error
error] java.lang.RuntimeException: Conflicting cross-version suffixes in: org.scala-lang.modules:scala-xml, org.scala-lang.modules:scala-parser-combinators
[error] at scala.sys.package$.error(package.scala:27)
[error] at sbt.librarymanagement.ConflictWarning$.processCrossVersioned(ConflictWarning.scala:39)
[error] at sbt.librarymanagement.ConflictWarning$.apply(ConflictWarning.scala:19)
[error] at sbt.Classpaths$.$anonfun$ivyBaseSettings$64(Defaults.scala:1995)
[error] at scala.Function1.$anonfun$compose$1(Function1.scala:44)
[error] at sbt.internal.util.$tilde$greater.$anonfun$$u2219$1(TypeFunctions.scala:39)
[error] at sbt.std.Transform$$anon$4.work(System.scala:66)
[error] at sbt.Execute.$anonfun$submit$2(Execute.scala:262)
[error] at sbt.internal.util.ErrorHandling$.wideConvert(ErrorHandling.scala:16)
[error] at sbt.Execute.work(Execute.scala:271)
[error] at sbt.Execute.$anonfun$submit$1(Execute.scala:262)
[error] at sbt.ConcurrentRestrictions$$anon$4.$anonfun$submitValid$1(ConcurrentRestrictions.scala:174)
[error] at sbt.Completion
I don't want to write the custom tasks in build.sbt itself (as the SBT documentation shows) because then I won't be able to import my custom tasks into other projects.

Answer 1

To write reusable tasks that you can "import" in different projects, you need to make an sbt plugin.
If you have a multi-project build and want to reuse your tasks in the subprojects, you can create a file project/MyPlugin.scala with
import sbt._
import sbt.Keys._
object MyPlugin extends AutoPlugin {
override def trigger = noTrigger
object autoImport {
val fooTask = taskKey[Foo]("Foo description")
val barTask = taskKey[Bar]("Bar description")
}
import autoImport._
override lazy val projectSettings = Seq(
fooTask := { ??? },
barTask := { ??? }
)
}
Then to enable this plugin (i.e. make those tasks available) in a subproject, you can write this in your build.sbt:
lazy val subproject = (project in file("subproject"))
.enablePlugins(MyPlugin)
On the contrast, if you want to reuse these tasks in other unrelated projects, you need to make this plugin a separate project and publish it. It's a normal sbt project, but instead of an explicit sbt dependency, you write in its build.sbt:
sbtPlugin := true
And the code defining tasks goes to src/main/scala/ (like in a normal project).
You can read in detail about writing plugins in the sbt documentation.

Answer 2

Change version of "org.scala-sbt" to "1.0.0-M4"
lazy val root = (project in file(".")).
settings(
inThisBuild(List(
organization := "com.example",
scalaVersion := "2.11.8",
version := "1.0.0",
name := "sbttasks"
)),
libraryDependencies ++= Seq(
"org.scala-sbt" % "sbt" % "1.0.0-M4" % "provided"
)
)
For entire compatibility matrix check
https://mvnrepository.com/artifact/org.scala-sbt/main