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How to be a part of Scala’s Open Community Build

Picture of Wojciech Mazur, Tooling Software Developer

Wojciech Mazur

Tooling Software Developer

23 minutes read


import scala.collection.SeqOps
extension[A, CC[B] <: SeqOps[B, CC, CC[B]]](seq: CC[A])
 def isRotationOf(that: CC[A]): Boolean = ???
@main def Test =
  Seq('A','B','C', 'D') isRotationOf "DAB" // ok
  ("ABCD": Seq[Char])   isRotationOf "DAB" // ok (1)
  wrapString("ABCD")    isRotationOf "DAB" // ok (2)
  "ABCD"                isRotationOf "DAB" // error, no such method (3)


someSetting := 
   if(scalaVersion.value == “3.1.3”) someValue
   else if (scalaVersion.value == Scala3) someOtherValue
   else defaultValue 


 someSetting := CrossVersion.partialVersion(scalaVersion.value) match {
    case Some((3, 2)) => someScala3Value
    case Some((2, 13)) => someScala2Value


 someSetting := CrossVersion.partialVersion(scalaVersion.value) match {
    case Some((3, 1)) => someVerySpecificScala31Value
    case Some((3, _)) => someScala3Value
    case Some((2, _)) => someScala2Value


someSetting := 
  if (scalaVersion.value.startsWith(“3.1.”)) someVerySpecificScala31Value
  else if (scalaVersion.value.startsWith(“3.”)) someScala3Value
  else defaultScala2Value 


tests = compile-only  // default for the project
projects.overrides {
  subModuleA.tests = full  // compile and execute tests in project named `subModuleA`
  benchmarks { tests = disabled } // ignore tests in project name `benchmarks`


mill.options = ["-J-Xss2M"]
sbt.options = [ “-Dproject.in.ci=true”, “-J-Xmx5G”]


sbt.commands = [
   "set every Test/classLoaderLayeringStrategy := ClassLoaderLayeringStrategy.Flat",
   """set Test/unmanagedSources/excludeFilter ~= { _ || “FailingTest.scala" }"""


  uses-compiler-plugins = true


scala-cli \ 
  https://raw.githubusercontent.com/VirtusLab/community-build3/master/cli/scb-cli.scala – \ 
  run virtuslab/avocado 3.2.1-RC1
Scala 3 Support and Migration

Curated by

Sebastian Synowiec

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VirtusLab has been an incredible partner since the early development of Scala 3, essential to a mature and stable Scala 3 ecosystem.

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