Compiler.scala

import sbt.Keys._
import sbt.{addCompilerPlugin, _}

object Compiler {

  val scala213Opts = Seq(
    "-deprecation", // Emit warning and location for usages of deprecated APIs.
    "-encoding",
    "utf-8", // Specify character encoding used by source files.
    "-explaintypes", // Explain type errors in more detail.
    "-feature",
    /* Emit warning and location for usages of features that should be imported
     * explicitly. */
    "-language:existentials", /* Existential types (besides wildcard types) can
     * be written and inferred */
    "-language:experimental.macros", /* Allow macro definition (besides
     * implementation and application) */
    "-language:higherKinds", // Allow higher-kinded types
    "-language:implicitConversions", /* Allow definition of implicit functions
     * called views */
    "-unchecked", /* Enable additional warnings where generated code depends on
     * assumptions. */
    "-Xcheckinit", /* Wrap field accessors to throw an exception on
     * uninitialized access. */
    "-Xfatal-warnings", // Fail the compilation if there are any warnings.
    // "-Xfuture", // Turn on future language features.
    "-Xlint:adapted-args", /* Warn if an argument list is modified to match the
     * receiver. */
    "-Xlint:constant", /* Evaluation of a constant arithmetic expression results
     * in an error. */
    "-Xlint:delayedinit-select", // Selecting member of DelayedInit.
    "-Xlint:doc-detached", /* A Scaladoc comment appears to be detached from its
     * element. */
    "-Xlint:inaccessible", /* Warn about inaccessible types in method
     * signatures. */
    "-Xlint:infer-any", // Warn when a type argument is inferred to be `Any`.
    "-Xlint:missing-interpolator", /* A string literal appears to be missing an
     * interpolator id. */
    "-Xlint:nullary-unit", // Warn when nullary methods return Unit.
    "-Xlint:option-implicit", // Option.apply used implicit view.
    "-Xlint:package-object-classes", /* Class or object defined in package
     * object. */
    "-Xlint:poly-implicit-overload", /* Parameterized overloaded implicit
     * methods are not visible as view bounds. */
    "-Xlint:private-shadow", /* A private field (or class parameter) shadows a
     * superclass field. */
    "-Xlint:stars-align", /* Pattern sequence wildcard must align with sequence
     * component. */
    "-Xlint:type-parameter-shadow", /* A local type parameter shadows a type
     * already in scope. */
    "-Xlint:adapted-args",
    /* Do not adapt an argument list (either by inserting () or creating a
     * tuple) to match the receiver. */
    "-Xlint:inaccessible", /* Warn about inaccessible types in method
     * signatures. */
    "-Xlint:infer-any", // Warn when a type argument is inferred to be `Any`.
    "-Xlint:nullary-unit", // Warn when nullary methods return Unit.
    // "-Xlint:nullary-override", // Warn when non-nullary `def f()' overrides
    // nullary `def f'.
    // "-Xlint:unsound-match", // Pattern match may not be typesafe.
    // "-Xlint:by-name-right-associative", // By-name parameter of right
    // associative operator.
    // "-Ypartial-unification", // Enable partial unification in type
    // constructor inference
    "-Ywarn-dead-code", // Warn when dead code is identified.
    "-Ywarn-extra-implicit", /* Warn when more than one implicit parameter
     * section is defined. */
    // "-Ywarn-nullary-override", // Warn when non-nullary `def f()' overrides
    // nullary `def f'.
    "-Ywarn-numeric-widen", // Warn when numerics are widened.
    "-Ywarn-unused:implicits", // Warn if an implicit parameter is unused.
    "-Ywarn-unused:imports", // Warn if an import selector is not referenced.
    "-Ywarn-unused:locals", // Warn if a local definition is unused.
    "-Ywarn-unused:params", // Warn if a value parameter is unused.
    "-Ywarn-unused:patvars", // Warn if a variable bound in a pattern is unused.
    "-Ywarn-unused:privates", // Warn if a private member is unused.
    "-Ywarn-value-discard", // Warn when non-Unit expression results are unused.
    "-Ymacro-annotations", // Macro annotations (for monocle)
    "-Yrangepos", // required by SemanticDB compiler plugin
  )

  val scala3Opts = Seq(
    "-Ykind-projector",
    "-source:3.0-migration",
    "-deprecation", // Emit warning and location for usages of deprecated APIs.
    "-encoding",
    "utf-8", // Specify character encoding used by source files.
    "-explaintypes", // Explain type errors in more detail.
    "-feature",
    /* Emit warning and location for usages of features that should be imported
     * explicitly. */
    "-unchecked", /* Enable additional warnings where generated code depends on
     * assumptions. */
    // "-Wunused", // Enable compiler warnings.
    // "-Xlint:-byname-implicit", // Enable compiler linter warnings.
    "-language:implicitConversions", // Enable implicit conversions
  )

  val consoleOptionsToRemove = Set(
    "-Xfatal-warnings",
    "-Ywarn-unused:implicits",
    "-Ywarn-unused:imports",
    "-Ywarn-unused:locals",
    "-Ywarn-unused:params",
    "-Ywarn-unused:patvars",
    "-Ywarn-unused:privates"
  )

  val settings = Seq(
    scalacOptions ++= {
      CrossVersion.partialVersion(scalaVersion.value) match {
        case Some((3, _)) => scala3Opts
        case _ => scala213Opts
      }
    },

    // Remove the errors related to unused entities, when launching scala repl,
    // so that the code with unused entities can be conveniently tested during
    // development
    Compile / console / scalacOptions := (CrossVersion.partialVersion(
      scalaVersion.value
    ) match {
      case Some((3, _)) => scala3Opts
      case _ => scala213Opts.filterNot(consoleOptionsToRemove)
    }),
    Test / console / scalacOptions := (Compile / console / scalacOptions).value,
    libraryDependencies ++= {
      CrossVersion.partialVersion(scalaVersion.value) match {
        case Some((3, _)) => Seq.empty
        case _ => Seq(
            "com.olegpy" %% "better-monadic-for" % "0.3.1",
            "org.typelevel" % "kind-projector" % "0.13.2" cross CrossVersion.full,
            scalafix.sbt.ScalafixPlugin.autoImport.scalafixSemanticdb,
          ).map(compilerPlugin)
      }
    }
  )

}