Scala example source code file (ToolBoxFactory.scala)

This example Scala source code file (ToolBoxFactory.scala) is included in my "Source Code Warehouse" project. The intent of this project is to help you more easily find Scala source code examples by using tags.

All credit for the original source code belongs to scala-lang.org; I'm just trying to make examples easier to find. (For my Scala work, see my Scala examples and tutorials.)

Scala tags/keywords

any, boolean, cmd, compiler, eol, io, list, nsc, reflection, string, symbol, termmode, termname, toolboxerror, tree, utilities

The ToolBoxFactory.scala Scala example source code

package scala
package tools
package reflect

import scala.tools.cmd.CommandLineParser
import scala.tools.nsc.Global
import scala.tools.nsc.reporters._
import scala.tools.nsc.CompilerCommand
import scala.tools.nsc.io.{AbstractFile, VirtualDirectory}
import scala.tools.nsc.util.AbstractFileClassLoader
import scala.reflect.internal.Flags._
import scala.reflect.internal.util.{BatchSourceFile, NoSourceFile, NoFile}
import java.lang.{Class => jClass}
import scala.compat.Platform.EOL
import scala.reflect.NameTransformer
import scala.reflect.api.JavaUniverse
import scala.reflect.io.NoAbstractFile
import scala.reflect.internal.FatalError

abstract class ToolBoxFactory[U <: JavaUniverse](val u: U) { factorySelf =>

  val mirror: u.Mirror

  def mkToolBox(frontEnd: FrontEnd = mkSilentFrontEnd(), options: String = ""): ToolBox[U] =
    new ToolBoxImpl(frontEnd, options)

  private class ToolBoxImpl(val frontEnd: FrontEnd, val options: String) extends ToolBox[U] { toolBoxSelf =>

    val u: factorySelf.u.type = factorySelf.u

    lazy val classLoader = new AbstractFileClassLoader(virtualDirectory, factorySelf.mirror.classLoader)
    lazy val mirror: u.Mirror = u.runtimeMirror(classLoader)

    lazy val arguments = CommandLineParser.tokenize(options)
    lazy val virtualDirectory =
      arguments.iterator.sliding(2).collectFirst{ case Seq("-d", dir) => dir } match {
        case Some(outDir) => AbstractFile.getDirectory(outDir)
        case None => new VirtualDirectory("(memory)", None)
      }

    class ToolBoxGlobal(settings: scala.tools.nsc.Settings, reporter0: Reporter)
    extends ReflectGlobal(settings, reporter0, toolBoxSelf.classLoader) {
      import definitions._

      private val trace = scala.tools.nsc.util.trace when settings.debug.value

      private var wrapCount = 0

      private final val wrapperMethodName = "wrapper"

      private def nextWrapperModuleName() = {
        wrapCount += 1
        // we need to use UUIDs here, because our toolbox might be spawned by another toolbox
        // that already has, say, __wrapper$1 in its virtual directory, which will shadow our codegen
        newTermName("__wrapper$" + wrapCount + "$" + java.util.UUID.randomUUID.toString.replace("-", ""))
      }

      // should be called after every use of ToolBoxGlobal in order to prevent leaks
      def cleanupCaches(): Unit = {
        perRunCaches.clearAll()
        undoLog.clear()
        analyzer.lastTreeToTyper = EmptyTree
        lastSeenSourceFile = NoSourceFile
        lastSeenContext = null
      }

      def verify(expr: Tree): Tree = {
        // Previously toolboxes used to typecheck their inputs before compiling.
        // Actually, the initial demo by Martin first typechecked the reified tree,
        // then ran it, which typechecked it again, and only then launched the
        // reflective compiler.
        //
        // However, as observed in https://issues.scala-lang.org/browse/SI-5464
        // current implementation typechecking is not always idempotent.
        // That's why we cannot allow inputs of toolboxes to be typechecked,
        // at least not until the aforementioned issue is closed.
        val typed = expr filter (t => t.tpe != null && t.tpe != NoType && !t.isInstanceOf[TypeTree])
        if (!typed.isEmpty) throw ToolBoxError("reflective toolbox has failed: cannot operate on trees that are already typed")

        if (expr.freeTypes.nonEmpty) {
          val ft_s = expr.freeTypes map (ft => s"  ${ft.name} ${ft.origin}") mkString "\n  "
          throw ToolBoxError(s"""
            |reflective toolbox failed due to unresolved free type variables:
            |$ft_s
            |have you forgotten to use TypeTag annotations for type parameters external to a reifee?
            |if you have troubles tracking free type variables, consider using -Xlog-free-types
            """.stripMargin.trim)
        }

        expr
      }

      def extractFreeTerms(expr0: Tree, wrapFreeTermRefs: Boolean): (Tree, scala.collection.mutable.LinkedHashMap[FreeTermSymbol, TermName]) = {
        val freeTerms = expr0.freeTerms
        val freeTermNames = scala.collection.mutable.LinkedHashMap[FreeTermSymbol, TermName]()
        freeTerms foreach (ft => {
          var name = ft.name.toString
          val namesakes = freeTerms takeWhile (_ != ft) filter (ft2 => ft != ft2 && ft.name == ft2.name)
          if (namesakes.length > 0) name += ("$" + (namesakes.length + 1))
          freeTermNames += (ft -> newTermName(name + nme.REIFY_FREE_VALUE_SUFFIX))
        })
        val expr = new Transformer {
          override def transform(tree: Tree): Tree =
            if (tree.hasSymbolField && tree.symbol.isFreeTerm) {
              tree match {
                case Ident(_) =>
                  val freeTermRef = Ident(freeTermNames(tree.symbol.asFreeTerm))
                  if (wrapFreeTermRefs) Apply(freeTermRef, List()) else freeTermRef
                case _ =>
                  throw new Error("internal error: %s (%s, %s) is not supported".format(tree, tree.productPrefix, tree.getClass))
              }
            } else {
              super.transform(tree)
            }
        }.transform(expr0)
        (expr, freeTermNames)
      }

      def transformDuringTyper(expr: Tree, mode: scala.reflect.internal.Mode, withImplicitViewsDisabled: Boolean, withMacrosDisabled: Boolean)(transform: (analyzer.Typer, Tree) => Tree): Tree = {
        def withWrapping(tree: Tree)(op: Tree => Tree) = if (mode == TERMmode) wrappingIntoTerm(tree)(op) else op(tree)
        withWrapping(verify(expr))(expr1 => {
          // need to extract free terms, because otherwise you won't be able to typecheck macros against something that contains them
          val exprAndFreeTerms = extractFreeTerms(expr1, wrapFreeTermRefs = false)
          var expr2 = exprAndFreeTerms._1
          val freeTerms = exprAndFreeTerms._2
          val dummies = freeTerms.map{ case (freeTerm, name) => ValDef(NoMods, name, TypeTree(freeTerm.info), Select(Ident(PredefModule), newTermName("$qmark$qmark$qmark"))) }.toList
          expr2 = Block(dummies, expr2)

          // !!! Why is this is in the empty package? If it's only to make
          // it inaccessible then please put it somewhere designed for that
          // rather than polluting the empty package with synthetics.
          // [Eugene] how can we implement that?
          val ownerClass       = rootMirror.EmptyPackageClass.newClassSymbol(newTypeName("<expression-owner>"))
          build.setInfo(ownerClass, ClassInfoType(List(ObjectTpe), newScope, ownerClass))
          val owner            = ownerClass.newLocalDummy(expr2.pos)
          val currentTyper     = analyzer.newTyper(analyzer.rootContext(NoCompilationUnit, EmptyTree).make(expr2, owner))
          val withImplicitFlag = if (!withImplicitViewsDisabled) (currentTyper.context.withImplicitsEnabled[Tree] _) else (currentTyper.context.withImplicitsDisabled[Tree] _)
          val withMacroFlag    = if (!withMacrosDisabled) (currentTyper.context.withMacrosEnabled[Tree] _) else (currentTyper.context.withMacrosDisabled[Tree] _)
          def withContext      (tree: => Tree) = withImplicitFlag(withMacroFlag(tree))

          val run = new Run
          run.symSource(ownerClass) = NoAbstractFile // need to set file to something different from null, so that currentRun.defines works
          phase = run.typerPhase // need to set a phase to something <= typerPhase, otherwise implicits in typedSelect will be disabled
          currentTyper.context.setReportErrors() // need to manually set context mode, otherwise typer.silent will throw exceptions
          reporter.reset()

          val expr3 = withContext(transform(currentTyper, expr2))
          var (dummies1, result) = expr3 match {
            case Block(dummies, result) => ((dummies, result))
            case result                 => ((Nil, result))
          }
          val invertedIndex = freeTerms map (_.swap)
          result = new Transformer {
            override def transform(tree: Tree): Tree =
              tree match {
                case Ident(name: TermName) if invertedIndex contains name =>
                  Ident(invertedIndex(name)) setType tree.tpe
                case _ =>
                  super.transform(tree)
              }
          }.transform(result)
          new TreeTypeSubstituter(dummies1 map (_.symbol), dummies1 map (dummy => SingleType(NoPrefix, invertedIndex(dummy.symbol.name.toTermName)))).traverse(result)
          result
        })
      }

      def typecheck(expr: Tree, pt: Type, mode: scala.reflect.internal.Mode, silent: Boolean, withImplicitViewsDisabled: Boolean, withMacrosDisabled: Boolean): Tree =
        transformDuringTyper(expr, mode, withImplicitViewsDisabled = withImplicitViewsDisabled, withMacrosDisabled = withMacrosDisabled)(
          (currentTyper, expr) => {
            trace("typing (implicit views = %s, macros = %s): ".format(!withImplicitViewsDisabled, !withMacrosDisabled))(showAttributed(expr, true, true, settings.Yshowsymowners.value, settings.Yshowsymkinds.value))
            currentTyper.silent(_.typed(expr, mode, pt), reportAmbiguousErrors = false) match {
              case analyzer.SilentResultValue(result) =>
                trace("success: ")(showAttributed(result, true, true, settings.Yshowsymkinds.value))
                result
              case error @ analyzer.SilentTypeError(_) =>
                trace("failed: ")(error.err.errMsg)
                if (!silent) throw ToolBoxError("reflective typecheck has failed: %s".format(error.err.errMsg))
                EmptyTree
            }
          })

      def inferImplicit(tree: Tree, pt: Type, isView: Boolean, silent: Boolean, withMacrosDisabled: Boolean, pos: Position): Tree =
        transformDuringTyper(tree, TERMmode, withImplicitViewsDisabled = false, withMacrosDisabled = withMacrosDisabled)(
          (currentTyper, tree) => {
            trace("inferring implicit %s (macros = %s): ".format(if (isView) "view" else "value", !withMacrosDisabled))(showAttributed(pt, true, true, settings.Yshowsymowners.value, settings.Yshowsymkinds.value))
            analyzer.inferImplicit(tree, pt, isView, currentTyper.context, silent, withMacrosDisabled, pos, (pos, msg) => throw ToolBoxError(msg))
          })

      private def wrapInPackageAndCompile(packageName: TermName, tree: ImplDef): Symbol = {
        val pdef = PackageDef(Ident(packageName), List(tree))
        val unit = new CompilationUnit(NoSourceFile)
        unit.body = pdef

        val run = new Run
        reporter.reset()
        run.compileUnits(List(unit), run.namerPhase)
        throwIfErrors()

        tree.symbol
      }

      def compile(expr0: Tree): () => Any = {
        val expr = build.SyntacticBlock(expr0 :: Nil)

        val freeTerms = expr.freeTerms // need to calculate them here, because later on they will be erased
        val thunks = freeTerms map (fte => () => fte.value) // need to be lazy in order not to distort evaluation order
        verify(expr)

        def wrapInModule(expr0: Tree): ModuleDef = {
          val (expr, freeTerms) = extractFreeTerms(expr0, wrapFreeTermRefs = true)

          val (obj, _) = rootMirror.EmptyPackageClass.newModuleAndClassSymbol(
            nextWrapperModuleName(), NoPosition, NoFlags)

          val minfo = ClassInfoType(List(ObjectTpe), newScope, obj.moduleClass)
          obj.moduleClass setInfo minfo
          obj setInfo obj.moduleClass.tpe

          val meth = obj.moduleClass.newMethod(newTermName(wrapperMethodName))
          def makeParam(schema: (FreeTermSymbol, TermName)) = {
            // see a detailed explanation of the STABLE trick in `GenSymbols.reifyFreeTerm`
            val (fv, name) = schema
            meth.newValueParameter(name, newFlags = if (fv.hasStableFlag) STABLE else 0) setInfo appliedType(definitions.FunctionClass(0).tpe, List(fv.tpe.resultType))
          }
          meth setInfo MethodType(freeTerms.map(makeParam).toList, AnyTpe)
          minfo.decls enter meth
          def defOwner(tree: Tree): Symbol = tree find (_.isDef) map (_.symbol) match {
            case Some(sym) if sym != null && sym != NoSymbol => sym.owner
            case _ => NoSymbol
          }
          trace("wrapping ")(defOwner(expr) -> meth)
          val methdef = DefDef(meth, expr changeOwner (defOwner(expr) -> meth))

          val moduledef = ModuleDef(
              obj,
              gen.mkTemplate(
                  List(TypeTree(ObjectTpe)),
                  noSelfType,
                  NoMods,
                  List(),
                  List(methdef),
                  NoPosition))
          trace("wrapped: ")(showAttributed(moduledef, true, true, settings.Yshowsymowners.value, settings.Yshowsymkinds.value))

          val cleanedUp = resetAttrs(moduledef)
          trace("cleaned up: ")(showAttributed(cleanedUp, true, true, settings.Yshowsymowners.value, settings.Yshowsymkinds.value))
          cleanedUp.asInstanceOf[ModuleDef]
        }

        val mdef = wrapInModule(expr)
        val msym = wrapInPackageAndCompile(mdef.name, mdef)

        val className = msym.fullName
        if (settings.debug) println("generated: "+className)
        def moduleFileName(className: String) = className + "$"
        val jclazz = jClass.forName(moduleFileName(className), true, classLoader)
        val jmeth = jclazz.getDeclaredMethods.find(_.getName == wrapperMethodName).get
        val jfield = jclazz.getDeclaredFields.find(_.getName == NameTransformer.MODULE_INSTANCE_NAME).get
        val singleton = jfield.get(null)

        // @odersky writes: Not sure we will be able to drop this. I forgot the reason why we dereference () functions,
        // but there must have been one. So I propose to leave old version in comments to be resurrected if the problem resurfaces.
        // @Eugene writes: this dates back to the days when one could only reify functions
        // hence, blocks were translated into nullary functions, so
        // presumably, it was useful to immediately evaluate them to get the result of a block
        // @Eugene writes: anyways, I'll stash the old sources here in comments in case anyone wants to revive them
        // val result = jmeth.invoke(singleton, freeTerms map (sym => sym.asInstanceOf[FreeTermVar].value.asInstanceOf[AnyRef]): _*)
        // if (etpe.typeSymbol != FunctionClass(0)) result
        // else {
        //   val applyMeth = result.getClass.getMethod("apply")
        //   applyMeth.invoke(result)
        // }
        () => {
          val result = jmeth.invoke(singleton, thunks map (_.asInstanceOf[AnyRef]): _*)
          if (jmeth.getReturnType == java.lang.Void.TYPE) ()
          else result
        }
      }

      def define(tree: ImplDef): Symbol = {
        val freeTerms = tree.freeTerms
        if (freeTerms.nonEmpty) throw ToolBoxError(s"reflective toolbox has failed: cannot have free terms in a top-level definition")
        verify(tree)
        wrapInPackageAndCompile(nextWrapperModuleName(), tree)
      }

      def parse(code: String): Tree = {
        reporter.reset()
        val tree = gen.mkTreeOrBlock(newUnitParser(code, "<toolbox>").parseStatsOrPackages())
        throwIfErrors()
        tree
      }

      def showAttributed(artifact: Any, printTypes: Boolean = true, printIds: Boolean = true, printOwners: Boolean = false, printKinds: Boolean = false): String = {
        val saved1 = settings.printtypes.value
        val saved2 = settings.uniqid.value
        val saved3 = settings.Yshowsymowners.value
        val saved4 = settings.Yshowsymkinds.value
        try {
          settings.printtypes.value = printTypes
          settings.uniqid.value = printIds
          settings.Yshowsymowners.value = printOwners
          settings.Yshowsymkinds.value = printKinds
          artifact.toString
        } finally {
          settings.printtypes.value = saved1
          settings.uniqid.value = saved2
          settings.Yshowsymowners.value = saved3
          settings.Yshowsymkinds.value = saved4
        }
      }

      // reporter doesn't accumulate errors, but the front-end does
      def throwIfErrors() = {
        if (frontEnd.hasErrors) throw ToolBoxError(
          "reflective compilation has failed:" + EOL + EOL + (frontEnd.infos map (_.msg) mkString EOL)
        )
      }
    }

    trait CompilerApi {
      val compiler: ToolBoxGlobal
      val importer: compiler.Importer { val from: u.type }
      val exporter: u.Importer { val from: compiler.type }
    }

    object withCompilerApi {
      private object api extends CompilerApi {
        lazy val compiler: ToolBoxGlobal = {
          try {
            val errorFn: String => Unit = msg => frontEnd.log(scala.reflect.internal.util.NoPosition, msg, frontEnd.ERROR)
            val command = new CompilerCommand(arguments.toList, errorFn)
            command.settings.outputDirs setSingleOutput virtualDirectory
            val instance = new ToolBoxGlobal(command.settings, frontEndToReporter(frontEnd, command.settings))
            if (frontEnd.hasErrors) {
              throw ToolBoxError(
                "reflective compilation has failed: cannot initialize the compiler:" + EOL + EOL +
                (frontEnd.infos map (_.msg) mkString EOL)
              )
            }
            instance
          } catch {
            case ex: Throwable =>
              throw ToolBoxError(s"reflective compilation has failed: cannot initialize the compiler due to $ex", ex)
          }
        }

        lazy val importer = compiler.mkImporter(u)
        lazy val exporter = importer.reverse
      }

      private val toolBoxLock = new Object
      def apply[T](f: CompilerApi => T): T = toolBoxLock.synchronized {
        try f(api)
        catch { case ex: FatalError => throw ToolBoxError(s"fatal compiler error", ex) }
        finally api.compiler.cleanupCaches()
      }
    }

    type TypecheckMode = scala.reflect.internal.Mode
    val TypecheckMode = scala.reflect.internal.Mode
    val TERMmode = TypecheckMode.EXPRmode
    val TYPEmode = TypecheckMode.TYPEmode | TypecheckMode.FUNmode
    val PATTERNmode = TypecheckMode.PATTERNmode

    def typecheck(tree: u.Tree, mode: TypecheckMode = TERMmode, expectedType: u.Type, silent: Boolean = false, withImplicitViewsDisabled: Boolean = false, withMacrosDisabled: Boolean = false): u.Tree = withCompilerApi { compilerApi =>
      import compilerApi._

      if (compiler.settings.verbose) println("importing "+tree+", expectedType = "+expectedType)
      val ctree: compiler.Tree = importer.importTree(tree)
      val cexpectedType: compiler.Type = importer.importType(expectedType)

      if (compiler.settings.verbose) println("typing "+ctree+", expectedType = "+expectedType)
      val ttree: compiler.Tree = compiler.typecheck(ctree, cexpectedType, mode, silent = silent, withImplicitViewsDisabled = withImplicitViewsDisabled, withMacrosDisabled = withMacrosDisabled)
      val uttree = exporter.importTree(ttree)
      uttree
    }

    def inferImplicitValue(pt: u.Type, silent: Boolean = true, withMacrosDisabled: Boolean = false, pos: u.Position = u.NoPosition): u.Tree = {
      inferImplicit(u.EmptyTree, pt, isView = false, silent = silent, withMacrosDisabled = withMacrosDisabled, pos = pos)
    }

    def inferImplicitView(tree: u.Tree, from: u.Type, to: u.Type, silent: Boolean = true, withMacrosDisabled: Boolean = false, pos: u.Position = u.NoPosition): u.Tree = {
      val functionTypeCtor = u.definitions.FunctionClass(1).asClass.toTypeConstructor
      val viewTpe = u.appliedType(functionTypeCtor, List(from, to))
      inferImplicit(tree, viewTpe, isView = true, silent = silent, withMacrosDisabled = withMacrosDisabled, pos = pos)
    }

    private def inferImplicit(tree: u.Tree, pt: u.Type, isView: Boolean, silent: Boolean, withMacrosDisabled: Boolean, pos: u.Position): u.Tree = withCompilerApi { compilerApi =>
      import compilerApi._

      if (compiler.settings.verbose) println(s"importing pt=$pt, tree=$tree, pos=$pos")
      val ctree: compiler.Tree = importer.importTree(tree)
      val cpt: compiler.Type = importer.importType(pt)
      val cpos: compiler.Position = importer.importPosition(pos)

      if (compiler.settings.verbose) println("inferring implicit %s of type %s, macros = %s".format(if (isView) "view" else "value", pt, !withMacrosDisabled))
      val itree: compiler.Tree = compiler.inferImplicit(ctree, cpt, isView = isView, silent = silent, withMacrosDisabled = withMacrosDisabled, pos = cpos)
      val uitree = exporter.importTree(itree)
      uitree
    }

    def resetLocalAttrs(tree: u.Tree): u.Tree = withCompilerApi { compilerApi =>
      import compilerApi._
      val ctree: compiler.Tree = importer.importTree(tree)
      val ttree: compiler.Tree = compiler.resetAttrs(ctree)
      val uttree = exporter.importTree(ttree)
      uttree
    }

    def untypecheck(tree: u.Tree): u.Tree = resetLocalAttrs(tree)

    def parse(code: String): u.Tree = withCompilerApi { compilerApi =>
      import compilerApi._
      if (compiler.settings.verbose) println("parsing "+code)
      val ctree: compiler.Tree = compiler.parse(code)
      val utree = exporter.importTree(ctree)
      utree
    }

    def compile(tree: u.Tree): () => Any = withCompilerApi { compilerApi =>
      import compilerApi._

      if (compiler.settings.verbose) println("importing "+tree)
      val ctree: compiler.Tree = importer.importTree(tree)

      if (compiler.settings.verbose) println("compiling "+ctree)
      compiler.compile(ctree)
    }

    def define(tree: u.ImplDef): u.Symbol = withCompilerApi { compilerApi =>
      import compilerApi._

      if (compiler.settings.verbose) println("importing "+tree)
      val ctree: compiler.ImplDef = importer.importTree(tree).asInstanceOf[compiler.ImplDef]

      if (compiler.settings.verbose) println("defining "+ctree)
      val csym: compiler.Symbol = compiler.define(ctree)
      val usym = exporter.importSymbol(csym)
      usym
    }

    def eval(tree: u.Tree): Any = compile(tree)()
  }
}