Scala example source code file (NodePrinters.scala)

This example Scala source code file (NodePrinters.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

app, eol, list, mirror, modifiers, reflection, reify, string, test, tree, typename, u

The NodePrinters.scala Scala example source code

/* NSC -- new Scala compiler
 * Copyright 2005-2013 LAMP/EPFL
 * @author  Martin Odersky
 */
package scala.reflect.reify
package utils

import scala.compat.Platform.EOL

trait NodePrinters {
  self: Utils =>

  import global._

  object reifiedNodeToString extends (Tree => String) {
    def apply(tree: Tree): String = {
      var mirrorIsUsed = false
      var flagsAreUsed = false

      // @PP: I fervently hope this is a test case or something, not anything being
      // depended upon.  Of more fragile code I cannot conceive.
      // @Eugene: This stuff is only needed to debug-print out reifications in human-readable format
      // Rolling a full-fledged, robust TreePrinter would be several times more code.
      // Also as of late we have tests that ensure that UX won't be broken by random changes to the reifier.
      val lines = (tree.toString.split(EOL) drop 1 dropRight 1).toList splitAt 2
      val (List(universe, mirror), reification0) = lines
      val reification = (for (line <- reification0) yield {
        var s = line substring 2
        s = s.replace(nme.UNIVERSE_PREFIX.toString, "")
        s = s.replace(".apply", "")
        s = "([^\"])scala\\.collection\\.immutable\\.".r.replaceAllIn(s, "$1")
        s = "List\\[List\\[.*?\\].*?\\]".r.replaceAllIn(s, "List")
        s = "List\\[.*?\\]".r.replaceAllIn(s, "List")
        s = s.replace("immutable.this.Nil", "List()")
        s = """internal\.reificationSupport\.FlagsRepr\((\d+)[lL]\)""".r.replaceAllIn(s, m => {
          flagsAreUsed = true
          show(m.group(1).toLong)
        })
        s = s.replace("Modifiers(0L, TypeName(\"\"), List())", "Modifiers()")
        s = """Modifiers\((\d+)[lL], TypeName\("(.*?)"\), List\((.*?)\)\)""".r.replaceAllIn(s, m => {
          val buf = new scala.collection.mutable.ListBuffer[String]

          val annotations = m.group(3)
          if (buf.nonEmpty || annotations != "")
            buf.append("List(" + annotations + ")")

          val privateWithin = "" + m.group(2)
          if (buf.nonEmpty || privateWithin != "")
            buf.append("TypeName(\"" + privateWithin + "\")")

          val bits = m.group(1)
          if (buf.nonEmpty || bits != "0L") {
            flagsAreUsed = true
            buf.append(show(bits.toLong))
          }

          val replacement = "Modifiers(" + buf.reverse.mkString(", ")  + ")"
          java.util.regex.Matcher.quoteReplacement(replacement)
        })
        s
      })

      val isExpr = reification.length > 0 && reification(0).trim.startsWith("Expr[")
      var rtree = reification dropWhile (!_.trim.startsWith(s"val ${nme.UNIVERSE_SHORT}: U = ${nme.MIRROR_UNTYPED}.universe;"))
      rtree = rtree drop 2
      rtree = rtree takeWhile (_ != "    }")
      rtree = rtree map (s0 => {
        var s = s0
        mirrorIsUsed |= s contains nme.MIRROR_PREFIX.toString
        s = s.replace(nme.MIRROR_PREFIX.toString, "")
        s.trim
      })

      val printout = scala.collection.mutable.ListBuffer[String]()
      printout += universe.trim
      if (mirrorIsUsed) printout += mirror.replace("Mirror[", "scala.reflect.api.Mirror[").trim
      val imports = scala.collection.mutable.ListBuffer[String]()
      imports += nme.UNIVERSE_SHORT.toString
      if (mirrorIsUsed) imports += nme.MIRROR_SHORT.toString
      if (flagsAreUsed) imports += nme.Flag.toString
      printout += s"""import ${imports map (_ + "._") mkString ", "}"""

      val name = if (isExpr) "tree" else "tpe"
      if (rtree(0) startsWith "val") {
        printout += s"val $name = {"
        printout ++= (rtree map ("  " + _))
        printout += "}"
      } else {
        printout += s"val $name = " + rtree(0)
      }
      if (isExpr) {
        if (mirror contains ".getClassLoader") {
          printout += "import scala.tools.reflect.ToolBox"
          printout += s"println(${nme.MIRROR_SHORT}.mkToolBox().eval(tree))"
        } else {
          printout += "println(tree)"
        }
      } else {
        printout += "println(tpe)"
      }

      // printout mkString EOL
      val prefix = "// produced from " + reifier.defaultErrorPosition
      (prefix +: "object Test extends App {" +: (printout map ("  " + _)) :+ "}") mkString EOL
    }
  }
}