CompilerCommand.scala

package dotty.tools.dotc
package config

import java.nio.file.{Files, Paths}
import Settings._
import core.Contexts._
import util.DotClass
import Properties._
import scala.collection.JavaConverters._

object CompilerCommand extends DotClass {

  /** The name of the command */
  def cmdName = "dotc"

  private def explainAdvanced = """
    |-- Notes on option parsing --
    |Boolean settings are always false unless set.
    |Where multiple values are accepted, they should be comma-separated.
    |  example: -Xplugin:plugin1,plugin2
    |<phases> means one or a comma-separated list of:
    |  - (partial) phase names with an optional "+" suffix to include the next phase
    |  - the string "all"
    |  example: -Xprint:all prints all phases.
    |  example: -Xprint:front,mixin prints the frontend and mixin phases.
    |  example: -Ylog:erasure+ logs the erasure phase and the phase after the erasure phase.
    |           This is useful because during the tree transform of phase X, we often
    |           already are in phase X + 1.
  """

  def shortUsage = s"Usage: $cmdName <options> <source files>"

  def versionMsg = s"Dotty compiler $versionString -- $copyrightString"

  /** Distill arguments into summary detailing settings, errors and files to compiler */
  def distill(args: Array[String])(implicit ctx: Context): ArgsSummary = {
    /**
     * Expands all arguments starting with @ to the contents of the
     * file named like each argument.
     */
    def expandArg(arg: String): List[String] = {
      def stripComment(s: String) = s takeWhile (_ != '#')
      val path = Paths.get(arg stripPrefix "@")
      if (!Files.exists(path))
        throw new java.io.FileNotFoundException("argument file %s could not be found" format path.getFileName)

      val lines = Files.readAllLines(path) // default to UTF-8 encoding

      val params = lines.asScala map stripComment mkString " "
      CommandLineParser.tokenize(params)
    }

    // expand out @filename to the contents of that filename
    def expandedArguments = args.toList flatMap {
      case x if x startsWith "@"  => expandArg(x)
      case x                      => List(x)
    }

    ctx.settings.processArguments(expandedArguments, processAll = true)
  }

  /** Provide usage feedback on argument summary, assuming that all settings
   *  are already applied in context.
   *  @return  The list of files to compile.
   */
  def checkUsage(summary: ArgsSummary, sourcesRequired: Boolean)(implicit ctx: Context): List[String] = {
    val settings = ctx.settings

    /** Creates a help message for a subset of options based on cond */
    def availableOptionsMsg(cond: Setting[_] => Boolean): String = {
      val ss                  = (ctx.settings.allSettings filter cond).toList sortBy (_.name)
      val width               = (ss map (_.name.length)).max
      def format(s: String)   = ("%-" + width + "s") format s
      def helpStr(s: Setting[_]) = s"${format(s.name)} ${s.description}"
      ss map helpStr mkString "\n"
    }

    def createUsageMsg(label: String, shouldExplain: Boolean, cond: Setting[_] => Boolean): String = {
      val prefix = List(
        Some(shortUsage),
        Some(explainAdvanced) filter (_ => shouldExplain),
        Some(label + " options include:")
      ).flatten mkString "\n"

      prefix + "\n" + availableOptionsMsg(cond)
    }

    def isStandard(s: Setting[_]): Boolean = !isAdvanced(s) && !isPrivate(s)
    def isAdvanced(s: Setting[_]): Boolean = s.name startsWith "-X"
    def isPrivate(s: Setting[_]) : Boolean = s.name startsWith "-Y"

    /** Messages explaining usage and options */
    def usageMessage    = createUsageMsg("where possible standard", shouldExplain = false, isStandard)
    def xusageMessage   = createUsageMsg("Possible advanced", shouldExplain = true, isAdvanced)
    def yusageMessage   = createUsageMsg("Possible private", shouldExplain = true, isPrivate)

    def shouldStopWithInfo = {
      import settings._
      Set(help, Xhelp, Yhelp) exists (_.value)
    }

    def infoMessage: String = {
      import settings._
      if (help.value) usageMessage
      else if (Xhelp.value) xusageMessage
      else if (Yhelp.value) yusageMessage
      else ""
    }

    // Print all warnings encountered during arguments parsing
    summary.warnings.foreach(ctx.warning(_))

    if (summary.errors.nonEmpty) {
      summary.errors foreach (ctx.error(_))
      ctx.echo("  dotc -help  gives more information")
      Nil
    }
    else if (settings.version.value) {
      ctx.echo(versionMsg)
      Nil
    } else if (!Properties.isJavaAtLeast("1.8")) {
      ctx.error("Dotty requires Java 8 to run")
      Nil
    }
    else if (shouldStopWithInfo) {
      ctx.echo(infoMessage)
      Nil
    } else {
      if (sourcesRequired && summary.arguments.isEmpty) ctx.echo(usageMessage)
      summary.arguments
    }
  }
}