Keep comments by default, add -Ydrop-comments

This commit removes `-Ykeep-comments` and adds a new `-Ydrop-comments`
flag. `-Ydrop-comments` is used to prevent the parser from keeping the
comments, and defaults to `false`.

Author: Duhemm

compiler/src/dotty/tools/dotc/Driver.scala

@@ -44,11 +44,11 @@ class Driver extends DotClass {
 
   /**
    * Should the `ContextDocstrings` be set for this context? The `ContextDocstrings` is used
-   * to store doc comments when `-Ykeep-comments` is set, or when TASTY is configured to
+   * to store doc comments unless `-Ydrop-comments` is set, or when TASTY is configured to
    * unpickle the doc comments.
    */
   protected def shouldAddDocContext(implicit ctx: Context): Boolean = {
-    ctx.settings.YkeepComments.value || ctx.mode.is(Mode.ReadComments)
+    !ctx.settings.YdropComments.value || ctx.mode.is(Mode.ReadComments)
   }
 
   def setup(args: Array[String], rootCtx: Context): (List[String], Context) = {

compiler/src/dotty/tools/dotc/config/ScalaSettings.scala

@@ -116,7 +116,7 @@ class ScalaSettings extends Settings.SettingGroup {
   val YshowPrintErrors = BooleanSetting("-Yshow-print-errors", "don't suppress exceptions thrown during tree printing.")
   val YtestPickler = BooleanSetting("-Ytest-pickler", "self-test for pickling functionality; should be used with -Ystop-after:pickler")
   val YcheckReentrant = BooleanSetting("-Ycheck-reentrant", "check that compiled program does not contain vars that can be accessed from a global root.")
-  val YkeepComments = BooleanSetting("-Ykeep-comments", "Keep comments when scanning source files.")
+  val YdropComments = BooleanSetting("-Ydrop-comments", "Drop comments when scanning source files.")
   val YcookComments = BooleanSetting("-Ycook-comments", "Cook the comments (type check `@usecase`, etc.)")
   val YforceSbtPhases = BooleanSetting("-Yforce-sbt-phases", "Run the phases used by sbt for incremental compilation (ExtractDependencies and ExtractAPI) even if the compiler is ran outside of sbt, for debugging.")
   val YdumpSbtInc = BooleanSetting("-Ydump-sbt-inc", "For every compiled foo.scala, output the API representation and dependencies used for sbt incremental compilation in foo.inc, implies -Yforce-sbt-phases.")

compiler/src/dotty/tools/dotc/parsing/Scanners.scala

@@ -172,7 +172,7 @@ object Scanners {
   }
 
   class Scanner(source: SourceFile, override val startFrom: Offset = 0)(implicit ctx: Context) extends ScannerCommon(source)(ctx) {
-    val keepComments = ctx.settings.YkeepComments.value
+    val keepComments = !ctx.settings.YdropComments.value
 
     /** All doc comments kept by their end position in a `Map` */
     private[this] var docstringMap: SortedMap[Int, Comment] = SortedMap.empty

compiler/src/dotty/tools/dotc/transform/Pickler.scala

@@ -60,7 +60,7 @@ class Pickler extends Phase {
       if (tree.pos.exists)
         new PositionPickler(pickler, treePkl.buf.addrOfTree).picklePositions(tree :: Nil)
 
-      if (ctx.settings.YkeepComments.value)
+      if (!ctx.settings.YdropComments.value)
         new CommentPickler(pickler, treePkl.buf.addrOfTree).pickleComment(tree)
 
       // other pickle sections go here.

compiler/test/dotty/tools/dotc/parsing/DocstringTest.scala

@@ -6,7 +6,6 @@ import ast.Trees._
 import core.Contexts.Context
 
 trait DocstringTest extends DottyTest {
-  ctx = ctx.fresh.setSetting(ctx.settings.YkeepComments, true)
 
   def checkDocString(actual: Option[String], expected: String): Unit = actual match {
     case Some(str) =>

doc-tool/src/dotty/tools/dottydoc/DocDriver.scala

@@ -22,7 +22,6 @@ class DocDriver extends Driver {
     val summary = CompilerCommand.distill(args)(ctx)
 
     ctx.setSettings(summary.sstate)
-    ctx.setSetting(ctx.settings.YkeepComments, true)
     ctx.setSetting(ctx.settings.YcookComments, true)
     ctx.setSetting(ctx.settings.YnoInline, true)
     ctx.setProperty(ContextDoc, new ContextDottydoc)

doc-tool/test/DottyDocTest.scala

@@ -23,7 +23,6 @@ trait DottyDocTest extends MessageRendering {
     import base.settings._
     val ctx = base.initialCtx.fresh
     ctx.setSetting(ctx.settings.language, List("Scala2"))
-    ctx.setSetting(ctx.settings.YkeepComments, true)
     ctx.setSetting(ctx.settings.YcookComments, true)
     ctx.setSetting(ctx.settings.Ycheck, "all" :: Nil)
     ctx.setSetting(ctx.settings.YnoInline, true)

doc-tool/test/MarkdownTests.scala

@@ -15,7 +15,6 @@ class MarkdownTests extends DottyDocTest {
     import base.settings._
     val ctx = base.initialCtx.fresh
     ctx.setSetting(ctx.settings.language, List("Scala2"))
-    ctx.setSetting(ctx.settings.YkeepComments, true)
     ctx.setSetting(ctx.settings.YnoInline, true)
     ctx.setSetting(ctx.settings.Ycheck, "all" :: Nil)
     // No wiki syntax!