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Improve REPL code, echo and exception highlighting with pprint and fansi (#24298)
Before: <img width="976" height="403" alt="Screenshot 2025-10-29 at 11 18 35 AM" src="https://github.com/user-attachments/assets/3741b542-ad42-4bc6-af33-90bf9092bfa1" /> After: <img width="932" height="343" alt="Screenshot 2025-10-29 at 11 18 36 AM" src="https://github.com/user-attachments/assets/fa4060b1-7cde-4595-8996-bd890cf92002" /> Rather than just rendering everything as plaintext and coloring it later, we: - Preserve the colors that PPrint applies to the pretty-printed text. - This means that for objects which are not handled via PPrint and go via their `toString`, we do not spuriously highlight parts of them depending on the specific hex hashcodes etc. - This also means we can distinguish between the integer `123` and `new Object{ override def toString = "123" }`, as the former will be colored as a literal while the latter will be white <img width="976" height="259" alt="Screenshot 2025-10-29 at 4 06 40 PM" src="https://github.com/user-attachments/assets/01353d8b-6bad-459f-a59d-e25ff24d76aa" /> - We manually color exception stack traces using Fansi. This generally just looks a lot better, again without random parts of it being highlighted or not depending or whether specific regexes match class names or file names. - I kept it mostly red-and-white, to avoid the "rainbow" of noisy colors that was there before and making it obviously it's a failure. The - I kept the exception `.getMessage` in white, in case the exceptions have their own colored messages so we don't over-write their colors - For everything else, we continue using the prior highlighting logic Some of the logic was refactored to pass around `fansi.Str`s rather than `java.lang.String`s to make it easier to keep track of colors, but otherwise I tried to minimize the churn and keep the overall code structure unchanged. Also tweaked some colors to improve the visual clarity of the REPL. Changes: - REPL prompts previously `BLUE`, now `MAGENTA` - Types previously `MAGENTA`, now `GREEN`. - Qualified types (e.g. `scala.Int`) are now correctly highlighted `GREEN` - `CYAN`, previously only used for term name bindings, is now used for all name bindings including `object`s, `class`s, `trait`s, and `type`s Before: <img width="976" height="419" alt="Screenshot 2025-11-12 at 6 12 09 PM" src="https://github.com/user-attachments/assets/a7fcc73c-95af-4479-b108-2b32b21c76e9" /> After: <img width="976" height="419" alt="Screenshot 2025-11-12 at 6 22 24 PM" src="https://github.com/user-attachments/assets/9129d571-dbb6-477f-8906-e23ad31c21af" /> Outcome: - REPL prompts are now uniquely colored and easy to identify, rather than sharing their color with comments. This is good as they are the most important thing on screen in a REPL session, demarcating top-level compilation units - Now code is limited to `YELLOW`, `GREEN`, and `CYAN`. This is a more restricted pallet than before (since they no longer use `MAGENTA`), but is still colorful enough to make things easy to read - The three colors have more consistent meaning despite the overlap: - `YELLOW` is for keywords and upper-case term references - `GREEN` is for literals and type expressions - `CYAN` is for all name bindings, both term and type
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11 files changed

+196
-190
lines changed

11 files changed

+196
-190
lines changed

‎compiler/src/dotty/tools/dotc/printing/PlainPrinter.scala‎

Lines changed: 2 additions & 3 deletions
Original file line numberDiff line numberDiff line change
@@ -705,7 +705,7 @@ class PlainPrinter(_ctx: Context) extends Printer {
705705
def toText(denot: Denotation): Text = toText(denot.symbol) ~ "/D"
706706

707707
def toText(const: Constant): Text = const.tag match {
708-
case StringTag => stringText(Chars.escapedString(const.value.toString, quoted = true))
708+
case StringTag => literalText(Chars.escapedString(const.value.toString, quoted = true))
709709
case ClazzTag => "classOf[" ~ toText(const.typeValue) ~ "]"
710710
case CharTag => literalText(Chars.escapedChar(const.charValue))
711711
case LongTag => literalText(const.longValue.toString + "L")
@@ -841,10 +841,9 @@ class PlainPrinter(_ctx: Context) extends Printer {
841841

842842
protected def keywordStr(text: String): String = coloredStr(text, SyntaxHighlighting.KeywordColor)
843843
protected def keywordText(text: String): Text = coloredStr(text, SyntaxHighlighting.KeywordColor)
844-
protected def valDefText(text: Text): Text = coloredText(text, SyntaxHighlighting.ValDefColor)
844+
protected def valDefText(text: Text): Text = coloredText(text, SyntaxHighlighting.DefinitionColor)
845845
protected def typeText(text: Text): Text = coloredText(text, SyntaxHighlighting.TypeColor)
846846
protected def literalText(text: Text): Text = coloredText(text, SyntaxHighlighting.LiteralColor)
847-
protected def stringText(text: Text): Text = coloredText(text, SyntaxHighlighting.StringColor)
848847

849848
protected def coloredStr(text: String, color: String): String =
850849
if (ctx.useColors) color + text + SyntaxHighlighting.NoColor else text

‎compiler/src/dotty/tools/dotc/printing/RefinedPrinter.scala‎

Lines changed: 1 addition & 1 deletion
Original file line numberDiff line numberDiff line change
@@ -598,7 +598,7 @@ class RefinedPrinter(_ctx: Context) extends PlainPrinter(_ctx) {
598598
case tree @ Inlined(call, bindings, body) =>
599599
val bodyText = if bindings.isEmpty then toText(body) else blockText(bindings :+ body)
600600
if homogenizedView || !ctx.settings.XprintInline.value then bodyText
601-
else if tree.inlinedFromOuterScope then stringText("{{") ~ stringText("/* inlined from outside */") ~ bodyText ~ stringText("}}")
601+
else if tree.inlinedFromOuterScope then literalText("{{") ~ literalText("/* inlined from outside */") ~ bodyText ~ literalText("}}")
602602
else keywordText("{{") ~ keywordText("/* inlined from ") ~ toText(call) ~ keywordText(" */") ~ bodyText ~ keywordText("}}")
603603
case tpt: untpd.DerivedTypeTree =>
604604
"<derived typetree watching " ~ tpt.watched.showSummary() ~ ">"

‎compiler/src/dotty/tools/dotc/printing/SyntaxHighlighting.scala‎

Lines changed: 9 additions & 9 deletions
Original file line numberDiff line numberDiff line change
@@ -26,11 +26,9 @@ object SyntaxHighlighting {
2626
val NoColor: String = Console.RESET
2727
val CommentColor: String = Console.BLUE
2828
val KeywordColor: String = Console.YELLOW
29-
val ValDefColor: String = Console.CYAN
29+
val DefinitionColor: String = Console.CYAN
3030
val LiteralColor: String = Console.GREEN
31-
val StringColor: String = Console.GREEN
32-
val TypeColor: String = Console.MAGENTA
33-
val AnnotationColor: String = Console.MAGENTA
31+
val TypeColor: String = Console.GREEN
3432

3533
def highlight(in: String)(using Context): String = {
3634
def freshCtx = ctx.fresh.setReporter(Reporter.NoReporter)
@@ -101,7 +99,7 @@ object SyntaxHighlighting {
10199

102100
def highlightAnnotations(tree: MemberDef): Unit =
103101
for (annotation <- tree.rawMods.annotations)
104-
highlightPosition(annotation.span, AnnotationColor)
102+
highlightPosition(annotation.span, TypeColor)
105103

106104
def highlight(trees: List[Tree])(using Context): Unit =
107105
trees.foreach(traverse)
@@ -112,14 +110,16 @@ object SyntaxHighlighting {
112110
()
113111
case tree: ValOrDefDef =>
114112
highlightAnnotations(tree)
115-
highlightPosition(tree.nameSpan, ValDefColor)
116-
highlightPosition(tree.endSpan, ValDefColor)
113+
highlightPosition(tree.nameSpan, DefinitionColor)
114+
highlightPosition(tree.endSpan, DefinitionColor)
117115
case tree: MemberDef /* ModuleDef | TypeDef */ =>
118116
highlightAnnotations(tree)
119-
highlightPosition(tree.nameSpan, TypeColor)
120-
highlightPosition(tree.endSpan, TypeColor)
117+
highlightPosition(tree.nameSpan, DefinitionColor)
118+
highlightPosition(tree.endSpan, DefinitionColor)
121119
case tree: Ident if tree.isType =>
122120
highlightPosition(tree.span, TypeColor)
121+
case tree: Select if tree.isType =>
122+
highlightPosition(tree.nameSpan, TypeColor)
123123
case _: TypeTree =>
124124
highlightPosition(tree.span, TypeColor)
125125
case _ =>

‎compiler/src/scala/quoted/runtime/impl/printers/SourceCode.scala‎

Lines changed: 48 additions & 48 deletions
Original file line numberDiff line numberDiff line change
@@ -152,12 +152,12 @@ object SourceCode {
152152
if (flags.is(Flags.Case)) this += highlightKeyword("case ")
153153

154154
if (name == "package$") {
155-
this += highlightKeyword("package object ") += highlightTypeDef(cdef.symbol.owner.name.stripSuffix("$"))
155+
this += highlightKeyword("package object ") += highlightType(cdef.symbol.owner.name.stripSuffix("$"))
156156
}
157-
else if (flags.is(Flags.Module)) this += highlightKeyword("object ") += highlightTypeDef(name.stripSuffix("$"))
158-
else if (flags.is(Flags.Trait)) this += highlightKeyword("trait ") += highlightTypeDef(name)
159-
else if (flags.is(Flags.Abstract)) this += highlightKeyword("abstract class ") += highlightTypeDef(name)
160-
else this += highlightKeyword("class ") += highlightTypeDef(name)
157+
else if (flags.is(Flags.Module)) this += highlightKeyword("object ") += highlightType(name.stripSuffix("$"))
158+
else if (flags.is(Flags.Trait)) this += highlightKeyword("trait ") += highlightType(name)
159+
else if (flags.is(Flags.Abstract)) this += highlightKeyword("abstract class ") += highlightType(name)
160+
else this += highlightKeyword("class ") += highlightType(name)
161161

162162
if (!flags.is(Flags.Module)) {
163163
for paramClause <- paramss do
@@ -237,7 +237,7 @@ object SourceCode {
237237
val Some(ValDef(name, tpt, _)) = self: @unchecked
238238
indented {
239239
val name1 = if (name == "_") "this" else name
240-
this += " " += highlightValDef(name1) += ": "
240+
this += " " += highlightDefinition(name1) += ": "
241241
printTypeTree(tpt)(using Some(cdef.symbol))
242242
this += " =>"
243243
}
@@ -279,7 +279,7 @@ object SourceCode {
279279
else this += highlightKeyword("val ")
280280

281281
val name1 = splicedName(vdef.symbol).getOrElse(name)
282-
this += highlightValDef(name1) += ": "
282+
this += highlightDefinition(name1) += ": "
283283
printTypeTree(tpt)
284284
rhs match {
285285
case Some(tree) =>
@@ -315,7 +315,7 @@ object SourceCode {
315315
printProtectedOrPrivate(ddef)
316316

317317
val name1: String = if (isConstructor) "this" else splicedName(ddef.symbol).getOrElse(name)
318-
this += highlightKeyword("def ") += highlightValDef(name1)
318+
this += highlightKeyword("def ") += highlightDefinition(name1)
319319
for clause <- paramss do
320320
clause match
321321
case TermParamClause(params) => printMethdArgsDefs(params)
@@ -337,7 +337,7 @@ object SourceCode {
337337

338338
case tree: Ident =>
339339
splicedName(tree.symbol) match {
340-
case Some(name) => this += highlightTypeDef(name)
340+
case Some(name) => this += highlightType(name)
341341
case _ => printType(tree.tpe)
342342
}
343343

@@ -438,7 +438,7 @@ object SourceCode {
438438
printTree(term)
439439
term match {
440440
case Repeated(_, _) | Inlined(None, Nil, Repeated(_, _)) => this
441-
case _ => this += ": " += highlightTypeDef("_*")
441+
case _ => this += ": " += highlightType("_*")
442442
}
443443
case _ =>
444444
inParens {
@@ -764,9 +764,9 @@ object SourceCode {
764764

765765
if (isDef) {
766766
if (argDef.symbol.flags.is(Flags.Covariant)) {
767-
this += highlightValDef("+")
767+
this += highlightDefinition("+")
768768
} else if (argDef.symbol.flags.is(Flags.Contravariant)) {
769-
this += highlightValDef("-")
769+
this += highlightDefinition("-")
770770
}
771771
}
772772

@@ -873,26 +873,26 @@ object SourceCode {
873873
printedPrefix = true
874874
}
875875
printedPrefix |= printProtectedOrPrivate(vdef)
876-
if (vdef.symbol.flags.is(Flags.Mutable)) this += highlightValDef("var ")
877-
else if (printedPrefix || !vdef.symbol.flags.is(Flags.CaseAccessor)) this += highlightValDef("val ")
876+
if (vdef.symbol.flags.is(Flags.Mutable)) this += highlightDefinition("var ")
877+
else if (printedPrefix || !vdef.symbol.flags.is(Flags.CaseAccessor)) this += highlightDefinition("val ")
878878
}
879879
}
880880
end if
881881

882-
this += highlightValDef(name) += ": "
882+
this += highlightDefinition(name) += ": "
883883
printTypeTree(arg.tpt)
884884
}
885885

886886
private def printCaseDef(caseDef: CaseDef): this.type = {
887-
this += highlightValDef("case ")
887+
this += highlightDefinition("case ")
888888
printPattern(caseDef.pattern)
889889
caseDef.guard match {
890890
case Some(t) =>
891891
this += " if "
892892
printTree(t)
893893
case None =>
894894
}
895-
this += highlightValDef(" =>")
895+
this += highlightDefinition(" =>")
896896
indented {
897897
caseDef.rhs match {
898898
case Block(stats, expr) =>
@@ -906,9 +906,9 @@ object SourceCode {
906906
}
907907

908908
private def printTypeCaseDef(caseDef: TypeCaseDef): this.type = {
909-
this += highlightValDef("case ")
909+
this += highlightDefinition("case ")
910910
printTypeTree(caseDef.pattern)
911-
this += highlightValDef(" => ")
911+
this += highlightDefinition(" => ")
912912
printTypeTree(caseDef.rhs)
913913
this
914914
}
@@ -921,7 +921,7 @@ object SourceCode {
921921
this += name
922922

923923
case Bind(name, Typed(Wildcard(), tpt)) =>
924-
this += highlightValDef(name) += ": "
924+
this += highlightDefinition(name) += ": "
925925
printTypeTree(tpt)
926926

927927
case Bind(name, pattern) =>
@@ -972,8 +972,8 @@ object SourceCode {
972972
case LongConstant(v) => this += highlightLiteral(v.toString + "L")
973973
case FloatConstant(v) => this += highlightLiteral(v.toString + "f")
974974
case DoubleConstant(v) => this += highlightLiteral(v.toString)
975-
case CharConstant(v) => this += highlightString(Chars.escapedChar(v))
976-
case StringConstant(v) => this += highlightString(Chars.escapedString(v, quoted = true))
975+
case CharConstant(v) => this += highlightLiteral(Chars.escapedChar(v))
976+
case StringConstant(v) => this += highlightLiteral(Chars.escapedString(v, quoted = true))
977977
case ClassOfConstant(v) =>
978978
this += "classOf"
979979
inSquare(printType(v))
@@ -1027,10 +1027,10 @@ object SourceCode {
10271027
printType(tree.tpe)
10281028

10291029
case TypeSelect(qual, name) =>
1030-
printTree(qual) += "." += highlightTypeDef(name)
1030+
printTree(qual) += "." += highlightType(name)
10311031

10321032
case TypeProjection(qual, name) =>
1033-
printTypeTree(qual) += "#" += highlightTypeDef(name)
1033+
printTypeTree(qual) += "#" += highlightType(name)
10341034

10351035
case Singleton(ref) =>
10361036
printTree(ref)
@@ -1053,7 +1053,7 @@ object SourceCode {
10531053
case tpe: TypeRef if tpe.typeSymbol == Symbol.requiredClass("scala.annotation.internal.Repeated") =>
10541054
val Types.Sequence(tp) = tpt.tpe: @unchecked
10551055
printType(tp)
1056-
this += highlightTypeDef("*")
1056+
this += highlightType("*")
10571057
case _ =>
10581058
printTypeTree(tpt)
10591059
this += " "
@@ -1066,16 +1066,16 @@ object SourceCode {
10661066
inBlock(printTypeCases(cases, lineBreak()))
10671067

10681068
case ByName(result) =>
1069-
this += highlightTypeDef("=> ")
1069+
this += highlightType("=> ")
10701070
printTypeTree(result)
10711071

10721072
case LambdaTypeTree(tparams, body) =>
10731073
printTargsDefs(tparams.zip(tparams), isDef = false)
1074-
this += highlightTypeDef(" =>> ")
1074+
this += highlightType(" =>> ")
10751075
printTypeOrBoundsTree(body)
10761076

10771077
case TypeBind(name, _) =>
1078-
this += highlightTypeDef(name)
1078+
this += highlightType(name)
10791079

10801080
case TypeBlock(_, tpt) =>
10811081
printTypeTree(tpt)
@@ -1121,23 +1121,23 @@ object SourceCode {
11211121
printType(prefix)
11221122
this += "."
11231123
}
1124-
this += highlightTypeDef(sym.name.stripSuffix("$"))
1124+
this += highlightType(sym.name.stripSuffix("$"))
11251125

11261126
case TermRef(prefix, name) =>
11271127
if fullNames then
11281128
prefix match {
11291129
case NoPrefix() =>
1130-
this += highlightTypeDef(name)
1130+
this += highlightType(name)
11311131
case ThisType(tp) if tp.typeSymbol == defn.RootClass || tp.typeSymbol == defn.EmptyPackageClass =>
1132-
this += highlightTypeDef(name)
1132+
this += highlightType(name)
11331133
case _ =>
11341134
printType(prefix)
11351135
if (name != "package")
1136-
this += "." += highlightTypeDef(name)
1136+
this += "." += highlightType(name)
11371137
this
11381138
}
11391139
else
1140-
this += highlightTypeDef(name)
1140+
this += highlightType(name)
11411141

11421142
case tpe @ Refinement(_, _, _) =>
11431143
printRefinement(tpe)
@@ -1175,12 +1175,12 @@ object SourceCode {
11751175

11761176
case AndType(left, right) =>
11771177
printType(left)
1178-
this += highlightTypeDef(" & ")
1178+
this += highlightType(" & ")
11791179
printType(right)
11801180

11811181
case OrType(left, right) =>
11821182
printType(left)
1183-
this += highlightTypeDef(" | ")
1183+
this += highlightType(" | ")
11841184
printType(right)
11851185

11861186
case MatchType(bound, scrutinee, cases) =>
@@ -1189,14 +1189,14 @@ object SourceCode {
11891189
inBlock(printTypes(cases, lineBreak()))
11901190

11911191
case ByNameType(tp) =>
1192-
this += highlightTypeDef(" => ")
1192+
this += highlightType(" => ")
11931193
printType(tp)
11941194

11951195
case ThisType(tp) =>
11961196
tp match {
11971197
case tp: TypeRef if !tp.typeSymbol.flags.is(Flags.Module) =>
11981198
printFullClassName(tp)
1199-
this += highlightTypeDef(".this")
1199+
this += highlightType(".this")
12001200
case TypeRef(prefix, name) if name.endsWith("$") =>
12011201
if (fullNames){
12021202
prefix match {
@@ -1207,18 +1207,18 @@ object SourceCode {
12071207
this += "."
12081208
}
12091209
}
1210-
this += highlightTypeDef(name.stripSuffix("$"))
1210+
this += highlightType(name.stripSuffix("$"))
12111211
case _ =>
12121212
printType(tp)
12131213
}
12141214

12151215
case SuperType(thistpe, supertpe) =>
12161216
printType(thistpe)
1217-
this += highlightTypeDef(".super")
1217+
this += highlightType(".super")
12181218

12191219
case TypeLambda(paramNames, tparams, body) =>
12201220
inSquare(printMethodicTypeParams(paramNames, tparams))
1221-
this += highlightTypeDef(" =>> ")
1221+
this += highlightType(" =>> ")
12221222
printType(body)
12231223

12241224
case ParamRef(lambda, idx) =>
@@ -1232,7 +1232,7 @@ object SourceCode {
12321232
printType(tpe)
12331233

12341234
case RecursiveThis(_) =>
1235-
this += highlightTypeDef("this")
1235+
this += highlightType("this")
12361236

12371237
case tpe: MethodType =>
12381238
this += "("
@@ -1283,10 +1283,10 @@ object SourceCode {
12831283
}
12841284

12851285
private def printDefinitionName(tree: Definition): this.type = tree match {
1286-
case ValDef(name, _, _) => this += highlightValDef(name)
1287-
case DefDef(name, _, _, _) => this += highlightValDef(name)
1288-
case ClassDef(name, _, _, _, _) => this += highlightTypeDef(name.stripSuffix("$"))
1289-
case TypeDef(name, _) => this += highlightTypeDef(name)
1286+
case ValDef(name, _, _) => this += highlightDefinition(name)
1287+
case DefDef(name, _, _, _) => this += highlightDefinition(name)
1288+
case ClassDef(name, _, _, _, _) => this += highlightType(name.stripSuffix("$"))
1289+
case TypeDef(name, _) => this += highlightType(name)
12901290
}
12911291

12921292
private def printAnnotation(annot: Term)(using elideThis: Option[Symbol]): this.type = {
@@ -1336,13 +1336,13 @@ object SourceCode {
13361336
this += lineBreak()
13371337
info match {
13381338
case info: TypeBounds =>
1339-
this += highlightKeyword("type ") += highlightTypeDef(name)
1339+
this += highlightKeyword("type ") += highlightType(name)
13401340
printBounds(info)
13411341
case ByNameType(_) | MethodType(_, _, _) | TypeLambda(_, _, _) =>
1342-
this += highlightKeyword("def ") += highlightTypeDef(name)
1342+
this += highlightKeyword("def ") += highlightType(name)
13431343
printMethodicType(info)
13441344
case info: TypeRepr =>
1345-
this += highlightKeyword("val ") += highlightValDef(name)
1345+
this += highlightKeyword("val ") += highlightDefinition(name)
13461346
printMethodicType(info)
13471347
}
13481348
}

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