improved help message format

Author: michelou

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

@@ -69,9 +69,30 @@ object CompilerCommand {
 
     /** 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
+      val ss    = (settings.allSettings filter cond).toList sortBy (_.name)
+      val width = (ss map (_.name.length)).max
+      val (nameWidth, descriptionWidth) = {
+        val maxNameWidth = 30
+        val maxTotalWidth = 100
+        val w = if width < maxNameWidth then width else maxNameWidth
+        (w, maxTotalWidth - w)
+      }
+      def formatName(name: String) =
+        if name.length <= nameWidth then ("%-" + nameWidth + "s") format name
+        else (name + "\n%-" + nameWidth + "s") format ""
+      def formatDescription(text: String): String =
+        if text.length < descriptionWidth then text
+        else {
+          val inx = text.substring(0, descriptionWidth).lastIndexOf(" ")
+          val str = text.substring(0, inx)
+          s"${str}\n${formatName("")} ${formatDescription(text.substring(inx + 1))}"
+        }
+      def formatSetting(name: String, value: String) =
+        if (value.nonEmpty)
+        // the format here is helping to make empty padding and put the additional information exactly under the description.
+          s"\n${formatName("")} $name: $value."
+        else
+          ""
       def helpStr(s: Setting[?]) = {
         def defaultValue = s.default match {
           case _: Int | _: String => s.default.toString
@@ -80,13 +101,7 @@ object CompilerCommand {
             // For example 'false' for the version command.
             ""
         }
-        def formatSetting(name: String, value: String) =
-          if (value.nonEmpty)
-          // the format here is helping to make empty padding and put the additional information exactly under the description.
-            s"\n${format("")} $name: $value."
-          else
-            ""
-        s"${format(s.name)} ${s.description}${formatSetting("Default", defaultValue)}${formatSetting("Choices", s.legalChoices)}"
+        s"${formatName(s.name)} ${formatDescription(s.description)}${formatSetting("Default", defaultValue)}${formatSetting("Choices", s.legalChoices)}"
       }
       ss map helpStr mkString "\n"
     }