Make sourcecode.{File,FileName,Line} magic-comment aware (#178)

User-land implementation of scala/scala3#21919

Author: lihaoyi

sourcecode/src-2/sourcecode/Macros.scala

@@ -94,21 +94,38 @@ object Macros {
     c.Expr[FullName.Machine](q"""${c.prefix}($fullName)""")
   }
 
+  private val filePrefix = "//SOURCECODE_ORIGINAL_FILE_PATH="
+  private def findOriginalFile(chars: Array[Char]): Option[String] = {
+    new String(chars).linesIterator.find(_.contains(filePrefix)).map(_.split(filePrefix).last)
+  }
+
   def fileImpl(c: Compat.Context): c.Expr[sourcecode.File] = {
     import c.universe._
-    val file = c.enclosingPosition.source.path
+
+    val file = findOriginalFile(c.enclosingPosition.source.content)
+      .getOrElse(c.enclosingPosition.source.path)
+
     c.Expr[sourcecode.File](q"""${c.prefix}($file)""")
   }
 
   def fileNameImpl(c: Compat.Context): c.Expr[sourcecode.FileName] = {
     import c.universe._
-    val fileName = c.enclosingPosition.source.path.split('/').last
+    val fileName = findOriginalFile(c.enclosingPosition.source.content)
+      .getOrElse(c.enclosingPosition.source.path)
+      .split('/').last
     c.Expr[sourcecode.FileName](q"""${c.prefix}($fileName)""")
   }
 
+  private val linePrefix = "//SOURCECODE_ORIGINAL_CODE_START_MARKER"
   def lineImpl(c: Compat.Context): c.Expr[sourcecode.Line] = {
     import c.universe._
-    val line = c.enclosingPosition.line
+    val offset = new String(c.enclosingPosition.source.content)
+      .linesIterator
+      .indexWhere(_.contains(linePrefix)) match{
+      case -1 => 0
+      case n => n
+    }
+    val line = c.enclosingPosition.line - offset
     c.Expr[sourcecode.Line](q"""${c.prefix}($line)""")
   }
 

sourcecode/src-3/sourcecode/Macros.scala

@@ -156,19 +156,37 @@ object Macros {
     '{new FullName.Machine(${Expr(fullName)})}
   }
 
+  private val filePrefix = "//SOURCECODE_ORIGINAL_FILE_PATH="
+
+  private def findOriginalFile(chars: Array[Char]): Option[String] = {
+    new String(chars).linesIterator.find(_.contains(filePrefix)).map(_.split(filePrefix).last)
+  }
   def fileImpl(using Quotes): Expr[sourcecode.File] = {
     import quotes.reflect._
-    val file = quotes.reflect.Position.ofMacroExpansion.sourceFile.path
+    val file = quotes.reflect.Position.ofMacroExpansion.sourceFile.content
+      .flatMap(s => findOriginalFile(s.toCharArray))
+      .getOrElse(quotes.reflect.Position.ofMacroExpansion.sourceFile.path)
     '{new sourcecode.File(${Expr(file)})}
   }
 
   def fileNameImpl(using Quotes): Expr[sourcecode.FileName] = {
-    val name = quotes.reflect.Position.ofMacroExpansion.sourceFile.name
+    val name = quotes.reflect.Position.ofMacroExpansion.sourceFile.content
+      .flatMap(s => findOriginalFile(s.toCharArray).map(_.split('/').last))
+      .getOrElse(quotes.reflect.Position.ofMacroExpansion.sourceFile.name)
+
     '{new sourcecode.FileName(${Expr(name)})}
   }
 
+  private val linePrefix = "//SOURCECODE_ORIGINAL_CODE_START_MARKER"
   def lineImpl(using Quotes): Expr[sourcecode.Line] = {
-    val line = quotes.reflect.Position.ofMacroExpansion.startLine + 1
+    val offset = quotes.reflect.Position.ofMacroExpansion.sourceFile.content
+      .iterator
+      .flatMap(_.linesIterator)
+      .indexWhere(_.contains(linePrefix)) match{
+      case -1 => 0
+      case n => n
+    }
+    val line = quotes.reflect.Position.ofMacroExpansion.startLine + 1 - offset
     '{new sourcecode.Line(${Expr(line)})}
   }