Allow overwrite of sources in stdlib-bootstrapped

Author: nicolasstucki

project/Build.scala

@@ -931,11 +931,11 @@ object Build {
     settings(
       moduleName := "scala-library",
       javaOptions := (`scala3-compiler-bootstrapped` / javaOptions).value,
-      Compile/scalacOptions += "-Yerased-terms",
       Compile/scalacOptions ++= {
         Seq(
           "-sourcepath",
           Seq(
+            baseDirectory.value / "stdlib-bootstrapped" / "src",
             (Compile/sourceManaged).value / "scala-library-src",
             (Compile/sourceManaged).value / "dotty-library-src",
           ).mkString(File.pathSeparator),
@@ -1009,9 +1009,59 @@ object Build {
         file.getPath.endsWith("scala-library-src/scala/Nothing.scala") ||
         file.getPath.endsWith("scala-library-src/scala/Null.scala") ||
         file.getPath.endsWith("scala-library-src/scala/Singleton.scala"))),
+      (Compile / sources) ~= (files =>
+        {
+          val overwritenSources = files.collect {
+            case file if file.getPath.contains("stdlib-bootstrapped/src") => file.getPath.split("stdlib-bootstrapped/src/")(1)
+          }.toSet
+          files.filterNot(file =>
+            file.getPath.contains("scala-library-src/") && overwritenSources(file.getPath.split("scala-library-src/")(1)))
+        }
+      ),
       (Test / managedClasspath) ~= {
         _.filterNot(file => file.data.getName == s"scala-library-${stdlibVersion(Bootstrapped)}.jar")
       },
+      run := {
+        val args: Seq[String] = spaceDelimited("<arg>").parsed
+        val reference = (Compile/sourceManaged).value / "scala-library-src"
+        args match {
+          case Seq("list") =>
+            println(s"List of non-overriden files in $reference")
+            reference.allPaths.get()
+              .flatMap(_.relativeTo(reference))
+              .filter(_.ext == "scala")
+              .sorted
+              .foreach(println)
+          case Seq(cmd @ ("clone" | "overwrite"), files*) =>
+            println("Cloning scala-library sources: " + files.mkString(", "))
+            for (file <- files) {
+              val referenceStdlibPaths = reference / file
+              val destination = baseDirectory.value / "src" / file
+              if (!referenceStdlibPaths.exists) {
+                println("Not found " + referenceStdlibPaths)
+              } else if (destination.exists && cmd == "clone") {
+                println(s"Already exists $file. (use `overwrite` command to overwrite)")
+              } else {
+                val action = if (cmd == "clone") "Cloning" else "Overwriting"
+                println(s"$action $file")
+                IO.copyFile(referenceStdlibPaths, destination)
+              }
+            }
+          case _ =>
+            println(
+              """Usage:
+                |> stdlib-bootstrapped/run list
+                |  -- lists all files that are not overriden in stdlib-bootstrapped/src
+                |
+                |> stdlib-bootstrapped/run clone <sources>*
+                |  -- clones the specified sources from the stdlib-bootstrapped/src
+                |  -- example: stdlib-bootstrapped/run clone scala/Option.scala
+                |
+                |> stdlib-bootstrapped/run overwrite <sources>*
+                |  -- (danger) overwrites the specified sources from the stdlib-bootstrapped/src
+                |""".stripMargin)
+        }
+      }
     )
 
   /** Test the tasty generated by `stdlib-bootstrapped`

stdlib-bootstrapped/README.md

@@ -0,0 +1,13 @@
+## stdlib-bootstrapped
+
+This project compiles the Scala standard library using the Scala 3 compiler.
+It uses the sources Scala (2/3) standard library sources from `stdlib-bootstrapped/src`
+and the Scala 3 library form `library/src`. It fetches any missing Scala (2/3) sources
+from `org.scala-lang" % "scala-library" % stdlibVersion(Bootstrapped) % "sourcedeps`.
+This implies that files in `stdlib-bootstrapped/src` override files override the Scala (2/3)
+sources. Currently we can not override files from `library/src`.
+
+To clone or list non-overridden sources execute `stdlib-bootstrapped/run`.
+
+This project generates a version of the Scala 3 library that contains the full library with
+TASTy files. The compiled library is located in `out/bootstrap/stdlib-bootstrapped/`.