From 86d492c0b79b265a596cae1e4d8fd05cc1b11d53 Mon Sep 17 00:00:00 2001
From: Stefan Zeiger <szeiger@novocode.com>
Date: Tue, 6 Sep 2016 21:55:16 +0200
Subject: Store buildcharacter.properties in scala-compiler.jar
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In addition to all the individual projects’ version properties files
that we already keep in `scala-compiler.jar` we now write a new
`scala-buildcharacter.properties` which is identical to the
`buildcharacter.properties` written to the root directory by
`generateBuildCharacterPropertiesFile`. The new task
`extractBuildCharacterPropertiesFile` extracts it from the bootstrap
Scala compiler and writes the usual `buildcharacter.properties`.

This can be used to reproduce the exact version information for all
modules in builds that start from an arbitrary published Scala version
instead of being triggered directly by a bootstrap job.
---
 build.sbt                 | 15 +++++++++++++++
 project/VersionUtil.scala |  9 ++++++---
 2 files changed, 21 insertions(+), 3 deletions(-)

diff --git a/build.sbt b/build.sbt
index 1105902a9d..0d27038a9f 100644
--- a/build.sbt
+++ b/build.sbt
@@ -364,6 +364,7 @@ lazy val reflect = configureAsSubproject(project)
 
 lazy val compiler = configureAsSubproject(project)
   .settings(generatePropertiesFileSettings: _*)
+  .settings(generateBuildCharacterFileSettings: _*)
   .settings(Osgi.settings: _*)
   .settings(
     name := "scala-compiler",
@@ -371,6 +372,8 @@ lazy val compiler = configureAsSubproject(project)
     libraryDependencies ++= Seq(antDep, asmDep),
     // These are only needed for the POM:
     libraryDependencies ++= Seq(scalaXmlDep, jlineDep % "optional"),
+    buildCharacterPropertiesFile := (resourceManaged in Compile).value / "scala-buildcharacter.properties",
+    resourceGenerators in Compile += generateBuildCharacterPropertiesFile.map(file => Seq(file)).taskValue,
     // this a way to make sure that classes from interactive and scaladoc projects
     // end up in compiler jar. note that we need to use LocalProject references
     // (with strings) to deal with mutual recursion
@@ -740,6 +743,18 @@ lazy val root: Project = (project in file("."))
     publish := {},
     publishLocal := {},
     commands ++= ScriptCommands.all,
+    extractBuildCharacterPropertiesFile := {
+      val jar = (scalaInstance in bootstrap).value.compilerJar
+      val bc = buildCharacterPropertiesFile.value
+      val packagedName = "scala-buildcharacter.properties"
+      IO.withTemporaryDirectory { tmp =>
+        val extracted = IO.unzip(jar, tmp, new SimpleFilter(_ == packagedName)).headOption.getOrElse {
+          throw new RuntimeException(s"No file $packagedName found in bootstrap compiler $jar")
+        }
+        IO.copyFile(extracted, bc)
+        bc
+      }
+    },
     // Generate (Product|TupleN|Function|AbstractFunction)*.scala files and scaladoc stubs for all AnyVal sources.
     // They should really go into a managedSources dir instead of overwriting sources checked into git but scaladoc
     // source links (could be fixed by shipping these sources with the scaladoc bundles) and scala-js source maps
diff --git a/project/VersionUtil.scala b/project/VersionUtil.scala
index 1c2fff27b7..fde55a5969 100644
--- a/project/VersionUtil.scala
+++ b/project/VersionUtil.scala
@@ -8,8 +8,10 @@ import BuildSettings.autoImport._
 object VersionUtil {
   lazy val copyrightString = settingKey[String]("Copyright string.")
   lazy val versionProperties = settingKey[Versions]("Version properties.")
-  lazy val generateVersionPropertiesFile = taskKey[File]("Generating version properties file.")
-  lazy val generateBuildCharacterPropertiesFile = taskKey[File]("Generating buildcharacter.properties file.")
+  lazy val buildCharacterPropertiesFile = settingKey[File]("The file which gets generated by generateBuildCharacterPropertiesFile")
+  lazy val generateVersionPropertiesFile = taskKey[File]("Generate version properties file.")
+  lazy val generateBuildCharacterPropertiesFile = taskKey[File]("Generate buildcharacter.properties file.")
+  lazy val extractBuildCharacterPropertiesFile = taskKey[File]("Extract buildcharacter.properties file from bootstrap scala-compiler.")
 
   lazy val globalVersionSettings = Seq[Setting[_]](
     // Set the version properties globally (they are the same for all projects)
@@ -24,6 +26,7 @@ object VersionUtil {
   )
 
   lazy val generateBuildCharacterFileSettings = Seq[Setting[_]](
+    buildCharacterPropertiesFile := ((baseDirectory in ThisBuild).value / "buildcharacter.properties"),
     generateBuildCharacterPropertiesFile := generateBuildCharacterPropertiesFileImpl.value
   )
 
@@ -101,7 +104,7 @@ object VersionUtil {
     writeProps(v.toMap ++ versionProps ++ Map(
       "maven.version.base" -> v.mavenBase,
       "maven.version.suffix" -> v.mavenSuffix
-    ), (baseDirectory in ThisBuild).value / "buildcharacter.properties")
+    ), buildCharacterPropertiesFile.value)
   }
 
   private def writeProps(m: Map[String, String], propFile: File): File = {
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