Recover sbtOn

build.sbt

@@ -497,6 +497,7 @@ lazy val sbtProj = (project in file("sbt"))
     normalizedName := "sbt",
     crossScalaVersions := Seq(baseScalaVersion),
     crossPaths := false,
+    javaOptions ++= Seq("-Xdebug", "-Xrunjdwp:transport=dt_socket,server=y,suspend=n,address=5005"),
     mimaSettings,
     mimaBinaryIssueFilters ++= sbtIgnoredProblems,
     BuildInfoPlugin.buildInfoDefaultSettings,
@@ -508,6 +509,9 @@ lazy val sbtProj = (project in file("sbt"))
       classDirectory in Compile,
       classDirectory in Test,
     ),
+    Test / run / connectInput := true,
+    Test / run / outputStrategy := Some(StdoutOutput),
+    Test / run / fork := true,
   )
   .configure(addSbtCompilerBridge)
 

sbt/src/test/scala/sbt/RunFromSourceMain.scala

@@ -7,7 +7,7 @@
 
 package sbt
 
-import scala.concurrent.Future
+import scala.util.Try
 import sbt.util.LogExchange
 import scala.annotation.tailrec
 import buildinfo.TestBuildInfo
@@ -17,21 +17,22 @@ object RunFromSourceMain {
   private val sbtVersion = "1.0.3" // "dev"
   private val scalaVersion = "2.12.4"
 
-  def fork(workingDirectory: File): Future[Unit] = {
+  def fork(workingDirectory: File): Try[Unit] = {
     val fo = ForkOptions()
-      .withWorkingDirectory(workingDirectory)
       .withOutputStrategy(OutputStrategy.StdoutOutput)
+    fork(fo, workingDirectory)
+  }
+
+  def fork(fo0: ForkOptions, workingDirectory: File): Try[Unit] = {
+    val fo = fo0
+      .withWorkingDirectory(workingDirectory)
     implicit val runner = new ForkRun(fo)
     val cp = {
       TestBuildInfo.test_classDirectory +: TestBuildInfo.fullClasspath
     }
     val options = Vector(workingDirectory.toString)
     val log = LogExchange.logger("RunFromSourceMain.fork", None, None)
-    import scala.concurrent.ExecutionContext.Implicits.global
-    Future {
-      Run.run("sbt.RunFromSourceMain", cp, options, log)
-      ()
-    }
+    Run.run("sbt.RunFromSourceMain", cp, options, log)
   }
 
   def main(args: Array[String]): Unit = args match {

sbt/src/test/scala/testpkg/ServerSpec.scala

@@ -71,7 +71,11 @@ case class TestServer(baseDirectory: File) {
   private val RetByte = '\r'.toByte
 
   hostLog("fork to a new sbt instance")
-  RunFromSourceMain.fork(baseDirectory)
+  import scala.concurrent.ExecutionContext.Implicits.global
+  Future {
+    RunFromSourceMain.fork(baseDirectory)
+    ()
+  }
   lazy val portfile = baseDirectory / "project" / "target" / "active.json"
 
   hostLog("wait 30s until the server is ready to respond")