From c72307ffad42f25777e27df68d6147e75d761fce Mon Sep 17 00:00:00 2001
From: Eugene Burmako <xeno.by@gmail.com>
Date: Tue, 5 Jun 2012 18:11:03 +0200
Subject: REPL no longer hangs after initialization crashes

---
 .../scala/tools/nsc/interpreter/ILoop.scala        |  2 +-
 .../scala/tools/nsc/interpreter/ILoopInit.scala    | 32 +++++++++++++++++-----
 .../scala/tools/nsc/interpreter/IMain.scala        |  1 +
 3 files changed, 27 insertions(+), 8 deletions(-)

diff --git a/src/compiler/scala/tools/nsc/interpreter/ILoop.scala b/src/compiler/scala/tools/nsc/interpreter/ILoop.scala
index de778e7469..d2e62e171e 100644
--- a/src/compiler/scala/tools/nsc/interpreter/ILoop.scala
+++ b/src/compiler/scala/tools/nsc/interpreter/ILoop.scala
@@ -554,7 +554,7 @@ class ILoop(in0: Option[BufferedReader], protected val out: JPrintWriter)
     // return false if repl should exit
     def processLine(line: String): Boolean = {
       if (isAsync) {
-        awaitInitialized()
+        if (!awaitInitialized()) return false
         runThunks()
       }
       if (line eq null) false               // assume null means EOF
diff --git a/src/compiler/scala/tools/nsc/interpreter/ILoopInit.scala b/src/compiler/scala/tools/nsc/interpreter/ILoopInit.scala
index 9072eaae46..5bc2ee1278 100644
--- a/src/compiler/scala/tools/nsc/interpreter/ILoopInit.scala
+++ b/src/compiler/scala/tools/nsc/interpreter/ILoopInit.scala
@@ -44,6 +44,7 @@ trait ILoopInit {
   }
   // a condition used to ensure serial access to the compiler.
   @volatile private var initIsComplete = false
+  @volatile private var initError: String = null
   private def elapsed() = "%.3f".format((System.nanoTime - initStart).toDouble / 1000000000L)
 
   // the method to be called when the interpreter is initialized.
@@ -63,9 +64,17 @@ trait ILoopInit {
   }
 
   // called from main repl loop
-  protected def awaitInitialized() {
+  protected def awaitInitialized(): Boolean = {
     if (!initIsComplete)
       withLock { while (!initIsComplete) initLoopCondition.await() }
+    if (initError != null) {
+      println("""
+        |Failed to initialize the REPL due to an unexpected error.
+        |This is a bug, please, report it along with the error diagnostics printed below.
+        |%s.""".stripMargin.format(initError)
+      )
+      false
+    } else true
   }
   // private def warningsThunks = List(
   //   () => intp.bind("lastWarnings", "" + typeTag[List[(Position, String)]], intp.lastWarnings _),
@@ -80,13 +89,22 @@ trait ILoopInit {
   // )
   // called once after init condition is signalled
   protected def postInitialization() {
-    postInitThunks foreach (f => addThunk(f()))
-    runThunks()
-    initIsComplete = true
+    try {
+      postInitThunks foreach (f => addThunk(f()))
+      runThunks()
+    } catch {
+      case ex =>
+        val message = new java.io.StringWriter()
+        ex.printStackTrace(new java.io.PrintWriter(message))
+        initError = message.toString
+        throw ex
+    } finally {
+      initIsComplete = true
 
-    if (isAsync) {
-      asyncMessage("[info] total init time: " + elapsed() + " s.")
-      withLock(initLoopCondition.signal())
+      if (isAsync) {
+        asyncMessage("[info] total init time: " + elapsed() + " s.")
+        withLock(initLoopCondition.signal())
+      }
     }
   }
   // code to be executed only after the interpreter is initialized
diff --git a/src/compiler/scala/tools/nsc/interpreter/IMain.scala b/src/compiler/scala/tools/nsc/interpreter/IMain.scala
index 956e282b26..c54b401f3f 100644
--- a/src/compiler/scala/tools/nsc/interpreter/IMain.scala
+++ b/src/compiler/scala/tools/nsc/interpreter/IMain.scala
@@ -149,6 +149,7 @@ class IMain(initialSettings: Settings, protected val out: JPrintWriter) extends
   private def _initSources = List(new BatchSourceFile("<init>", "class $repl_$init { }"))
   private def _initialize() = {
     try {
+      // [Eugene] todo. if this crashes, REPL will hang
       new _compiler.Run() compileSources _initSources
       _initializeComplete = true
       true
-- 
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