Adds debugger-like capabilities to repl.

with -Ydebugger, then calls to breakIf(assertion, arg1, arg2, ...) will
drop out to a repl if assertion proves true. This is very primitive at
present and will improve.

5 files changed, 46 insertions, 1 deletions

diff --git a/src/compiler/scala/tools/nsc/Interpreter.scala b/src/compiler/scala/tools/nsc/Interpreter.scala
index df14417565..78ac10b021 100644
--- a/src/compiler/scala/tools/nsc/Interpreter.scala
+++ b/src/compiler/scala/tools/nsc/Interpreter.scala
@@ -888,6 +888,25 @@ class Interpreter(val settings: Settings, out: PrintWriter) {
 
 /** Utility methods for the Interpreter. */
 object Interpreter {
+  def breakIf(assertion: => Boolean, args: Any*): Unit =
+    if (assertion) break(args.toList)
+
+  // start a repl binding supplied args to p1, p2, etc.
+  def break(args: List[Any]): Unit = {
+    val intLoop = new InterpreterLoop
+    intLoop.settings = new Settings(Console.println)
+    intLoop.createInterpreter
+    intLoop.in = InteractiveReader.createDefault(intLoop.interpreter)
+
+    // rebind exit so people don't accidentally call System.exit by way of predef
+    intLoop.interpreter.beQuietDuring {
+      intLoop.interpreter.interpret("""def exit = println("Type :quit to resume program execution.")""")
+      println(intLoop.inject(args))
+    }
+    intLoop.repl()
+    intLoop.closeInterpreter
+  }
+
   /** Delete a directory tree recursively.  Use with care! */
   private[nsc] def deleteRecursively(path: File): Unit =
     if (path.exists) {
diff --git a/src/compiler/scala/tools/nsc/InterpreterLoop.scala b/src/compiler/scala/tools/nsc/InterpreterLoop.scala
index 796fb4bbf9..ea387b39dc 100644
--- a/src/compiler/scala/tools/nsc/InterpreterLoop.scala
+++ b/src/compiler/scala/tools/nsc/InterpreterLoop.scala
@@ -352,6 +352,26 @@ class InterpreterLoop(in0: Option[BufferedReader], out: PrintWriter) {
     }
   }
 
+  // injects one value into the repl; returns pair of name and class
+  def injectOne(name: String, obj: Any): Tuple2[String, String] = {
+    val className = obj.asInstanceOf[AnyRef].getClass.getName
+    interpreter.bind(name, className, obj)
+    (name, className)
+  }
+
+  // injects list of values into the repl; returns summary string
+  def inject(args: List[Any]): String = {
+    val strs =
+      for ((arg, i) <- args.zipWithIndex) yield {
+        val varName = "p" + (i + 1)
+        val (vname, vtype) = injectOne(varName, arg)
+        vname + ": " + vtype
+      }
+
+    if (strs.size == 0) "Set no variables."
+    else "Variables set:\n" + strs.mkString("\n")
+  }
+
   /** process command-line arguments and do as they request */
   def main(args: Array[String]) {
     def error1(msg: String) = out println ("scala: " + msg)
diff --git a/src/compiler/scala/tools/nsc/Settings.scala b/src/compiler/scala/tools/nsc/Settings.scala
index e1d40df66d..53fb2e014d 100644
--- a/src/compiler/scala/tools/nsc/Settings.scala
+++ b/src/compiler/scala/tools/nsc/Settings.scala
@@ -137,6 +137,7 @@ class Settings(error: String => Unit) {
   val Xcloselim     = BooleanSetting    ("-Yclosure-elim", "Perform closure elimination")
   val Xcodebase     = StringSetting     ("-Ycodebase", "codebase", "Specify the URL containing the Scala libraries", "").hideToIDE
   val debug         = BooleanSetting    ("-Ydebug", "Output debugging messages").hideToIDE
+  val debugger      = BooleanSetting    ("-Ydebugger", "Enable interactive debugger").hideToIDE
   val Xdce          = BooleanSetting    ("-Ydead-code", "Perform dead code elimination")
   val Xdetach       = BooleanSetting    ("-Ydetach", "Perform detaching of remote closures")
 //  val doc           = BooleanSetting    ("-Ydoc", "Generate documentation").hideToIDE
diff --git a/src/compiler/scala/tools/nsc/interpreter/InteractiveReader.scala b/src/compiler/scala/tools/nsc/interpreter/InteractiveReader.scala
index 4ae04b76ee..9cc23381f0 100644
--- a/src/compiler/scala/tools/nsc/interpreter/InteractiveReader.scala
+++ b/src/compiler/scala/tools/nsc/interpreter/InteractiveReader.scala
@@ -42,7 +42,7 @@ object InteractiveReader {
     try {
       new JLineReader(interpreter)
     } catch {
-      case e: Exception => new SimpleReader
+      case _: Exception | _: NoClassDefFoundError => new SimpleReader
     }
 }
 
diff --git a/src/compiler/scala/tools/nsc/symtab/SymbolTable.scala b/src/compiler/scala/tools/nsc/symtab/SymbolTable.scala
index c735bb246c..090d534f3a 100644
--- a/src/compiler/scala/tools/nsc/symtab/SymbolTable.scala
+++ b/src/compiler/scala/tools/nsc/symtab/SymbolTable.scala
@@ -110,6 +110,11 @@ abstract class SymbolTable extends Names
     }
   }
 
+  /** Break into repl debugger if assertion is true and debugging enabled */
+  def breakIf(assertion: => Boolean, args: Any*): Unit =
+    if (settings.debugger.value && assertion)
+      Interpreter.break(args.toList)
+
   /** The set of all installed infotransformers */
   var infoTransformers = new InfoTransformer {
     val pid = NoPhase.id