The repl becomes more intense about making sure...

The repl becomes more intense about making sure you wanted file
completion before offering it. Closes #4130, no review.

3 files changed, 34 insertions, 8 deletions

diff --git a/src/compiler/scala/tools/nsc/Interpreter.scala b/src/compiler/scala/tools/nsc/Interpreter.scala
index 348342c4b4..09c75c6fa3 100644
--- a/src/compiler/scala/tools/nsc/Interpreter.scala
+++ b/src/compiler/scala/tools/nsc/Interpreter.scala
@@ -72,6 +72,12 @@ import Interpreter._
 class Interpreter(val settings: Settings, out: PrintWriter) {
   repl =>
 
+  /** whether to print out result lines */
+  private[nsc] var printResults: Boolean = true
+
+  /** whether to print errors */
+  private[nsc] var totalSilence: Boolean = false
+
   private val RESULT_OBJECT_PREFIX = "RequestResult$"
 
   def println(x: Any) = {
@@ -89,6 +95,9 @@ class Interpreter(val settings: Settings, out: PrintWriter) {
   /** reporter */
   object reporter extends ConsoleReporter(settings, null, out) {
     override def printMessage(msg: String) {
+      if (totalSilence)
+        return
+
       out println (
         if (truncationOK) clean(msg)
         else cleanNoTruncate(msg)
@@ -170,9 +179,6 @@ class Interpreter(val settings: Settings, out: PrintWriter) {
   import compiler.definitions
   import definitions.{ EmptyPackage, getMember }
 
-  /** whether to print out result lines */
-  private[nsc] var printResults: Boolean = true
-
   /** Temporarily be quiet */
   def beQuietDuring[T](operation: => T): T = {
     val wasPrinting = printResults
@@ -181,6 +187,12 @@ class Interpreter(val settings: Settings, out: PrintWriter) {
       operation
     }
   }
+  def beSilentDuring[T](operation: => T): T = {
+    val saved = totalSilence
+    totalSilence = true
+    try operation
+    finally totalSilence = saved
+  }
 
   /** whether to bind the lastException variable */
   private var bindLastException = true
@@ -529,6 +541,14 @@ class Interpreter(val settings: Settings, out: PrintWriter) {
       else                      Some(trees)
     }
   }
+  def isParseable(line: String): Boolean = {
+    beSilentDuring {
+      parse(line) match {
+        case Some(xs) => xs.nonEmpty
+        case _        => false
+      }
+    }
+  }
 
   /** Compile an nsc SourceFile.  Returns true if there are
    *  no compilation errors, or false otherwise.
diff --git a/src/compiler/scala/tools/nsc/InterpreterLoop.scala b/src/compiler/scala/tools/nsc/InterpreterLoop.scala
index 6d65f74924..7c25b36d7d 100644
--- a/src/compiler/scala/tools/nsc/InterpreterLoop.scala
+++ b/src/compiler/scala/tools/nsc/InterpreterLoop.scala
@@ -549,10 +549,11 @@ class InterpreterLoop(in0: Option[BufferedReader], protected val out: PrintWrite
       interpretStartingWith(interpreter.mostRecentVar + code)
     }
     else {
-      val result = for (comp <- in.completion ; res <- comp execute code) yield res
-      result match {
-        case Some(res)  => injectAndName(res) ; None   // completion took responsibility, so do not parse
-        case _          => reallyInterpret
+      if (interpreter.isParseable(code)) reallyInterpret
+      else {
+        val res = in.completion flatMap (_ execute code) map injectAndName
+        if (res.isDefined) None // completion took responsibility, so do not parse
+        else reallyInterpret    // we know it will fail, this is to show the error
       }
     }
   }
diff --git a/src/compiler/scala/tools/nsc/interpreter/Completion.scala b/src/compiler/scala/tools/nsc/interpreter/Completion.scala
index e242c90c0c..6dcdbf4579 100644
--- a/src/compiler/scala/tools/nsc/interpreter/Completion.scala
+++ b/src/compiler/scala/tools/nsc/interpreter/Completion.scala
@@ -20,6 +20,9 @@ object Completion {
     && !(code startsWith "./")
     && !(code startsWith "..")
   )
+  def looksLikePath(code: String) = (code != null) && (code.length >= 2) && (
+    Set("/", "\\", "./", "../", "~/") exists (code startsWith _)
+  )
 
   object Forwarder {
     def apply(forwardTo: () => Option[CompletionAware]): CompletionAware = new CompletionAware {
@@ -348,7 +351,9 @@ class Completion(val repl: Interpreter) extends CompletionOutput {
         else tryCompletion(Parsed.dotted(buf drop 1, cursor), lastResultFor)
 
       def regularCompletion = tryCompletion(mkDotted, topLevelFor)
-      def fileCompletion    = tryCompletion(mkUndelimited, FileCompletion completionsFor _.buffer)
+      def fileCompletion    =
+        if (!looksLikePath(buf)) None
+        else tryCompletion(mkUndelimited, FileCompletion completionsFor _.buffer)
 
       /** This is the kickoff point for all manner of theoretically possible compiler
        *  unhappiness - fault may be here or elsewhere, but we don't want to crash the