REPL: call 'toString()' for returned values explicitly and correctly report exceptions

#KT-12389 Fixed

compiler/cli/src/org/jetbrains/kotlin/cli/jvm/repl/ReplFromTerminal.kt

@@ -100,7 +100,7 @@ class ReplFromTerminal(
             is ValueResult, UnitResult -> {
                 writer.notifyCommandSuccess()
                 if (lineResult is ValueResult) {
-                    writer.outputCommandResult(lineResult.value)
+                    writer.outputCommandResult(lineResult.valueAsString)
                 }
             }
             Incomplete -> writer.notifyIncomplete()

compiler/cli/src/org/jetbrains/kotlin/cli/jvm/repl/ReplInterpreter.kt

@@ -132,25 +132,28 @@ class ReplInterpreter(
 
             val scriptInstanceConstructor = scriptClass.getConstructor(*constructorParams)
             val scriptInstance = try {
-                onUserCodeExecuting(true)
-                scriptInstanceConstructor.newInstance(*constructorArgs)
+                executeUserCode { scriptInstanceConstructor.newInstance(*constructorArgs) }
             }
             catch (e: Throwable) {
-                return LineResult.Error.Runtime(renderStackTrace(e.cause!!))
-            }
-            finally {
-                onUserCodeExecuting(false)
+                // ignore everything in the stack trace until this constructor call
+                return LineResult.Error.Runtime(renderStackTrace(e.cause!!, startFromMethodName = "${scriptClass.name}.<init>"))
             }
 
             val rvField = scriptClass.getDeclaredField(SCRIPT_RESULT_FIELD_NAME).apply { isAccessible = true }
-            val rv = rvField.get(scriptInstance)
+            val rv: Any? = rvField.get(scriptInstance)
 
             earlierLines.add(EarlierLine(line, scriptDescriptor, scriptClass, scriptInstance))
 
             if (!state.replSpecific.hasResult) {
                 return LineResult.UnitResult
             }
-            return LineResult.ValueResult(rv)
+            val valueAsString: String = try {
+                executeUserCode { rv.toString() }
+            }
+            catch (e: Throwable) {
+                return LineResult.Error.Runtime(renderStackTrace(e, startFromMethodName = "java.lang.String.valueOf"))
+            }
+            return LineResult.ValueResult(valueAsString)
         }
         catch (e: Throwable) {
             val writer = PrintWriter(System.err)
@@ -160,6 +163,16 @@ class ReplInterpreter(
         }
     }
 
+    private fun <T> executeUserCode(body: () -> T): T {
+        try {
+            onUserCodeExecuting(true)
+            return body()
+        }
+        finally {
+            onUserCodeExecuting(false)
+        }
+    }
+
     fun dumpClasses(out: PrintWriter) {
         classLoader.dumpClasses(out)
     }
@@ -176,13 +189,11 @@ class ReplInterpreter(
             override fun getScriptName(script: KtScript): Name = StandardScriptDefinition.getScriptName(script)
         }
 
-        private fun renderStackTrace(cause: Throwable): String {
+        private fun renderStackTrace(cause: Throwable, startFromMethodName: String): String {
             val newTrace = arrayListOf<StackTraceElement>()
             var skip = true
             for ((i, element) in cause.stackTrace.withIndex().reversed()) {
-                // All our code happens in the script constructor, and no reflection/native code happens in constructors.
-                // So we ignore everything in the stack trace until the first constructor
-                if (element.methodName == "<init>") {
+                if ("${element.className}.${element.methodName}" == startFromMethodName) {
                     skip = false
                 }
                 if (!skip) {
@@ -190,7 +201,6 @@ class ReplInterpreter(
                 }
             }
 
-            // throw away last element which contains Line1.kts<init>(Unknown source)
             val resultingTrace = newTrace.reversed().dropLast(1)
 
             @Suppress("PLATFORM_CLASS_MAPPED_TO_KOTLIN", "UsePropertyAccessSyntax")
@@ -220,7 +230,7 @@ class ReplInterpreter(
 }
 
 sealed class LineResult {
-    class ValueResult(val value: Any?): LineResult()
+    class ValueResult(val valueAsString: String): LineResult()
 
     object UnitResult: LineResult()
     object Incomplete : LineResult()

compiler/cli/src/org/jetbrains/kotlin/cli/jvm/repl/messages/ReplConsoleWriter.kt

@@ -1,5 +1,5 @@
 /*
- * Copyright 2010-2015 JetBrains s.r.o.
+ * Copyright 2010-2016 JetBrains s.r.o.
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
@@ -20,7 +20,7 @@ class ReplConsoleWriter : ReplWriter {
     override fun printlnWelcomeMessage(x: String) = println(x)
     override fun printlnHelpMessage(x: String) = println(x)
     override fun outputCompileError(x: String) = println(x)
-    override fun outputCommandResult(x: Any?) = println(x)
+    override fun outputCommandResult(x: String) = println(x)
     override fun outputRuntimeError(x: String) = println(x)
 
     override fun notifyReadLineStart() {}

compiler/cli/src/org/jetbrains/kotlin/cli/jvm/repl/messages/ReplSystemOutWrapperForIde.kt

@@ -1,5 +1,5 @@
 /*
- * Copyright 2010-2015 JetBrains s.r.o.
+ * Copyright 2010-2016 JetBrains s.r.o.
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
@@ -60,7 +60,7 @@ class ReplSystemOutWrapperForIde(standardOut: PrintStream) : PrintStream(standar
 
     override fun printlnWelcomeMessage(x: String) = printlnWithEscaping(x, EscapeType.INITIAL_PROMPT)
     override fun printlnHelpMessage(x: String) = printlnWithEscaping(x, EscapeType.HELP_PROMPT)
-    override fun outputCommandResult(x: Any?) = printlnWithEscaping(x.toString(), EscapeType.REPL_RESULT)
+    override fun outputCommandResult(x: String) = printlnWithEscaping(x, EscapeType.REPL_RESULT)
     override fun notifyReadLineStart() = printlnWithEscaping("", EscapeType.READLINE_START)
     override fun notifyReadLineEnd() = printlnWithEscaping("", EscapeType.READLINE_END)
     override fun notifyCommandSuccess() = printlnWithEscaping("", EscapeType.SUCCESS)

compiler/cli/src/org/jetbrains/kotlin/cli/jvm/repl/messages/ReplWriter.kt

@@ -1,5 +1,5 @@
 /*
- * Copyright 2010-2015 JetBrains s.r.o.
+ * Copyright 2010-2016 JetBrains s.r.o.
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
@@ -19,7 +19,7 @@ package org.jetbrains.kotlin.cli.jvm.repl.messages
 interface ReplWriter {
     fun printlnWelcomeMessage(x: String)
     fun printlnHelpMessage(x: String)
-    fun outputCommandResult(x: Any?)
+    fun outputCommandResult(x: String)
     fun notifyReadLineStart()
     fun notifyReadLineEnd()
     fun notifyIncomplete()

compiler/testData/repl/exceptionInValueToString.repl

@@ -0,0 +1,9 @@
+>>> class B { override fun toString(): String { return foo() } ; fun foo(): String { return error("message") } }
+>>> B().toString()
+java.lang.IllegalStateException: message
+	at Line1$B.foo(line1.kts:1)
+	at Line1$B.toString(line1.kts:1)
+>>> B()
+java.lang.IllegalStateException: message
+	at Line1$B.foo(line1.kts:1)
+	at Line1$B.toString(line1.kts:1)

compiler/tests/org/jetbrains/kotlin/repl/AbstractReplInterpreterTest.kt

@@ -93,7 +93,7 @@ abstract class AbstractReplInterpreterTest : KtUsefulTestCase() {
             }
 
             val actual = when (lineResult) {
-                is LineResult.ValueResult -> "${lineResult.value}"
+                is LineResult.ValueResult -> lineResult.valueAsString
                 is LineResult.Error -> lineResult.errorText
                 LineResult.Incomplete -> INCOMPLETE_LINE_MESSAGE
                 LineResult.UnitResult -> ""

compiler/tests/org/jetbrains/kotlin/repl/ReplInterpreterTestGenerated.java

@@ -59,6 +59,12 @@ public class ReplInterpreterTestGenerated extends AbstractReplInterpreterTest {
         doTest(fileName);
     }
 
+    @TestMetadata("exceptionInValueToString.repl")
+    public void testExceptionInValueToString() throws Exception {
+        String fileName = KotlinTestUtils.navigationMetadata("compiler/testData/repl/exceptionInValueToString.repl");
+        doTest(fileName);
+    }
+
     @TestMetadata("function.repl")
     public void testFunction() throws Exception {
         String fileName = KotlinTestUtils.navigationMetadata("compiler/testData/repl/function.repl");