Ensure that exception message is printed.

frog/corejs.dart

 // Copyright (c) 2011, the Dart project authors.  Please see the AUTHORS file
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 
 /**
  * Generates JS helpers for dart:core. This used to be in a file "core.js".
  * Having them in Dart code means we can easily control which are generated.
  */
 // TODO(jmesserly): one idea to make this cleaner: put these as private "native"
 // methods somewhere in a library that we import. This would be rather elegant
@@ skipping 235 matching lines @@
   // Need to mangle it.
   return  (e && e.stack) ? e.stack : null;
 }""");
     }
 
     if (useToDartException) {
       w.writeln(@"""
 // Translate a JavaScript exception to a Dart exception
 // TODO(jmesserly): cross browser support. This is Chrome specific.
 function $toDartException(e) {
-  var res = e;
+  function attachStack(dartEx) {
+    // TODO(jmesserly): setting the stack property is not a long term solution.
+    var stack = e.stack;
+    // The stack contains the error message, and the stack is all that is
+    // printed (the exception's toString() is never called).  Attempt to replace
+    // the JS message (e.g. TypeError) with the Dart exception's toString().
+    if (typeof stack == 'string') {
+      try {  // toString is in a try-catch due to Issue 470.

[Jennifer Messerly, 2011/11/29 00:46:18]

Issue 470 is fixed--can you see if the try-catch can be removed?

+        var message = dartEx.toString();
+        if (/^(Type|Range)Error:/.test(stack)) {
+          // Remove JS message.
+          stack = stack.substring(stack.indexOf('\n') + 1);
+        }
+        stack = message + '\n' + stack;
+      } catch(_) {
+        stack = '' + dartEx.constructor.name + ': (corrupt)\n' + stack;
+      }
+    }
+    dartEx.stack = stack;
+    return dartEx;
+  }
+
   if (e instanceof TypeError) {
     switch(e.type) {
       case 'property_not_function':
       case 'called_non_callable':
         if (e.arguments[0] == null) {
-          res = new NullPointerException();
+          return attachStack(new NullPointerException());
         } else {
-          res = new ObjectNotClosureException();
+          return attachStack(new ObjectNotClosureException());
         }
         break;
       case 'non_object_property_call':
       case 'non_object_property_load':
-        res = new NullPointerException();
+        return attachStack(new NullPointerException());
         break;
       case 'undefined_method':
         if (e.arguments[0] == 'call' || e.arguments[0] == 'apply') {
-          res = new ObjectNotClosureException();
+          return attachStack(new ObjectNotClosureException());
         } else {
           // TODO(jmesserly): can this ever happen?
-          res = new NoSuchMethodException('', e.arguments[0], []);
+          // sra: Yes.

[Jennifer Messerly, 2011/11/29 00:46:18]

Can you add context about what conditions it happens? e.g.
// This happens with operators that aren't found because noSuchMethod fallbacks
are not correctly generated

(I think that's the only condition this should happen, but maybe you hit a
different one)

+          return attachStack(new NoSuchMethodException('', e.arguments[0], []));
         }
         break;
     }
   } else if (e instanceof RangeError) {
     if (e.message.indexOf('call stack') >= 0) {
-      res = new StackOverflowException();
+      return attachStack(new StackOverflowException());
     }
   }
-  if (res) {
-    // TODO(jmesserly): setting the stack property is not a long term solution.
-    // Also it causes the exception to print as if it were a JS TypeError or
-    // RangeError, instead of using the proper toString.
-    res.stack = e.stack;
-  }
-  return res;
+  return e;
 }""");
     }
 
     if (useNotNullBool) {
       useThrow = true;
       // This pattern chosen because IE9 does really badly with typeof, and
       // it's still decent on other browsers.
       w.writeln(@"""
 function $notnull_bool(test) {
   return (test === true || test === false) ? test : test.is$bool(); // TypeError
@@ skipping 133 matching lines @@
         w.writeln(@"function $wrap_call$1(fn) { return fn; }");
       }
     }
 
     // Write operator helpers
     for (var opImpl in orderValuesByKeys(_usedOperators)) {
       w.writeln(opImpl);
     }
   }
 }