Canonicalize closures passed to native functions.

frog/leg/lib/js_helper.dart

 // Copyright (c) 2012, 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.
 
 #library('js_helper');
 
 #import('coreimpl.dart');
 
 #source('date_helper.dart');
 #source('regexp_helper.dart');
@@ skipping 1255 matching lines @@
 /**
  * Called from catch blocks in generated code to extract the Dart
  * exception from the thrown value. The thrown value may have been
  * created by [captureStackTrace] or it may be a 'native' JS
  * exception.
  *
  * Some native exceptions are mapped to new Dart instances, others are
  * returned unmodified.
  */
 unwrapException(ex) {
+  // Note that we are checking if the object has the property. If it
+  // has, it could be set null if the thrown value is null.

[ahe, 2012/03/08 18:32:02]

"set null" -> "null"

   if (JS('bool', @'"dartException" in $0', ex)) {
     return JS('Object', @'$0.dartException', ex);
   } else if (JS('bool', @'$0 instanceof TypeError', ex)) {
     // TODO(ahe): ex.type is Chrome specific.
     var type = JS('String', @'$0.type', ex);
     var jsArguments = JS('Object', @'$0.arguments', ex);
     var name = jsArguments[0];
     if (type == 'property_not_function' ||
         type == 'called_non_callable' ||
         type == 'non_object_property_call' ||
@@ skipping 40 matching lines @@
     result[key] = value;
   }
   return result;
 }
 
 /**
  * Called by generated code to convert a Dart closure to a JS
  * closure when the Dart closure is passed to the DOM.
  */
 convertDartClosureToJS(closure) {
-  return JS("var", @"""function() {
+  var function = JS('var', @'$0.$identity', closure);
+  if (JS('bool', @'!!$0', function)) return function;
+  function = JS("var", @"""function() {
     var dartClosure = $0;
     switch (arguments.length) {
       case 0: return $1(dartClosure);
       case 1: return $2(dartClosure, arguments[0]);
       case 2: return $3(dartClosure, arguments[0], arguments[1]);
       default:
         throw new Error('Unsupported number of arguments for wrapped closure');
     }
   }""",
   closure,
   callClosure0,
   callClosure1,
   callClosure2);
+  JS('void', @'$0.$identity = $1', closure, function);
+  return function;
 }
 
 /**
  * Helper methods when converting a Dart closure to a JS closure.
  */
 callClosure0(closure) => closure();
 callClosure1(closure, arg1) => closure(arg1);
 callClosure2(closure, arg1, arg2) => closure(arg1, arg2);
 
 class StackTrace {
   var stack;
   StackTrace(this.stack);
   String toString() => stack != null ? stack : '';
 }