Handle Object.observe notifications for setting Array.length

test/mjsunit/harmony/object-observe.js

 // Copyright 2012 the V8 project authors. All rights reserved.
 // Redistribution and use in source and binary forms, with or without
 // modification, are permitted provided that the following conditions are
 // met:
 //
 //     * Redistributions of source code must retain the above copyright
 //       notice, this list of conditions and the following disclaimer.
 //     * Redistributions in binary form must reproduce the above
 //       copyright notice, this list of conditions and the following
 //       disclaimer in the documentation and/or other materials provided
@@ skipping 314 matching lines @@
   { object: obj, name: "1", type: "reconfigured", oldValue: 7 },
   // TODO(observe): oldValue should not be present below.
   { object: obj, name: "1", type: "deleted", oldValue: undefined },
   { object: obj, name: "1", type: "new" },
   // TODO(observe): oldValue should be absent below, and type = "reconfigured".
   { object: obj, name: "1", type: "updated", oldValue: undefined },
   { object: obj, name: "1", type: "updated", oldValue: 9 },
   { object: obj, name: "1", type: "deleted", oldValue: 10 },
   { object: obj, name: "1", type: "new" },
 ]);
+
+// Observing array length (including truncation)
+reset();
+var arr = ['a', 'b', 'c', 'd'];
+Object.defineProperty(arr, '0', {configurable: false});
+Object.defineProperty(arr, '2', {get: function(){}});

[rossberg, 2012/11/08 14:26:22]

Perhaps add the case of a non-configurable accessor.

[adamk, 2012/11/08 14:48:01]

Done.

+Object.observe(arr, observer.callback);
+arr.length = 2;
+arr.length = 0;
+arr.length = 10;
+Object.deliverChangeRecords(observer.callback);
+observer.assertCallbackRecords([
+  { object: arr, name: '3', type: 'deleted', oldValue: 'd' },
+  // TODO(adamk): oldValue should not be present below
+  { object: arr, name: '2', type: 'deleted', oldValue: undefined },
+  { object: arr, name: 'length', type: 'updated', oldValue: 4 },
+  { object: arr, name: '1', type: 'deleted', oldValue: 'b' },
+  { object: arr, name: 'length', type: 'updated', oldValue: 2 },
+  { object: arr, name: 'length', type: 'updated', oldValue: 1 },
+]);