Array.observe emit splices for array length change and update index >= 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 939 matching lines @@
 }
 
 
 // Observing array length (including truncation)
 reset();
 var arr = ['a', 'b', 'c', 'd'];
 var arr2 = ['alpha', 'beta'];
 var arr3 = ['hello'];
 arr3[2] = 'goodbye';
 arr3.length = 6;
-var slow_arr = new Array(1000000000);
-slow_arr[500000000] = 'hello';
 Object.defineProperty(arr, '0', {configurable: false});
 Object.defineProperty(arr, '2', {get: function(){}});
 Object.defineProperty(arr2, '0', {get: function(){}, configurable: false});
 Object.observe(arr, observer.callback);
+Array.observe(arr, observer2.callback);
 Object.observe(arr2, observer.callback);
+Array.observe(arr2, observer2.callback);
 Object.observe(arr3, observer.callback);
-Object.observe(slow_arr, observer.callback);
+Array.observe(arr3, observer2.callback);
 arr.length = 2;
 arr.length = 0;
 arr.length = 10;
 Object.defineProperty(arr, 'length', {writable: false});
 arr2.length = 0;
 arr2.length = 1; // no change expected
 Object.defineProperty(arr2, 'length', {value: 1, writable: false});
 arr3.length = 0;
 ++arr3.length;
 arr3.length++;
 arr3.length /= 2;
 Object.defineProperty(arr3, 'length', {value: 5});
-Object.defineProperty(arr3, 'length', {value: 10, writable: false});
-slow_arr.length = 100;
+arr3[4] = 5;
+Object.defineProperty(arr3, 'length', {value: 1, writable: false});
 Object.deliverChangeRecords(observer.callback);
 observer.assertCallbackRecords([
   { object: arr, name: '3', type: 'deleted', oldValue: 'd' },
   { object: arr, name: '2', type: 'deleted' },
   { 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 },
   { object: arr, name: 'length', type: 'reconfigured' },
   { object: arr2, name: '1', type: 'deleted', oldValue: 'beta' },
   { object: arr2, name: 'length', type: 'updated', oldValue: 2 },
-  { object: arr2, name: 'length', type: 'reconfigured', oldValue: 1 },
+  { object: arr2, name: 'length', type: 'reconfigured' },
   { object: arr3, name: '2', type: 'deleted', oldValue: 'goodbye' },
   { object: arr3, name: '0', type: 'deleted', oldValue: 'hello' },
   { object: arr3, name: 'length', type: 'updated', oldValue: 6 },
   { object: arr3, name: 'length', type: 'updated', oldValue: 0 },
   { object: arr3, name: 'length', type: 'updated', oldValue: 1 },
   { object: arr3, name: 'length', type: 'updated', oldValue: 2 },
   { object: arr3, name: 'length', type: 'updated', oldValue: 1 },
-  { object: arr3, name: 'length', type: 'reconfigured', oldValue: 5 },
+  { object: arr3, name: '4', type: 'new' },
+  { object: arr3, name: '4', type: 'deleted', oldValue: 5 },
+  { object: arr3, name: 'length', type: 'updated', oldValue: 5 },
+  { object: arr3, name: 'length', type: 'reconfigured' }

[rossberg, 2013/05/27 14:48:41]

Not sure I understand, why is it correct that this a separate change now?

[rafaelw, 2013/05/28 11:38:53]

It isn't correct, but Adam and I discussed and decided that

a) It's fine to break with spec compliance here because it's an extreme edge
case and even if hit, two records vs one is almost certain not to confuse any
observer.

b) Making it spec compliant in this minor way isn't worth layering hacks on top
of more hacks here. Once the todo mentioned by mstarzinger is fixed, the right
change record sequence will return.

On 2013/05/27 14:48:41, rossberg wrote:

[rossberg, 2013/06/04 10:56:58]

OK, can you add a TODO then?

[rafaelw, 2013/06/04 23:42:21]

Done.

+]);
+Object.deliverChangeRecords(observer2.callback);
+observer2.assertCallbackRecords([
+  { object: arr, type: 'splice', index: 2, removed: [, 'd'], addedCount: 0 },
+  { object: arr, type: 'splice', index: 1, removed: ['b'], addedCount: 0 },
+  { object: arr, type: 'splice', index: 1, removed: [], addedCount: 9 },
+  { object: arr2, type: 'splice', index: 1, removed: ['beta'], addedCount: 0 },
+  { object: arr3, type: 'splice', index: 0, removed: ['hello',, 'goodbye',,,,], addedCount: 0 },
+  { object: arr3, type: 'splice', index: 0, removed: [], addedCount: 1 },
+  { object: arr3, type: 'splice', index: 1, removed: [], addedCount: 1 },
+  { object: arr3, type: 'splice', index: 1, removed: [,], addedCount: 0 },
+  { object: arr3, type: 'splice', index: 1, removed: [], addedCount: 4 },
+  { object: arr3, name: '4', type: 'new' },
+  { object: arr3, type: 'splice', index: 1, removed: [,,,5], addedCount: 0 }
+]);
+
+
+// Updating length on large (slow) array
+reset();
+var slow_arr = new Array(1000000000);
+slow_arr[500000000] = 'hello';
+Object.observe(slow_arr, observer.callback);
+var spliceRecords;
+function slowSpliceCallback(records) {
+  spliceRecords = records;
+}
+Array.observe(slow_arr, slowSpliceCallback);
+slow_arr.length = 100;
+Object.deliverChangeRecords(observer.callback);
+observer.assertCallbackRecords([
   { object: slow_arr, name: '500000000', type: 'deleted', oldValue: 'hello' },
   { object: slow_arr, name: 'length', type: 'updated', oldValue: 1000000000 },
 ]);
+Object.deliverChangeRecords(slowSpliceCallback);
+assertEquals(spliceRecords.length, 1);
+// Have to custom assert this splice record because the removed array is huge.
+var splice = spliceRecords[0];
+assertSame(splice.object, slow_arr);
+assertEquals(splice.type, 'splice');
+assertEquals(splice.index, 100);
+assertEquals(splice.addedCount, 0);
+var array_keys = %GetArrayKeys(splice.removed, splice.removed.length);
+assertEquals(array_keys.length, 1);
+assertEquals(array_keys[0], 499999900);
+assertEquals(splice.removed[499999900], 'hello');
+assertEquals(splice.removed.length, 999999900);
 
 
 // Assignments in loops (checking different IC states).
 reset();
 var obj = {};
 Object.observe(obj, observer.callback);
 for (var i = 0; i < 5; i++) {
   obj["a" + i] = i;
 }
 Object.deliverChangeRecords(observer.callback);
@@ skipping 14 matching lines @@
 Object.deliverChangeRecords(observer.callback);
 observer.assertCallbackRecords([
   { object: obj, name: "0", type: "new" },
   { object: obj, name: "1", type: "new" },
   { object: obj, name: "2", type: "new" },
   { object: obj, name: "3", type: "new" },
   { object: obj, name: "4", type: "new" },
 ]);
 
 
-// Adding elements past the end of an array should notify on length
+// Adding elements past the end of an array should notify on length for
+// Object.observe and emit "splices" for Array.observe.
 reset();
 var arr = [1, 2, 3];
 Object.observe(arr, observer.callback);
+Array.observe(arr, observer2.callback);
 arr[3] = 10;
 arr[100] = 20;
 Object.defineProperty(arr, '200', {value: 7});
 Object.defineProperty(arr, '400', {get: function(){}});
 arr[50] = 30; // no length change expected
 Object.deliverChangeRecords(observer.callback);
 observer.assertCallbackRecords([
   { object: arr, name: '3', type: 'new' },
   { object: arr, name: 'length', type: 'updated', oldValue: 3 },
   { object: arr, name: '100', type: 'new' },
   { object: arr, name: 'length', type: 'updated', oldValue: 4 },
   { object: arr, name: '200', type: 'new' },
   { object: arr, name: 'length', type: 'updated', oldValue: 101 },
   { object: arr, name: '400', type: 'new' },
   { object: arr, name: 'length', type: 'updated', oldValue: 201 },
   { object: arr, name: '50', type: 'new' },
 ]);
+Object.deliverChangeRecords(observer2.callback);
+observer2.assertCallbackRecords([
+  { object: arr, type: 'splice', index: 3, removed: [], addedCount: 1 },
+  { object: arr, type: 'splice', index: 4, removed: [], addedCount: 97 },
+  { object: arr, type: 'splice', index: 101, removed: [], addedCount: 100 },
+  { object: arr, type: 'splice', index: 201, removed: [], addedCount: 200 },
+  { object: arr, type: 'new', name: '50' },
+]);
 
 
 // Tests for array methods, first on arrays and then on plain objects
 //
 // === ARRAYS ===
 //
 // Push
 reset();
 var array = [1, 2];
 Object.observe(array, observer.callback);
@@ skipping 316 matching lines @@
     for (var n1 = 0; n1 < 3; ++n1)
       for (var n2 = 0; n2 < 3; ++n2)
         for (var i in mutation)
           TestFastElementsLength(mutation[i], b1 != 0, b2 != 0, 20*n1, 20*n2);
 
 for (var b1 = 0; b1 < 2; ++b1)
   for (var b2 = 0; b2 < 2; ++b2)
     for (var n = 0; n < 3; ++n)
       for (var i in mutationByIncr)
         TestFastElementsLength(mutationByIncr[i], b1 != 0, b2 != 0, 7*n, 7*n+1);