Make Function.length and Function.name configurable properties.

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 957 matching lines @@
 obj[symbol]++;
 obj[symbol] *= 3;
 delete obj[symbol];
 obj.__defineSetter__(symbol, function() {});
 obj.__defineGetter__(symbol, function() {});
 Object.deliverChangeRecords(observer.callback);
 observer.assertNotCalled();
 
 
 // Test all kinds of objects generically.
-function TestObserveConfigurable(obj, prop) {
+function TestObserveConfigurable(obj, prop, is_writable) {
   reset();
+  var valueWhenDeleted = is_writable ? 3 : obj[prop];
   Object.observe(obj, observer.callback);
   Object.unobserve(obj, observer.callback);
   obj[prop] = 1;
   Object.observe(obj, observer.callback);
   obj[prop] = 2;
-  obj[prop] = 3;
+  obj[prop] = valueWhenDeleted;
   delete obj[prop];
-  obj[prop] = 4;
+  // If the deleted obj[prop] exposed another 'prop' along the
+  // prototype chain, only update it if it has compatible attributes.

[rossberg, 2014/01/09 14:59:35]

This comment seems misleading. You never update the inherited property, you only
make sure that assignment will create a new property on the child.

+  // If not, create an own property with the descriptor that [[Put]]
+  // mandates for a new property (ES-5.1, 8.12.5.6)
+  var createOwnProperty = false;
+  for (var o = Object.getPrototypeOf(obj); o; o = Object.getPrototypeOf(o)) {
+    var desc = Object.getOwnPropertyDescriptor(o, prop);
+    if (desc) {
+      // Have to be able to re-configure and update the property.
+      if (!desc.configurable || !desc.writable || desc.set)

[rossberg, 2014/01/09 14:59:35]

I think this should be more like

  if (!desc.writable || !('value' in desc))

because desc.set will be absent for read-only accessors; configurability doesn't
inherit.

In fact,

  if (!desc.writable)

should be enough, since this will already be true for accessor properties
(because their descriptor has no 'writable').

+        createOwnProperty = true;
+      break;
+    }
+  }
+  if (createOwnProperty)
+    Object.defineProperty(obj, prop, {
+      value: 4,
+      writable: true,
+      enumerable: true,
+      configurable: true
+    });
+  else
+    obj[prop] = 4;
   obj[prop] = 4;  // ignored
   obj[prop] = 5;
   Object.defineProperty(obj, prop, {value: 6});
   Object.defineProperty(obj, prop, {writable: false});
   obj[prop] = 7;  // ignored
   Object.defineProperty(obj, prop, {value: 8});
   Object.defineProperty(obj, prop, {value: 7, writable: true});
   Object.defineProperty(obj, prop, {get: function() {}});
   Object.defineProperty(obj, prop, {get: frozenFunction});
   Object.defineProperty(obj, prop, {get: frozenFunction});  // ignored
   Object.defineProperty(obj, prop, {get: frozenFunction, set: frozenFunction});
   Object.defineProperty(obj, prop, {set: frozenFunction});  // ignored
   Object.defineProperty(obj, prop, {get: undefined, set: frozenFunction});
   obj.__defineSetter__(prop, frozenFunction);  // ignored
   obj.__defineSetter__(prop, function() {});
   obj.__defineGetter__(prop, function() {});
   delete obj[prop];
   delete obj[prop];  // ignored
   obj.__defineGetter__(prop, function() {});
   delete obj[prop];
   Object.defineProperty(obj, prop, {get: function() {}, configurable: true});
   Object.defineProperty(obj, prop, {value: 9, writable: true});
   obj[prop] = 10;
   ++obj[prop];
   obj[prop]++;
   obj[prop] *= 3;
   delete obj[prop];
   Object.defineProperty(obj, prop, {value: 11, configurable: true});
   Object.deliverChangeRecords(observer.callback);
-  observer.assertCallbackRecords([
-    { object: obj, name: prop, type: "update", oldValue: 1 },
-    { object: obj, name: prop, type: "update", oldValue: 2 },
-    { object: obj, name: prop, type: "delete", oldValue: 3 },
+
+  var expected = [
+    { object: obj, name: prop, type: "delete", oldValue: valueWhenDeleted },
     { object: obj, name: prop, type: "add" },
     { object: obj, name: prop, type: "update", oldValue: 4 },
     { object: obj, name: prop, type: "update", oldValue: 5 },
     { object: obj, name: prop, type: "reconfigure" },
     { object: obj, name: prop, type: "update", oldValue: 6 },
     { object: obj, name: prop, type: "reconfigure", oldValue: 8 },
     { object: obj, name: prop, type: "reconfigure", oldValue: 7 },
     { object: obj, name: prop, type: "reconfigure" },
     { object: obj, name: prop, type: "reconfigure" },
     { object: obj, name: prop, type: "reconfigure" },
     { object: obj, name: prop, type: "reconfigure" },
     { object: obj, name: prop, type: "reconfigure" },
     { object: obj, name: prop, type: "delete" },
     { object: obj, name: prop, type: "add" },
     { object: obj, name: prop, type: "delete" },
     { object: obj, name: prop, type: "add" },
     { object: obj, name: prop, type: "reconfigure" },
     { object: obj, name: prop, type: "update", oldValue: 9 },
     { object: obj, name: prop, type: "update", oldValue: 10 },
     { object: obj, name: prop, type: "update", oldValue: 11 },
     { object: obj, name: prop, type: "update", oldValue: 12 },
     { object: obj, name: prop, type: "delete", oldValue: 36 },
     { object: obj, name: prop, type: "add" },
-  ]);
+  ];
+
+  if (is_writable) {
+    expected.unshift(
+      { object: obj, name: prop, type: "update", oldValue: 1 },
+      { object: obj, name: prop, type: "update", oldValue: 2 });
+  }
+
+  observer.assertCallbackRecords(expected);
   Object.unobserve(obj, observer.callback);
   delete obj[prop];
 }
 
 function TestObserveNonConfigurable(obj, prop, desc) {
   reset();
   Object.observe(obj, observer.callback);
   Object.unobserve(obj, observer.callback);
   obj[prop] = 1;
   Object.observe(obj, observer.callback);
@@ skipping 81 matching lines @@
          (obj instanceof ArrayBuffer && prop == 1)
 }
 
 for (var i in objects) for (var j in properties) {
   var obj = objects[i];
   var prop = properties[j];
   if (blacklisted(obj, prop)) continue;
   var desc = Object.getOwnPropertyDescriptor(obj, prop);
   print("***", typeof obj, stringifyNoThrow(obj), prop);
   if (!desc || desc.configurable)
-    TestObserveConfigurable(obj, prop);
+    TestObserveConfigurable(obj, prop, !desc || desc.writable);
   else if (desc.writable)
     TestObserveNonConfigurable(obj, prop, desc);
 }
 
 
 // Observing array length (including truncation)
 reset();
 var arr = ['a', 'b', 'c', 'd'];
 var arr2 = ['alpha', 'beta'];
 var arr3 = ['hello'];
@@ skipping 622 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);