Make Function.length and Function.name configurable properties.

test/mjsunit/harmony/object-observe.js

Index: test/mjsunit/harmony/object-observe.js
diff --git a/test/mjsunit/harmony/object-observe.js b/test/mjsunit/harmony/object-observe.js
index 72a9cadbf8ecb9df05a37593055e58e3c44f7efc..56c0fe4565f56fe2c4669e7e9db1e0d88d849dc2 100644
--- a/test/mjsunit/harmony/object-observe.js
+++ b/test/mjsunit/harmony/object-observe.js
@@ -975,16 +975,39 @@ 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});
@@ -1014,10 +1037,9 @@ function TestObserveConfigurable(obj, prop) {
   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 },
@@ -1041,7 +1063,15 @@ function TestObserveConfigurable(obj, prop) {
     { 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];
 }
@@ -1143,7 +1173,7 @@ for (var i in objects) for (var j in properties) {
   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);
 }