Object.observe support for Function 'prototype' property

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 d88c24eac5bcd87c98ecf0e7b6899ada76c0e050..ffb1e2451c4f5356f61b0a9c7335d66d3f37e855 100644
--- a/test/mjsunit/harmony/object-observe.js
+++ b/test/mjsunit/harmony/object-observe.js
@@ -447,7 +447,7 @@ function TestObserveConfigurable(obj, prop) {
   delete obj[prop];
 }
 
-function TestObserveNonConfigurable(obj, prop) {
+function TestObserveNonConfigurable(obj, prop, desc) {
   reset();
   obj[prop] = 1;
   Object.observe(obj, observer.callback);
@@ -457,10 +457,10 @@ function TestObserveNonConfigurable(obj, prop) {
   Object.defineProperty(obj, prop, {value: 6});
   Object.defineProperty(obj, prop, {value: 6});  // ignored
   Object.defineProperty(obj, prop, {value: 7});
-  Object.defineProperty(obj, prop, {enumerable: true});  // ignored
+  Object.defineProperty(obj, prop,
+                        {enumerable: desc.enumerable});  // ignored
   Object.defineProperty(obj, prop, {writable: false});
   obj[prop] = 7;  // ignored
-  Object.defineProperty(obj, prop, {get: function() {}});  // ignored
   Object.deliverChangeRecords(observer.callback);
   observer.assertCallbackRecords([
     { object: obj, name: prop, type: "updated", oldValue: 1 },
@@ -537,8 +537,6 @@ function blacklisted(obj, prop) {
     (obj instanceof ArrayBuffer && prop == 1) ||
     // TODO(observe): oldValue when reconfiguring array length
     (obj instanceof Array && prop === "length") ||
-    // TODO(observe): prototype property on functions
-    (obj instanceof Function && prop === "prototype") ||
     // TODO(observe): global object
     obj === this;
 }
@@ -552,7 +550,7 @@ for (var i in objects) for (var j in properties) {
   if (!desc || desc.configurable)
     TestObserveConfigurable(obj, prop);
   else if (desc.writable)
-    TestObserveNonConfigurable(obj, prop);
+    TestObserveNonConfigurable(obj, prop, desc);
 }
 
 
@@ -810,3 +808,33 @@ observer.assertCallbackRecords([
   { object: array, name: '0', type: 'deleted', oldValue: 0 },
   { object: array, name: 'length', type: 'updated', oldValue: 1},
 ]);
+
+// Function.prototype
+reset();
+var fun = function(){};
+Object.observe(fun, observer.callback);
+var myproto = {foo: 'bar'};
+fun.prototype = myproto;
+fun.prototype = 7;
+fun.prototype = 7;  // ignored
+Object.deliverChangeRecords(observer.callback);
+observer.assertRecordCount(2);
+assertSame(fun, observer.records[0].object);

[rossberg, 2012/12/05 12:02:29]

What is the reason you check the first record outside assertCallbackRecords?

[adamk, 2012/12/05 17:38:17]

Because of line 827: the only handle to the oldValue is in the record itself, so
the thing I compare is oldValue.constructor instead of simply oldValue.

[rossberg, 2012/12/06 09:50:01]

Well, you can save the old fun.prototype before replacing it in line 844. ;)

+assertEquals('prototype', observer.records[0].name);
+assertEquals('updated', observer.records[0].type);
+// The oldValue should be the same object it would have been if
+// it had been accessed before being set.
+assertSame(fun, observer.records[0].oldValue.constructor);
+observer.records.splice(0, 1);
+observer.assertCallbackRecords([
+  { object: fun, name: 'prototype', type: 'updated', oldValue: myproto },
+]);
+
+// Function.prototype should not be observable except on the object itself
+reset();
+var fun = function(){};
+var obj = { __proto__: fun };
+Object.observe(obj, observer.callback);
+obj.prototype = 7;
+Object.deliverChangeRecords(observer.callback);
+observer.assertNotCalled();