From ee1cce94ef1bec8d03441ad15c5a88e61f524a9c Mon Sep 17 00:00:00 2001
From: Robert Krimen <robertkrimen@gmail.com>
Date: Thu, 13 Feb 2014 21:38:20 -0800
Subject: [PATCH] If set === undefined => writable = false

---
 object_class.go |  6 +++++-
 object_test.go  | 16 ++++++++++++++++
 2 files changed, 21 insertions(+), 1 deletion(-)

diff --git a/object_class.go b/object_class.go
index deb6261..2a1947f 100644
--- a/object_class.go
+++ b/object_class.go
@@ -306,7 +306,11 @@ func objectDefineOwnProperty(self *_object, name string, descriptor _property, t
 				property.writeClear()
 				property.value = descriptor.value
 			} else {
-				property.writeOn()
+				if descriptor.writable() {
+					property.writeOn()
+				} else {
+					property.writeOff()
+				}
 				property.value = descriptor.value
 			}
 		} else if isDataDescriptor && descriptor.isDataDescriptor() {
diff --git a/object_test.go b/object_test.go
index 92b0301..42d1295 100644
--- a/object_test.go
+++ b/object_test.go
@@ -445,6 +445,22 @@ func TestObjectGetterSetter(t *testing.T) {
     var def = Object.getOwnPropertyDescriptor(abc, "def");
     [ abc.def, typeof def.get, typeof def.set, typeof def.value, def.configurable, def.enumerable, typeof def.writable ];
     `, "5,function,undefined,undefined,true,false,undefined")
+
+	test(`
+    var abc = {};
+    Object.defineProperty(abc, "def", {
+        get: function() {
+            return 5;
+        }
+        configurable: true
+    });
+    Object.preventExtensions(abc);
+    Object.defineProperty(abc, "def", {
+        value: "xyzzy",
+    });
+    var def = Object.getOwnPropertyDescriptor(abc, "def");
+    [ abc.def, typeof def.get, typeof def.set, def.value, def.configurable, def.enumerable, def.writable ];
+    `, "xyzzy,undefined,undefined,xyzzy,true,false,false")
 }
 
 func TestProperty(t *testing.T) {