From c036e81169d82dde519e994f0049ed2e4f8c68c0 Mon Sep 17 00:00:00 2001
From: Jeff Walden <jwalden@mit.edu>
Date: Fri, 12 Nov 2010 16:15:55 -0800
Subject: [PATCH] Bug 599464 - Object.preventExtensions should be idempotent. 
 r=brendan

---
 js/src/jsobj.cpp                              |  7 +++--
 js/src/jsobj.h                                | 10 ++++---
 js/src/tests/ecma_5/Object/jstests.list       |  1 +
 .../Object/preventExtensions-idempotent.js    | 30 +++++++++++++++++++
 4 files changed, 42 insertions(+), 6 deletions(-)
 create mode 100644 js/src/tests/ecma_5/Object/preventExtensions-idempotent.js

diff --git a/js/src/jsobj.cpp b/js/src/jsobj.cpp
index 5ccb9558ba9f..e8b1062f437c 100644
--- a/js/src/jsobj.cpp
+++ b/js/src/jsobj.cpp
@@ -2542,15 +2542,18 @@ obj_preventExtensions(JSContext *cx, uintN argc, Value *vp)
         return false;
 
     vp->setObject(*obj);
+    if (!obj->isExtensible())
+        return true;
 
     AutoIdVector props(cx);
     return obj->preventExtensions(cx, &props);
 }
 
 bool
-JSObject::sealOrFreeze(JSContext *cx, bool freeze)
+JSObject::sealOrFreeze(JSContext *cx, ImmutabilityType it)
 {
     assertSameCompartment(cx, this);
+    JS_ASSERT(it == SEAL || it == FREEZE);
 
     AutoIdVector props(cx);
     if (isExtensible()) {
@@ -2573,7 +2576,7 @@ JSObject::sealOrFreeze(JSContext *cx, bool freeze)
 
         /* Make all attributes permanent; if freezing, make data attributes read-only. */
         uintN new_attrs;
-        if (freeze && !(attrs & (JSPROP_GETTER | JSPROP_SETTER)))
+        if (it == FREEZE && !(attrs & (JSPROP_GETTER | JSPROP_SETTER)))
             new_attrs = JSPROP_PERMANENT | JSPROP_READONLY;
         else
             new_attrs = JSPROP_PERMANENT;
diff --git a/js/src/jsobj.h b/js/src/jsobj.h
index c60c942b427e..89da8ba9a67f 100644
--- a/js/src/jsobj.h
+++ b/js/src/jsobj.h
@@ -708,22 +708,24 @@ struct JSObject : js::gc::Cell {
      */
 
   private:
+    enum ImmutabilityType { SEAL, FREEZE };
+
     /*
      * The guts of Object.seal (ES5 15.2.3.8) and Object.freeze (ES5 15.2.3.9): mark the
      * object as non-extensible, and adjust each property's attributes appropriately: each
      * property becomes non-configurable, and if |freeze|, data properties become
      * read-only as well.
      */
-    bool sealOrFreeze(JSContext *cx, bool freeze = false);
+    bool sealOrFreeze(JSContext *cx, ImmutabilityType it);
 
   public:
     bool isExtensible() const { return !(flags & NOT_EXTENSIBLE); }
     bool preventExtensions(JSContext *cx, js::AutoIdVector *props);
-    
+
     /* ES5 15.2.3.8: non-extensible, all props non-configurable */
-    inline bool seal(JSContext *cx) { return sealOrFreeze(cx); }
+    inline bool seal(JSContext *cx) { return sealOrFreeze(cx, SEAL); }
     /* ES5 15.2.3.9: non-extensible, all properties non-configurable, all data props read-only */
-    bool freeze(JSContext *cx) { return sealOrFreeze(cx, true); }
+    bool freeze(JSContext *cx) { return sealOrFreeze(cx, FREEZE); }
         
     /*
      * Primitive-specific getters and setters.
diff --git a/js/src/tests/ecma_5/Object/jstests.list b/js/src/tests/ecma_5/Object/jstests.list
index 4c11d45682c7..019cfe990360 100644
--- a/js/src/tests/ecma_5/Object/jstests.list
+++ b/js/src/tests/ecma_5/Object/jstests.list
@@ -41,3 +41,4 @@ script object-toString-01.js
 script vacuous-accessor-unqualified-name.js
 script add-property-non-extensible.js
 skip-if(!xulRuntime.shell) script freeze-global-eval-const.js # uses evalcx
+script preventExtensions-idempotent.js
diff --git a/js/src/tests/ecma_5/Object/preventExtensions-idempotent.js b/js/src/tests/ecma_5/Object/preventExtensions-idempotent.js
new file mode 100644
index 000000000000..c0b16d890f6c
--- /dev/null
+++ b/js/src/tests/ecma_5/Object/preventExtensions-idempotent.js
@@ -0,0 +1,30 @@
+/*
+ * Any copyright is dedicated to the Public Domain.
+ * http://creativecommons.org/licenses/publicdomain/
+ * Contributor:
+ *   Jeff Walden <jwalden+code@mit.edu>
+ */
+
+var gTestfile = 'preventExtensions-idempotent.js';
+//-----------------------------------------------------------------------------
+var BUGNUMBER = 599459;
+var summary = 'Object.preventExtensions should be idempotent';
+
+print(BUGNUMBER + ": " + summary);
+
+/**************
+ * BEGIN TEST *
+ **************/
+
+var obj = {};
+assertEq(Object.preventExtensions(obj), obj);
+assertEq(Object.isExtensible(obj), false);
+assertEq(Object.preventExtensions(obj), obj);
+assertEq(Object.isExtensible(obj), false);
+
+/******************************************************************************/
+
+if (typeof reportCompare === "function")
+  reportCompare(true, true);
+
+print("All tests passed!");