From d36ff061fae00f79f8cd7e124a8ebe25d4937f95 Mon Sep 17 00:00:00 2001
From: Jason Orendorff <jorendorff@mozilla.com>
Date: Fri, 12 Aug 2011 07:44:14 -0500
Subject: [PATCH] Address review comments from bhackett (bug 672829 comment
 82).

---
 .../tests/debug/Object-preventExtensions-01.js   | 16 ++++++++++++++++
 js/src/vm/Debugger.cpp                           |  6 ++++--
 2 files changed, 20 insertions(+), 2 deletions(-)
 create mode 100644 js/src/jit-test/tests/debug/Object-preventExtensions-01.js

diff --git a/js/src/jit-test/tests/debug/Object-preventExtensions-01.js b/js/src/jit-test/tests/debug/Object-preventExtensions-01.js
new file mode 100644
index 00000000000..6a2cfc882f8
--- /dev/null
+++ b/js/src/jit-test/tests/debug/Object-preventExtensions-01.js
@@ -0,0 +1,16 @@
+// Basic preventExtensions test.
+
+var g = newGlobal('new-compartment');
+var obj = g.eval("({x: 1})");
+assertEq(g.Object.isExtensible(obj), true);
+
+var dbg = new Debugger;
+var objw = dbg.addDebuggee(obj);
+assertEq(objw.isExtensible(), true);
+
+assertEq(objw.preventExtensions(), undefined);
+assertEq(g.Object.isExtensible(obj), false);
+assertEq(objw.isExtensible(), false);
+
+// Calling preventExtensions again has no effect.
+assertEq(objw.preventExtensions(), undefined);
diff --git a/js/src/vm/Debugger.cpp b/js/src/vm/Debugger.cpp
index cf94a1eb7c4..0d71c3f5a04 100644
--- a/js/src/vm/Debugger.cpp
+++ b/js/src/vm/Debugger.cpp
@@ -3102,7 +3102,7 @@ UnwrapPropDesc(JSContext *cx, Debugger *dbg, JSObject *obj, PropDesc *desc)
 
 /*
  * Rewrap *idp and the fields of *desc for the current compartment.  Also:
- * defining a property on a proxy requiers the pd field to contain a descriptor
+ * defining a property on a proxy requires the pd field to contain a descriptor
  * object, so reconstitute desc->pd if needed.
  */
 static bool
@@ -3232,8 +3232,10 @@ DebuggerObject_sealHelper(JSContext *cx, uintN argc, Value *vp, SealHelperOp op,
         ok = obj->freeze(cx);
     } else {
         JS_ASSERT(op == PreventExtensions);
-        if (!obj->isExtensible())
+        if (!obj->isExtensible()) {
+            args.rval().setUndefined();
             return true;
+        }
         AutoIdVector props(cx);
         ok = obj->preventExtensions(cx, &props);
     }