vm: pass attributes from sandbox

GlobalPropertyQueryCallback() was returning `None`
as attributes for all properties, without regard
to actual properties settings.

This patch looks up attributes for sandbox-defined
properties and returns them.  Partial fix for nodejsgh-864

Add test for nodejsgh-864, non-default settings of
object properties (e.g., `enumerable: false`) are not
visible when object is used as a sandbox

src/node_contextify.cc

@@ -387,11 +387,15 @@ class ContextifyContext {
     Local<Object> proxy_global = PersistentToLocal(isolate,
                                                    ctx->proxy_global_);
 
-    bool in_sandbox = sandbox->GetRealNamedProperty(property).IsEmpty();
+    bool in_sandbox = !(sandbox->GetRealNamedProperty(property).IsEmpty());
     bool in_proxy_global =
-        proxy_global->GetRealNamedProperty(property).IsEmpty();
-    if (!in_sandbox || !in_proxy_global) {
-      args.GetReturnValue().Set(None);
+      !(proxy_global->GetRealNamedProperty(property).IsEmpty());
+    if (in_sandbox || in_proxy_global) {
+      v8::PropertyAttribute attr = None;
+      if (in_sandbox) {
+        attr = sandbox->GetPropertyAttributes(property);
+      }
+      args.GetReturnValue().Set(attr);
     }
   }
 

test/parallel/test-vm-preserves-property.js

@@ -0,0 +1,24 @@
+var common = require('../common');
+var assert = require('assert');
+
+var vm = require('vm');
+
+var code = 'Object.getOwnPropertyDescriptor(this, "prop")';
+
+var x = {};
+Object.defineProperty(x, "prop", {
+  configurable: false,
+  enumerable: false,
+  writable: false,
+  value: "val"
+});
+var o = vm.createContext(x);
+
+var res = vm.runInContext(code, o, 'test');
+
+assert(res);
+assert.equal(typeof res, 'object');
+assert.equal(res.value, "val");
+assert.equal(res.configurable, false, "should not be configurable");
+assert.equal(res.enumerable, false, "should not be enumerable");
+assert.equal(res.writable, false, "should not be writable");