Change from 0.10 => 1.2; enumerable of this.escape in vm.runInNewContext was false, now true

[smikes]

Here's the behavior from node 0.10:

$ node -p 'require("vm").runInNewContext("Object.getOwnPropertyDescriptor(this,\"escape\")", {})'
{ value: [Function: escape],
  writable: true,
  enumerable: false,
  configurable: true }

And in io.js@1.2.0:

$ nvm use 1.2
Now using io.js v1.2.0
$ node -p 'require("vm").runInNewContext("Object.getOwnPropertyDescriptor(this,\"escape\")", {})'
{ value: [Function: escape],
  writable: true,
  enumerable: true,
  configurable: true }

Is this an intentional change? Is it documented anywhere? FWIW this is present in node@0.11 as well

[anba]

I guess this is related to https://code.google.com/p/v8/issues/detail?id=3861. GetOwnPropertyNames() is called here.

[smikes]

Testing with cloneProperty in the REPL correctly generates an escape with enumerable: false:

> c = require('./cloneProperty')
[Function: cloneProperty]
> s = {}
{}
> c(global, "escape", s)
undefined
> s
{}
> Object.getOwnPropertyDescriptor(s, "escape")
{ value: [Function: escape],
  writable: true,
  enumerable: false,
  configurable: true }

where cloneProperty.js is:

function cloneProperty(source, key, target) {
                if (key === 'Proxy') return;
                try {
                  var desc = Object.getOwnPropertyDescriptor(source, key);
                  if (desc.value === source) desc.value = target;
                  Object.defineProperty(target, key, desc);
                } catch (e) {
                 // Catch sealed properties errors
                }
              }

module.exports = cloneProperty;

[bnoordhuis]

I suspect that's caused by the named property interceptor for the global object here.

if (!in_sandbox || !in_proxy_global) {
  args.GetReturnValue().Set(None);
}

Not sure what the best way to fix it is. The interceptor needs to retrieve the actual property attributes somehow without causing infinite recursion.

[smikes]

@boordhuis - Indeed, getting attributes for properties of the global is tricky. I have a PR (#885) for the sandbox side, which was easy.

I tried something like this:

    Local<Context> context = PersistentToLocal(isolate, ctx->context_);
    attr = context->Global()->GetPropertyAttributes(property);

But that set off an infinite recursion, as you predicted. Any suggestions?

[bnoordhuis]

@smikes I commented on that here. It looks like V8 needs to grow some new APIs to fix this issue. I have it on my radar but I'm stretched rather thin at the moment.

[bnoordhuis]

https://codereview.chromium.org/942003003/

[Fishrock123]

Looks like the v8 patch landed.

[domenic]

This can be closed as it's fixed in next.