VM module doesn't handle undefined/NaN/null correctly

[TimothyGu]

• Version: v8.2.1
• Platform: Linux 4.9.0-3-amd64 SMP Debian 4.9.30-2+deb9u2 (2017-06-26) x86_64 GNU/Linux
• Subsystem: vm

> vm.runInNewContext('undefined', { undefined: 123 })
123
> vm.runInNewContext('this.undefined', { undefined: 123 })
123
> // Compare:
> this.undefined = 123
> undefined
undefined
> this.undefined
undefined

undefined (and NaN and Infinity) is defined as unwritable, unconfigurable, unenumerable properties on the global object, and thus IMO should not be overridable through the VM module.

It is unclear if #13265 fixes this, probably not though as this issue concerns getting the value.

[TimothyGu]

(I discovered it when debugging jsdom/jsdom#1932, which turns out to be primarily a bug on jsdom's side. I'm okay with closing this, but still keeping this open to see what anyone else thinks.)

[bnoordhuis]

I suspect this is a V8 bug that has since been fixed because I can't reproduce with today's master; I can with the v8.x branch.

[TimothyGu]

@bnoordhuis In master the first case returns undefined but the second still evaluates to 123…

[bnoordhuis]

Sorry yes, I was referring to the first case. The second one is a bug in the vm module, not V8.

(Or bug... it makes perfect sense in the proxy-to-another-object model, but it's different from a native context.)

[maclover7]

As of f1d6b04, it looks like this behavior has changed a little bit:

> vm.runInNewContext('undefined', { undefined: 123 })
undefined
> vm.runInNewContext('this.undefined', { undefined: 123 })
123
> this.undefined = 123
123
> this.undefined
undefined

[TimothyGu]

I'm going to call this one of the things that one has to take care of when trying to use the vm module "correctly". It's not within our power to fix as it originates in V8, and it's pretty difficult to fix even on the V8 end.