vm: TypeError thrown instead of ReferenceError when a Proxy is the vm context
Nobody has claimed this yet.
- Dominant language
- JavaScript
- Stars
- 122k
- Forks
- 37.3k
- Avg merge
- 4d 2h
- Merged PRs (30d)
- 283
Description
Version
v22.7.0
Platform
Microsoft Windows NT 10.0.22631.0 x64
Subsystem
vm
What steps will reproduce the bug?
"use strict";
const vm = require("vm");
const context = vm.createContext({
__proto__: new Proxy({}, {
get(target, property, receiver) {
return Reflect.get(target, property, receiver);
}
})
});
vm.runInContext("thisFunctionDoesNotExist()", context);
Output:
How often does it reproduce? Is there a required condition?
Always.
What is the expected behavior? Why is that the expected behavior?
If I instead do
const context = vm.createContext({
__proto__: new Proxy({}, {})
});
vm.runInContext("thisFunctionDoesNotExist()", context);
or simply
const context = vm.createContext({});
vm.runInContext("thisFunctionDoesNotExist()", context);
then I get the expected output:
$ node test.js
evalmachine.<anonymous>:1
thisFunctionDoesNotExist()
^
ReferenceError: thisFunctionDoesNotExist is not defined
at evalmachine.<anonymous>:1:1
at Script.runInContext (node:vm:148:12)
at Object.runInContext (node:vm:300:6)
What do you see instead?
evalmachine.<anonymous>:1
thisFunctionDoesNotExist()
^
TypeError: thisFunctionDoesNotExist is not a function
at evalmachine.<anonymous>:1:1
at Script.runInContext (node:vm:148:12)
at Object.runInContext (node:vm:300:6)
at Object.<anonymous> (C:\Users\d\OneDrive - domenic.me\Code\GitHub\jsdom\jsdom\test.js:31:4)
at Module._compile (node:internal/modules/cjs/loader:1546:14)
at Module._extensions..js (node:internal/modules/cjs/loader:1691:10)
at Module.load (node:internal/modules/cjs/loader:1317:32)
at Module._load (node:internal/modules/cjs/loader:1127:12)
at TracingChannel.traceSync (node:diagnostics_channel:315:14)
at wrapModuleLoad (node:internal/modules/cjs/loader:217:24)
Node.js v22.7.0
Additional information
I am not 100% sure this is a vm bug. It may be a fundamental limitation of Proxy and the complicated ECMAScript spec rules governing ReferenceError vs. TypeError. But I am pretty sure this is a vm limitation instead:
- Browsers manage to give a ReferenceError here
- Browsers have something very similar to proxies (the WindowProperties object) as part of their global object
- I can't see anything in the spec for WindowProperties that cannot be emulated by a Proxy.
This is blocking jsdom from passing the web platform test window-runtime-error.html once I implement the WindowProperties object (https://github.com/jsdom/jsdom/pull/3765).
Contributor guide
First steps
- Read the whole issue, then the project's contributing guide.
- Comment on the issue to say you are picking it up — it saves two people doing the same work.
- Fork the repository and make your change on a branch.
- Open a pull request that references the issue number.
Research direction
Start by running the minimal vm.createContext and vm.runInContext reproducer from the issue, comparing the Proxy variants and the plain context. Use the linked window-runtime-error.html test as the compatibility target; done means the Proxy-backed context reports a ReferenceError for the missing function, matching browsers and the non-Proxy cases.
Written by the indexing model from the issue text.
Assessment
- Tech stack
- javascript, nodejs
- Domain
- backend
- Issue type
- Bug
- Difficulty
- 4/5
- Estimated time
- 3-5 days
- Activity status
- Quiet
- Clarity
- Mostly clear
- Newbie friendliness
- 45/100