vm.runInContext Function Prototype Issue

[mathewgeola]

What is the problem this feature will solve?

I'm having an issue with the vm module in Node.js.The function prototypes defined within a script using vm.runInContext do not match Function.prototype.

const vm = require('vm');

const context = vm.createContext({
    console,
    Function: Function
});

const script = new vm.Script(`
    function test() {
        return "Hello, World!";
    }
    console.log(test.prototype === Function.prototype); // Expected: true, Actual: false
`);

script.runInContext(context);

What is the feature you are proposing to solve the problem?

Tried using proxies, manual prototype setting, custom constructors, but none worked.

What alternatives have you considered?

No response

[ljharb]

This is expected, because things created syntactically (like test) don't use globals (like your injected Function).

[mathewgeola]

Thank you for your response and explanation!

I understand that functions created syntactically do not use the globals, including the Function constructor that I inject into the context. This indeed explains why my previous attempts have not been successful.

To further address this issue, I am looking for a way to ensure that all functions defined within vm.runInContext, regardless of whether they are created syntactically or through other means, share the same Function.prototype. If there are any suggestions or alternative approaches to achieve this, I would greatly appreciate it.

Thank you once again for your help and time!

[ljharb]

There's no way to do that - Function.prototype is what's called "undeniable" which makes it unvirtualizable. In other words, you can't change its object identity.

What's the overarching goal of this?

[Patrikoska1]

😃