globals are set twice? (using a proxy as VM context)

[axkibe]

Following minimal example code:

import fs from 'node:fs/promises';
import vm from 'node:vm';

let proxy;
const handler =
{
    get: function( obj, key )
    {
        console.log( 'getting', key );
        return proxy;
    },
    set: function( obj, key, value )
    {
        console.log( 'setting', key, '=', value );
        return true;
    },
};
proxy = new Proxy( { }, handler );

console.log( '-- simple --' );
proxy.admin = 'admin';
proxy.network.protocol = 'http';

console.log( '-- as script --' );
const script = new vm.Script(
`admin = 'admin';
network.protocol = 'http';
` );
const context = vm.createContext( proxy );
script.runInContext( context );

produces (node 21.1.0)

-- simple --
setting admin = admin
getting network
setting protocol = http
-- as script --
setting admin = admin
getting admin
setting admin = admin
getting network
setting protocol = http
getting protocol
setting protocol = http

simple is as expected, but why in case of a VM script are globals set twice?

Posting it as discussion since technically its not an issue*, just wondering, is this a result because I contextified a Proxy, or does node/V8 always set globals twice? (it wouldn't be noticed otherwise, or I can think of a way to make this without the vm module).

• not an issue even for my idea of using it for config files, so the values are set twice via the proxy, no big deal, but why?

[axkibe]

Its not a general issue, I found a way to test it without vm:

Object.defineProperty(
    globalThis,
    'foo',
    {
        get: ( ) => { console.log( 'get' ); return 'bar'; },
        set: ( v ) => { console.log( 'set', v ); }
    }
);
foo = 'sup';

works as expected. IMO it has something to do with contextifying a Proxy.