`SourceTextModule` example snippet does not behave as hinted in the docs

[davidebombelli]

Affected URL(s)

https://nodejs.org/api/vm.html#new-vmsourcetextmodulecode-options

Description of the problem

I am trying to understand the example snippet:

import vm from 'node:vm';

const contextifiedObject = vm.createContext({ secret: 42 });

const module = new vm.SourceTextModule(
 'Object.getPrototypeOf(import.meta.prop).secret = secret;',
 {
 initializeImportMeta(meta) {
 // Note: this object is created in the top context. As such,
 // Object.getPrototypeOf(import.meta.prop) points to the
 // Object.prototype in the top context rather than that in
 // the contextified object.
 meta.prop = vm.runInContext('{}', contextifiedObject);
 },
 });
// The module has an empty `moduleRequests` array.
module.linkRequests([]);
module.instantiate();
await module.evaluate();

// Now, Object.prototype.secret will be equal to 42.
//
// To fix this problem, replace
// meta.prop = {};
// above with
// meta.prop = vm.runInContext('{}', contextifiedObject);

According to the comment on line 21, the script should execute and should modify the Object.prototype.secret to be 42. However, when I run the script I get the error:

vm:module(0):1
Object.getPrototypeOf(import.meta.prop).secret = secret;
 ^

ReferenceError: secret is not defined
 at vm:module(0):1:50
 at SourceTextModule.evaluate (node:internal/vm/module:233:26)
 at file:///home/username/test.mjs:19:14
 at ModuleJob.run (node:internal/modules/esm/module_job:439:25)
 at async node:internal/modules/esm/loader:646:26
 at async asyncRunEntryPointWithESMLoader (node:internal/modules/run_main:101:5)

Node.js v26.3.0

and if I try to modify meta.prop = {}; with meta.prop = vm.runInContext('{}', contextifiedObject);, I get the error:

vm:module(0):1
Object.getPrototypeOf(import.meta.prop).secret = secret;
 ^

TypeError: Cannot convert undefined or null to object
 at Object.getPrototypeOf (<anonymous>)
 at vm:module(0):1:8
 at SourceTextModule.evaluate (node:internal/vm/module:233:26)
 at file:///home/username/test.mjs:19:14
 at ModuleJob.run (node:internal/modules/esm/module_job:439:25)
 at async node:internal/modules/esm/loader:646:26
 at async asyncRunEntryPointWithESMLoader (node:internal/modules/run_main:101:5)

Node.js v26.3.0

[DivyanshuX9]

it seems more like a doc problem than a regression issue

try this corrected example:

import vm from 'node:vm';

const contextifiedObject = vm.createContext({ secret: 42 });

const module = new vm.SourceTextModule(
 'Object.getPrototypeOf(import.meta.prop).secret = secret;',
 {
 context: contextifiedObject,
 initializeImportMeta(meta) {
 // Vulnerable: meta.prop = {};
 // Fixed:
 meta.prop = vm.runInContext('({})', contextifiedObject);
 },
 });
module.linkRequests([]);
module.instantiate();
await module.evaluate();