vm.Module

import vm from 'node:vm';

const contextifiedObject = vm.createContext({
  secret: 42,
  print: console.log,
});

// Step 1
//
// Create a Module by constructing a new `vm.SourceTextModule` object. This
// parses the provided source text, throwing a `SyntaxError` if anything goes
// wrong. By default, a Module is created in the top context. But here, we
// specify `contextifiedObject` as the context this Module belongs to.
//
// Here, we attempt to obtain the default export from the module "foo", and
// put it into local binding "secret".

const rootModule = new vm.SourceTextModule(`
  import s from 'foo';
  s;
  print(s);
`, { context: contextifiedObject });

// Step 2
//
// "Link" the imported dependencies of this Module to it.
//
// Obtain the requested dependencies of a SourceTextModule by
// `sourceTextModule.moduleRequests` and resolve them.
//
// Even top-level Modules without dependencies must be explicitly linked. The
// array passed to `sourceTextModule.linkRequests(modules)` can be
// empty, however.
//
// Note: This is a contrived example in that the resolveAndLinkDependencies
// creates a new "foo" module every time it is called. In a full-fledged
// module system, a cache would probably be used to avoid duplicated modules.

const moduleMap = new Map([
  ['root', rootModule],
]);

function resolveAndLinkDependencies(module) {
  const requestedModules = module.moduleRequests.map((request) => {
    // In a full-fledged module system, the resolveAndLinkDependencies would
    // resolve the module with the module cache key `[specifier, attributes]`.
    // In this example, we just use the specifier as the key.
    const specifier = request.specifier;

    let requestedModule = moduleMap.get(specifier);
    if (requestedModule === undefined) {
      requestedModule = new vm.SourceTextModule(`
        // The "secret" variable refers to the global variable we added to
        // "contextifiedObject" when creating the context.
        export default secret;
      `, { context: referencingModule.context });
      moduleMap.set(specifier, linkedModule);
      // Resolve the dependencies of the new module as well.
      resolveAndLinkDependencies(requestedModule);
    }

    return requestedModule;
  });

  module.linkRequests(requestedModules);
}

resolveAndLinkDependencies(rootModule);
rootModule.instantiate();

// Step 3
//
// Evaluate the Module. The evaluate() method returns a promise which will
// resolve after the module has finished evaluating.

// Prints 42.
await rootModule.evaluate();