Not working with native ES modules

I’m moving a project over to using node’s native ES modules (enabled with the --experimental-modules flag). After updating my code, module-alias is no longer working. I tried adding this to the root of my app (this is the method I was using before transitioning to esm):

require('module-alias/register')

I tried changing it to:

import 'module-alias/register'

I tried requiring when starting the server:

node --experimental-modules -r module-alias/register server/app.js

The first aliased import in my app is this:

import {responseError} from '@app/lib/response'

I’m getting this error from it:

internal/modules/esm/default_resolve.js:69
  let url = moduleWrapResolve(specifier, parentURL);
            ^

Error: Cannot find package '@app/lib' imported from server/app.js
    at Loader.resolve [as _resolve] (internal/modules/esm/default_resolve.js:69:13)
    at Loader.resolve (internal/modules/esm/loader.js:70:33)
    at Loader.getModuleJob (internal/modules/esm/loader.js:143:40)
    at ModuleWrap.<anonymous> (internal/modules/esm/module_job.js:43:40)
    at link (internal/modules/esm/module_job.js:42:36)

The relevant lines in my package.json are:

"_moduleAliases": {
    "@app": "./server"
},

I’m starting the app like this:

node --experimental-modules server/app.js

module-alias worked fine using CommonJS. The only change I made to the code was changing requires to imports.

[jdt3969]

@cullylarson Ran into the same issue.

It appears that the new esm code isn’t running the _resolveFilename which is the core of this library. Based on the docs it looks as though they are moving off of this library’s hack and onto a standard feature: https://github.com/nodejs/node/blob/master/doc/api/esm.md#experimental-loader-hooks It’s still experimental though.

I rewrote and reduced a lot based on known things within my library but this code is working for me:

// custom-loader.mjs
import path from 'path';
import npmPackage from './package.json';

const getAliases = () => {

  const base = process.cwd();

  const aliases = npmPackage.aliases || {};

  const absoluteAliases = Object.keys(aliases).reduce((acc, key) =>
    aliases[key][0] === '/'
      ? acc
      : { ...acc, [key]: path.join(base, aliases[key]) },
    aliases)

  return absoluteAliases;

}

const isAliasInSpecifier = (path, alias) => {
  return path.indexOf(alias) === 0
    && (path.length === alias.length || path[alias.length] === '/')
}

const aliases = getAliases();

export const resolve = (specifier, parentModuleURL, defaultResolve) => {
  
  const alias = Object.keys(aliases).find((key) => isAliasInSpecifier(specifier, key));

  const newSpecifier = alias === undefined
    ? specifier
    : path.join(aliases[alias], specifier.substr(alias.length));

  return defaultResolve(newSpecifier, parentModuleURL);
}

Then: node --no-warnings --experimental-modules --es-module-specifier-resolution=node --loader ./custom-loader.mjs index.js

[eouia]

Not yet solved natively without execution flags?