Error [ERR_UNSUPPORTED_DIR_IMPORT]: Directory import when attempting to start Nodejs App locally

Question

I'm caught in a bit of a loop trying to deploy my app to Heroku. My import statements (e.g. import cors from 'cors') seem to prevent the app from launching in production, due to the "Cannot Load ES6 Modules in Common JS" error. Locally it runs just fine.

However, when I attempt to resolve the above error by adding "type": "module" to my package.json I get a whole new set of errors and the app will no longer run locally. I believe this error is due to the way I'm initializing sequelize and associated models but I am unsure. I'd like to resolve this error but need a hand with new syntax for the imports... I think.

Error, package.json and index.js include below.

Error Text

[nodemon] starting `babel-node src/index.js`
internal/process/esm_loader.js:74
    internalBinding('errors').triggerUncaughtException(
                              ^

Error [ERR_UNSUPPORTED_DIR_IMPORT]: Directory import '/Users/jeff/Clients/Bummer/Code/Server/src/models' is not supported resolving ES modules imported from /Users/jeff/Clients/Bummer/Code/Server/src/index.js
    at finalizeResolution (internal/modules/esm/resolve.js:272:17)
    at moduleResolve (internal/modules/esm/resolve.js:699:10)
    at Loader.defaultResolve [as _resolve] (internal/modules/esm/resolve.js:810:11)
    at Loader.resolve (internal/modules/esm/loader.js:85:40)
    at Loader.getModuleJob (internal/modules/esm/loader.js:229:28)
    at ModuleWrap.<anonymous> (internal/modules/esm/module_job.js:51:40)
    at link (internal/modules/esm/module_job.js:50:36) {
  code: 'ERR_UNSUPPORTED_DIR_IMPORT',
  url: 'file:///Users/jeff/Clients/Bummer/Code/Server/src/models'
}
[nodemon] app crashed - waiting for file changes before starting...

Package.JSON

{
  "name": "bummer",
  "type": "module",
  "version": "1.0.0",
  "description": "",
  "main": "index.js",
  "scripts": {
    "start": "node src/index.js",
    "dev": "nodemon --exec babel-node src/index.js",
    "test": "echo \"Error: no test specified\" && exit 1"
  },
  "keywords": [],
  "author": "",
  "license": "ISC",
  "devDependencies": {
    "@babel/core": "^7.9.6",
    "@babel/node": "^7.8.7",
    "@babel/preset-env": "^7.9.6",
    "nodemon": "^2.0.4",
    "sequelize-cli": "^6.2.0"
  },
  "dependencies": {
    "cookie-parser": "^1.4.5",
    "cors": "^2.8.5",
    "dotenv": "^8.2.0",
    "express": "^4.17.1",
    "pg": "^8.2.1",
    "querystring": "^0.2.0",
    "request": "^2.88.2",
    "sequelize": "^6.3.5",
    "sequelize-auto-migrations": "^1.0.3",
    "uuid": "^8.0.0"
  }
}

Index.js

import cors from 'cors';
import express from 'express';
import models, { sequelize } from './models';
// import routes from './routes';

//Initiaze Express
const app = express();
const routes = require('./routes');


//Helpers for Spotify oAuth
const cookieParser = require('cookie-parser')


// Include Middleware
app.use(express.static(__dirname + '/public'))
   .use(cors())
   .use(cookieParser())
   .use(express.json())
   .use(express.urlencoded({ extended: true }))
   require('dotenv').config()

   

// Include all Models
app.use((req, res, next) => {
  req.context = {
    models,
  };
  next();
});



// Load Routes from Router Index
app.use('/', routes);

sequelize.sync().then(() => {
  app.listen(process.env.PORT, () => {
    console.log(`Example app listening on port ${process.env.PORT}!`)
  });
});

Thoughts or pointers? Thank you!

Answer 1

Explicitly, point to your main file (usually index.js). E. g.

import ... from './models'          // ❌
import ... from './models/index.js' // ✅

---

Alternative way:

Use --experimental-specifier-resolution=node flag. For example:

node --experimental-specifier-resolution=node main.js

See: https://nodejs.org/api/esm.html#esm_customizing_esm_specifier_resolution_algorithm

Answer 2

In Node.js, import statements are permitted only in ES modules. so, directory imports do not work in Node.js. Read Node.js Documentation.

Answer 3

Try adding the --experimental-specifier-resolution=node flag to your start script in package.json, particularly if you're using this flag when running locally - this is the script Heroku will use to start your server.

scripts": {
    "start": "node --experimental-specifier-resolution=node index",
    ...
},