ERR_REQUIRE_ESM from webpack's importing an ESM package - node.js

Question

I am building an app using Nx for modularisation and Geckos for the server part. With Nx' default Webpack 5 config for Node I get this error when running the app:
/Users/hgrzeskowiak/hugo-game/fresh-nx-geckos/nx-geckos-test/dist/apps/geckos-server-app/main.js:8
module.exports = require("#geckos.io/server");
^
Error [ERR_REQUIRE_ESM]: require() of ES Module /Users/hgrzeskowiak/hugo-game/fresh-nx-geckos/nx-geckos-test/node_modules/#geckos.io/server/lib/index.js from /Users/hgrzeskowiak/hugo-game/fresh-nx-geckos/nx-geckos-test/dist/apps/geckos-server-app/main.js not supported.
Instead change the require of index.js in /Users/hgrzeskowiak/hugo-game/fresh-nx-geckos/nx-geckos-test/dist/apps/geckos-server-app/main.js to a dynamic import() which is available in all CommonJS modules.
(...)
Here are steps to reproduce:
$ npx create-nx-workspace#latest nx-geckos-test
Need to install the following packages:
create-nx-workspace#latest
Ok to proceed? (y) y
✔ What to create in the new workspace · express
✔ Application name · geckos-server-app
✔ Use Nx Cloud? (It's free and doesn't require registration.) · No
> NX Nx is creating your v13.4.1 workspace.
To make sure the command works reliably in all environments, and that the preset is applied correctly,
Nx will run "npm install" several times. Please wait.
✔ Installing dependencies with npm
✔ Nx has successfully created the workspace.
$ npm run start
> nx-geckos-test#0.0.0 start
> nx serve
> nx run geckos-server-app:serve
chunk (runtime: main) main.js (main) 552 bytes [entry] [rendered]
webpack compiled successfully (26ac6f288b082854)
Debugger listening on ws://localhost:9229/70a1d9b4-af2b-4fc9-90f7-f3502e5fdf2e
Debugger listening on ws://localhost:9229/70a1d9b4-af2b-4fc9-90f7-f3502e5fdf2e
For help, see: https://nodejs.org/en/docs/inspector
Issues checking in progress...
Listening at http://localhost:3333/api
At this stage, the default Express app builds and runs.
Now I replace the contents of apps/geckos-server-app/src/main.ts to the Geckos server example from the README:
import geckos from '#geckos.io/server'
const io = geckos()
io.listen(3000) // default port is 9208
io.onConnection(channel => {
channel.onDisconnect(() => {
console.log(`${channel.id} got disconnected`)
})
channel.on('chat message', data => {
console.log(`got ${data} from "chat message"`)
// emit the "chat message" data to all channels in the same room
io.room(channel.roomId).emit('chat message', data)
})
})
...and install the geckos server package using
$ npm install #geckos.io/server
added 4 packages, and audited 785 packages in 7s
87 packages are looking for funding
run `npm fund` for details
found 0 vulnerabilities
Ok, time to run it again:
$ npm run start
> nx-geckos-test#0.0.0 start
> nx serve
> nx run geckos-server-app:serve
chunk (runtime: main) main.js (main) 610 bytes [entry] [rendered]
webpack compiled successfully (90920432a9d246ea)
Debugger listening on ws://localhost:9229/dc6d9e1a-1a15-432f-a46c-d2ac83b923ea
Debugger listening on ws://localhost:9229/dc6d9e1a-1a15-432f-a46c-d2ac83b923ea
For help, see: https://nodejs.org/en/docs/inspector
/Users/hgrzeskowiak/hugo-game/fresh-nx-geckos/nx-geckos-test/dist/apps/geckos-server-app/main.js:8
module.exports = require("#geckos.io/server");
^
Error [ERR_REQUIRE_ESM]: require() of ES Module /Users/hgrzeskowiak/hugo-game/fresh-nx-geckos/nx-geckos-test/node_modules/#geckos.io/server/lib/index.js from /Users/hgrzeskowiak/hugo-game/fresh-nx-geckos/nx-geckos-test/dist/apps/geckos-server-app/main.js not supported.
Instead change the require of index.js in /Users/hgrzeskowiak/hugo-game/fresh-nx-geckos/nx-geckos-test/dist/apps/geckos-server-app/main.js to a dynamic import() which is available in all CommonJS modules.
at Object.#geckos.io/server (/Users/hgrzeskowiak/hugo-game/fresh-nx-geckos/nx-geckos-test/dist/apps/geckos-server-app/main.js:8:18)
at __webpack_require__ (/Users/hgrzeskowiak/hugo-game/fresh-nx-geckos/nx-geckos-test/dist/apps/geckos-server-app/main.js:32:41)
at /Users/hgrzeskowiak/hugo-game/fresh-nx-geckos/nx-geckos-test/dist/apps/geckos-server-app/main.js:45:18
at /Users/hgrzeskowiak/hugo-game/fresh-nx-geckos/nx-geckos-test/dist/apps/geckos-server-app/main.js:59:3
at Object.<anonymous> (/Users/hgrzeskowiak/hugo-game/fresh-nx-geckos/nx-geckos-test/dist/apps/geckos-server-app/main.js:64:12)
I tested quite a few Webpack config overrides and using type: "module" in package.json, but to no avail. The output main.js looks mostly the same no matter what webpack settings I change. Things I tried changing in the app's webpack override config:
module.exports = function(webpackConfig, context) {
webpackConfig.target = "async-node16";
webpackConfig.output.libraryTarget = "module";
webpackConfig.output.library = {type: "module"};
webpackConfig.output.chunkFormat = "module";
webpackConfig.experiments.outputModule = true;
console.log("webpack config:");
console.log(webpackConfig);
console.log("module rules:");
console.log(webpackConfig.module.rules);
return webpackConfig;
}
The console logs in the config verify that the script is being run.
The app works when I manually change the require to import in the transpiled output, but that's not a sustainable solution.
I suspect the error has something to do with Geckos being an ESM package, and Webpack only using require instead of import as it should, but I couldn't find any way of changing that behaviour.
Any ideas?
Node version 16.13.0
Nx version 13.4.1
Webpack (transitive dep of Nx): 5.65.0

Answer 1

Here's the cleanest solution I could find that works with Type Script versions older than 4.6 (which should add support for this feature). This is essentially patching ESM support into WebPack with older TypeScript versions (including latest at the time of writing).
A custom Webpack plugin that changes the type of the external module to import.
// TypeScript before version 4.6 does not support transpiling ESM imports to
// `import()`, but uses `require()` instead. NodeJS does not support the use
// of `require() for ECMAScript modules (ESM).
//
// Good reads:
// https://www.typescriptlang.org/docs/handbook/esm-node.html
// https://devblogs.microsoft.com/typescript/announcing-typescript-4-5/#esm-nodejs
/**
* A Webpack 5 plugin that can be passed a list of packages that are of type
* ESM. The typescript compiler will then be instructed to use the `import`
* external type.
*/
class ESMLoader {
static defaultOptions = {
esmPackages: "all"
};
constructor(options = {}) {
this.options = { ...ESMLoader.defaultOptions, ...options };
}
apply(compiler) {
compiler.hooks.compilation.tap(
"ECMAScript Module (ESM) Loader. Turns require() into import()",
(
compilation
) => {
compilation.hooks.buildModule.tap("Hello World Plugin", (module) => {
if (
module.type === "javascript/dynamic" &&
(
this.options.esmPackages === "all" ||
this.options.esmPackages.includes(module.request)
)
) {
// All types documented at
// https://webpack.js.org/configuration/externals/#externalstype
module.externalType = "import";
}
}
)
;
}
);
}
}
module.exports = function(webpackConfig, context) {
// NodeJS supports dynamic imports since version 12.
webpackConfig.target = "node16";
webpackConfig.plugins.push(
// Manually specify the ESM modules or leave blank for using `import()`
// on all packages.
//new ESMLoader()
new ESMLoader({esmPackages: "#geckos.io/server"})
);
return webpackConfig;
};
The custom webpack config can be set on an Nx app through the project.json:
{
"targets": {
"build": {
"executor": "#nrwl/node:build",
"options": {
...
"webpackConfig": "apps/your-app/webpackConfig.js"
},
...
This solution also requires tsconfig.json to have set the module type to something more modern than commonjs, e.g. es2020:
{
"extends": "./tsconfig.json",
"compilerOptions": {
"outDir": "../../dist/out-tsc",
"module": "es2020",
"types": ["node"],
},
"exclude": ["**/*.spec.ts", "**/*.test.ts"],
"include": ["**/*.ts"]
}
Once this is done, the built file can be ran using the usual nx serve.