Next.js + Transpile node_modules

Transpile modules from node_modules using the Next.js Babel configuration.

Makes it easy to have local libraries and keep a slick, manageable dev experience.

• Supports transpilation of all extensions supported by Next.js: .js, .jsx, .ts, .tsx, .mjs, .css, .scss and .sass
• Enable hot-reloading on local packages
• Most setups should work out of the box (npm, yarn, pnpm, ...)

What problems does it solve?

This plugin aims to solve the following challenges:

• code transpilation from local packages (think: a monorepo with a styleguide package)
• code transpilation from NPM modules using ES6 imports (e.g lodash-es)

What this plugin does not aim to solve:

• any-package IE11-compatible maker

Compatibility table

Next.js version	Plugin version
Next.js 11	8.x
Next.js 9.5+ / 10	4.x, 5.x, 6.x, 7.x
Next.js 9.2	3.x
Next.js 8 / 9	2.x
Next.js 6 / 7	1.x

Latest Next.js version tested: 11.0.0.

Installation

npm install --save next-transpile-modules

or

yarn add next-transpile-modules

Usage

withTM(transpileModules [, options])

• transpileModules String[]: modules to be transpiled
• options Object (optional)
  • resolveSymlinks Boolean: Enable symlinks resolution to their real path by Webpack (default to true)
  • debug Boolean: Display some informative logs in the console (can get noisy!) (default to false)
  • __unstable_matcher (path) => boolean: Custom matcher that will override the default one. Don't use it.

Note on resolveSymlinks

Node.js resolution is based on the fact that symlinks are resolved. Not resolving them will alter the behavior, but there are some cases where the alternative behavior makes things a lot easier.

If:

• You are using npm/yarn link to link packages into node_modules.
• You are using npm with file: dependencies that live outside of your project directory
  • npm will create symlinks in this case. Yarn will copy instead.

you should set resolveSymlinks: false, which results which will make things work as expected.

For other scenarios like:

• pnpm
• yarn/npm workspaces
• yarn 2 portals

you should keep resolveSymlinks: true (default).

Examples

// next.config.js
const withTM = require('next-transpile-modules')(['somemodule', 'and-another']); // pass the modules you would like to see transpiled

module.exports = withTM();

// next.config.js
const withTM = require('next-transpile-modules')(['somemodule', 'and-another']);

module.exports = withTM({
  webpack5: false, // you want to keep using Webpack 4
});

Notes:

• please declare withTM as your last plugin (the "most nested" one).
• make sure all your packages have a valid main field. (not needed anymore since 7.1.0)
• there is currently no way to transpile only parts of a package, it's all or nothing

Scoped packages

You can include scoped packages or nested ones:

const withTM = require('next-transpile-modules')(['@shared/ui', '@shared/utils']);

// ...

const withTM = require('next-transpile-modules')(['styleguide/node_modules/lodash-es']);

// ...

With next-compose-plugins:

const withPlugins = require('next-compose-plugins');
const withTM = require('next-transpile-modules')(['some-module', 'and-another']);

module.exports = withPlugins([withTM], {
  // ...
});

CSS/SCSS support

Since next-transpile-modules@3 and next@>9.2, this plugin can also transpile CSS included in your transpiled packages. SCSS/SASS is also supported since [email protected].

In your transpiled package:

// shared-ui/components/Button.js
import styles from './Button.module.css';

function Button(props) {
  return (
    <button type='button' className={styles.error}>
      {props.children}
    </button>
  );
}

export default Button;

/* shared-ui/components/Button.module.css */
.error {
  color: white;
  background-color: red;
}

In your app:

// next.config.js
const withTM = require('next-transpile-modules')(['shared-ui']);

// ...

// pages/home.jsx
import React from 'react';
import Button from 'shared-ui/components/Button';

const HomePage = () => {
  return (
    <main>
      {/* will output <button class="Button_error__xxxxx"> */}
      <Button>Styled button</Button>
    </main>
  );
};

export default HomePage;

It also supports global CSS import packages located in node_modules:

// pages/_app.js
import 'shared-ui/styles/global.css'; // will be imported globally

export default function MyApp({ Component, pageProps }) {
  return <Component {...pageProps} />;
}

FAQ

What is the difference with @weco/next-plugin-transpile-modules?

• it is maintained, @weco's seems dead
• it supports TypeScript
• it supports CSS modules (since Next.js 9.2)
• it supports .mjs

A new version of Next.js is available/I just setup my project, and my build is breaking because of this plugin

It is important to understand that this plugin is a big hack of the Next.js Webpack configuration. When the Next.js team pushes an update to their build configuration, the changes next-transpile-modules bring may be outdated, and the plugin needs to be updated (which is a breaking change for this plugin, as the updated plugin is usually not retro-compatible with the previous versions of Next.js).

Now, this build problem can happen when you install your dependencies with npm install/yarn install (in your CI pipeline for example). Those commands may re-resolve your next dependency of your package.json to a newer one, and this newer one may have critical Webpack changes, hence breaking your build.

The way to fix it is easy, and it is what you should always do: install your dependencies with npm ci ("clean install") or yarn --frozen-lockfile. This will force npm or yarn to use the version of Next.js declared in your lock file, instead of downloading the latest one compatible with the version accepted by your package.json.

So basically: use your lock files right, and understand what problems they are solving ;)

more:

• check the compatibility table of this plugin
• read more about semver and version resolutions: https://docs.npmjs.com/misc/semver

I have trouble making it work after upgrading to v5/v6

Please make sure to read the changelog.

I have trouble with transpilation and my custom .babelrc

If you get a transpilation error when using a custom Babel configuration, make sure you are using a babel.config.js and not a .babelrc.

The former is a project-wide Babel configuration, when the latter works for relative paths only (and may not work for Yarn for example, as it installs dependencies in a parent directory).

I have trouble with Yarn and hot reloading

If you add a local library (let's say with yarn add ../some-shared-module), Yarn will copy those files by default, instead of symlinking them. So your changes to the initial folder won't be copied to your Next.js node_modules directory.

You can go back to npm, or use Yarn workspaces. See an example in the official Next.js repo.

How do I find out which package is causing a runtime exception?

• add config.optimization.minimize = false; to you next.config.js's Webpack configuration
• run a production build
• run it on the browser throwing the error
• open the console, jump to the line where it failed
• goes a little bit up in the lines of code, and check the Webpack comments telling you which module is affected

I have trouble making it work with Lerna

Lerna's purpose is to publish different packages from a monorepo, it does not help for and does not intend to help local development with local modules (<- this, IN CAPS).

This is not coming from me, but from Lerna's maintainer.

So you are probably using it wrong, and I advice you to use npm or Yarn workspaces instead.

But... I really need to make it work with Lerna!

Again, most probably a bad idea. You may need to tell your Webpack configuration how to properly resolve your scoped packages, as they won't be installed in your Next.js directory, but the root of your Lerna setup.

const withTM = require('next-transpile-modules')(['@your-project/shared', '@your-project/styleguide']);

module.exports = withTM({
  webpack: (config, options) => {
    config.resolve.alias = {
      ...config.resolve.alias,
      // Will make webpack look for these modules in parent directories
      '@your-project/shared': require.resolve('@your-project/shared'),
      '@your-project/styleguide': require.resolve('@your-project/styleguide'),
      // ...
    };
    return config;
  },
});

I have trouble with duplicated dependencies or the Invalid hook call error in react

It can happen that when using next-transpile-modules with a local package and npm, you end up with duplicated dependencies in your final Next.js build. It is important to understand why it happens.

Let's take the following setup: one Next.js app ("Consumer"), and one Styleguide library.

You will probably have react as a peerDependencies and as a devDependecy of the Styleguide. If you use npm i, it will create a symlink to your Styleguide package in your "Consumer" node_modules.

The thing is in this shared package, you also have a node_modules. So when your shared modules requires, let's say react, Webpack will resolve it to the version in your Styleguide's node_modules, and not your Consumer's node_modules. Hence the duplicated react in your final bundles.

You can tell Webpack how to resolve the react of your Styleguide to use the version in your Next.js app like that:

const withTM = require('next-transpile-modules')(['styleguide']);

module.exports = withTM({
  webpack: (config, options) => {
+   if (options.isServer) {
+     config.externals = ['react', ...config.externals];
+   }
+
+   config.resolve.alias['react'] = path.resolve(__dirname, '.', 'node_modules', 'react');

    return config
  },
});

Please note, the above will only work if react is properly declared as peerDependencies or devDependencies in your referenced package.

It is not a great solution, but it works. Any help to find a more future-proof solution is welcome.

Credits

All the honor goes to James Gorrie who created the first version of this plugin.