Import ES module in Next.js ERR_REQUIRE_ESM

I came upon this error when trying to use ky in a Next.js project:

Error [ERR_REQUIRE_ESM]: Must use import to load ES Module: /foo/node_modules/ky/index.js

I think the problem is that Webpack (or Babel) is transforming all imports to require()s but ky is a pure ES module.

I got it working by dynamically importing ky before using it but it's not elegant nor efficient.

const handleFormSubmit = async (event) => {
  const ky = (await import("ky")).default;

  const response = await ky
    .get('http://localhost/api/foo')
    .json();
};

Any suggestions?

From Next.js 12, support for ES Modules is now enabled by default, as long as the ESM library has "type": "module" in its package.json. Using next-transpile-modules to transpile ESM libraries is no longer required.

Before Next.js 12

Since ky is exported as ESM you can transpile it with next-transpile-modules in next.config.js.

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

module.exports = withTM(/* your Next.js config */);

You can try upgrading nextjs to v11.1.0, it has some support for ESM.

See: https://github.com/vercel/next.js/pull/27069

More info in this issue discussion from https://github.com/vercel/next.js/issues/9607#issuecomment-906155992

Since Next.js 12 (official announcement), support for ESM modules is automatically enabled. See #29878.

Since Next.js 12.1, you can add "type": "module" to your package.json. See #33637.