Documentation needed for ESM modules in a CSJ world

[joelnet]

Problem
Jest not compatible with ESM modules.

Environment
Jest: 26.6.3
babel-jest: 26.6.3

jest.config.js

const esModules = ["p-timeout"].join("|");

module.exports = {
  transformIgnorePatterns: [`/node_modules/(?!${esModules})`],
};

.babelrc

{
  "presets": ["next/babel"],
}

Error

  Test suite failed to run

    Jest encountered an unexpected token

    This usually means that you are trying to import a file which Jest cannot parse, e.g. it's not plain JavaScript.

    By default, if Jest sees a Babel config, it will use that to transform your files, ignoring "node_modules".

    Here's what you can do:
     • If you are trying to use ECMAScript Modules, see https://jestjs.io/docs/en/ecmascript-modules for how to enable it.
     • To have some of your "node_modules" files transformed, you can specify a custom "transformIgnorePatterns" in your config.
     • If you need a custom transformation specify a "transform" option in your config.
     • If you simply want to mock your non-JS modules (e.g. binary assets) you can stub them out with the "moduleNameMapper" config option.

    You'll find more details and examples of these config options in the docs:
    https://jestjs.io/docs/en/configuration.html

    Details:

    /Users/jthoms/dev/@paciolan/evenue-next-server/src/node_modules/p-timeout/index.js:1
    ({"Object.<anonymous>":function(module,exports,require,__dirname,__filename,global,jest){export class TimeoutError extends Error {
                                                                                             ^^^^^^

    SyntaxError: Unexpected token 'export'

      11 | import { promiseHandler } from "./lib/promises";
      12 | import { logger } from "./logger";
    > 13 | import pTimeout from "p-timeout";
         | ^
      14 |
      15 | const remoteComponentCacheAge = ms(process.env.REMOTE_COMPONENT_CACHE_AGE || "24 hours"); // prettier-ignore
      16 | const zookeeperUrl = process.env.ZKP_URL || "localhost:2181";

      at Runtime.createScriptFromCode (node_modules/jest-runtime/build/index.js:1350:14)
      at Object.<anonymous>

I have tried solutions from:

• https://jestjs.io/docs/ecmascript-modules
• How to set transformIgnorePatterns to fix "Jest encountered an unexpected token" nrwl/nx#812

My next options:

• Using an old version of this library (v4)
• Rolling my own lib

I am unsure how to get this module working with Jest and am seeking some help.

[sindresorhus]

I am unsure how to get this module working with Jest and am seeking some help.

This would be a question to ask on the Jest issue tracker. This package is valid ESM.