How to run jest when using es6 packages in node_modules #5241
Description
Is this a bug report?
Not sure. More of a configuration issue I guess.
TLDR
Trying out the feature described in #1125 which should allow the usage of libraries distributed as es6 modules in an app create with create-react-app, the app runs fine but the Jest test suite will not.
How to reproduce
- create a new create-react-app application
npx create-react-app jest-es6-modules - in the new application,
yarn add lodash-es - modify
src/App.jsadding any named import, such asimport { isEmpty } from 'lodash-es' - run
yarn start(everything works) - run
yarn test
Here's the Jest error, related to Jest not babel-transforming the modules in es6 format:
● 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.
[...]
Details:
/Users/nerfologist/test/jest-es6-modules/node_modules/lodash-es/lodash.js:10
export { default as add } from './add.js';
^^^^^^
SyntaxError: Unexpected token export
1 | import React, {Component} from 'react';
2 | import logo from './logo.svg';
> 3 | import {isEmpty} from 'lodash-es';
| ^
4 | import './App.css';
5 |
6 | class App extends Component {
at ScriptTransformer._transformAndBuildScript (node_modules/jest-runtime/build/script_transformer.js:403:17)
at Object.<anonymous> (src/App.js:3:1)
Test Suites: 1 failed, 1 total
Tests: 0 total
Snapshots: 0 total
Time: 1.279s
Ran all test suites related to changed files.
Question
What is the best/recommended way to have Jest transform one or more of these node_modules?
I'm thinking of adding a Jest configuration containing the transformIgnorePatterns directive.
Thanks in advance!