Jest encountered an unexpected token + react markdown

Question

I'm getting an error when trying to run my test file (I'm using react typescript)

  ● Test suite failed to run

    Jest encountered an unexpected token

    Jest failed to parse a file. This happens e.g. when your code or its dependencies use non-standard JavaScript syntax, or when Jest is not configured to support such syntax.

    Out of the box Jest supports Babel, which will be used to transform your files into valid JS based on your Babel configuration.

    By default "node_modules" folder is ignored by transformers.

    Here's what you can do:
     • If you are trying to use ECMAScript Modules, see https://jestjs.io/docs/ecmascript-modules for how to enable it.
     • If you are trying to use TypeScript, see https://jestjs.io/docs/getting-started#using-typescript
     • 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/configuration
    For information about custom transformations, see:
    https://jestjs.io/docs/code-transformation

    Details:

    export {uriTransformer} from './lib/uri-transformer.js'
    ^^^^^^

    SyntaxError: Unexpected token 'export'

       5 | const Markdown = ({ text, classStyle }: ITextMedia) => (
       6 |   <div className={`${classes.mediaParagraph} ${classStyle ?? ''}`}>
    >  7 |     <ReactMarkdown>{text}</ReactMarkdown>
         |                                             ^
       8 |   </div>
       9 | );
      10 | export default Markdown;

      at Runtime.createScriptFromCode (node_modules/jest-runtime/build/index.js:1728:14)
      at Object.<anonymous> (components/media/markdown/index.tsx:7:45)

I already tried adding the React markdown to the transform ignore patterns, but it still doesn't work

here's my jest.config

{
  setupFilesAfterEnv: ['<rootDir>/jest.setup.js'],
  moduleDirectories: ['node_modules', '<rootDir>/'],
  testEnvironment: 'jest-environment-jsdom',
  moduleNameMapper: {
    'next/router': '<rootDir>/__mocks__/next/router.js',
    '^.+\\.module\\.(css|sass|scss)$': 'identity-obj-proxy',
    '^.+\\.(jpg|jpeg|png|gif|webp|avif|svg)$': '<rootDir>/__mocks__/file-mock.js',
  },
  transform: {
    '^.+\\.(js|jsx)$': 'babel-jest'
  },
  transformIgnorePatterns: [
    'node_modules/(?!react-markdown/)'
  ]
}

my babel config:

{
    "presets": [
        "next/babel",
        "@babel/preset-env"
    ],
    "plugins": []
}

I'm new to jest, so I'm not sure if I'm doing something wrong

score 36 · Accepted Answer · answered Jun 03 '22 at 22:15

36

In the jest.config file, you need to add the following to the moduleNameMapper attribute:

"react-markdown": "<rootDir>/node_modules/react-markdown/react-markdown.min.js"

So effectively, your moduleNameMapper should really look like this:

  ...
  moduleNameMapper: {
    'next/router': '<rootDir>/__mocks__/next/router.js',
    '^.+\\.module\\.(css|sass|scss)$': 'identity-obj-proxy',
    '^.+\\.(jpg|jpeg|png|gif|webp|avif|svg)$': '<rootDir>/__mocks__/file-mock.js',
    'react-markdown': '<rootDir>/node_modules/react-markdown/react-markdown.min.js',
  },
  ...

Good luck!

answered Jun 03 '22 at 22:15

poweratom

2,270
23
25

thank you, that worked for me, can you explain why this step is needed? – Anne Mar 14 '23 at 18:05
1

Hi @Anne, the purpose of the `moduleNameMapper` is essentially to stub out resources for the purpose of testing. But sometimes it can also be used to help Jest find the right modules to run tests with. In the case of `react-markdown`, it just needs a little help to point to the right directory to run the right file for the tests. I hope this helps. – poweratom Mar 15 '23 at 21:17

score 2 · Answer 2 · answered Mar 23 '23 at 18:02

You need to add not only react-markdown to the transformIgnorePatterns, but also all its dependencies which are pure ESM.

When running your tests you can see the dependencies one by one in the jest error. Remember about ones inside react-markdown node_modules.

Details:

/{...}/node_modules/react-markdown/node_modules/comma-separated-tokens/index.js:23

Add one by one in the transformIgnorePatterns and run the tests again to get the next error.

You have to add the react-markdown, comma-separated-tokens, and others. It'll depend on the react-markdown version you use. In my case it was:

"transformIgnorePatterns": [
  "/node_modules/(?!comma-separated-tokens|space-separated-tokens|hast-util-whitespace|property-information|trim-lines|remark-rehype|remark-parse|trough|is-plain-obj|bail|unified|vfile|react-markdown)"
]

score 1 · Answer 3 · answered May 25 '23 at 12:01

1

Its a simple fix in the code, just change the import statement from

import ReactMarkdown from 'react-markdown';

to

import ReactMarkdown from 'react-markdown/react-markdown.min';

answered May 25 '23 at 12:01

Ashvin777

1,446
13
19

score 0 · Answer 4 · answered Aug 18 '23 at 10:13

I had the same problem in my environment. We use nx in a monorepo and manage our packages with pnpm. Since pnpm caches modules by default, it does not work with the <rootDir>/node_modules/. However, you can also do without this path, then it works with pnpm as well (jest also mentions in its docs that the usage of <rootDir> is optional):

…
moduleNameMapper: {
  'react-markdown': 'react-markdown/react-markdown.min.js',
},
…

Jest encountered an unexpected token + react markdown

4 Answers4