`next-intl/link` and `useRouter` is causing an error in Jest tests

[cjambrosi]

Description

Environment

• Node: v18.16.0
• OS: MacOS Ventura 13.4
• Yarn: v1.22.19

Libs

• nextjs: v13.4.6
• next-intl: v2.20.0
• Jest: v29.6.2

The errors occur in all component tests that use next-intl/link or useRouter (maybe it happens to others too).
This error has already been reported in another issue, but in next-intl 3.0.0-beta.9 version.

next-intl/link error:

$ jest --config=jest.config.js --no-cache
 FAIL  src/components/Card/index.test.tsx
  ● 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:

    /Users/cjambrosi/GitHub/next-intl-jest-error-reproduce/node_modules/next-intl/dist/src/link/index.js:1
    ({"Object.<anonymous>":function(module,exports,require,__dirname,__filename,jest){export { default } from './Link';
                                                                                      ^^^^^^

    SyntaxError: Unexpected token 'export'

      10 | }
      11 |

      at Runtime.createScriptFromCode (node_modules/jest-runtime/build/index.js:1505:14)
      at Object.<anonymous> (src/components/I18nLink.tsx:12:54)
      at Object.<anonymous> (src/components/Card/Card.tsx:12:58)
      at Object.<anonymous> (src/components/Card/index.test.tsx:6:54)

useRouter error:

$ jest --config=jest.config.js --no-cache
 FAIL  src/components/Card/index.test.tsx
  ● 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:

    /Users/cjambrosi/GitHub/next-intl-jest-error-reproduce/node_modules/next-intl/dist/src/client/index.js:4
    export { default as useRouter } from './useRouter';
    ^^^^^^

    SyntaxError: Unexpected token 'export'

      10 |   }

Mandatory reproduction URL (CodeSandbox or GitHub repository)

https://github.com/cjambrosi/next-intl-jest-error-reproduce

Reproduction description

Steps to reproduce:

1. Open reproduction
2. Install dependencies
3. Run tests with yarn test command
4. See the error SyntaxError: Unexpected token 'export'

Expected behaviour

No error.

[amannn]

Thank you for the great report!

Hmm, I'm really curious why jest works internally in the monorepo of next-intl but not when next-intl is installed externally. When I copy example-next-13 outside of the repo and install the dependencies, then I can reproduce your error there too.

Anyway, jest doesn't support ES modules out of the box and currently in the stable release, the entry point for /client points to one. #149 improves the bundling and will fix this issue since it uses CommonJS for all entrypoints.

In the meantime, you can use this workaround:

index b1df010..5145857 100644
--- a/jest.config.js
+++ b/jest.config.js
@@ -22,4 +22,21 @@ const customJestConfig = {
   setupFilesAfterEnv: ['@testing-library/jest-dom', '<rootDir>/jest.setup.tsx'],
 };
 
-module.exports = createJestConfig(customJestConfig);
+module.exports = async () => ({
+  ...(await createJestConfig(customJestConfig)()),
+
+  // https://github.com/vercel/next.js/issues/36077#issuecomment-1096635363
+  transformIgnorePatterns: [
+    'node_modules/(?!(' +
+      [
+        '@formatjs/icu-messageformat-parser',
+        '@formatjs/icu-skeleton-parser',
+        '@formatjs/fast-memoize',
+        'next-intl',
+        'use-intl',
+        'intl-messageformat',
+        'tslib'
+      ].join('|') +
+      ')/)'
+  ]
+});

Thanks to @barbarah, this is based on https://github.com/colonial-heritage/colonial-collections/blob/main/apps/researcher/jest.config.js.

Sorry for the inconvenience!

[cjambrosi]

Thanks for the sugestion. I chose to use the next-intl@3.0.0-beta.10 version, but now the following error occurs when trying to use useRouter().
Is it missing some configuration or could it really be an incompatibility error?

useRouter error with next-intl@3.0.0-beta.10:

  console.error
    The above error occurred in the <Card> component:
    
        at useRouter (/Users/cjambrosi/GitHub/next-intl-jest-error-reproduce/src/components/Card/Card.tsx:7:18)
        at children (/Users/cjambrosi/GitHub/next-intl-jest-error-reproduce/node_modules/use-intl/dist/use-intl.cjs.development.js:663:23)
        at children (/Users/cjambrosi/GitHub/next-intl-jest-error-reproduce/node_modules/next-intl/dist/shared/next-intl.cjs.development.js:17:23)
    
    Consider adding an error boundary to your tree to customize error handling behavior.
    Visit https://reactjs.org/link/error-boundaries to learn more about error boundaries.

      19 | ) => {
      20 |   const locale = providerProps?.locale || defaultProviderProps.locale;
    > 21 |   return render(
         |          ^
      22 |     <NextIntlClientProvider
      23 |       locale={locale}
      24 |       messages={{

      at logCapturedError (node_modules/react-dom/cjs/react-dom.development.js:18687:23)
      at Function.render [as customRender] (jest.setup.tsx:21:10)
      at Object.customRender (src/components/Card/index.test.tsx:6:10)

src/components/Card/index.test.tsx
  Home
    ✕ Should render Card component (86 ms)

  ● Home › Should render Card component

    invariant expected app router to be mounted

       5 |
       6 | export default function Card() {
    >  7 |   const router = useRouter()
         |                  ^
       8 |
       9 |   const handleClick = (e) => {
      10 |     e.preventDefault()

      at Object.useRouter (node_modules/next/src/client/components/navigation.ts:123:11)
      at useRouter (src/components/Card/Card.tsx:7:18)
      at Function.render [as customRender] (jest.setup.tsx:21:10)
      at Object.customRender (src/components/Card/index.test.tsx:6:10)

[amannn]

You probably have to mock next/navigation, since as it mentions:

expected app router to be mounted

[amannn]

FWIW I've also just resolved a bug with jest where I got the same error message, but I think it's more related to me using pnpm and symlinks here.

This was the fix: 88df0fe

[cjambrosi]

Thank you for helping me @amannn. I managed to solve the useRouter problem in my project using the yoshiomiyamae solution in discussion #48937.