Jest babel - Spread Operator - Jest encountered an unexpected token

Question

I am use Single SPA frameowrk to create a micro frontend using React.

When rub build there is no error. But following error is thrown while running test or coverage.

Error Details :

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:

D:\source\projects\system-ui-components\node_modules\@babel\runtime\helpers\esm\extends.js:1
({"Object.<anonymous>":function(module,exports,require,__dirname,__filename,global,jest){export default function _extends() {
                                                                                         ^^^^^^

SyntaxError: Unexpected token 'export'

After some analysis my finding:

Issue is due to the spread operator. (Works if remvoed)
Spread operator work when used in function but doesnt in a React compoenents.

Eg: Fails: <MyReactComponent {...props} /> Works fine: const a = { id:1 , ...props }

Other Info:

Using Babel7, babel config as follows

  "presets": [
    "@babel/preset-env",
    "@babel/preset-react",
    "@babel/preset-typescript"
  ],
  "plugins": [
    [
      "@babel/plugin-transform-runtime",
      {
        "useESModules": true,
        "regenerator": false
      }
    ]
  ],
  "env": {
    "test": {
      "presets": [
        [
          "@babel/preset-env",
          {
            "targets": "current node"
          }
        ]
      ]
    }
  }
}

Any guidance would be helpful.

i am trying to write a wrapper around existing React component like react-select and would like to use some props and pass others to the react-select. — Jayesh Nathwani, Jul 02 '21 at 13:41

score 0 · Answer 1 · edited Mar 05 '22 at 20:30

0

I had exactly the same problem. In my case it was fixed by adding:

"@babel/modules" on "presets" array in babel.config.json

"presets": [
    "@babel/preset-env",
    "@babel/preset-react",
    "@babel/preset-typescript",
    "@babel/modules"
  ],

edited Mar 05 '22 at 20:30

ouflak

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answered Mar 05 '22 at 17:27

Jose Aparici

1

Jest babel - Spread Operator - Jest encountered an unexpected token

1 Answers1