jest: Importing json files result in SyntaxError: Unexpected token m in JSON at position 0

💥 Regression Report

After upgrade of jest-runtime to 24.8.0 the json file import stopped working because the json file is not imported but transformed into following string

module.exports = "permanentComponentConfigurations.json";

As a workaround I provided a json transformation like so

package.json

    "transform": {
      ".+\\.(js|jsx|ts|tsx)$": "<rootDir>/node_modules/babel-jest",
      ".+\\.css$": "<rootDir>/config/jest/cssTransform.js",
      ".+\\.json": "<rootDir>/config/jest/jsonTransform.js",
      "(?!.*\\.(js|jsx|ts|tsx|css|json)$)": "<rootDir>/config/jest/fileTransform.js"
    },

(The configuration from package.json is based on Create-React-App)

jsonTransform.js

module.exports = {
  process(src) {
    return src;
  }
};

Last working version

Worked up to version: 24.7.1

Stopped working in version: 24.8.0

To Reproduce

Import a json file in js like

import PERMANENT_CONFIGURATIONS from 'core/service/config/permanentComponentConfigurations.json';

With 24.8.0 json files are transformed as well. But the resulting json file import results to following content

module.exports = "permanentComponentConfigurations.json";

Expected behavior

The imported json file should be JSON.parsed like before with 24.7.1 per default. If someone needs custom transformation, providing a transformation file is fine, but it should not be a requirement.

Link to repl or repo (highly encouraged)

Please provide either a repl.it demo or a minimal repository on GitHub.

Issues without a reproduction link are likely to stall.

Run `npx envinfo --preset jest`

  System:
    OS: Windows 10
    CPU: (4) x64 Intel(R) Xeon(R) CPU E3-1226 v3 @ 3.30GHz
  Binaries:
    Node: 10.15.3 - C:\Program Files\nodejs\node.EXE
    Yarn: 1.15.2 - C:\Program Files (x86)\Yarn\bin\yarn.CMD
    npm: 6.4.1 - C:\Program Files\nodejs\npm.CMD

About this issue

Original URL
State: closed
Created 5 years ago
Comments: 15 (5 by maintainers)

Most upvoted comments

just a small addition for people accidentally stepping over this:

if you’ve been using

transform: {
    ...,
    '*.': 'babel-jest'
}

28.8 was a breaking change as it will break your json imports. You might want to e.g. restrict the transform to only transform js files.

transform: {
   ...,
    '^.+\\.(js)$': 'babel-jest'
}

+69

sakulstra on May 7, 2019

@sakulstra After 3 hours of debugging, I must say… You saved my day! I’m almost in tears !!!

FlaviooLima on May 15, 2019

The default json transform should work fine, you just need to make sure your own transform does not hit it.

@scotthovestadt might consider reverting and landing in 25? We can add a warning if the pattern matches .json today saying that json is not supported until 25, and if the user does not want to transform json to fix the pattern?

SimenB on May 21, 2019

I am getting this issue still, I pushed what I have to a branch: https://github.com/amzn/style-dictionary/tree/updating-jest

Using Jest 24.8.0, my transform looks like:

    "transform": {
      "^.+\\.json5?$": "json5-jest",
      "^.+\\.jsx?$": "babel-jest"
    }

Travis build with tests failing: https://travis-ci.org/amzn/style-dictionary/builds/552967613

dbanksdesign on Jul 1, 2019

Hi Guys! Im using jest 24.8.0 and this is my transform config

“transform”: { “^.+\.json”: “<rootDir>/scripts/test/transformJSON.js”, -> I had to add this dummy transformer for JSONs to work, what am I doing wrong? “^.+\.js”: “babel-jest”, “^.+\.(ts|js|html)$”: “ts-jest” }

tscislo on Jun 25, 2019

I’d guess this is from https://github.com/facebook/jest/pull/8278, not sure though. Could you provide a reproduction repo?

SimenB on May 6, 2019