setting up lint-staged for jest

Question

I have to try to set up a husky with lint-staged. Initially, I was trying to set up like the following but that does not work.

"lint-staged": {
    "*.js": [
      "prettier --write",
      "eslint src/ --fix",
      "npm run test",
      "git add"
    ]
  }

then I after some searching I changed my setting to the following but thats again reported diff error

"lint-staged": {
    "*.js": [
      "prettier --write",
      "eslint src/ --fix",
      "jest --bail --findRelatedTests",
      "git add"
    ]
  }

Error description

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:
   • To have some of your "node_modules" files transformed, you can specify a custom "transformIgnorePatterns" in your config.
   • If you need a custom transformation to 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.

when I run npm run test in terminal it works fine. So why it is not working with `lint-staged. Am I doing something wrong here?

my package.json

{
  "name": "myproject",
  "version": "0.1.0",
  "private": true,
  "dependencies": {
    "axios": "^0.18.0",
    "react": "^16.8.4",
    "react-dom": "^16.8.4",
    "react-redux": "^6.0.1",
    "react-router-dom": "^5.0.0",
    "react-scripts": "2.1.8",
    "redux": "^4.0.1",
    "redux-thunk": "^2.3.0",
    "standard-http-error": "^2.0.1",
    "styled-components": "^4.1.3"
  },
  "scripts": {
    "start": "react-scripts start",
    "build": "react-scripts build",
    "test": "react-scripts test",
    "eject": "react-scripts eject"
  },
  "eslintConfig": {
    "extends": "react-app"
  },
  "browserslist": [
    ">0.2%",
    "not dead",
    "not ie <= 11",
    "not op_mini all"
  ],
  "devDependencies": {
    "eslint-config-airbnb": "^17.1.0",
    "eslint-config-prettier": "^4.1.0",
    "eslint-plugin-import": "^2.16.0",
    "eslint-plugin-jsx-a11y": "^6.2.1",
    "eslint-plugin-prettier": "^3.0.1",
    "eslint-plugin-react": "^7.12.4",
    "husky": "^1.3.1",
    "install": "^0.12.2",
    "lint-staged": "^8.1.5",
    "prettier": "1.16.4"
  },
  "husky": {
    "hooks": {
      "pre-commit": "lint-staged"
    }
  },
  "lint-staged": {
    "*.js": [
      "prettier --write",
      "eslint src/ --fix",
      "jest --bail --findRelatedTests",
      "git add"
    ]
  }
}

Answer 1

Your lint-staged glob pattern is only set to run on *.js files on root. You have to change it to **/*.js to include ALL *.js files in your project.

"lint-staged": {
  "**/*.js": [
    "prettier --write",
    "eslint src/ --fix",
    "jest --bail --findRelatedTests",
    "git add"
  ]
}

Answer 2

Using a Create React App means that you have to test using the react-scripts because they have the babel configuration that jest alone is missing.

There is a work around to set husky lint-staged using react-scripts test and avoid ejecting and configuring your own babel and jest.

Use the package cross-env that will allow us to configure a CI environment variable in whatever environment we’re currently in.

Install using:

yarn add --dev cross-env

or

npm install cross-env --save-dev

Then on your package.json you should have something like this:

{
   "scripts" {
     ...,
     "lint": "eslint src --fix"
     "test": "cross-env CI=true react-scripts test --env=jsdom",
   },
   "husky": {
     "hooks": {
       "pre-commit": "lint-staged"
     }
   },
   "lint-staged": {
     "**/*.js": [
       "yarn lint",
       "yarn test"
     ]
   },
}

If you are using npm you can change yarn test for npm run test, same for lint.

Hope it helps ;).

Main source of this answer: here