Eslint error causing create-react-app failed to compile

Question

I am building a website using create-react-app and have just installed eslint to it.

For some reason what was supposed to be shown as eslint warnings are showing up as errors and causing npm run start to fail.

How can I bypass this issue and have them shown as warnings like before ?

My .eslintrc.js

  env: {
    browser: true,
    es6: true,
    jest: true,
  },
  extends: [
    'airbnb-typescript',
    'plugin:@typescript-eslint/recommended',
    'prettier/react',
    'prettier/@typescript-eslint',
    'plugin:prettier/recommended',
  ],
  globals: {
    Atomics: 'readonly',
    SharedArrayBuffer: 'readonly',
  },
  parser: '@typescript-eslint/parser',
  parserOptions: {
    ecmaFeatures: {
      jsx: true,
    },
    ecmaVersion: 2018,
    sourceType: 'module',
    project: './tsconfig.json',
  },
  plugins: ['react', '@typescript-eslint'],
  rules: {
    'class-methods-use-this': 'off',
    'additional-rule': 'warn',
  },
  ignorePatterns: ['**/node_modules/*', '**/build/*', 'config-overrides.js'],
};

My package.json

  "name": "device-protection-renewal-web",
  "version": "0.1.0",
  "private": true,
  "dependencies": {
    "@testing-library/jest-dom": "^5.11.5",
    "@testing-library/react": "^11.1.0",
    "@testing-library/user-event": "^12.1.10",
    "@types/jest": "^26.0.15",
    "@types/node": "^12.19.3",
    "@types/react": "^16.9.55",
    "@types/react-dom": "^16.9.9",
    "babel-polyfill": "^6.26.0",
    "core-js": "^3.6.5",
    "i18next": "^19.8.3",
    "react": "^17.0.1",
    "react-app-polyfill": "^2.0.0",
    "react-dom": "^17.0.1",
    "react-i18next": "^11.7.3",
    "react-scripts": "4.0.0",
    "web-vitals": "^0.2.4"
  },
  "scripts": {
    "start": "react-scripts start",
    "build": "react-scripts build",
    "test": "react-scripts test",
    "eject": "react-scripts eject"
  },
  "eslintConfig": {
    "extends": [
      "react-app",
      "react-app/jest"
    ]
  },
  "browserslist": {
    "production": [
      ">0.2%",
      "not dead",
      "not op_mini all",
      "ie >= 9"
    ],
    "development": [
      "last 1 chrome version",
      "last 1 firefox version",
      "last 1 safari version",
      "ie >= 9"
    ]
  },
  "devDependencies": {
    "@babel/plugin-transform-arrow-functions": "^7.12.1",
    "@typescript-eslint/eslint-plugin": "^4.6.1",
    "@typescript-eslint/parser": "^4.6.1",
    "eslint": "^7.11.0",
    "eslint-config-airbnb-typescript": "^9.0.0",
    "eslint-config-prettier": "^6.11.0",
    "eslint-plugin-import": "^2.22.0",
    "eslint-plugin-jsx-a11y": "^6.3.1",
    "eslint-plugin-prettier": "^3.1.4",
    "eslint-plugin-react": "^7.20.6",
    "eslint-plugin-react-hooks": "^4.1.0",
    "prettier": "^2.1.2",
    "typescript": "^4.0.5"
  }
}```


  [1]: https://i.sstatic.net/WUKcz.png

Answer 1

I assume that you have installed ESLint using npm install eslint --save-dev and defined a default configuration with node_modules/.bin/eslint --init answering the questions in the prompt.

I noticed that in your .eslintrc.js file, the ESLint settings is missing in the extends option:

extends: [
    'eslint:recommended',
    'airbnb-typescript',
    'plugin:@typescript-eslint/recommended',
    'prettier/react',
    'prettier/@typescript-eslint',
    'plugin:prettier/recommended',
  ],

Also in the package.json is recommended ESLint to have its own script that you run using npm run lint and use it combined with a eslint-plugin in your favorite code editor:

{
  "scripts": {
    "start": "react-scripts start",
    // ...
    "lint": "eslint ."
  },
}

Probably you will build your application at some point, so you should create a .eslintignore file and inside of it add build since files in the build directory also get checked by default when the command is ran.

Source: https://fullstackopen.com/en/part3/validation_and_es_lint#lint