.eslintrc.js

module.exports = {
  extends: "react-app",
  rules: {
    'import/first': ['warn', 'absolute-first'],
    // https://github.com/airbnb/javascript#commas--dangling
    'comma-dangle': ['warn', 'always-multiline'],
    // Semicolons:
    'no-extra-semi': 'warn',
    // https://github.com/airbnb/javascript#semicolons--required
    semi: ['warn', 'always'],
    'semi-spacing': ['warn', { before: false, after: true }],
    // Vars:
    'no-var': 'warn',
    'prefer-const': ['warn', {
      destructuring: 'any',
      ignoreReadBeforeAssign: true,
    }],
    'one-var': ['warn', 'never'],
    'one-var-declaration-per-line': ['warn', 'always'],
    // https://github.com/airbnb/javascript#comparison--switch-blocks
    'no-case-declarations': 'warn',
    // PropTypes:
    'react/prop-types': ['warn', { ignore: [], customValidators: [] }],
    'react/no-unused-prop-types': ['warn', {
      customValidators: [
      ],
      skipShapeProps: true,
    }],
    // Based on https://github.com/airbnb/javascript/blob/master/packages/eslint-config-airbnb-base/rules/best-practices.js:
    // require return statements to either always or never specify values
    'consistent-return': 'warn',
    // specify curly brace conventions for all control statements
    curly: ['warn', 'multi-line'],
    // encourages use of dot notation whenever possible
    'dot-notation': ['warn', { allowKeywords: true }],
    // disallow use of multiple spaces
    'no-multi-spaces': ['warn', {
      ignoreEOLComments: false,
    }],
    // disallow use of new operator when not part of the assignment or comparison
    'no-new': 'warn',
    // disallow use of assignment in return statement
    'no-return-assign': ['warn', 'always'],
    // disallow redundant `return await`
    'no-return-await': 'warn',
    // disallow use of void operator
    // https://eslint.org/docs/rules/no-void
    'no-void': 'warn',
    // require or disallow Yoda conditions
    yoda: 'warn',
    // Disallow await inside of loops
    // https://eslint.org/docs/rules/no-await-in-loop
    'no-await-in-loop': 'warn',
    // disallow use of constant expressions in conditions
    'no-constant-condition': 'warn',
    // disallow use of debugger
    'no-debugger': 'warn',
    // disallow empty statements
    'no-empty': 'warn',
    // Disallow using indexOf when we have includes
    'no-restricted-syntax': [
      'warn',
      {
        selector: "BinaryExpression > CallExpression > MemberExpression > Identifier[name = 'indexOf']",
        message: 'Please use `includes` instead of `indexOf`. If you use `indexOf` to actually get the index of something, this is a false positive that can be ignored with // eslint-disable-next-line no-restricted-syntax',
      },
      'WithStatement',
      {
        selector: "BinaryExpression[operator='in']",
        message: 'Please do a comparison for `undefined` rather than use the `in` operator (consistent with the rest of the codebase)',
      },
    ],
    // disallow negating the left operand of relational operators
    // https://eslint.org/docs/rules/no-unsafe-negation
    'no-unsafe-negation': 'warn',
    // React
    // Specify whether double or single quotes should be used in JSX attributes
    // https://eslint.org/docs/rules/jsx-quotes
    'jsx-quotes': ['warn', 'prefer-double'],
    // Enforce boolean attributes notation in JSX
    // https://github.com/yannickcr/eslint-plugin-react/blob/master/docs/rules/jsx-boolean-value.md
    'react/jsx-boolean-value': ['warn', 'never', { always: [] }],
    // Enforce or disallow spaces inside of curly braces in JSX attributes
    // https://github.com/yannickcr/eslint-plugin-react/blob/master/docs/rules/jsx-curly-spacing.md
    'react/jsx-curly-spacing': ['warn', 'never', { allowMultiline: true }],
    // Validate props indentation in JSX
    // https://github.com/yannickcr/eslint-plugin-react/blob/master/docs/rules/jsx-indent-props.md
    'react/jsx-indent-props': ['warn', 2],
    // Require that the first prop in a JSX element be on a new line when the element is multiline
    // https://github.com/yannickcr/eslint-plugin-react/blob/master/docs/rules/jsx-first-prop-new-line.md
    // 'react/jsx-first-prop-new-line': ['warn', 'multiline'],
    // Enforce spacing around jsx equals signs
    // https://github.com/yannickcr/eslint-plugin-react/blob/master/docs/rules/jsx-equals-spacing.md
    'react/jsx-equals-spacing': ['warn', 'never'],
    // warn against using findDOMNode()
    // https://github.com/yannickcr/eslint-plugin-react/blob/master/docs/rules/no-find-dom-node.md
    'react/no-find-dom-node': 'warn',
    // Prevent passing of children as props
    // https://github.com/yannickcr/eslint-plugin-react/blob/master/docs/rules/no-children-prop.md
    'react/no-children-prop': 'warn',
    // Validate whitespace in and around the JSX opening and closing brackets
    // https://github.com/yannickcr/eslint-plugin-react/blob/843d71a432baf0f01f598d7cf1eea75ad6896e4b/docs/rules/jsx-tag-spacing.md
    'react/jsx-tag-spacing': ['warn', {
      closingSlash: 'never',
      beforeSelfClosing: 'always',
      afterOpening: 'never',
      // beforeClosing: 'never',
    }],
    // Prevent void DOM elements from receiving children
    // https://github.com/yannickcr/eslint-plugin-react/blob/master/docs/rules/void-dom-elements-no-children.md
    'react/void-dom-elements-no-children': 'warn',
    // Prevent usage of shouldComponentUpdate when extending React.PureComponent
    // https://github.com/yannickcr/eslint-plugin-react/blob/9e13ae2c51e44872b45cc15bf1ac3a72105bdd0e/docs/rules/no-redundant-should-component-update.md
    'react/no-redundant-should-component-update': 'warn',
    // Prevents common casing typos
    // https://github.com/yannickcr/eslint-plugin-react/blob/73abadb697034b5ccb514d79fb4689836fe61f91/docs/rules/no-typos.md
    'react/no-typos': 'warn',
    // Enforce curly braces or disallow unnecessary curly braces in JSX props and/or children
    // https://github.com/yannickcr/eslint-plugin-react/blob/master/docs/rules/jsx-curly-brace-presence.md
    // props can't be "never" because multiline template literals would be broken
    'react/jsx-curly-brace-presence': ['warn', { props: 'ignore', children: 'never' }],
    // Prevent extra closing tags for components without children
    // https://github.com/yannickcr/eslint-plugin-react/blob/master/docs/rules/self-closing-comp.md
    'react/self-closing-comp': 'warn',


    // TODO: Let's try to have a more consistent codestyle

    // enforce one true brace style
    'brace-style': ['warn', '1tbs', { allowSingleLine: true }],

    // require camel case names
    camelcase: ['warn', { properties: 'never', ignoreDestructuring: false, allow: ["^on_"] }],

    // // enforce spacing before and after comma
    // 'comma-spacing': ['warn', { before: false, after: true }],
  },
};