.eslintrc.js

const path = require('path');

const forbidTopLevelMessage = [
  'Prefer one level nested imports to avoid bundling everything in dev mode',
  'See https://github.com/mui/material-ui/pull/24147 for the kind of win it can unlock.',
].join('\n');
// This only applies to packages published from this monorepo.
// If you build a library around `@mui/material` you can safely use `createStyles` without running into the same issue as we are.
const forbidCreateStylesMessage =
  'Use `MuiStyles<ClassKey, Props>` instead if the styles are exported. Otherwise use `as const` assertions. ' +
  '`createStyles` will lead to inlined, at-compile-time-resolved type-imports. ' +
  'See https://github.com/microsoft/TypeScript/issues/36097#issuecomment-578324386 for more information';

module.exports = {
  root: true, // So parent files don't get applied
  env: {
    es6: true,
    browser: true,
    node: true,
  },
  extends: [
    'plugin:import/recommended',
    'plugin:import/typescript',
    'airbnb-typescript',
    'prettier',
  ],
  parser: '@typescript-eslint/parser',
  parserOptions: {
    ecmaVersion: 7,
  },
  plugins: [
    'eslint-plugin-material-ui',
    'eslint-plugin-react-hooks',
    '@typescript-eslint/eslint-plugin',
  ],
  settings: {
    'import/resolver': {
      webpack: {
        config: path.join(__dirname, './webpackBaseConfig.js'),
      },
    },
  },
  /**
   * Sorted alphanumerically within each group. built-in and each plugin form
   * their own groups.
   */
  rules: {
    'consistent-this': ['error', 'self'],
    curly: ['error', 'all'],
    // Just as bad as "max components per file"
    'max-classes-per-file': 'off',
    // Too interruptive
    'no-alert': 'error',
    // Stylistic opinion
    'arrow-body-style': 'off',
    // Allow warn and error for dev environments
    'no-console': ['error', { allow: ['warn', 'error'] }],
    'no-param-reassign': 'off', // It's fine.
    // Airbnb use warn https://github.com/airbnb/javascript/blob/63098cbb6c05376dbefc9a91351f5727540c1ce1/packages/eslint-config-airbnb-base/rules/style.js#L97
    // but eslint recommands error
    'func-names': 'error',
    'no-restricted-imports': [
      'error',
      {
        patterns: [
          '@mui/*/*/*',
          // Begin block: Packages with files instead of packages in the top level
          // Importing from the top level pulls in CommonJS instead of ES modules
          // Allowing /icons as to reduce cold-start of dev builds significantly.
          // There's nothing to tree-shake when importing from /icons this way:
          // '@mui/icons-material/*/',
          '@mui/system/*',
          '@mui/utils/*',
          // End block
          // Macros are fine since their import path is transpiled away
          '!@mui/utils/macros',
          '@mui/utils/macros/*',
          '!@mui/utils/macros/*.macro',
        ],
      },
    ],
    'no-constant-condition': 'error',
    // Use the proptype inheritance chain
    'no-prototype-builtins': 'off',
    'no-underscore-dangle': 'error',
    'nonblock-statement-body-position': 'error',
    'prefer-arrow-callback': ['error', { allowNamedFunctions: true }],
    // Destructuring harm grep potential.
    'prefer-destructuring': 'off',

    // disabled type-aware linting due to performance considerations
    '@typescript-eslint/dot-notation': 'off',
    'dot-notation': 'error',
    // disabled type-aware linting due to performance considerations
    '@typescript-eslint/no-implied-eval': 'off',
    'no-implied-eval': 'error',
    // disabled type-aware linting due to performance considerations
    '@typescript-eslint/no-throw-literal': 'off',
    'no-throw-literal': 'error',
    // disabled type-aware linting due to performance considerations
    '@typescript-eslint/return-await': 'off',
    'no-return-await': 'error',

    // Not sure why it doesn't work
    'import/named': 'off',
    // Missing yarn workspace support
    'import/no-extraneous-dependencies': 'off',
    // The code is already coupled to webpack. Prefer explicit coupling.
    'import/no-webpack-loader-syntax': 'off',

    // doesn't work?
    'jsx-a11y/label-has-associated-control': [
      'error',
      {
        // airbnb uses 'both' which requires nesting i.e. <label><input /></label>
        // 'either' allows `htmlFor`
        assert: 'either',
      },
    ],
    // We are a library, we need to support it too
    'jsx-a11y/no-autofocus': 'off',

    'material-ui/docgen-ignore-before-comment': 'error',
    'material-ui/rules-of-use-theme-variants': 'error',

    'react-hooks/exhaustive-deps': ['error', { additionalHooks: 'useEnhancedEffect' }],
    'react-hooks/rules-of-hooks': 'error',

    'react/default-props-match-prop-types': [
      'error',
      {
        // Otherwise the rule thinks inner props = outer props
        // But in TypeScript we want to know that a certain prop is defined during render
        // while it can be ommitted from the callsite.
        // Then defaultProps (or default values) will make sure that the prop is defined during render
        allowRequiredDefaults: true,
      },
    ],
    // Can add verbosity to small functions making them harder to grok.
    // Though we have to manually enforce it for function components with default values.
    'react/destructuring-assignment': 'off',
    'react/forbid-prop-types': 'off', // Too strict, no time for that
    'react/jsx-curly-brace-presence': 'off', // broken
    // airbnb is using .jsx
    'react/jsx-filename-extension': ['error', { extensions: ['.js', '.tsx'] }],
    // Prefer <React.Fragment> over <>.
    'react/jsx-fragments': ['error', 'element'],
    // Enforces premature optimization
    'react/jsx-no-bind': 'off',
    // We are a UI library.
    'react/jsx-props-no-spreading': 'off',
    // This rule is great for raising people awareness of what a key is and how it works.
    'react/no-array-index-key': 'off',
    'react/no-danger': 'error',
    'react/no-direct-mutation-state': 'error',
    // Not always relevant
    'react/require-default-props': 'off',
    'react/sort-prop-types': 'error',
    // This depends entirely on what you're doing. There's no universal pattern
    'react/state-in-constructor': 'off',
    // stylistic opinion. For conditional assignment we want it outside, otherwise as static
    'react/static-property-placement': 'off',
  },
  overrides: [
    {
      files: [
        // matching the pattern of the test runner
        '*.test.js',
        '*.test.ts',
        '*.test.tsx',
      ],
      extends: ['plugin:mocha/recommended'],
      rules: {
        // does not work with wildcard imports. Mistakes will throw at runtime anyway
        'import/named': 'off',
        'no-restricted-imports': [
          'error',
          {
            // Use named import from `test/utils` instead.
            // The other files are private.
            patterns: ['test/utils/*'],
          },
        ],

        'material-ui/disallow-active-element-as-key-event-target': 'error',

        // upgraded level from recommended
        'mocha/no-exclusive-tests': 'error',
        'mocha/no-skipped-tests': 'error',

        // no rationale provided in /recommended
        'mocha/no-mocha-arrows': 'off',
        // definitely a useful rule but too many false positives
        // due to `describeConformance`
        // "If you're using dynamically generated tests, you should disable this rule.""
        'mocha/no-setup-in-describe': 'off',
        // `beforeEach` for a single case is optimized for change
        // when we add a test we don't have to refactor the existing
        // test to `beforeEach`.
        // `beforeEach`+`afterEach` also means that the `beforeEach`
        // is cleaned up in `afterEach` if the test causes a crash
        'mocha/no-hooks-for-single-case': 'off',

        // disable eslint-plugin-jsx-a11y
        // tests are not driven by assistive technology
        // add `jsx-a11y` rules once you encounter them in tests
        'jsx-a11y/click-events-have-key-events': 'off',
        'jsx-a11y/control-has-associated-label': 'off',
        'jsx-a11y/iframe-has-title': 'off',
        'jsx-a11y/label-has-associated-control': 'off',
        'jsx-a11y/mouse-events-have-key-events': 'off',
        'jsx-a11y/no-noninteractive-tabindex': 'off',
        'jsx-a11y/no-static-element-interactions': 'off',
        'jsx-a11y/tabindex-no-positive': 'off',

        // In tests this is generally intended.
        'react/button-has-type': 'off',
        // They are accessed to test custom validator implementation with PropTypes.checkPropTypes
        'react/forbid-foreign-prop-types': 'off',
        // components that are defined in test are isolated enough
        // that they don't need type-checking
        'react/prop-types': 'off',
      },
    },
    {
      files: ['docs/src/modules/components/**/*.js'],
      rules: {
        'material-ui/no-hardcoded-labels': [
          'error',
          { allow: ['MUI', 'Twitter', 'GitHub', 'StackOverflow'] },
        ],
      },
    },
    {
      files: ['docs/pages/**/*.js'],
      rules: {
        'react/prop-types': 'off',
      },
    },
    // demos
    {
      files: [
        'docs/src/pages/**/*.js',
        'docs/src/pages/**/*.tsx',
        'docs/data/**/*.js',
        'docs/data/**/*.tsx',
      ],
      rules: {
        // This most often reports data that is defined after the component definition.
        // This is safe to do and helps readability of the demo code since the data is mostly irrelevant.
        '@typescript-eslint/no-use-before-define': 'off',
        'react/prop-types': 'off',
        'no-alert': 'off',
        'no-console': 'off',
      },
    },
    {
      files: ['*.d.ts'],
      rules: {
        'import/export': 'off', // Not sure why it doesn't work
      },
    },
    {
      files: ['*.tsx'],
      excludedFiles: '*.spec.tsx',
      rules: {
        // WARNING: If updated, make sure these rules are merged with `no-restricted-imports` (#ts-source-files)
        'no-restricted-imports': [
          'error',
          {
            patterns: [
              // Allow deeper imports for TypeScript types. TODO?
              '@mui/*/*/*/*',
              // Macros are fine since they're transpiled into something else
              '!@mui/utils/macros/*.macro',
            ],
          },
        ],
        'react/prop-types': 'off',
      },
    },
    // Files used for generating TypeScript declaration files (#ts-source-files)
    {
      files: ['packages/*/src/**/*.tsx'],
      excludedFiles: '*.spec.tsx',
      rules: {
        'no-restricted-imports': [
          'error',
          {
            paths: [
              {
                name: '@mui/material/styles',
                importNames: ['createStyles'],
                message: forbidCreateStylesMessage,
              },
              {
                name: '@mui/styles',
                importNames: ['createStyles'],
                message: forbidCreateStylesMessage,
              },
              {
                name: '@mui/styles/createStyles',
                message: forbidCreateStylesMessage,
              },
            ],
            patterns: [
              // Allow deeper imports for TypeScript types. TODO?
              '@mui/*/*/*/*',
              // Macros are fine since they're transpiled into something else
              '!@mui/utils/macros/*.macro',
            ],
          },
        ],
        'react/prop-types': 'off',
      },
    },
    {
      files: ['*.spec.tsx', '*.spec.ts'],
      rules: {
        'no-alert': 'off',
        'no-console': 'off',
        'no-empty-pattern': 'off',
        'no-lone-blocks': 'off',
        'no-shadow': 'off',

        '@typescript-eslint/no-unused-expressions': 'off',
        '@typescript-eslint/no-unused-vars': 'off',
        '@typescript-eslint/no-use-before-define': 'off',

        // Not sure why it doesn't work
        'import/export': 'off',
        'import/prefer-default-export': 'off',

        'jsx-a11y/anchor-has-content': 'off',
        'jsx-a11y/anchor-is-valid': 'off',
        'jsx-a11y/tabindex-no-positive': 'off',

        'react/default-props-match-prop-types': 'off',
        'react/no-access-state-in-setstate': 'off',
        'react/no-unused-prop-types': 'off',
        'react/prefer-stateless-function': 'off',
        'react/prop-types': 'off',
        'react/require-default-props': 'off',
        'react/state-in-constructor': 'off',
        'react/static-property-placement': 'off',
      },
    },
    {
      files: ['packages/typescript-to-proptypes/src/**/*.ts'],
      rules: {
        // Working with flags is common in TypeScript compiler
        'no-bitwise': 'off',
      },
    },
    {
      files: ['packages/*/src/**/*{.ts,.tsx,.js}'],
      excludedFiles: ['*.d.ts', '*.spec.ts', '*.spec.tsx'],
      rules: {
        'no-restricted-imports': [
          'error',
          {
            paths: [
              {
                name: '@mui/material',
                message: forbidTopLevelMessage,
              },
              {
                name: '@mui/lab',
                message: forbidTopLevelMessage,
              },
            ],
          },
        ],

        'material-ui/mui-name-matches-component-name': [
          'error',
          {
            customHooks: [
              'useDatePickerDefaultizedProps',
              'useDateTimePickerDefaultizedProps',
              'useTimePickerDefaultizedProps',
            ],
          },
        ],
      },
    },
    {
      files: ['test/bundling/scripts/**/*.js'],
      rules: {
        // ES modules need extensions
        'import/extensions': ['error', 'ignorePackages'],
      },
    },
  ],
};