base.js

const importX = require('eslint-plugin-import-x');
const globals = require('globals');
const jestPlugin = require('eslint-plugin-jest');
const cypress = require('eslint-plugin-cypress/flat');
const eslintConfigPrettier = require('eslint-config-prettier');
const tseslint = require('typescript-eslint');

const OFF = 0;
const ERROR = 2;

const baseRules = {
  // Possible Errors
  'no-console': ERROR,
  'no-unexpected-multiline': ERROR,
  'block-scoped-var': ERROR,
  curly: [ERROR, 'all'],
  'default-case': ERROR,
  'dot-notation': ERROR,
  eqeqeq: [ERROR, 'always', { null: 'ignore' }],
  'guard-for-in': ERROR,
  'no-alert': ERROR,
  'no-caller': ERROR,
  'no-div-regex': ERROR,
  'no-else-return': ERROR,
  'no-eval': ERROR,
  'no-extend-native': ERROR,
  'no-extra-bind': ERROR,
  'no-fallthrough': ERROR,
  'no-floating-decimal': ERROR,
  'no-implicit-coercion': ERROR,
  'no-implied-eval': ERROR,
  'no-iterator': ERROR,
  'no-labels': ERROR,
  'no-lone-blocks': ERROR,
  'no-loop-func': ERROR,
  'no-multi-str': ERROR,
  'no-new-func': ERROR,
  'no-new-wrappers': ERROR,
  'no-new': ERROR,
  'no-octal-escape': ERROR,
  'no-param-reassign': ERROR,
  'no-proto': ERROR,
  'no-return-assign': ERROR,
  'no-script-url': ERROR,
  'no-self-compare': ERROR,
  'no-sequences': ERROR,
  'no-throw-literal': ERROR,
  'no-useless-call': ERROR,
  'no-void': ERROR,
  radix: ERROR,
  'vars-on-top': ERROR,
  yoda: ERROR,
  strict: [ERROR, 'never'],
  'no-label-var': ERROR,
  'no-shadow': ERROR,
  'no-undef-init': ERROR,
  'no-unused-vars': [
    ERROR,
    { argsIgnorePattern: '^_', ignoreRestSiblings: true },
  ],
  'handle-callback-err': ERROR,
  'no-new-require': ERROR,
  'no-path-concat': ERROR,
  'no-process-exit': ERROR,
  'no-restricted-modules': ERROR,
  'no-sync': ERROR,
  'linebreak-style': [ERROR, 'unix'],
  'new-cap': ERROR,
  'no-lonely-if': ERROR,
  'no-nested-ternary': ERROR,
  'no-unneeded-ternary': ERROR,
  'spaced-comment': [ERROR, 'always'],
  'no-var': ERROR,
  'object-shorthand': ERROR,
  'prefer-const': ERROR,
  'prefer-spread': ERROR,
  'prefer-template': ERROR,
  // Allow devs to choose between performance and richer stack traces
  // https://eslint.org/docs/rules/no-return-await#when-not-to-use-it
  // https://github.com/goldbergyoni/nodebestpractices/blob/master@%7B2022-01-01T00:00:00Z%7D/sections/errorhandling/returningpromises.md
  'no-return-await': OFF,
};

const { js: jsExtensions, ts: tsExtensions } = require('./extensions');
const allExtensions = [...jsExtensions, ...tsExtensions];

const settings = {
  'import-x/resolver': {
    typescript: true,
    node: true,
  },
};

module.exports = [
  {
    plugins: {
      jest: jestPlugin,
      cypress,
      '@typescript-eslint': tseslint.plugin,
    },
  },
  importX.flatConfigs.typescript,
  {
    rules: importX.flatConfigs.errors.rules,
    files: [`**/*.{${jsExtensions}}`],
  },
  {
    rules: importX.flatConfigs.warnings.rules,
    files: [`**/*.{${jsExtensions}}`],
  },
  {
    languageOptions: {
      globals: {
        ...globals.node,
      },

      parserOptions: {
        requireConfigFile: false,
        ecmaVersion: 'latest',
        sourceType: 'module',
      },
    },
    settings,
    rules: baseRules,
  },
  eslintConfigPrettier,
  ...[...tseslint.configs.recommended, ...tseslint.configs.stylistic].map(
    ({ plugins, ...config }) => ({
      ...config,
      files: [`**/*.{${tsExtensions}}`],
    }),
  ),
  {
    files: [`**/*.{${tsExtensions}}`],

    languageOptions: {
      parser: tseslint.parser,

      parserOptions: {
        projectService: true,
        warnOnUnsupportedTypeScriptVersion: false,
      },
    },
    settings,
    rules: {
      '@typescript-eslint/array-type': [ERROR, { default: 'array-simple' }],
      '@typescript-eslint/consistent-type-definitions': OFF,
      '@typescript-eslint/no-unused-expressions': ERROR,
      '@typescript-eslint/no-unused-vars': [
        ERROR,
        { argsIgnorePattern: '^_', ignoreRestSiblings: true },
      ],
      '@typescript-eslint/no-use-before-define': OFF,
      '@typescript-eslint/no-non-null-assertion': OFF,
      '@typescript-eslint/ban-ts-comment': OFF,
      '@typescript-eslint/no-explicit-any': OFF,
      '@typescript-eslint/explicit-function-return-type': OFF,
      '@typescript-eslint/no-empty-function': OFF,
      '@typescript-eslint/no-empty-interface': OFF,
      '@typescript-eslint/no-inferrable-types': [
        ERROR,
        { ignoreParameters: true },
      ],
      // prefer TypeScript exhaustiveness checking
      // https://www.typescriptlang.org/docs/handbook/advanced-types.html#exhaustiveness-checking
      'default-case': OFF,
      'arrow-body-style': [ERROR, 'as-needed'],
      // Use `typescript-eslint`'s no-shadow to avoid false positives with enums
      // https://github.com/typescript-eslint/typescript-eslint/blob/master/packages/eslint-plugin/docs/rules/no-shadow.md
      'no-shadow': OFF,
      '@typescript-eslint/no-shadow': ERROR,

      // These two rules deal with autofixing type imports/exports
      // https://typescript-eslint.io/rules/consistent-type-imports
      '@typescript-eslint/consistent-type-imports': [
        ERROR,
        { fixStyle: 'inline-type-imports' },
      ],
      // https://typescript-eslint.io/rules/consistent-type-exports
      '@typescript-eslint/consistent-type-exports': [
        ERROR,
        { fixMixedExportsWithInlineTypeSpecifier: true },
      ],
      // https://typescript-eslint.io/rules/no-import-type-side-effects
      '@typescript-eslint/no-import-type-side-effects': ERROR,

      // This rule deals with merging multiple imports from the same module.
      // In this case, we want type imports to be inlined when merging with the other imports.
      // However, there is a pending PR which improves the behaviour of this rule https://github.com/import-js/eslint-plugin-import/pull/2716
      // https://github.com/import-js/eslint-plugin-import/blob/main/docs/rules/no-duplicates.md#inline-type-imports
      'import-x/no-duplicates': [ERROR, { 'prefer-inline': true }],
      'import-x/export': ERROR,
    },
  },
  {
    files: [`**/*.{${jsExtensions}}`],
    languageOptions: {
      globals: {},
    },
    settings,
    rules: {
      'no-undef': ERROR,
      'no-use-before-define': [ERROR, { functions: false }],
      'no-unused-expressions': ERROR,
      'import-x/no-unresolved': [
        ERROR,
        { commonjs: true, amd: true, ignore: ['.svg$', '^file?'] },
      ],
      'import-x/no-duplicates': ERROR,
      'import-x/export': ERROR,
    },
  },
  {
    ...jestPlugin.configs['flat/recommended'],
    files: [
      `**/__tests__/**/*.{${allExtensions}}`,
      `**/*.@(spec|test).{${allExtensions}}`,
    ],
  },
  {
    files: [
      `**/__tests__/**/*.{${allExtensions}}`,
      `**/*.@(spec|test).{${allExtensions}}`,
    ],
    languageOptions: {
      globals: {
        ...globals.jest,
      },
    },
  },
  {
    ...cypress.configs.recommended,
    files: [`**/cypress/**/*.{${allExtensions}}`],
  },
];