.eslintrc.js

const typescriptEslintEslintPlugin = require('@typescript-eslint/eslint-plugin');

// Overrides do not work with extends.
const ruleOverridesForJs = Object.keys(
  typescriptEslintEslintPlugin.rules
).reduce(
  (overrides, rule) => ({ ...overrides, [`@typescript-eslint/${rule}`]: 0 }),
  {}
);

const sharedRules = {
  indent: 0,
  'brace-style': 0,
  'chai-friendly/no-unused-expressions': 0,
  'mocha/no-exclusive-tests': 2,
  'no-cond-assign': [2, 'except-parens'],
  'no-console': [1, { allow: ['warn', 'error', 'info'] }],
  'no-empty-function': 0,
  'no-shadow': 0,
  'no-use-before-define': 0,
  'object-curly-spacing': [2, 'always'],
  'react/sort-comp': 0, // Does not seem work as expected with TypeScript.
  'restrict-template-expressions': 0,
  'space-before-function-paren': 0,
  'valid-jsdoc': 0,
};

module.exports = {
  plugins: ['mocha', '@typescript-eslint'],
  parser: '@typescript-eslint/parser', // Specifies the ESLint parser.
  parserOptions: {
    ecmaVersion: 2018,
    sourceType: 'module',
  },
  extends: [
    'eslint-config-mongodb-js/react',
    'plugin:@typescript-eslint/eslint-recommended',
    'plugin:@typescript-eslint/recommended',
    'plugin:@typescript-eslint/recommended-requiring-type-checking',
  ],
  overrides: [
    {
      files: ['*.ts', '*.tsx'],
      rules: {
        ...sharedRules,
        semi: 0,
        '@typescript-eslint/no-empty-function': 0,
        '@typescript-eslint/no-use-before-define': 0,
        '@typescript-eslint/no-explicit-any': 0,
        '@typescript-eslint/no-unused-vars': 2,
        '@typescript-eslint/explicit-module-boundary-types': 0,
        '@typescript-eslint/ban-types': 0,
        '@typescript-eslint/semi': [2, 'always'],
        '@typescript-eslint/restrict-template-expressions': 0,
        '@typescript-eslint/no-floating-promises': 2,
        // VV These rules we'd like to turn off one day so they error.
        '@typescript-eslint/no-unsafe-assignment': 0,
        '@typescript-eslint/no-unsafe-member-access': 0,
        '@typescript-eslint/no-unsafe-call': 0,
        '@typescript-eslint/no-unsafe-return': 0,
        '@typescript-eslint/no-unsafe-argument': 0,
        '@typescript-eslint/consistent-type-imports': [
          'error',
          { prefer: 'type-imports' },
        ],
        '@typescript-eslint/explicit-function-return-type': [
          'warn',
          {
            allowHigherOrderFunctions: true,
          },
        ],
      },
      parserOptions: {
        project: ['./tsconfig.json'], // Specify it only for TypeScript files.
      },
    },
    {
      files: ['**/*.js'],
      rules: {
        ...ruleOverridesForJs,
        ...sharedRules,
        semi: [2, 'always'],
      },
    },
  ],
};