Wantedly TypeScript ESLint Configuration

Common errors

• ESLint: Cannot find module 'eslint-config-wantedly-typescript'

  cause Attempting to use `eslint-config-wantedly-typescript` v4.x with a legacy `.eslintrc` file's `extends` property, which expects a CommonJS module or an old configuration format.
  fix For v4.x, ensure you are using an `eslint.config.js` file and importing the configuration using ESM syntax: `import { base as configWantedlyTS } from 'eslint-config-wantedly-typescript';`

• Error: You are attempting to use a flat configuration file with a legacy eslint config. You should be using `eslint.config.js` or `eslint.config.mjs` or `eslint.config.cjs`.

  cause Running ESLint < v9 or an ESLint instance not configured for Flat Config with an `eslint.config.js` file containing `eslint-config-wantedly-typescript` v4.x.
  fix Upgrade ESLint to version 9.x or later (`npm install eslint@latest --save-dev`) and ensure your main configuration file is named `eslint.config.js` (or `.mjs`/`.cjs`).

• Parsing error: 'import' and 'export' may only appear with 'sourceType: "module"'

  cause Your ESLint configuration is not set up for ESM syntax, but `eslint-config-wantedly-typescript` v4.x itself uses ESM.
  fix Ensure your `eslint.config.js` or relevant parser options specify `sourceType: 'module'` in the parser configuration. For example: `parserOptions: { ecmaVersion: 'latest', sourceType: 'module' }`.

Warnings

• breaking Version 4.0.0 of `eslint-config-wantedly-typescript` introduces support for ESLint v9 and its new Flat Config format. This is a breaking change for users on ESLint v8 or older, or those using the legacy `.eslintrc` configuration format.
  Fix: Upgrade your ESLint installation to v9 or higher. If you must remain on ESLint v8, use `eslint-config-wantedly-typescript` version 3.x and maintain your legacy `.eslintrc` configuration files. Migrate your ESLint configuration to `eslint.config.js` using ESM import syntax.
• gotcha The package has a peer dependency on `typescript`. Ensure you have a compatible version installed in your project. Incompatible TypeScript versions can lead to parsing errors or incorrect linting results.
  Fix: Check your `package.json` for the `typescript` peer dependency range (e.g., `>=3.3.1`). Install a `typescript` version that satisfies this requirement, e.g., `npm install typescript@latest --save-dev`.
• breaking The `eslint-config-wantedly-typescript` package is now published under the `frolint` monorepo. While the package name remains the same, be aware of related packages like `eslint-plugin-wantedly` and `eslint-plugin-use-macros` also being updated to support ESLint v9.
  Fix: Ensure all related `frolint` packages (e.g., `eslint-plugin-wantedly`) are updated to their v4.x versions to maintain compatibility when upgrading to ESLint v9.

Install

• npm install eslint-config-wantedly-typescript npm
• yarn add eslint-config-wantedly-typescript yarn
• pnpm add eslint-config-wantedly-typescript pnpm

Imports

• configWantedlyTS
  wrong:

  const configWantedlyTS = require('eslint-config-wantedly-typescript');

  correct:

  import { base as configWantedlyTS } from 'eslint-config-wantedly-typescript';

  Version 4.x and above use ESLint Flat Config, which requires ESM import syntax. The 'base' export contains the main configuration array.

Quickstart

Demonstrates how to set up `eslint-config-wantedly-typescript` v4.x using ESLint's Flat Config format in an `eslint.config.js` file, including basic customization.

import { base as configWantedlyTS } from 'eslint-config-wantedly-typescript';

export default [
  ...configWantedlyTS,
  {
    // Optional: Add project-specific overrides or additional rules here.
    // For example, to disable a rule:
    rules: {
      '@typescript-eslint/explicit-module-boundary-types': 'off',
      'react/react-in-jsx-scope': 'off' // Example for React 17+ / New JSX Transform
    }
  },
  {
    // Define files glob patterns for this configuration scope
    files: ['**/*.ts', '**/*.tsx', '**/*.js', '**/*.jsx'],
    // You might need to specify parserOptions if your project uses different TypeScript settings
    parserOptions: {
      project: './tsconfig.json',
      ecmaVersion: 'latest',
      sourceType: 'module',
      ecmaFeatures: {
        jsx: true
      }
    }
  }
];