About me

• Yosuke Kurami (@Quramy)
• Web front-end developer

Which linter do you use with TypeScript ?

TSLint / ESLint

Announce on 8 Jan 2019

• https://github.com/Microsoft/TypeScript/issues/29288

@typescript-eslint 🎉

I'm a TSLint user. How do I migrate ?

How to write .eslintrc ?

Google it 😇

How to write .eslintrc ?

How to configure IDE ?

Options to integrate ESLint to IDEs

• ALE (for Vim)
• Flycheck (for Emacs)
• vscode-eslint (for VSC)
• etc,,,

I've released typescript-eslint-language-service

How to setup

npm i typescript-eslint-language-service -D

// tsconfig.json
{
  "compilerOptions": {
    // ...other settings
    "plugins": [
      {
        "name": "typescript-eslint-language-service"
      }
    ]
  }
}

Plugins...? 🤔

TypeScript's plugin system

Why plugin ?

A1. Editor agnostic

Plugin's functions are provided as tsserver features.

A2. Fast

• Using AST tokenized by TypeScript language server
  • Only converting from TypeScript AST to estree
  • See also my slide to get incremental parsing
• Caching ESLint configurations
  • Purge cache when .eslintrc.* files change

Using some internal APIs...

https://github.com/typescript-eslint/typescript-eslint/issues/774

Appendix

BTW

/* tslint.json */
{
  "defaultSeverity": "error",
  "extends": [
    "tslint-eslint-rules"
  ],
  "rules": {
    "no-duplicate-variable": true,
    "no-eval": true,
    "no-debugger": true,
    "no-internal-module": true,
    "no-unsafe-finally": true,
    "object-curly-spacing": [true, "always"],
    "no-trailing-whitespace": [true, "ignore-comments"],
    "no-reference": true,
    "no-console": [true, "log", "warn", "error"],
    // more rules
  },
  "rulesDirectory": []
} 

It's easy to migrate to ESLint because of using tslint-eslint-rules .

Thank you!