balanza

# get latest commit with passing tests
while true; do npm test && break || git checkout HEAD~1; done

# count how many commits in between
echo $(($(git rev-list --count HEAD..master) - 1))

# checkout where things got broken
while true; do npm test && break || git checkout HEAD~1; done; git checkout master~$(($(git rev-list --count HEAD..master) - 1))

balanza

import Swagger from 'swagger-client';

const url = 'https://petstore.swagger.io/v2/swagger.json'; // or where the spec is

const requestInterceptor = req => {
  // Here you can add custom headers 
  // ex: req.headers['Authorization'] = 'Bearer <YOUR TOKEN>';
  return req;
};

balanza

// email.ts

import { Email } from './mobile';
export type Email = string & { __phantom_1549009918142: never }

export const createEmail = (input: string): Email | Error => {
 const pattern = /^(([^<>()\[\]\\.,;:\s@"]+(\.[^<>()\[\]\\.,;:\s@"]+)*)|(".+"))@((\[[0–9]{1,3}\.[0–9]{1,3}\.[0–9]{1,3}\.[0–9]{1,3}])|(([a-zA-Z\-0–9]+\.)+[a-zA-Z]{2,}))$/
 if(pattern.test(input)) return createOf<Email, string>(input)
 else return new Error(`invalid email format: ${input}`)
}

balanza

type Foo = {
    value: string, 
    __phantom: never
}
const f = () => { throw '' }
const x: Foo = { value: 'foo', __phantom: f() }

balanza

type ConfirmedMobile = string & { __phantom_1548946378096: never }
const createConfirmedMobile = (num: String) => createOf<ConfirmedMobile, String>(num)

type CertifiedMobile = string & { __phantom_1548946391842: never }
const createCertifiedMobile = (num: String) => createOf<CertifiedMobile, String>(num)

const confirmed = createConfirmedMobile('2984829202') 
// ^^^ ConfirmedMobile
const certified = createCertifiedMobile('2984829202') 
// ^^^ CertifiedMobile

balanza

// it's just a cast ;)
const createOf = <T extends Base, Base>(original: Base) => <T>original

balanza

type ConfirmedMobile = string & { __random_transparent_property: never }
type UnconfirmedMobile = string & { __another_random_transparent_property: never }
type CertifiedMobile = string & { __again_random_transparent_property: never }
type Mobile =  // ConfirmedMobile | UnconfirmedMobile | CertifiedMobile :)
    ConfirmedMobile 
    | UnconfirmedMobile 
    | CertifiedMobile

const printString = (p: string) => console.log(`print String ${p}`)
const printConfirmedMobile = (p: ConfirmedMobile) => console.log(`print ConfirmedMobile ${p}`)

balanza

type ConfirmedMobile = string
type UnconfirmedMobile = string
type CertifiedMobile = string
type Mobile =  // just string :(
    ConfirmedMobile 
    | UnconfirmedMobile 
    | CertifiedMobile

balanza

const exhaustionCheck = (e: never) => console.log('this will never be executed')

const printMobileSafe = (mobile: Mobile) => {
  if(mobile.status === 'confirmed') {
    console.log('Your mobile is confirmed!')
  } else if(mobile.status === 'unconfirmed') {
    console.warn('Your mobile is not confirmed!')
  } else {
    exhaustionCheck(mobile) // <-- you'll get a compilation error here!
  }

balanza

const certified: CertifiedMobile = { status: 'certified', value: '543234531' }

printMobile(certified) // warn: Your mobile is not confirmed!

printMobileAlternative(certified) // unhandled exception: illegal state! mobile.status=certified