nested-promise-translation-error-fail.js

const databaseGetUser = id =>
  id === 'not-exists'
    ? Promise.reject('some weird database error')
    : Promise.resolve({id, username: 'username'})

const databaseGetPosts = user =>
  user.id === 'fail-to-get-posts'
    ? Promise.reject('some weird database error')
    : Promise.resolve([{title: 'A'}, {title: 'B'}])

function getUserWithPosts(id) {
  return databaseGetUser(id)
    .then(user =>
      databaseGetPosts(user)
        .then(posts => {
          return {user, posts}
        })
        .catch(err => { throw 'failed to load posts' }) // you expect this to work right?
    )
    .catch(err => { throw `user ${id} doesn't exists ` })
}

getUserWithPosts('lubien').then(console.log)               // works fine
getUserWithPosts('not-exists').catch(console.error)        // 'user not-exists doesn't exists'
getUserWithPosts('fail-to-get-posts').catch(console.error) // 'user fail-to-get-posts doesn't exists'