Flatten nested promises

[Elias]

stackMatch/src/oauth.js

Lines 35 to 56 in a84d27c

   checkOrgMembership(accessToken).then((res) => { 
     if (res === false) { 
       return next(null, false, { message: 'Not FAC member' }); 
     } else { 
       return getMemberData(memberProfile.github_id) 
       .then((userDataObj) => { 
         if(!userDataObj){ 
           postMemberInfo(memberProfile) 
           .then(() => { 
             getMemberData(memberProfile.github_id) 
             .then((newUserDataObj) => { 
               return next(null, newUserDataObj, { message: 'Signup successful' }) 
             }) 
           }) 
         } else { 
           return next(null, userDataObj, { message: 'Login successful' }) 
         } 
       }) 
     } 
   }) 
   .catch(error => { throw new Error(error.message) }); 
 }), 

You're not able to build a flat promise chain here because you want an early exit condition, and also have conditional logic to deal with signup/login, but making two changes can simplify things a bit.

1. Use a RETURNING statement in the postMemberInfo function to retrieve the newly created user object without having to make an additional query.
2. Create a custome error type to deal with the early exit condition.

Example:

class AuthenticationError extends Error {}

checkOrgMembership(accessToken)
  .then(isMember => {
    if (!isMember) {
      throw new AuthenticationError('Not a FAC member')
    }

    return getMemberData(memberProfile.github_id)
  })
  .then(user => 
    !user
      ? postMemberInfo(memberProfile).then(user => ({ user, message: 'Signup' }))
      : { user, message: 'Login' }
   )
  .then(({ user, message }) => next(null, user, message))
  .catch(err => {
    if (err instanceof AuthenticationError) {
      return next(null, false, { message: err.message })
    } else {
      return next(err)
    }
  })

I can understand if you don't find every element of the above example clearer than what you already have. Feel free to take what you like and leave the rest, though I would recommend adding the RETURNING statement as described above.