[feature request]: throwIfEmpty

[ashleygwilliams]

this is a feature request for an option to pass to filter(). i am open to there being a completely different solution to this problem tho, so i will spend most of my time explaining the problem to be solved.

the problem

consider the following code:

function deleteBannedEmail (req, context) {
   const email = context.get('email')

  return BannedEmail.objects.get({
     'deleted:isNull': true,
    email
  }).then(email => {
    return BannedEmail.objects.filter({id: email.id}).delete().return()
  }).catch(BannedEmail.objects.NotFound, rethrow(404))
}

in order to throw a NotFound error, this code uses the get method to retrieve the object to be deleted. however, then, in order to actually delete the object, this function re-queries the db using the filter method which delete is then called on.

to avoid an extra query, but still throw if the object is empty, i use filter, then update, and then finally check the count returned by update, in code that looks like this:

function deleteBannedEmail (req, context) {
  const email = context.get('email')

  return BannedEmail.objects.filter({
    'deleted:isNull': true,
    email
  }).update({
    deleted: new Date()
  }).then((count) => {
    if (Number(count) < 1) {
      throw new reply.NotFoundError()
    }
    return reply.empty()
  })
}

proposed solution

checking this count seems a lil icky to me. therefore i propose a throwIfEmpty option on filter which will throw a NotFound error if filter returns no objects. this way, i don't have to check the count. the resulting code would look like this:

function deleteBannedEmail (req, context) {
  const email = context.get('email')

  return BannedEmail.objects.filter({
    'deleted:isNull': true,
    email
  }, { throwIfEmpty: true }).update({
    deleted: new Date()
  }).then(() => {
    return reply.empty()
  }).catch(BannedEmail.objects.NotFound, rethrow(404))
}

as i said, super open to other solutions! this is just the one i thought of. this is a pretty common use case, so conventionalizing an ergonomic way to accomplish this would be great. thanks!