Allow $select to catch and use string syntax

[jamesjnadeau]

mongoose allows a string to be passed to the .select() function ie. select('+someExtraField').

Using this syntax allows you to keep all existing fields selected, but select additional fields you might have hidden in your schema by using select: false as a "column/field" option. It's also a more succinct and flexible way of passing the select information IMHO.

I hope that this change will allow the other forms to be used, but allow this use case.

I still need to check/write tests and clean up the code a bit, but getting this out early for concerns/comment.

[marshallswain]

I think you might be able to just add this check to line 51, which would pass the string to the mongoose query.select()

[jamesjnadeau]

I don't think I can because of how the current check works on line 43, a string has a length right?(I just double checked in my console :)

I could modify it, but I'd rather leave it alone....

[jamesjnadeau]

ok, I've added test for $select on strings, arrays and objects. Works for me! thanks so much for you time and this wonderful codebase!

[marshallswain]

Can you try this with your tests?

if (filters.$select) {
  // $select uses a specific find syntax, so it has to come first.
  if (typeof filters.$select === 'string' || typeof filters.$select === 'object') {
    q.select(filters.$select);
  } else if (Array.isArray(filters.$select)) {
    let fields = {};

    for (let key of filters.$select) {
      fields[key] = 1;
    }

    q.select(fields);
  }
}

I think it's actually more lines of code, but it's a bit cleaner.

[marshallswain]

Actually, I don't think the outer if is even needed:

// $select uses a specific find syntax, so it has to come first.
if (typeof filters.$select === 'string' || typeof filters.$select === 'object') {
  q.select(filters.$select);
} else if (Array.isArray(filters.$select)) {
  let fields = {};

  for (let key of filters.$select) {
    fields[key] = 1;
  }

  q.select(fields);
}

[jamesjnadeau]

@marshallswain I've updated the logic to simplify it, take a look when you have a chance, thanks!

Close to what you had suggested, but I found the array needs to be checked first because an array is an object.

[marshallswain]

Oh right. Looks good to me.

[daffl]

Nice, I didn't know this was possible. Released as v3.6.2. Thanks @jamesjnadeau!