Inserting field with undefined value inserts null instead of undefined

[jedborovik]

For example:

collection.insert({ name: undefined })

inserts { name: {} } and not { name: undefined }. I'm using monk 3.0.4.

The mongo shell inserts { name: undefined } for same insert command.

[mathieudutour]

it's fixed in monk@3.0.6

[jedborovik]

Just tried with monk@3.0.6 and rather than inserting { name: undefined }, it is inserting { name: null }.

One nice thing about having undefined over null is ES6 default values only act on undefined, not null.

The benefit of { name: undefined } is it allows something like:

collection.findOne({ email: 'me@email.com' }).then(({ name = 'No name' }) => {
  // yadda yadda
});

We can definitely delete undefined fields before inserting, but it would be nice to have some control over null vs undefined.

[mathieudutour]

Indeed, it would be nice but the difference between undefined and null is not supported in the nodejs mongo driver (http://devblog.me/wtf-mongo part 2) (meteor/meteor#1646 (comment))

I'll think about what we can do but I'm afraid it's not much

[mathieudutour]

maybe deleting the undefined fields on insert?

[jedborovik]

Yikes, I didn't realize the BSON spec deprecated undefined.

Deleting the undefined fields on insert sounds like a great suggestion. That does seem to mimic the behavior of a javascript object more than having a null value.

[mathieudutour]

This can be implemented as a middleware (see https://automattic.github.io/monk/docs/middlewares.html) in user-land.

Will close this as it probably shouldn't be core

[jaredpalmer]

@mathieudutour can you show what the middleware would look like?

[mathieudutour]

hum maybe something like:

module.exports = function (context) {
  return function (next) {
    return function (args, method) {
      if (!args.data) {
        return next(args, method)
      }

      if (typeof args.data !== 'object') {
        return next(args, method)
      }

      const dataWithoutUndefined = Object.keys(args.data).reduce((prev, k) => {
        if (typeof args.data[k] !== 'undefined') {
          prev[k] = args.data[k]
        }
        return prev
      }, {})

      args.data = dataWithoutUndefined
      return next(args, method)
    }
  }
}

[ceoworks]

it seems like mongo has connection option ignoreUndefined, which could solve this issue.
https://mongodb.github.io/node-mongodb-native/2.1/reference/connecting/connection-settings/