Nested projections do not function correctly

[whitfin]

If you have a nested projection, it fails to match:

var Mingo = require('mingo');

var db = [{ "name": "Steve", "age": 15, "features": { "hair": "brown", "eyes": "brown" } } ];

Mingo.find(db, {}, { "features.hair": 1 }).all(); // [ { } ]

In MongoDB, this would return [ { "_id" : ObjectId("57b86248bc6b3372ac511267"), "features" : { "hair" : "brown" } } ].

[whitfin]

So I did some research on this and it seems that the issue is getValue.

var obj = { name: 'Steve',
  age: 15,
  features: { hair: 'brown', eyes: 'brown' } };

var key = 'features.hair';

_.result(obj, key); // undefined

[whitfin]

I can hand roll a nested retrieval get/set but I filed another issue about replacing Underscore with Lodash (maybe in a v0.7.0) which would solve this issue.

[kofrasa]

You are right about the issue being getValue. There is already an internal function which handles nested retrieval correctly called resolve. However, that alone is not sufficient to address the problem. The root cause is that we resolve to the exact value of the given selector and not to the full object graph leading to the value.

For instance given the object

var obj = { "name": "Steve", "age": 15, "features": { "hair": "brown", "eyes": "brown" } };

Currently:

getValue(obj, "features.hair"); // undefined
resolve(obj, "features.hair"); // "brown"

We desire the full object graph leading to the value so that.

resolveObj(obj, "features.hair"); // {"features": {"hair": "brown"}}

I have a working fix for this at the moment, but I still need to do some extra to also handle dropping nested keys which will also not be working correctly.

Concerning lodash however I don't think we gain much switching. Even with their _.get implementation, looking at the example in the docs shows that it is not consistent with MongoDB semantics as required by this project.

[kofrasa]

Fixed in v0.7.0