Consider a collection with documents of the shape

{
    loc: {type: "Point", coordinates: [1.2, 1.1]},
    nested: {field: 7}
}

This aggregation using the $geoNear stage computes new fields in "nested":

db.collection.aggregate({
    $geoNear: {
        near: {type: "Point", coordinates: [0, 0]},
        distanceField: "nested.dist",
        includeLocs: "nested.pt"
    }
})

However, the aggregation system overwrites the field "nested.field", even though it could be preserved. This behavior occurs if the existing document field shares a prefix with either the "distanceField" or "includeLocs" options.

This ticket is a request to preserve as much existing information as possible.