Sort MongoDB Document by field/key name - mongodb

Question

I'm reviewing my MongoDB documents using Robo 3T, and I'd like to sort the keys in the document by their name.
My document might look like
{"Y":3,"X":"Example","A":{"complex_obj":{}}
and at the end I'd like the returned document to look like when I run a find query and apply a sort to it. {"A":{"complex_obj":{},"X":"Example","Y":3}
Is there a way to sort the returned keys / fields of a document? All the examples I see are for applying sort based on the value of a field, rather than the name of the key.

Answer 1

Not sure why the order of field does matter in a JSON document but you can try below aggregation query :
db.collection.aggregate([
{
$project: { data: { $objectToArray: "$$ROOT" } }
},
{
$unwind: "$data"
},
{
$sort: { "data.k": 1 }
},
{
$group: { _id: "_id", data: { $push: "$$ROOT.data" } }
},
{
$replaceRoot: { newRoot: { $arrayToObject: "$data" } }
},
{
$project: { _id: 0 }
}
])
Test : mongoplayground

Answer 2

There is a way but you won't like it. Technically you can do it with aggregation by converting objects to arrays, unwinding, sorting, grouping it back and converting the group to the object:
db.collection.aggregate([
{
$project: {
o: {
$objectToArray: "$$ROOT"
}
}
},
{
$unwind: "$o"
},
{
$sort: {
"o.k": 1
}
},
{
$group: {
_id: "$_id",
o: {
$push: "$o"
}
}
},
{
$replaceRoot: {
newRoot: {
$arrayToObject: "$o"
}
}
}
])
but you don't want to do it. Too much hassle, too expensive, too little benefits.
Mongo by design preserve order of keys as they were inserted. Well, apart from _id, and few other edge cases.