set() does not create a nested structure

[olastor]

Perhaps this is expected behaviour, but I do not understand why this does not work:

const obj = {};
mpath.set('a.b', 3, obj);
console.log(obj); // => {}

It returns an empty object {}, while I was expecting it to return { a: { b: 3 } }. Using .get() it works the other way around:

const obj = { a: { b: 3 } };
console.log(mpath.get('a.b', obj)); // => 3

[chetverikov]

@olastor Yeah, it looks like a bug because mpath is an implementation of a MongoDB-like path notation and MongoDB works as you expect. @vkarpov15 Are there any similar bugs in mongoose?

[Uzlopak]

What is the actual behavior if you do a

mpath.set('a.3.3', 3, obj);

I mean it could be {"a": { "3": { "3": 3}}} or { "a": [ undefined, undefined, [ undefined, undefined, 3]]} or ...

[vkarpov15]

@Uzlopak I think mpath should err on the side of consistency with the MongoDB server. So the first one you listed is the "correct" behavior.

MongoDB Enterprise > db.test.insertOne({})
{
	"acknowledged" : true,
	"insertedId" : ObjectId("61ea0ffcf42ebc54036f1abc")
}
MongoDB Enterprise > db.test.count()
1
MongoDB Enterprise > db.test.updateOne({}, { $set: { 'a.3.3': 3 } })
{ "acknowledged" : true, "matchedCount" : 1, "modifiedCount" : 1 }
MongoDB Enterprise > db.test.findOne()
{
	"_id" : ObjectId("61ea0ffcf42ebc54036f1abc"),
	"a" : {
		"3" : {
			"3" : 3
		}
	}
}
MongoDB Enterprise > 

But anyway, I ran into this limitation recently with Mongoose as well. I'll open an issue to track this in Mongoose

[Uzlopak]

@vkarpov15 could be solved like this... https://github.com/Uzlopak/mpath/commit/1e3b4318c79563041b2d243d420aa426b08c6483