GraphQL Mutation Updating Users Followers with Mongoose/MongodDB - $set is empty error - mongodb

Question

I have this mutation set up:
followUser: {
type: UserType,
args: {
_id: { type: GraphQLString },
firebaseUid: { type: GraphQLString },
following: { type: new GraphQLList(GraphQLString)},
},
resolve(parentValue, { firebaseUid, _id, following}) {
const update = {
$set: { "following": [firebaseUid] },
$push: { "following": { firebaseUid } }
}
return UserSchema.findOneAndUpdate(
{ _id },
update,
{new: true, upsert: true}
)
}
},
I'm trying to add new followers into my graphql user's collection. My user model:
const UserSchema = new Schema(
{
firebaseUid: String,
following: [{ type: Schema.Types.ObjectId, ref: 'User' }],
followers: [{ type: Schema.Types.ObjectId, ref: 'User' }],
},
{ timestamps: true }
);
module.exports = mongoose.model("User", UserSchema);
So at first, the user doesn't have any followers, so it won't have that field yet. When user adds someone to their friends list, thats when the field will appear in mongodb. Right now I'm getting this error:
"message": "'$set' is empty. You must specify a field like so: {$set: {<field>: ...}}",
I'm not sure if I'm doing the $set correctly.
The UserType
const UserType = new GraphQLObjectType({
name: "User",
fields: () => ({
_id: { type: GraphQLString },
firebaseUid: { type: GraphQLString },
following: { type: new GraphQLList(GraphQLString) },
followers: { type: new GraphQLList(GraphQLString) },
...
})
});
edit:
current mongodb data collection:
_id: ObjectId("5e5c24111c9d4400006d0001")
name: "Mr. Smith"
username: "mrsmith"
after running the update
_id: ObjectId("5e5c24111c9d4400006d0001")
name: "Mr. Smith"
username: "mrsmith"
following: ["fdsaduybfeaf323dfa"] // <-- this gets added

Answer 1

Currently mongooses validator is rejecting the update. To fix this you need the following:
You only need to $push since it will automatically create an array if the property does not exist
You should remove the extra { } around the firebaseUid in the $push because otherwise the following array will contain objects with a firebaseUid property instead of directly containing the Uid (or would if the schema validator allowed it)
Mongo ObjectIds can only be converted from strings when they are 12-byte hexadecimal, and firebaseUid is not, so the schema should be typed to String instead of ObjectId as the validator will reject the field for update otherwise.