I have the following schema which contains a property with an array:

const projectSchema = new mongoose.Schema(
  {
    title: {
      type: String,
      required: [true, "Please add a title"],
    },
    users: [{ type: mongoose.Schema.Types.ObjectId, ref: "User" }],
  },
);

In my project controller, I'm trying to add users to this array without getting a duplicate user. So I use $addToSet. It works fine but it doesn't return an error when there is a duplicate user.

const project = await Project.findOneAndUpdate(
  { _id: id },
  { $addToSet: { users: userID } },
  { new: true }
);

How can I detect that it didn't add a user (because the user already exists in the array) and return an error?