using "or" operator when using .populate on a query? - node.js

Question

I have my invoices model which has a "sales" field ,which is array of sales. In my sales model I have item field which either can come from Vehicles schema or AfterSale schema.
export const Sales = new Schema<ISale>(
{
customer: { type: Schema.Types.ObjectId, ref: "Customer", required: true },
category: { type: String, enum: enu, required: true },
item: {
type: Schema.Types.ObjectId,
required: true,
ref: (doc) => doc.category,
},
total: { type: Number, required: true },
discount: { type: Number },
purchaseDate: { type: Date, required: true },
branch: { type: Schema.Types.ObjectId, ref: "Branch", required: true },
},
{ timestamps: true },
);
I want to populate the sales.item on my invoice schema, but the problem is , since item can reference to multiple schemas, I can only populate one of them.
async findAll(req: any, query: SharedPreferences): Promise<InvoiceClass[]> {
const invoices = this.invoiceModel
.find(req.searchObj)
.sort({ [query.sort]: query.orderBy === "desc" ? -1 : 1 })
.populate([
"customer",
"sales",
{
path: "sales",
populate: [
{
path: "customer",
model: "Customer",
},
{
path: "branch",
model: "Branch",
},
{
path: "item",
model: "Vehicle",
},
{
path: "item",
model: "AfterSale", //in this case only AfterSale will be populated since
// its last and has same path
}
],
},
]);
my perfect solution would have been using the or operator , but that doesnt work
async findAll(req: any, query: SharedPreferences): Promise<InvoiceClass[]> {
const invoices = this.invoiceModel
.find(req.searchObj)
.sort({ [query.sort]: query.orderBy === "desc" ? -1 : 1 })
.populate([
"customer",
"sales",
{
path: "sales",
populate: [
{
path: "customer",
model: "Customer",
},
{
path: "branch",
model: "Branch",
},
{
path: "item",
model: { $or: ["Vehicle", "AfterSale"] },
},
],
},
]);
any reference/help will be appreciated, thanks.