Populating Mongoose virtual that aggregates two different collections - mongodb

Question

My app currently has a bit of a complicated situation that is causing me all sorts of problems. As part of the app we are building recipes, and the recipes are made of ingredients (here simply called "foods" because they can also be used on their own). We have a collection of static recipes and one of dynamic ("user") recipes that are copied from the static version when associated with a user. Technically these recipes all live in one collection but use a discriminator.
However, for foods, we have a database we purchased from a third party, but we also may need to add our own foods. Because updates from the third party database may need to overwrite that database, we need to separate foods from the third party from foods we create. So here we need two entirely separate collections, which we'll call "foodsTP" and "foodsAdmin". However, because these should function exactly the same way from a user's perspective, we don't want the front end to care which collection the foods are coming from.
When getting foods directly, this isn't a problem. We have a virtual getter on the recipe that combines the foods from both collections:
RecipeBaseSchema.virtual('foods').get(function get() {
return this.foodsTP.concat(this.foodsAdmin);
});
However, once the foods have been added to the recipe, API requests to get the recipe are not correctly populating the food information. I have seen this document about Virtual Populate but it doesn't seem to be what I need here. My virtual here isn't just a reference to one other collection, it's actively combining the references to two other collections. When we pull this combined array of foods, we should be able to get all the food info from both collections. However, this is the error I get in the console:
If you are populating a virtual, you must set the localField and
foreignField options
Is there any way I can do this with my combined virtual array?
EDIT: Here's a simplified Recipe Schema.
const RecipeBaseSchema = new Schema({
name: {
type: String,
required: true,
},
foodsTP: [{
quantity: {
type: Number,
default: 1,
},
measureUnit: String,
food: {
type: Schema.Types.ObjectId,
ref: 'Food',
},
}],
foodsAdmin: [{
quantity: {
type: Number,
default: 1,
},
measureUnit: String,
food: {
type: Schema.Types.ObjectId,
ref: 'FoodAdmin',
},
}],
dateAdded: Date,
dateModified: Date,
},
{
toJSON: { virtuals: true },
toObject: { virtuals: true },
}); // options
const RecipeUserSchema = new Schema({});
const RecipeAdminSchema = new Schema({});
API query:
export function getRecipeUser(params) {
params.populate = [
{
path: 'foods',
populate: { path: 'food' },
},
];
params.query = {
_id: params.recipeId,
};
return apiCall('get', `/recipeuser`, omit(params, ['recipeId'])).then(
recipesUser => {
console.log(recipesUser);
return recipesUser[0];
}
);
}