{ $match: { user: mongodb.ObjectId(userId) } }, { $unwind: '$products' }, { $project: { item: '$products.item', quantity: '$products.quantity' } }, { $lookup: { from: collection.PRODUCT_COLLECTION, localField: 'item', foreignField: '_id', as: 'product' } }, { $project: { item: 1, quantity: 1, product: { $arrayElemAt: ['$product', 0] } } }, { $group: { _id: null, total: { $sum: { $multiply: [{ $toInt: '$quantity' }, { $toInt: '$product.Price' }] } } } } ])

pero dice UnhandledPromiseRejectionWarning: MongoServerError: Error de PlanExecutor durante la agregación :: causado por :: Intento de convertir el valor NaN a tipo entero en $convert sin valor onError