Should we return all resolver fields for an extended entity?

Let’s say I have this schema:

# Service A
type Product @key(fields: "id") {
  id: ID!

# Service B
extend type Product @key(fields: "id") {
  id: ID! @external
  foo: Int
  bar: String!

type Review {
  product: Product!

If Service B did not add any field to Product, I’d just return a representation for Product resolver in Review like this:

(productId) => ({
  type: "Product",
  id: productId

However, here there are 2 additional fields foo and bar. These fields are resolved like this:

const resolvers = {
  Product: {
    foo: fooResolver,
    bar: barResolver,
  Review: {
    product: (review) => ({ type: "Product", id: review.productId}) // do I need to add foo & bar resolvers?

The question is: do I need to add foo & bar resolvers when I’m returning the representation of Product?

In any case, I’m using graphql-codegen to generate my resolvers types, and it compels me to do so. But I find very laborious to add all the fields resolvers anytime I’m returning a representation…

Any thought about this?