Using resolve to modify field

[avocadowastaken]

Sorry for bad issue title, not sure how to properly name it.

While rewriting app to nexus I found problem with resolvers that modify. For example:

export const ProductType = objectType({
  name: "Product",
  definition(type) {
    type.id("id");
    type.string("title");
    type.float("price");
  }
});

Both title and price stored in database, but during request I want to modify them based on request details:

export const ProductType = objectType({
  name: "Product",
  definition(type) {
    type.id("id");
    type.string("title", {
      async resolve({ id, title }, _, { language, loaders }) {
        const i18n = await loaders.productI18n.load({
          language,
          productId: id
        });

        return !i18n ? title : i18n.title;
      }
    });

    type.float("price", {
      async resolve({ price }, _, { country, services }) {
        return services.price.convertPrice(price, country);
      }
    });
  }
});

JavaScript code works, because these fields exist in root, but TypeScript bugs me because NexusGenRootTypes[] does not have price and title fields.

---

I see two ways to resolve this:

1. Add extra "resolver" named transform, which would work like authorize resolver, but should be called last (authorize -> resolve -> transform)
2. Add boolean key to notify transformer to include current property to NexusGenRootTypes. (e.g: belongsToRoot: true).

---

Related to #36.

[Nayni]

The problem here is how @tgriesser already explained in the related issue, which comes down to the chicken or the egg problem. You define a field on the type that is computed, but the value you compute from is actually be supposed to be on the root object already. I think the only way(and cleanest way) to do this is to let Nexus know your underlying data models which if you're working with TypeScript are probably already defined with an interface/type/class. You can do this by adding sources to the typegenAutoConfig option of makeSchema.

The star-wars example shows how to do this:

export const schema = makeSchema({
  types: allTypes,
  outputs: {
    schema: path.join(__dirname, "../star-wars-schema.graphql"),
    typegen: path.join(__dirname, "./star-wars-typegen.ts"),
  },
  typegenAutoConfig: {
    sources: [
      {
        source: path.join(__dirname, "./types/backingTypes.ts"),
        alias: "swapi",
      },
    ],
    contextType: "swapi.ContextType",
  },
});

The docs (https://nexus.js.org/docs/type-generation) also have a section about this although I think it should be shown more in depth of what the power of this feature is.

[avocadowastaken]

The problem here is how @tgriesser already explained in the related issue, which comes down to the chicken or the egg problem.

Oh, I guess missed it.

You can do this by adding sources to the typegenAutoConfig option of makeSchema.

@Nayni thank you for detailed explanation.