Request: Field Resolver Example for Nested Types

[danstarns]

Hi team,

I wanted to make an issue here to request an example using nested field resolvers. One of the benefits of GraphQL is that only what you call is resolved.

Say we have a posts query that also has comments. We don't want to fetch the comments unless they are specifically requested in the GraphQL query. This would make a great example using the JSONPlaceholder API.

I found an example of nested types in the dgraph-101 project:

modus-recipes/dgraph-101/api-as/assembly/index.ts

Line 34 in f119281

export function getProduct(id: string): Product | null {

However, this always fetches the category data even if it's not requested in the GraphQL query. I'm not sure if nested resolvers are currently supported, but it would be valuable to demonstrate this pattern.

Proposed Implementation using JSONPlaceholder:

import { http } from "@hypermode/modus-sdk-as"

@json
export class Comment {
  postId!: number
  id!: number 
  name!: string
  email!: string
  body!: string
}

@json
export class Post {
  id!: number
  userId!: number
  title!: string
  body!: string
  comments: Comment[] = []
}


/**
 * Get a list of posts. Comments will only be fetched when the comments field is requested.
 */
export function getPosts(): Post[] {
  const request = new http.Request("https://jsonplaceholder.typicode.com/posts")
  const response = http.fetch(request)
  return response.json<Post[]>()
}

/**
 * Field resolver for Post.comments - only called when comments are requested
 */
export function resolvePostComments(post: Post): Comment[] {
  const request = new http.Request(
    `https://jsonplaceholder.typicode.com/posts/${post.id}/comments`
  )
  const response = http.fetch(request)
  return response.json<Comment[]>()
}

This would allow queries like:

# Just posts - comments not fetched
query {
  posts {
    id
    title
  }
}

# Posts with comments - comments fetched via resolver
query {
  posts {
    id
    title
    comments {
      id 
      body
    }
  }
}

Can someone confirm if field resolvers are supported? If so, this would make a great example here.