Leaky abstraction on typescript types generation for apollo project.

[JustFly1984]

I'm working on apollo server app. I have a schema from another app written in Ruby, and using types generated with graphql-code-generator

a graphql type, for example:

type Page {
 id: String!
 title: String!
 name: String
 items: [String!]!
 paragraphs: [Paragraph!]
 images: [Image]
}

results in typescript type declaration which looks like this:

  interface Page {
    id: string
    title: string
    name?: string | null
    items: string[]
    paragraphs?: {
      // not relevant
    }[] | null
    images?: ({
     // not relevant
    } | null)[] | null
  }

Two issues I see here is over-fetch data from DataBase, for fields not requested by the client.

The solution is pretty simple: It requires to wrap imported type in Partial utility type, to not , do not make joins in SQL, etc.

type PartialPage = Partial<Page>

and that is pretty much equal to

interface PartialPage {
  id?: string
  title?: string
  name?: string | null
  items?: string[]
  paragraphs?: {
    // not relevant
  }[] | null
  images?: ({
   // not relevant
  } | null)[] | null
}

But here is a second issue: you can't replace values with async functions, which should be possible due to existing apollo server functionality, to escape over-fetching in query and mutation function resolvers.

Am I missing something? Should type generation to be improved for apollo projects?

[JustFly1984]

I also had to change generated types

before:

export type ResolverTypeWrapper<T> = Promise<T> | T

after:

export type ResolverTypeWrapper<T> = Promise<Partial<T>> | Partial<T>

still thinking how to change types to add support for async functions as props in T for top level queries and mutations

[dotansimha]

@JustFly1984 I fixed it in: #6307

[dotansimha]

Fixed in @graphql-codegen/typescript-resolvers@1.20.0.

[JustFly1984]

@dotansimha Actually today I had implemented correct type:

export type PartialAsync<T> = Partial<
  {
    [K in keyof T]: T[K] extends infer R ? R | (() => Promise<R>) : T
  }
>

but I'm not sure how to provide PartialAsync type for generator. I'm importing the same PartialAsync for using in return values of every mutation function.

In this case I could use defaultMapper PartialAsync<{T}>

meanwhile I'm editing autogenerated types manually.

While I'm editing, I see that some Scalar types get wrapped in Partial. Partial<Scalar['Json']> for example and several others. I think that it is incorrect typing generation.

This type allows me to return async nullable values from mutation functions in apollo-server project.

[JustFly1984]

@dotansimha How do I import PartialAsync type into generated types, to use it in defaultMapper ?

[dotansimha]

You can either specify it as mapper syntax: ./utils#PartialAsync or, you can use add plugin to add the import you need.