Adding a custom type to codegen.yml

Question

My GraphQL schema uses a type called PointScalar, which in Typescript would be defined as

export type PointScalar = {
  coordinates: [number, number]
}

Without any modification, codegen declares PointScalar fields as Scalars['PointScalar'], which in turn is any.

I can add this to GraphQL:

config:
  scalars:
    PointScalar: PointScalar

which causes codegen to declare PointScalar as PointScalar, which is great ... but it doesn’t know what a PointScalar is.

How do I get codegen to add an import file or a type statement to the generated Typescript?

Answer 1

You're almost there.

// Name this file as (or anything you prefer): scalar-types.ts
// Place it relative to your codegen-generated types file.

export type PointScalar = {
  coordinates: [number, number]
}

Modify your code to point a file instead. #-points a exported type in the file.

// file: codegen.yml
schema: "my-graphql-schema.graphql"
generates:
  ./index.ts:
config:
   scalars:
      PointScalar: ./scalar-types#PointScalar

Run Codegen and the following import is at the top of your output.

import { PointScalar } from './scalar-types';