Reusing swagger-generated graphql schema with pothos

[b-barry]

My setup

i'm building a graphql api with pothos and hono.js. my resolvers call internal rest apis that have swagger definitions.

for example, my getPage query:

• calls a rest api with swagger
• transforms the data
• returns a subset plus some extra fields

The problem

i converted the swagger schema to graphql schema (works fine). but now i don't know how to leverage this generated schema in pothos without duplicating all the type definitions.

right now i'd have to do:

// generated from swagger
type Page {
  id: ID!
  title: String!
  content: String!
  // ... 20 more fields
}

// then duplicate everything in pothos
builder.objectType('Page', {
  fields: (t) => ({
    id: t.exposeID('id'),
    title: t.exposeString('title'),
    content: t.exposeString('content'),
    // ... same 20 fields again
  }),
});

this feels wrong - i'm maintaining the same types twice.

What i'm trying to achieve

it's like schema stitching but at the type definition level. i want to import the graphql schema and use it in pothos without manual duplication.

ideally something like:

import { pageSchema } from './generated/graphql-schemas';

builder.objectType('Page', {
  schema: pageSchema, // reuse generated schema
  fields: (t) => ({
    // extend with custom fields
    isPublished: t.boolean({
      resolve: (page) => page.status === 'published',
    }),
  }),
});

My questions

1. can pothos import/reference external graphql schema definitions?
2. is there a way to merge an existing graphql schema with pothos types?
3. should i generate typescript types from swagger and use those instead?
4. am i thinking about this wrong?

Why this matters

the rest apis are managed by other teams and their swagger specs change. i want to avoid manually updating my graphql layer every time.

any suggestions on how to handle this use case?

[hayes]

I think this plugin probably does a large portion of what you want: https://pothos-graphql.dev/docs/plugins/add-graphql

There are a lot of different ways to go about something like this with different tradeoffs.

If you already have a way to build working graphql types, and just need to reference them in a few places in your Pothos schema this plugin should work great.

There's lots of other options (schema stitching, federation, generating Pothos code directly, dynamically building schemas at runtime) that have different tradeoffs, so it's hard to say what's actually best without knowing a lot about your specific use case. Hopefully this plugin is what you need though as it's one of the easiest to use options.

[hayes]

Assuming you are just generating graphql SDL and don't need resolvers, you would probably need to parse the schema text into a GraphQLSchema object to use the plugin, but that should be relatively easy.

You'll probably also need to generate typescript types to add either to the schema types of object refs when using them with Pothos

[b-barry]

Thanks for the quick answer to more context. We have CMS that produce an array of component (widget) that will be used to render a page like

[
{
  "type": "Foo",
  "props": {
    "children": {
      "type": "Bar",
      "props": {
        "baz": "Hello, world"
      }
    }
  }
}]

It is already documented in our Rest API with the swagger. We are adding an GraphQL layer on top of it because we want to use the same thing to render web and mobile.
The reason why we don't use the REST directly is we wanted observability ie we want to track requests to see how API is utilized and by what applications. It is difficult to do with REST. We don't know which field is really used and if a old application mobile is calling us so we don't remove the field etc

In the GraphQL, we will have one query getPage with one resolver that is doing orchestration of different internal API and is calling this REST api of the CMS to get all widgets. I don't want to redo the typing in Pothos and introducing any errors.
I want to leverage directly all the type from this REST API. To make my life easier, I am converting this swagger to GraphQL schema so I can share easily.
I want full type safety and automatic Graphql schema update based on the swagger

I hope it helps clarify a bit

[hayes]

Sounds like the plugin I linked should work

[b-barry]

Ok I will try it and see how to handle. Thanks @hayes