graphql-compose-mongoose can't generate useful types for nested objects

[bibekg]

I'm setting up a stack that includes Typescript, Mongoose, and GraphQL so I was hoping to get the type safety of TS while keeping everything DRY by having my Mongoose schema be my absolute source of truth for types. However, it seems like ts-mongoose's approach to generating the schema conflicts with the way graphql-compose-mongoose converts Mongoose schemas to GraphQL types. A tiny case to reproduce the issue:

// User.ts

import { createSchema, typedModel } from 'ts-mongoose'

const UserSchema = createSchema(
  {
    name: Type.object().of({
      first: Type.string({ required: true, validate: (v) => v.length > 0 }),
      last: Type.string({ required: true, validate: (v) => v.length > 0 }),
    }),
  }
)

export default typedModel('User', UserSchema, undefined, undefined, staticMethods)

I then try to generate my GraphQL schema from this schema as follows

// generateSchema.ts

import composeWithMongoose from 'graphql-compose-mongoose'
import { schemaComposer, ObjectTypeComposer } from 'graphql-compose'
import User from './User'

const UserTC = composeWithMongoose(User)
const graphqlSchema = schemaComposer.buildSchema()
export default graphqlSchema

I'd expect the generated types to include definitions for both User and UserName (the nested name object)

type User {
  name: UserName
}

type UserName {
  first: String!
  last: String!
}

but instead I get unhelpful JSON types like

type User {
  name: JSON
}

---

I dug into it and narrowed down the problem a bit. It seems that in order for graphql-compose-mongoose to generate types properly, nested fields like name in this example need to have User.schema.paths['name'].instance equal to Embedded. However, when generating the schema using ts-mongoose, the instance property ends up being Mixed instead, at which point graphql-compose-mongoose gives up trying to figure out the nested type and just calls it a JSON blob.

I don't think I have enough of an understanding of mongoose to know the solution though.

[dandv]

In case you figure this out with ts-mongoose or typegoose, I've also been trying to have a single source of truth, but can't seem to find a way to define GraphQL schema comments for types, queries, and query parameters, other than by actually writing out a GraphQL schema. Any ideas?

[bibekg]

Yeah, I actually switched over to an approach that uses TypeGraphQL and Typegoose and from initial explorations, it seems to be a good solution!