Converting a TypeScript Schema File to GraphQL Schema File

28.04.2023 — node.js, typescript — 1 min read

In a recent project, I needed to convert a TypeScript schema file, schema.ts, to a GraphQL schema file, schema.graphql. In this blog post, I will share the steps I took to accomplish this task, including how to resolve a common issue related to TypeScript and the fs module.

My original TypeScript file, schema.ts, contained the following content:

const typeDefs = `#graphql
  type Query {
    hello: String
    jobs(companyId: String!): [Job]
    job(companyId: String!, jobNo: String!): Job
    user(email: String!): User
  }
`

export default typeDefs

To convert schema.ts to schema.graphql, I used an npm script:

"print:schema": "ts-node convertSchema.ts"

The convertSchema.ts file contained the following code:

import * as fs from 'fs'
import typeDefs from './src/graphql/schema'

fs.writeFileSync('schema.graphql', typeDefs)

During my first run, the npm script failed with an error message:

Cannot find module 'fs' or its corresponding type declarations.

The error occurred because my project was a TypeScript project, and the required fs module was missing its type declarations. After some research, I found this helpful resource: https://bobbyhadz.com/blog/typescript-cannot-find-module-fs

Based on the recommendations in the resource, I added "node" to the "types" array in my tsconfig.json file:

{
  "compilerOptions": {
    // ...
    "types": ["node"]
    // ...
  }
}

After updating the tsconfig.json file, I ran the npm script again:

yarn print:schema

This time, the script successfully converted schema.ts to schema.graphql.

Converting a TypeScript schema file to a GraphQL schema file can be a simple process, but you may encounter issues related to TypeScript and the fs module. By following the steps outlined in this blog post, you can successfully convert your schema files while resolving any errors related to TypeScript and the fs module