How to convert GraphQL schema to JSON and best to GraphQL schema?

Question

I have figured out that this gives me GraphQLSchema, which I expect I can convert to JSON. How?

// @flow

import path from 'path';
import fs from 'fs';
import {
  buildSchema,
} from 'graphql';

const main = () => {
  const schemaPath = path.resolve(__dirname, '../schema.graphql');

  console.log(buildSchema(fs.readFileSync(schemaPath, 'UTF8')));
};

main();

And how to do the inverse – how to convert JSON representation of GraphQL schema to GraphQL markup?

One way I have found to do it is:

import {
  printSchema,
  buildSchema,
  buildClientSchema,
  printIntrospectionSchema,
  introspectionFromSchema,
} from 'graphql';

printSchema(buildClientSchema(introspectionFromSchema(buildSchema(fs.readFileSync('./schema.graphql', 'UTF8')))))

However, this looses a lot of data, e.g.

type Venue implements Node @preLoad {
  # test
  id: ID!
  fuid: String!
  url: String!
  name: String!
  cinema: Cinema!
  futureEventCount: Int!
  globalCinemaVenue: GlobalCinemaVenue
}

becomes:

type Venue implements Node {
  id: ID!
  fuid: String!
  url: String!
  name: String!
  cinema: Cinema!
  futureEventCount: Int!
  globalCinemaVenue: GlobalCinemaVenue
}

Answer 1

You could use the following package which wasn't available at the time of this post I believe: https://www.npmjs.com/package/graphql-2-json-schema

import {
    graphqlSync,
    getIntrospectionQuery,
    IntrospectionQuery
} from 'graphql';

import { fromIntrospectionQuery } from 'graphql-2-json-schema';

const options = {
  ignoreInternals: true,
  nullableArrayItems: true
}

const introspection = graphqlSync(schema, getIntrospectionQuery()).data as IntrospectionQuery;

const jsonSchema = fromIntrospectionQuery(introspection, options);

Answer 2

You do not need an external library here, you have all you need with graphql-js :

import { introspectionFromSchema } from "graphql"
import { GraphQLFileLoader } from "@graphql-tools/graphql-file-loader"
import { loadSchema } from "@graphql-tools/load"

// it can be any source you want here
const schema = loadSchema("./schema.graphql", {
  loaders: [new GraphQLFileLoader()],
})  
const introspection = introspectionFromSchema(schema)

// Tada, you have your introspection