GraphQL: Error: Schema query must be Object Type b

Question

I'm currently trying to inherit schemas for a rootQuery in order to get more modularity. The setup currently looks as follows:

invoiceSchema.js

import {
    GraphQLObjectType,
    GraphQLInt,
} from 'graphql';
export default new GraphQLObjectType({
    name: 'Invoice',
    description: 'A monthly billing invoice for an organization',
    fields: () => ({
        amountDue: {
            type: GraphQLInt,
            description: 'The amount the card will be charged (total + startingBalance with a min value of 0)'
        },
    })
});

rootQuery.js

import {
    GraphQLObjectType,
    GraphQLString,
    GraphQLInt,
    GraphQLList,
    GraphQLID
} from 'graphql';
import Invoice from './invoiceSchema';

export default {
    Invoice: {
        type: Invoice,
        resolve(parentValue, args){
            return 'Hello world';
        } 
    }
};  

schema.js

import query from './rootQuery';
import {GraphQLSchema} from 'graphql';

export default new GraphQLSchema({query});

---

When trying to do the following error and hoped for some help and insight, as what I'm exporting in invoiceSchema.js is clearly an ObjectType and not an object Object.

C:\project\node_modules\graphql\jsutils\invariant.js:19
    throw new Error(message);
    ^

Error: Schema query must be Object Type but got: [object Object].
    at invariant (C:\project\node_modules\graphql\jsutils\invariant.js:19:11)
    at new GraphQLSchema (C:\project\node_modules\graphql\type\schema.js:72:88)
    at Object.<anonymous> (C:/project/api/schema/schema.js:6:16)
    at Module._compile (module.js:573:30)
    at loader (C:\project\node_modules\babel-register\lib\node.js:144:5)
    at Object.require.extensions.(anonymous function) [as .js] (C:\project\node_modules\babel-register\lib\node.js:154:7)
    at Module.load (module.js:507:32)
    at tryModuleLoad (module.js:470:12)
    at Function.Module._load (module.js:462:3)
    at Module.require (module.js:517:17)
[nodemon] app crashed - waiting for file changes before starting...  

Actually got the idea from here and I'm wondering why it doesn't work...

Answer 1

Your root query needs to be an instance of GraphQLObjectType, however, rootQuery.js is exporting a plain Object instead. You'll need to change your export to something like this:

export default new GraphQLObjectType({
  name: 'RootQuery',
  fields: () => ({
    invoice: {
        type: Invoice,
        resolve(parentValue, args){
            return 'Hello world';
        } 
    }
  })
};

Note: it's common practice to keep all field names, including query and mutation names, in camelCase and use PascalCase for type names, to help distinguish between the two.

Also, if you are modularizing your schema, you may find it helpful to utilize graphql-tools for generating your schema instead. IMO, it makes your schema more readable and helps avoid some of the more common pitfalls you may face when modularizing a schema. The docs have a great example of how to modularize your schema with makeExecutableSchema here.