GraphQL schema won't import - express

Question

I'm trying setup an express GraphQL server. Following a tutorial when I put the following in the server startup like this:
// ENTIRE SCHEMA IN MAIN FILE THIS WORKS!!!
...
var graphql = require('graphql');
const RootQuery = new graphql.GraphQLObjectType({
name: 'RootQuery',
description: 'The root query',
fields: {
viewer: {
type: graphql.GraphQLString,
resolve() {
return 'viewer!';
}
}
}
});
const Schema = new graphql.GraphQLSchema({
query: RootQuery
});
app.use('/graphql', graphqlHTTP({ schema: Schema }));
...
it works, returning the data 'viewer! But as I don't want everything in the main file, I tried to transfer this exact code to another file and import it like this:
//THIS DOES NOT WORK
...
var Schema = require('./build/models/graphql/schema');
app.use('/graphql', graphqlHTTP({ schema: Schema }));
...
I get the following error:
{
"errors": [
{
"message": "Schema must be an instance of GraphQLSchema. Also ensure that there are not multiple versions of GraphQL installed in your node_modules directory."
}
]
}
I'm not sure what I'm doing wrong. In case this has anything to do with it, I am writing in es6 then transpiling back to 5 in a build script. Here's the build of the schema file:
// TRANSPILED SCHEMA
'use strict';
Object.defineProperty(exports, "__esModule", {
value: true
});
var graphql = require('graphql');
var RootQuery = new graphql.GraphQLObjectType({
name: 'RootQuery',
description: 'The root query',
fields: {
viewer: {
type: graphql.GraphQLString,
resolve: function resolve() {
return 'viewer!';
}
}
}
});
var Schema = new graphql.GraphQLSchema({
query: RootQuery
});
exports.default = Schema;
And here is my package.json:
"express": "^4.13.4",
"express-graphql": "^0.5.3",
"graphql": "^0.6.0",
I've checked that only one graphql is in the node_modules folder. Does graphql expect the same INSTANCE across all modules, like a shared global instance? Does express-graphql use it's own version? How do I check? I'm new to node, is there a way to check the instances?

Answer 1

I don't think this is a GraphQL problem, but a problem with how you're using require and exports in JS. The problem is probably:
var Schema = require('./build/models/graphql/schema')
along with
var Schema = new graphql.GraphQLSchema({
query: RootQuery
});
exports.default = Schema;
You're not importing the same value that you're exporting. Try either exporting Schema as module.exports = Schema or importing it as Schema = require("./...").default

Answer 2

Also ensure that there are not multiple versions of GraphQL installed in your node_modules directory.
As the error indicates, this most likely has to do with more than one copy of GraphQL in your node_modules directory. Have you checked that? If there is more than one copy, you might be able to solve it by running npm dedupe if you're using npm version 2. If you're using npm 3, then most likely you've installed two different versions of the graphql module.
Either way, you have to make sure that after the compile step, express-graphql and your schema both point to the same copy of the graphql module.

Answer 3

If you think implementing & maintaining Graphql services (mainly their schemas), please have a look at graphqly. Here's a sample code to define Graphql schemas:
import graphly from "graphqly";
const gBuilder = graphly.createBuilder();
// define types, inputs ... (in any order)
gBuilder.type("Products").implements("List").def(`
products: [Product]!
`);
gBuilder.type("Product").def(`
id: ID!
name: String!
link: String
price: Int
`);
// we're too lazy to define a separate input, so we can `extend` other structure
gBuilder.input("ProductInput").ext("Product");
gBuilder.enum("ProductOrder").def(`
PRICE_DESCENDING
PRICE_ASCENDING
NEWEST
`);