mixing ES6 import and require triggers misleading error

[stevvvn]

The following does not work, though it seems to me it should (node@9.8.0):

import graphqlHTTP from 'express-graphql'; // @0.6.12
import { buildSchema } from 'graphql'; // @1.13.2
import express from 'express';

const app = express();
app.use('/graphql', graphqlHTTP({
  'schema': buildSchema('type Query { hello: String }'),
  'rootValue': { 'hello': () => 'Hello, world!' }
}));
app.listen(4000);

$ curl -s -X POST -H "Content-type: application/json" http://localhost:4000/graphql --data '{ "query": "{ hello }" }'|jq
{
  "errors": [
    {
      "message": "Cannot use GraphQLSchema \"[object Object]\" from another module or realm.\n\nEnsure that there is only one instance of \"graphql\" in the node_modules\ndirectory. If different versions of \"graphql\" are the dependencies of other\nrelied on modules, use \"resolutions\" to ensure only one version is installed.\n\nhttps://yarnpkg.com/en/docs/selective-version-resolutions\n\nDuplicate \"graphql\" modules cannot be used at the same time since different\nversions may have different capabilities and behavior. The data from one\nversion used in the function from another could produce confusing and\nspurious results."
    }
  ]
}

Creating a wrapper to require buildSchema instead:

req.js

module.exports = require('graphql').buildSchema;

And changing the initial example:

//import { buildSchema } from 'graphql';
import buildSchema from './req';

works as expected:

$ curl -s -X POST -H "Content-type: application/json" http://localhost:4000/graphql --data '{ "query": "{ hello }" }'|jq
{
  "data": {
    "hello": "Hello, world!"
  }
}

Arguably this is a problem with express-graphql; it could be resolved by their build including a .mjs file that imports GraphQL to match like-for-like module conventions, instead of just a .js file that requires it regardless of context. However, I think GraphQL is wrong to complain about the mixed arrangement, and in any case the error message is a red herring.

[IvanGoncharov]

@stevvvn Thanks for reporting 👍

However, I think GraphQL is wrong to complain about the mixed arrangement, and in any case the error message is a red herring.

It's intentional, see here: #491 (comment)

Arguably this is a problem with express-graphql;

Would be great if you report this issue on express-graphql and I will try to fix it in the next release.

[stevvvn]

Thanks for the reference!