Authenticate a GraphQL Schema

auth-graph.js

// @flow
import { forEachField } from 'graphql-tools';
import { get } from 'lodash/fp';

export default (schema: Object) => {
  forEachField(schema, (field: Object) => {
    if (field.authenticate) {
      // eslint-disable-next-line no-param-reassign
      field.resolve = (...args) => {
        const [,, context] = args;
        if (get('locals.user', context)) {
          return field.resolve(...args);
        }
        throw new Error('Unauthorized');
      };
    }
  });
  return schema;
};