title: GraphQL Expected Iterable, but did not find one for field xxx.yyy
body: <p>I'm currently trying GraphQL with NodeJS and I don't know, why this error occurs with the following query:</p>
  
  <pre><code>{
    library{
      name,
      user {
        name
        email
      }
    }
  }
  </code></pre>
  
  <p>I am not sure if the <code>type</code> of my <code>resolveLibrary</code> is right, because at any example I had a look at they used <code>new GraphQL.GraphQLList()</code>, but in my case I really want to return a single user object, not an array of users.</p>
  
  <p>My code:</p>
  
  <pre><code>const GraphQL = require('graphql');
  const DB = require('../database/db');
  const user = require('./user').type;
  
  const library = new GraphQL.GraphQLObjectType({
      name: 'library',
      description: `This represents a user's library`,
      fields: () =&gt; {
          return {
              name: {
                  type: GraphQL.GraphQLString,
                  resolve(library) {
                      return library.name;
                  }
              },
              user: {
                  type: user,
                  resolve(library) {
                      console.log(library.user);
                      return library.user
                  }
              }
          }
      }
  });
  
  const resolveLibrary = {
      type: library,
      resolve(root) {
          return {
              name: 'My fancy library',
              user: {
                  name: 'User name',
                  email: {
                      email: 'test@123.de'
                  }
             }
          }
      }
  }
  
  module.exports = resolveLibrary;
  </code></pre>
  
  <p>Error:</p>
  
  <pre><code>Error: Expected Iterable, but did not find one for field library.user.
  </code></pre>
  
  <p>So my <code>library</code> schema provides a <code>user</code> field which returns the right data (the console.log is called).</p>