GraphQL with RESTful returning empty response

Question

I am connecting GraphQL with REST endpoints, I confirmed that whenever I am calling http://localhost:3001/graphql it is hitting REST endpoint and it is returning JSON response to GraphQL server, but I am getting an empty response from GraphQL server to GUI as follows:

{
  "data": {
    "merchant": {
      "id": null
    }
  }
}

Query (decoded manually):

http://localhost:3001/graphql?query={
  merchant(id: 1) {
    id
  }
}

Below is how my GraphQLObjectType looks like:

const MerchantType = new GraphQLObjectType({
  name: 'Merchant',
  description: 'Merchant details',
  fields : () => ({
    id : {
      type: GraphQLString // ,
      // resolve: merchant => merchant.id
    },
    email: {type: GraphQLString}, // same name as field in REST response, so resolver is not requested
    mobile: {type: GraphQLString}
  })
});


const QueryType = new GraphQLObjectType({
  name: 'Query',
  description: 'The root of all... queries',
  fields: () => ({
    merchant: {
      type: merchant.MerchantType,
      args: {
        id: {type: new GraphQLNonNull(GraphQLID)},
      },
      resolve: (root, args) => rest.fetchResponseByURL(`merchant/${args.id}/`)
    },
  }),
});

Response from REST endpoint (I also tried with single object in JSON instead of JSON array):

[
  {
    "merchant": {
      "id": "1",
      "email": "[email protected]",
      "mobile": "1234567890"
    }
  }
]

REST call using node-fetch

function fetchResponseByURL(relativeURL) {

  return fetch(`${config.BASE_URL}${relativeURL}`, {
    method: 'GET',
    headers: {
      Accept: 'application/json',
    }
  })
  .then(response => {
    if (response.ok) {
      return response.json();
    }
  })
  .catch(error => { console.log('request failed', error); });

}

const rest = {
  fetchResponseByURL
}

export default rest

GitHub: https://github.com/vishrantgupta/graphql
JSON endpoint (dummy): https://api.myjson.com/bins/8lwqk

Edit: Adding node.js tag, may be issue with promise object.

Answer 1

Your fetchResponseByURL function get empty string.

I think the main problem is that you are using wrong function to get the your JSON string, please try to install request-promise and use it to get your JSON string.

https://github.com/request/request-promise#readme

something like

var rp = require('request-promise');
function fetchResponseByURL(relativeURL) {
  return rp('https://api.myjson.com/bins/8lwqk')
    .then((html) => {
      const data = JSON.parse(html)
      return data.merchant
    })
    .catch((err) => console.error(err));
  // .catch(error => { console.log('request failed', error); });

}

Answer 2

In this case using data.merchant solved my problem. But the above suggested solution i.e., use of JSON.parse(...) might not be the best practice because if there are no object in JSON, then expected response might be as follows:

{
  "data": {
    "merchant": null
  }
}

Instead of fields to be null.

{
  "data": {
    "merchant": {
      "id": null // even though merchant is null in JSON, 
                 // I am getting a merchant object in response from GraphQL
    }
  }
}

I have updated my GitHub: https://github.com/vishrantgupta/graphql with working code.