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By Paul Scanlon

Modify Gatsby's GraphQL data types using createSchemaCustomization

Hi friends, yesterday I published a little post about how to Add data to Gatsby’s GraphQL layer using sourceNodes, this post will be expanding on the topic of data management but this time i’m going to hone in on how to modify GraphQL’s inferred data types so that you can use the new upgraded gatsby-plugin-image with remotely sourced images.

If you’d prefer to jump ahead here’s a demo repo: https://github.com/PaulieScanlon/nasa-image-type

… and a live demo can be seen here: https://nasaimagetype.gatsbyjs.io/

The Problem

The “problem” with remotely sourced images is that they are usually returned by API’s as url’s, E.g http://example.com/images/some-image.jpg

When GraphQL see’s this it correctly infers the data type as a String. However, in order for gatsby-plugin-image to process the image there are two requirements.

  1. The GraphQL node must be of type File
  2. The image needs to have been downloaded and exist on your local filesystem

In this post i’ll explain how you can satisfy both of these requirements using a combination of createRemoteFileNode from gatsby-source-filesystem and createSchemaCustomization which is utility function available in the Gatsby Node API

The code i’ll be explaining below expands on yesterday’s post: Add data to Gatsby’s GraphQL layer using sourceNodes so i’d advise you have a read of that before diving in.

Pre-Flight Checks

You’ll need to have all the following dependencies installed and configured in gatsby-config.js The docs can be found here: gatsby-plugin-image

yarn add gatsby-plugin-image gatsby-plugin-sharp gatsby-source-filesystem gatsby-transformer-sharp # npm install gatsby-plugin-image gatsby-plugin-sharp gatsby-source-filesystem gatsby-transformer-sharp --save

To use the approach I’ll be using below you’ll also need to have gatsby-source-filesystem installed, but don’t worry about adding it to gatsby-config.js

yarn add gatsby-source-filesystem # npm install gatsby-source-filesystem --save

If you don’t already have one, you’ll need a gatsby-config.js at the root of you project:

...
src
gatsby-config.js
package.json

And finally you’ll need to add the following to gatsby-config.js

// gatsby-config.js

module.exports = {
  plugins: [
    `gatsby-plugin-image`,
    `gatsby-transformer-sharp`,
    {
      resolve: `gatsby-plugin-sharp`,
      options: {
        defaults: {
          quality: 70,
          formats: ['auto', 'webp', 'avif'],
          placeholder: 'blurred',
        },
      },
    },
  ],
};

I prefer to set the defaults for gatsby-plugin-sharp in my gatsby-config.js, this is optional, but i’d advise it.

1. Source The Image

The following code can all be written in gatsby-node.js

I use onCreateNode which is a Gatsby function called each time a new node is created. By using an if condition I’m able to only call createRemoteFileNode if the node.internal.type equals apod, which is the new node I created in yesterday’s post.

// gatsby-node.js
const { createRemoteFileNode } = require('gatsby-source-filesystem');

exports.onCreateNode = async ({ node, actions: { createNode }, createNodeId, cache, store }) => {
  if (node.internal.type === 'apod') {
    node.image = await createRemoteFileNode({
      url: node.url,
      parentNodeId: node.id,
      createNode,
      createNodeId,
      cache,
      store,
    });
  }
};

Starting from the top I destructure createRemoteFileNode from gatsby-source-filesystem, more on that in a moment.

Next I define and export onCreateNode. onCreateNode can be an async function and accepts a number of parameters including but not limited to the following.

  • node
  • actions
  • createNodeId,
  • cache
  • store

node

This is the new node type sourced from the NASA API and already exists in Gatsby’s data layer

actions

Actions are the equivalent to actions bound with bindActionCreators in Redux. actions contains a function called createNode and this is how you add data to the Redux state object / Gatsby’s data layer

createNodeId

This is effectively a helper function that aids in the creation of unique id’s. Under the hood Gatsby are using uuid, you can of course use your preferred method but since uuid is already part of the Gatsby bundle it makes sense to use it.

cache

Cache is the .cache directory Gatsby creates in/on your local filesystem

store

This is Gatsby’s Data layer / The Redux state object

To the best of my knowledge all of the above are required. You might not see errors if you don’t include cache or store when creating a remote file node but I have experienced odd behavior if I failed to included them.

The next bit deals with sourcing the image using the image url returned by the NASA API.

node.image

I create a new object on the node and call it image which will be the response from createRemoteFileNode.

createRemoteFileNode | params

This function comes from gatsby-source-filesystem and accepts the following parameters

  • url
  • parentNodeId
  • createNode
  • createNodeId
  • cache
  • store

url

The source url of the remote file

parentNodeId

The id of the parent node (i.e. the node to which the new remote File node will be linked to.

createNode

The action used to create nodes, I covered this in more detail in yesterday’s post #actions-createNode

createNodeId

A helper function for creating node ids, I covered this in more detail in yesterday’s post #createNodeId

cache

As above

store

As Above

With all of the above in place you should now be able to query the new image node in the GraphiQL explorer. Visit http://localhost:8000/___graphql to investigate.

{
  apod {
    url
    image {
      relativePath
    }
  }
}

Which should give you a response similar to the below

{
  "data": {
    "apod": {
      "url": "https://apod.nasa.gov/apod/image/2107/AR2835_20210701_W2x1024.jpg",
      "image": {
        "relativePath": ".cache/caches/default-site-plugin/bcd18c3c0f372d1ad0d180fa82cde702/AR2835_20210701_W2x1024.jpg"
      }
    }
  },
}

You can see the new image node and by querying the relativePath you can see that the file exists on disc in the .cache/caches directory. Compare this to the url which has remained as it was, a remote url.

This satisfies one of the two requirements I mentioned above, but GraphQL still thinks the data type is a String… but we know it’s now actually a File

2. Modify the GraphQL type

To see GraphQL’s inferred types Gatsby have exposed an additional action called printTypeDefinitions which can be called from Gatsby Node using this function: createSchemaCustomization

// gatsby-node.js

exports.createSchemaCustomization = ({ actions: { createTypes, printTypeDefinitions } }) => {
  printTypeDefinitions({ path: './typeDefs.txt' });
};

If you’ve added the above to gatsby-node.js you can now run gatsby build and you should see a file pop up in your filesystem called typeDefs.txt. Open it and scroll to the bottom, i’ve removed quite a lot from the below snippet for brevity, but the main thing to notice is that GraphQL has inferred that the new image node has a child node called url and is typed as a String 👎

type apod implements Node @derivedTypes @dontInfer {
  ...
  title: String
  url: String
  image: apodImage
}

type apodImage @derivedTypes {
  ...
  url: String
}

To correct this you can manually override GraphQL’s type inference and provide your own type definitions. You can do this by using createTypes from actions

exports.createSchemaCustomization = ({
  actions: { createTypes, printTypeDefinitions }
}) => {
+  createTypes(`
+    type apod implements Node {
+      image: apodImage
+    }
+    type apodImage @dontInfer {
+      url: File @link(by: "url")
+    }
+  `);

  printTypeDefinitions({ path: './typeDefs.txt' });
};

This looks a little peculiar if you’re new to GraphQL and being honest I found this really difficult so here’s my best attempt to explain what’s going on.

type apodImage

apodImage first needs to be set to @dontInfer. This is a way to tell GraphQL that I know best and i’ll handle the types so don’t worry about inferring the data type.

url

Finally it’s here where I tell GraphQL that the image.url is of type File and I link it to the url defined by the url parameter from createRemoteFileNode 🥵

If you delete the typeDefs.txt file from your local filesystem and run gatsby build again and investigate the types you should now see the following.


type apod implements Node @dontInfer {
  ...
  title: String
  url: String
  image: apodImage
}

type apodImage {
  url: File @link(by: "url")
}

And now GraphQL correctly understands that image.url is of type File — Hooray! 🎉

This now satisfies both of the above mentioned requirements!

If you see any weird looking errors in your terminal it might be best to run gatsby clean before running gatsby build since we’re messing with a few low level things

Using GatsbyImage

gatsby-plugin-image exports two components, <StaticImage /> and <GatsbyImage /> I won’t explain why we need to use <GatsbyImage /> but there’s a good explanation in the docs: Using the Gatsby Image components

With the type now set as File you can now query the image.url using childImageSharp.gatsbyImageData. The query i’ve used in index.js looks a little something like this

{
  apod {
    id
    date
    explanation
    media_type
    service_version
    title
    url
    image {
      url {
        childImageSharp {
          gatsbyImageData
        }
      }
    }
  }
}

Which should return something similar to the below. You should be able to see the various image data objects, placeholder, images, and sources. All of this can be passed on to the <GatsbyImage /> component.

{
  "data": {
    "apod": {
      "id": "63a09eef-2a28-5632-94c6-50061b62a0bf",
      "date": "2021-07-02",
      "explanation": "Awash in a sea of incandescent plasma and anchored in strong magnetic fields, sunspots are planet-sized dark islands in the solar photosphere, the bright surface of the Sun. Found in solar active regions, sunspots look dark only because they are slightly cooler though, with temperatures of about 4,000 kelvins compared to 6,000 kelvins for the surrounding solar surface. These sunspots lie in active region AR2835. The largest active region now crossing the Sun, AR2835 is captured in this sharp telescopic close-up from July 1 in a field of view that spans about 150,000 kilometers or over ten Earth diameters. With powerful magnetic fields, solar active regions are often responsible for solar flares and coronal mass ejections, storms which affect space weather near planet Earth.",
      "media_type": "image",
      "service_version": "v1",
      "title": "AR2835: Islands in the Photosphere",
      "url": "https://apod.nasa.gov/apod/image/2107/AR2835_20210701_W2x1024.jpg",
      "image": {
        "url": {
          "childImageSharp": {
            "gatsbyImageData": {
              "layout": "constrained",
              "placeholder": {
                "fallback": "data:image/jpeg;base64,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"
              },
              "images": {
                "fallback": {
                  "src": "/static/8574311e0c9d3b7520b2714c8baa995e/862d2/AR2835_20210701_W2x1024.jpg",
                  "srcSet": "/static/8574311e0c9d3b7520b2714c8baa995e/ac769/AR2835_20210701_W2x1024.jpg 256w,\n/static/8574311e0c9d3b7520b2714c8baa995e/0e233/AR2835_20210701_W2x1024.jpg 512w,\n/static/8574311e0c9d3b7520b2714c8baa995e/862d2/AR2835_20210701_W2x1024.jpg 1024w",
                  "sizes": "(min-width: 1024px) 1024px, 100vw"
                },
                "sources": [
                  {
                    "srcSet": "/static/8574311e0c9d3b7520b2714c8baa995e/c4e41/AR2835_20210701_W2x1024.avif 256w,\n/static/8574311e0c9d3b7520b2714c8baa995e/542bf/AR2835_20210701_W2x1024.avif 512w,\n/static/8574311e0c9d3b7520b2714c8baa995e/59a35/AR2835_20210701_W2x1024.avif 1024w",
                    "type": "image/avif",
                    "sizes": "(min-width: 1024px) 1024px, 100vw"
                  },
                  {
                    "srcSet": "/static/8574311e0c9d3b7520b2714c8baa995e/053d8/AR2835_20210701_W2x1024.webp 256w,\n/static/8574311e0c9d3b7520b2714c8baa995e/93623/AR2835_20210701_W2x1024.webp 512w,\n/static/8574311e0c9d3b7520b2714c8baa995e/41185/AR2835_20210701_W2x1024.webp 1024w",
                    "type": "image/webp",
                    "sizes": "(min-width: 1024px) 1024px, 100vw"
                  }
                ]
              },
              "width": 1024,
              "height": 683
            }
          }
        }
      }
    }
  },
}

Jsx

To return the above image data you can use <GatsbyImage /> with the getImage helper to pass the data on to <GatsbyImage /> via theimage prop

import React from 'react';
import { useStaticQuery, graphql } from 'gatsby';
import { GatsbyImage, getImage } from 'gatsby-plugin-image';

const IndexPage = () => {
  const {
    apod: { id, date, explanation, media_type, service_version, title, image },
  } = useStaticQuery(graphql`
    query {
      apod {
        id
        date
        explanation
        media_type
        service_version
        title
        image {
          url {
            childImageSharp {
              gatsbyImageData
            }
          }
        }
      }
    }
  `);

  return (
    <main>
      <p>{date}</p>
      <h1>{title}</h1>
      <p>{explanation}</p>
      <GatsbyImage alt={title} image={getImage(image.url)} /> // oh hai!
      <p>{`id: ${id}`}</p>
      <p>{`media_type: ${media_type}`}</p>
      <p>{`service_version: ${service_version}`}</p>
    </main>
  );
};

export default IndexPage;

… and there you have it, modifying GraphQL’s data types for remotely sourced images! I’ve used this approach many times in various projects and covered it quite conclusively with Benedicte Raae on our pokey internet show Gatsby Deep Dives with Queen Raae and the Nattermobs Pirates

If you’re looking for a similar solution when working with remote images in Markdown or MDX I wrote a post that can be found on the Gatsby blog: MDX Embedded Images with the All-New Gatsby Image Plugin

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