Extending Mdx nodes results in other fields (e.g. body, excerpt) not being available

Description

I’m trying to extend the Mdx node type created by gatsby-plugin-mdx, with gatsby-node’s createResolvers or createSchemaCustomization API. In either case, this results in the body and excerpt fields (as well as others) not being available on the Mdx node anymore.

Steps to reproduce

Simply adding a field to Mdx will cause it to break, e.g.:

export const createSchemaCustomization = async ({ actions: { createTypes } }) => {
  const typeDefs = `
    type Mdx implements Node {
      foo: String!
    }
  `;

  createTypes(typeDefs);
};

Expected result

I expect the new field foo to be available alongside all the other fields (like body and excerpt).

Actual result

The new field is available, but body, excerpt and other important field are not:

This results in errors when trying to query for these fields.

 ERROR #85923  GRAPHQL

There was an error in your GraphQL query:

Cannot query field "body" on type "Mdx".

Environment

  System:
    OS: Linux 5.7 Arch Linux
    CPU: (16) x64 AMD Ryzen 7 3800X 8-Core Processor
    Shell: 5.8 - /usr/bin/zsh
  Binaries:
    Node: 12.16.1 - /tmp/yarn--1596878937010-0.33041929112915125/node
    Yarn: 1.22.4 - /tmp/yarn--1596878937010-0.33041929112915125/yarn
    npm: 6.13.4 - ~/.nvm/versions/node/v12.16.1/bin/npm
  Languages:
    Python: 3.8.5 - /usr/bin/python
  Browsers:
    Firefox: 79.0
  npmPackages:
    gatsby: ^2.24.36 => 2.24.36
    gatsby-plugin-canonical-urls: ^2.3.4 => 2.3.4
    gatsby-plugin-catch-links: ^2.1.25 => 2.3.5
    gatsby-plugin-favicons: ^1.0.4 => 1.0.4
    gatsby-plugin-git-clone: ^0.1.0 => 0.1.0
    gatsby-plugin-matomo: ^0.8.0 => 0.8.3
    gatsby-plugin-mdx: ^1.2.34 => 1.2.34
    gatsby-plugin-react-helmet-async: ^1.0.15 => 1.0.16
    gatsby-plugin-s3: ^0.3.3 => 0.3.3
    gatsby-plugin-sharp: ^2.4.5 => 2.6.11
    gatsby-plugin-sitemap: ^2.2.27 => 2.4.5
    gatsby-plugin-styled-components: ^3.1.19 => 3.3.4
    gatsby-plugin-ts-config: ^0.2.3 => 0.2.3
    gatsby-plugin-typescript: ^2.4.6 => 2.4.6
    gatsby-remark-external-links: ^0.0.4 => 0.0.4
    gatsby-remark-images: ^3.1.44 => 3.3.10
    gatsby-remark-static-images: ^1.2.1 => 1.2.1
    gatsby-source-filesystem: ^2.3.0 => 2.3.11
    gatsby-transformer-yaml: ^2.2.25 => 2.4.4

[github-actions[bot]]

Hiya!

This issue has gone quiet. Spooky quiet. 👻

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Thanks for being a part of the Gatsby community! 💪💜

[Mrtenz]

Looks like this was fixed in one of the updates. 👍 Using the following code, I was able to query foo, as well as body, excerpt, etc.

module.exports.createSchemaCustomization = ({ actions: { createTypes } }) => {
  const typeDefs = `
    type Mdx implements Node {
      foo: String!
    }
  `;

  createTypes(typeDefs);
};

module.exports.createResolvers = ({ createResolvers }) => {
  const resolvers = {
    Mdx: {
      foo: {
        resolve() {
          return 'bar';
        }
      }
    }
  };

  createResolvers(resolvers);
};