gatsby-node.js

const path = require("path");
const { createFilePath } = require("gatsby-source-filesystem");
const { fmImagesToRelative } = require("gatsby-remark-relative-images");

exports.createPages = ({ actions, graphql }) => {
  const { createPage } = actions;

  return graphql(`
    {
      allMarkdownRemark(limit: 1000) {
        edges {
          node {
            id
            frontmatter {
              templateKey
              path
            }
          }
        }
      }
    }
  `).then((result) => {
    if (result.errors) {
      result.errors.forEach((e) => console.error(e.toString()));
      return Promise.reject(result.errors);
    }

    const posts = result.data.allMarkdownRemark.edges;

    posts
      .filter((edge) => edge.node.frontmatter.templateKey)
      .forEach((edge) => {
        const id = edge.node.id;
        createPage({
          path: edge.node.frontmatter.path,
          component: path.resolve(
            `src/templates/${String(edge.node.frontmatter.templateKey)}.js`
          ),
          // additional data can be passed via context
          context: {
            id,
          },
        });
      });
  });
};

exports.onCreateNode = ({ node, actions, getNode }) => {
  const { createNodeField } = actions;
  fmImagesToRelative(node); // convert image paths for gatsby images

  if (node.internal.type === `MarkdownRemark`) {
    const value = createFilePath({ node, getNode });
    createNodeField({
      name: `slug`,
      node,
      value,
    });
  }
};

exports.createSchemaCustomization = ({ actions }) => {
  const { createTypes } = actions;
  const typeDefs = `
    type MarkdownRemark implements Node {
      frontmatter: Frontmatter
    }
    type Frontmatter {
      partners: [Partner]
      videos: [Video]
    }
    type Partner {
      title: String
      description: String
      link: String
    }
    type Video {
      title: String
      description: String
      link: String
    }
  `;
  createTypes(typeDefs);
};