gatsby-node.ts

import { reporter } from "gatsby-cli/lib/reporter/reporter";
import path from "path";

const { createFilePath } = require(`gatsby-source-filesystem`);

exports.onCreateNode = ({ node, actions, getNode }) => {
  const { createNodeField } = actions;
  if (node.internal.type === `Mdx`) {
    const value = createFilePath({ node, getNode, basePath: "pages" });
    createNodeField({
      node,
      name: `slug`,
      value: `/post${value}`
    });
  }
};

exports.createPages = async ({ actions, graphql }) => {
  const result = await graphql(`
    query {
      allMdx(sort: { fields: [frontmatter___date], order: DESC }) {
        edges {
          node {
            id
            fields {
              slug
            }
            frontmatter {
              title
            }
          }
        }
      }
    }
  `);

  if (result.errors) {
    reporter.panicOnBuild('ERROR: Loading "createPages" query');
  }

  const posts = result.data.allMdx.edges;

  posts.forEach(({ node }, index) => {
    actions.createPage({
      path: node.fields.slug,
      component: path.resolve(`./src/templates/BlogPost/BlogPost.tsx`),
      context: {
        id: node.id,
        next: index === 0 ? null : posts[index - 1].node,
        prev: index === posts.length - 1 ? null : posts[index + 1].node
      }
    });
  });
};