gatsby-node.js

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

exports.onCreateWebpackConfig = ({ actions }) => {
  actions.setWebpackConfig({
    resolve: {
      modules: [path.resolve(__dirname, "src"), "node_modules"]
    }
  });
};

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

exports.createPages = async ({ graphql, actions }) => {
  const { createPage } = actions;
  const result = await graphql(`
    query {
      allMdx {
        edges {
          node {
            id
            fields {
              slug
            }
          }
        }
      }
    }
  `);
  result.data.allMdx.edges.forEach(({ node }) => {
    createPage({
      path: node.fields.slug,
      component: path.resolve("./src/templates/mdx_template.js"),
      context: {
        slug: node.fields.slug
      }
    });
  });
};