gatsby-node.js

// const path = require('path')

exports.onCreateNode = ({ node, actions, getNode }) => {
  const { createNodeField } = actions

  // Sometimes, optional fields tend to get not picked up by the GraphQL
  // interpreter if not a single content uses it. Therefore, we're putting them
  // through `createNodeField` so that the fields still exist and GraphQL won't
  // trip up. An empty string is still required in replacement to `null`.

  switch (node.internal.type) {
    case 'MarkdownRemark':
      {
        const { permalink, layout } = node.frontmatter
        const { relativePath } = getNode(node.parent)

        let slug = permalink

        if (!slug) {
          slug = `/${relativePath.replace('.md', '')}/`
        }

        // Used to generate URL to view this content.
        createNodeField({
          node,
          name: 'slug',
          value: slug || ''
        })

        // Used to determine a page layout.
        createNodeField({
          node,
          name: 'layout',
          value: layout || ''
        })
      }
      break
    default:
      break
  }
}

exports.createPages = async (/* { graphql, actions } */) => {
  // const { createPage } = actions
  // const allMarkdown = await graphql(`
  //   {
  //     allMarkdownRemark(limit: 1000) {
  //       edges {
  //         node {
  //           fields {
  //             layout
  //             slug
  //           }
  //         }
  //       }
  //     }
  //   }
  // `)
  // if (allMarkdown.errors) {
  //   console.error(allMarkdown.errors)
  //   throw new Error(allMarkdown.errors)
  // }
  // allMarkdown.data.allMarkdownRemark.edges.forEach(({ node }) => {
  //   const { slug, layout } = node.fields
  //   createPage({
  //     path: slug,
  //     // This will automatically resolve the template to a corresponding
  //     // `layout` frontmatter in the Markdown.
  //     //
  //     // Feel free to set any `layout` as you'd like in the frontmatter, as
  //     // long as the corresponding template file exists in src/templates.
  //     // If no template is set, it will fall back to the default `page`
  //     // template.
  //     //
  //     // Note that the template has to exist first, or else the build will fail.
  //     component: path.resolve(`./src/templates/${layout || 'page'}.tsx`),
  //     context: {
  //       // Data passed to context is available in page queries as GraphQL variables.
  //       slug
  //     }
  //   })
  // })
}