gatsby-node.js

/*eslint-env node */
const _ = require(`lodash`)
const Promise = require(`bluebird`)
const path = require(`path`)
const { createFilePath } = require(`gatsby-source-filesystem`)

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

  return new Promise((resolve, reject) => {
    const blogPost = path.resolve(`./src/components/blog-post/index.js`)
    resolve(
      graphql(
        `
          {
            allMarkdownRemark(
              limit: 1000
              filter: { frontmatter: { draft: { ne: true } } }
            ) {
              edges {
                node {
                  fields {
                    slug
                  }
                }
              }
            }
          }
        `
      ).then(result => {
        if (result.errors) {
          // console.log(result.errors)
          reject(result.errors)
        }

        // Create blog posts pages.
        _.each(result.data.allMarkdownRemark.edges, edge => {
          createPage({
            path: edge.node.fields.slug,
            component: blogPost,
            context: {
              slug: edge.node.fields.slug,
            },
          })
        })
      })
    )
  })
}

exports.onCreateNode = ({ node, actions, getNode }) => {
  const { createNodeField } = actions
  if (node.internal.type === `MarkdownRemark`) {
    let slug = ``
    if (node.frontmatter && node.frontmatter.slug) slug = node.frontmatter.slug
    else {
      slug = createFilePath({ node, getNode })
      // return only the first folder/file, from first slash to second slash (including)
      slug = /^\/[\s\S]*?\//.exec(slug)[0]
    }
    createNodeField({
      node,
      name: `slug`,
      value: slug,
    })
  }
}

exports.onCreatePage = ({ page, actions }) => {
  const { createPage } = actions

  // page.matchPath is a special key that's used for matching pages
  // only on the client.
  // we use it to make the categories page work
  if (page.path.match(/^\/categories/)) {
    page.matchPath = `/categories/*`

    createPage(page)
  }
}