gatsby-node.js

const _ = require('lodash')
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
            fields {
              slug
            }
            frontmatter {
              templateKey
              id
            }
          }
        }
      }
    }
  `).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.forEach(edge => {
            const id = edge.node.id;
            createPage({
                path: edge.node.fields.slug,
                component: path.resolve(
                    `src/templates/${String(edge.node.frontmatter.templateKey)}.js`
                ),
                // additional data can be passed via context
                context: {
                    id,
                    projectId: edge.node.frontmatter.id
                },
            })
        })
        // Tag pages:
        let tags = []
        // Iterate through each post, putting all found tags into `tags`
        // posts.forEach(edge => {
        //     if (_.get(edge, `node.frontmatter.tags`)) {
        //         tags = tags.concat(edge.node.frontmatter.tags)
        //     }
        // })
        // // Eliminate duplicate tags
        // tags = _.uniq(tags)
        //
        // // Make tag pages
        // tags.forEach(tag => {
        //     const tagPath = `/tags/${_.kebabCase(tag)}/`
        //
        //     createPage({
        //         path: tagPath,
        //         component: path.resolve(`src/templates/tags.js`),
        //         context: {
        //             tag,
        //         },
        //     })
        // })
    })
}

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,
        })
    }
}