gatsby-node.js

const path = require('path')
const { createFilePath } = require('gatsby-source-filesystem')
const fs = require('fs-extra')


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

  return graphql(`
  {
    site {
      siteMetadata {
        languages {
          langs
        }
      }
    }
    markdownRemark {
      frontmatter {
        HeroTaglineDescription
      }
    }
    allMarkdownRemark(sort: {frontmatter: {date: DESC}}, limit: 1000) {
      edges {
        node {
          id
          fields {
            slug
            langKey
            tagSlugs {
              tag
              link
            }
          }
          frontmatter {
            id
            date
            path
            tags
            templateKey
            lang
            title
            HeroTaglineDescription
          }
        }
      }
    }
  }
  `).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)}.tsx`
        ),
        // additional data can be passed via context
        context: {
          id: edge.node.id,
          lang: edge.node.frontmatter.lang
        },
      })
    })

  })
}


exports.onCreateWebpackConfig = ({ actions, getConfig, stage }) => {
  const config = getConfig()
  if (stage.startsWith('develop') && config.resolve) {
    config.resolve.alias = {
      ...config.resolve.alias
    }
  }
  if (stage === 'build-javascript') {
    actions.setWebpackConfig({
      devtool: false
    })
  }
}

exports.onCreatePage = async ({ page, actions }) => {
  const { createPage } = actions
  // page.matchPath is a special key that's used for matching pages
  // only on the client.
  if (page.path.match(/^\/app/)) {
    page.matchPath = "/app/*"
    // Update the page.
    createPage(page)
  }
}