gatsby-node.js

const path = require(`path`)

const { createFilePath } = require(`gatsby-source-filesystem`)

exports.onCreateNode = ({ node, getNode, boundActionCreators }) => {
    const { createNodeField } = boundActionCreators
    if(node.internal.type === "MarkdownRemark") {
        //const slug = createFilePath({ node, getNode, basePath: 'pages' })
        createNodeField({
            node,
            name: 'slug',
            value: "test",
        })
    }
}

/*exports.createPages = ({ graphql, boundActionCreators }) => {
  const { createPage } = boundActionCreators
  return new Promise((resolve, reject) => {
    const blogPostTemplate = path.resolve(`src/templates/blog-post.js`)
    // Query for markdown nodes to use in creating pages.
    resolve(
      graphql(
        `
      {
        allMarkdownRemark(limit: 1000) {
          edges {
            node {
              fields {
                slug
              }
            }
          }
        }
      }
    `
      ).then(result => {
        if (result.errors) {
          reject(result.errors)
        }

        console.log(result)

        return
      })
    )
  })
}*/