Unknown argument “fields” on field “markdownRemark” of type “Query”

Question

I facing a trouble to access fields property at markdownRemark , when enter to graghql playground I can't find the fields gatsby-node.js

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

exports.onCreate = ({ node, getNode, actions }) => {
    const { createNodeField } = actions
    if (node.internal.type === `MarkdownRemark`) {
        const slug = createFilePath({ node, getNode })

        createNodeField({
            node,
            name: `slug`,
            value: slug
        })
    } 
}

exports.createPage = ({ graphql, actions }) => {
    const { createPage } = actions
    return grapgh(`
        allMarkdownRemark {
            edges {
                node {
                    fields {
                        slug
                    }
                }
            }
        }
    `).then(result => {
        result.data.allMarkdownRemark.edges.forEach(({node}) => {          
            createPage({
                path: node.fields.slug,
                component: path.resolve(`./src/templates/blog-post.js`),
                context: node.fields.slug
            })
        })

    })
}

gatsby-config.js

module.exports = {
  siteMetadata: {
    title: `OB blog`,
    description: `Kick off your next, great Gatsby project with this default starter. This barebones starter ships with the main Gatsby configuration files you might need.`,
    author: `@gatsbyjs`,
  },
  plugins: [
    `gatsby-plugin-react-helmet`,
    {
      resolve: `gatsby-source-filesystem`,
      options: {
        name: `images`,
        path: `${__dirname}/src/images`,
      },
      resolve: `gatsby-source-filesystem`,
      options: {
        name: `markdowns`,
        path: `${__dirname}/src/markdown-pages`,
      }
    },
    `gatsby-transformer-remark`,
    `gatsby-transformer-sharp`,
    `gatsby-plugin-sharp`,
    {
      resolve: `gatsby-plugin-manifest`,
      options: {
        name: `gatsby-starter-default`,
        short_name: `starter`,
        start_url: `/`,
        background_color: `#663399`,
        theme_color: `#663399`,
        display: `minimal-ui`,
        icon: `src/images/gatsby-icon.png`, // This path is relative to the root of the site.
      },
    },
    // this (optional) plugin enables Progressive Web App + Offline functionality
    // To learn more, visit: https://gatsby.dev/offline
    // `gatsby-plugin-offline`,
  ],
}

Answer 1

You should use:

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

exports.onCreateNode = ({ node, getNode, actions }) => {
  const { createNodeField } = actions
  if (node.internal.type === `MarkdownRemark`) {
    const slug = createFilePath({ node, getNode, basePath: `pages` })
    createNodeField({
      node,
      name: `slug`,
      value: slug,
    })
  }
}

Note that you are using onCreate instead of onCreateNode API. Further information about Gatsby Node APIs . From the documentation:

Called when a new node is created. Plugins wishing to extend or transform nodes created by other plugins should implement this API. See also the documentation for createNode and createNodeField .