Programmatically create multiple types of pages in Gatsby.js

Question

I'm building a website with GatsbyJS. I have markdown files in two different folders: /content/collections and /content/posts and I want Gatsby to create a page for each markdown file, with the respective template (collection.js and post.js).

So I wrote this in my gatsby-node.js file:

const path = require('path');
const { createFilePath } = require('gatsby-source-filesystem');
exports.onCreateNode = ({ node, getNode, actions }) => {
  const { createNodeField } = actions;
  if (node.internal.type === 'MarkdownRemark') {
    const longSlug = createFilePath({ node, getNode, basePath: 'content' });
    const slug = longSlug.split('/');
    createNodeField({
      node,
      name: 'slug',
      value: `/${slug[slug.length - 2]}/`,
    });
  }
};

exports.createPages = async ({ graphql, actions }) => {
  const { createPage } = actions;
  const result = await graphql(`
    query {
      allFile(filter: {relativeDirectory: {eq: "collections"}}) {
        edges {
          node {
            childMarkdownRemark {
              fields {
                slug
              }
            }
          }
        }
      }
    }
  `);
  result.data.allFile.edges.forEach(({ node }) => {
    createPage({
      path: node.childMarkdownRemark.fields.slug,
      component: path.resolve('./src/templates/collection.js'),
      context: {
        slug: node.childMarkdownRemark.fields.slug,
      },
    });
  });
};

exports.createPages = async ({ graphql, actions }) => {
  const { createPage } = actions;
  const result = await graphql(`
    query {
      allFile(filter: {relativeDirectory: {eq: "posts"}}) {
        edges {
          node {
            childMarkdownRemark {
              fields {
                slug
              }
            }
          }
        }
      }
    }
  `);
  result.data.allFile.edges.forEach(({ node }) => {
    createPage({
      path: node.childMarkdownRemark.fields.slug,
      component: path.resolve('./src/templates/post.js'),
      context: {
        slug: node.childMarkdownRemark.fields.slug,
      },
    });
  });
};

Thinking that it would work. It does work for the second type that I put in. (in this case it creates the posts, but not the collections. If I invert the order in which I call createPages it swaps, but it never creates all of them)

This is the error that I get in the console:

warning The GraphQL query in the non-page component "/Users/matteocarpi/Documents/Web/Ledue/src/templates/collection.js" will not be run.
Exported queries are only executed for Page components. It's possible you're
trying to create pages in your gatsby-node.js and that's failing for some
reason.

If the failing component(s) is a regular component and not intended to be a page
component, you generally want to use a <StaticQuery> (https://gatsbyjs.org/docs/static-query)
instead of exporting a page query.

If you're more experienced with GraphQL, you can also export GraphQL
fragments from components and compose the fragments in the Page component
query and pass data down into the child component — https://graphql.org/learn/queries/#fragments

The two templates are very similar:

import React from 'react';

import { graphql } from 'gatsby';
import PropTypes from 'prop-types';

const Post = ({data}) => {
  return (
    <div>
      <h1>{data.postData.frontmatter.title}</h1>
    </div>
  );
};

export default Post;

export const query = graphql`
query PostData($slug: String!) {
  postData: markdownRemark(fields: {slug: {eq: $slug}}) {
    frontmatter {
      title
    }
  }
}
`;

Post.propTypes = {
  data: PropTypes.node,
};

import React from 'react';

import { graphql } from 'gatsby';
import PropTypes from 'prop-types';

const Collection = ({data}) => {
  return (
    <div>
      <h1>{data.collectionData.frontmatter.title}</h1>
    </div>
  );
};

export default Collection;

export const query = graphql`
query CollectionData($slug: String!) {
  collectionData: markdownRemark(fields: {slug: {eq: $slug}}) {
    frontmatter {
      title
    }
  }
}
`;

Collection.propTypes = {
  data: PropTypes.node,
};

I tried refactoring all of the gatsby-node.js file following this answer but I end up in the same situation.

Where am I getting it wrong?

Answer 1

The issue is that you're overriding your first function declaration with the second. A bit like this:

var a = "hello"
a = "world"

Instead you should do all of your querying and call createPage for all pages you want to create in a single function, something like this:

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

  const collections = graphql(`
    query {
      allFile(filter: {relativeDirectory: {eq: "collections"}}) {
        edges {
          node {
            childMarkdownRemark {
              fields {
                slug
              }
            }
          }
        }
      }
    }
  `).then(result => {
    result.data.allFile.edges.forEach(({ node }) => {
      createPage({
        path: node.childMarkdownRemark.fields.slug,
        component: path.resolve('./src/templates/collection.js'),
        context: {
          slug: node.childMarkdownRemark.fields.slug,
        },
      });
    });
  })

  const posts = graphql(`
    query {
      allFile(filter: {relativeDirectory: {eq: "posts"}}) {
        edges {
          node {
            childMarkdownRemark {
              fields {
                slug
              }
            }
          }
        }
      }
    }
  `).then(result => {
    result.data.allFile.edges.forEach(({ node }) => {
      createPage({
        path: node.childMarkdownRemark.fields.slug,
        component: path.resolve('./src/templates/post.js'),
        context: {
          slug: node.childMarkdownRemark.fields.slug,
        },
      });
    });
  })

  return Promise.all([collections, posts])
};