Gatsby Create Pages

Question

I am trying to create a gatsby site where I have projects posted, each with tags. I followed a basic tutorial on creating a gatsby blog, and am now working through gatsby's tags as documented on their website. Along the way while changing variable names from path to slug to avoid reserved words, I seem to have messed up because I can no longer create blogpost pages, nor tag pages. Each post is enclosed in a folder named by the post title, holding an index.md file defining its content, date, tag etc.

The following error is output when I try to run gatsby develop,

ERROR #11323

Your site's "gatsby-node.js" must set the page path when creating a page.

The page object passed to createPage:
{
    "slug": "/an-example-post",
    "component": "C:\\Users\\Monolith\\Documents\\programming\\webdev\\Gatsby-Portfolio\\src\\templates\\post.js",
    "context": {
        "slug": "/an-example-post"
    }
}

My gatsby-node.js

const path = require('path');

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

     const postTemplate = path.resolve('src/templates/post.js');
     const tagTemplate = path.resolve("src/templates/tags.js")
     //const postTemplate = require.resolve('src/templates/post.js');
     //const tagTemplate = require.resolve("src/templates/tags.js")
     
     return graphql(`{
        allMarkdownRemark{
            edges{
                node {
                    html
                    id
                    frontmatter{
                        slug
                        title
                    }
                }
            }
        }
    
        tagsGroup: allMarkdownRemark(limit: 2000) {
            group(field: frontmatter___tags) {
              fieldValue
            }
          }

    }`)
    .then(res => {
        if(res.errors){
            return Promise.reject(res.errors);
        }


        
        res.data.allMarkdownRemark.edges.forEach( ({node}) => {
            createPage({
                slug: node.frontmatter.slug,
                component: postTemplate,
                context: {
                    slug:node.frontmatter.slug
                },
            })
        })

          // Extract tag data from query
        const tags = res.data.tagsGroup.group

        // Make tag pages
        tags.forEach(tag => {
            createPage({
                // path: `/tags/${_.kebabCase(tag.fieldValue)}/`,
                slug: `/tags/${(tag.fieldValue)}/`,
                component: tagTemplate,
                context: {
                    tag: tag.fieldValue,
                },
            })
        })

    }) 
}

As previously mentioned I was concerned the path variable being a reserved word could be an issue, but I got further using it than omitting it so for now it has stayed.

Example post.js

import React from 'react';
import { graphql } from 'gatsby';
import Layout from "../components/layout"

export default function Template({data}) {
    const {markdownRemark: post} = data;

    return(
        <Layout>
        <div>
            <h1 className="postTitle">{post.frontmatter.title}</h1>
            <div className="tagGroup">
                {post.frontmatter.tags.map((tag, index) => (
                    <div key={index}>
                        <h2 className = "tagStyle">{tag}</h2>
                    </div>
                ))}
            </div>
            <p>{post.frontmatter.description}</p>
            <p>{post.frontmatter.date}</p>            
            {/* <h2 className="tagStyle">{post.frontmatter.tags + " "}</h2> */}
            <div dangerouslySetInnerHTML={{__html: post.html}} />
        </div>
        </Layout>
    )
}


export const postQuery = graphql`
    #query BlogPostByPath($slug: String!) {
    query($slug: String!) {
        markdownRemark(frontmatter: { slug: {eq: $slug} }) {
            html
            frontmatter {
                slug
                title
                description
                date
                tags
            }
        }
    }
`

The tags.js is very similar to gatsby's default with slight alterations for content. Here is the Graphql query I am using.

Tags.propTypes = {
  pageContext: PropTypes.shape({
    tag: PropTypes.string.isRequired,
  }),
  data: PropTypes.shape({
    allMarkdownRemark: PropTypes.shape({
      totalCount: PropTypes.number.isRequired,
      edges: PropTypes.arrayOf(
        PropTypes.shape({
          node: PropTypes.shape({
            frontmatter: PropTypes.shape({
              title: PropTypes.string.isRequired,
           //   slug: PropTypes.string.isRequired,
            }),
            fields: PropTypes.shape({
              slug: PropTypes.string.isRequired,
            }),
          }),
        }).isRequired
      ),
    }),
  }),
}

export default Tags

export const pageQuery = graphql`
  query($tag: String) {
    allMarkdownRemark(
      limit: 2000
      sort: { fields: [frontmatter___date], order: DESC }
      filter: { frontmatter: { tags: { in: [$tag] } } }
    ) {
      totalCount
      edges {
        node {
           fields {
             slug
           }
          frontmatter {
            title
          }
        }
      }
    }
  }
`

If anyone has any information to help point me in the right direction I would greatly appreciate it. I have been running through gatsby's documentation for hours and have yet to make substantial progress.

Answer 1

You are passing a tag in your context but expecting a slug:

    createPage({
        slug: `/tags/${(tag.fieldValue)}/`,
        component: tagTemplate,
        context: {
            tag: tag.fieldValue,
        },
    })

And:

   query($slug: String!) {}

The context is a way to pass data to your component template to use it to filter your data. Ideally should be a unique parameter (like a slug, id, etc). In that way, in your gatsby-node.js you should fetch all your posts, pass a unique field by context, and use that variable in your template to get all your needed data of each post.

In addition, you must provide a path, not a slug to your function.

You should change your createPage function to:

    createPage({
        path: `/tags/${tag.fieldValue}/`,
        component: tagTemplate,
        context: {
            slug: tag.fieldValue,
        },
    })

Keep in mind that fieldValue should be a slug (or kind of) despite having different naming.

I would recommmend reading Gatsby's tutorial: https://www.gatsbyjs.com/tutorial/part-seven/