Is there a way to query/gain access to other markdown files/nodes when resolving a Graphql query?

Is there a way to query/gain access to other markdown files/nodes when resolving a Graphql query?

I have pages as markdown files with a front matter field for a list of widget names. These widgets are markdown files of their own with a bunch of front-matter fields that I will use as props in a react component.

I have all of the widgets in a separate folder and am not directly using them to create pages. What I would like to do is create a query that functions like this:

{
    allMarkdownRemark(filter: { fileAbsolutePath: {regex : "/src\/pages/"} }) {
        edges {
            node {
                excerpt(pruneLength: 400)
                html
                id
                frontmatter {
                    templateKey
                    path
                    date
                    title
                    // This frontmatter widgetlist has the names of the markdown files that I need to resolve the widgetList on the node.
                    widgetList {
                        widget 
                    }
                }
                widgetList {
                    widget {
                        widgetStyle
                        isCenter
                        isFullWidth
                    }
                }
            }
        }
    }
}

I am currently stuck because I have the names of the widgets that are supposed to be on each page in the front matter, but to resolve the widgetList type, I need to to find the markdown nodes in question in the page-components folder.

I used the code from gatsby-transformer-remark to get started creating my custom plugin in plugins/markdown-extender. Gatsby-transformer-remark has a file extend-node-type.js which I have been modifying. But a lot of this code is completely foreign to me other than the Graphql bits. @KyleAMathews would you be able to shed some light on this so I can start digging in a better direction? That would be much appreciated!

Here’s a link to the repo: https://github.com/luczaki114/Lajkonik-Gatsby-NetlifyCMS-Site

[pieh]

Oh, we currently only map to ids. But we can make it work with some additional custom code in gatsby-node.js:

// we use sourceNodes instead of onCreateNode because at this time plugins
// will have created all nodes already and we can link both books to authors
// and reverse link on authors to books
exports.sourceNodes = ({ boundActionCreators, getNodes, getNode }) => {
  const { createNodeField } = boundActionCreators

  const booksOfAuthors = {}
  // iterate thorugh all markdown nodes to link books to author
  // and build author index
  const markdownNodes = getNodes()
    .filter(node => node.internal.type === `MarkdownRemark`)
    .forEach(node => {
      if (node.frontmatter.author) {
        const authorNode = getNodes().find(
          node2 =>
            node2.internal.type === `MarkdownRemark` &&
            node2.frontmatter.title === node.frontmatter.author
        )

        if (authorNode) {
          createNodeField({
            node,
            name: `author`,
            value: authorNode.id,
          })

          // if it's first time for this author init empty array for his books
          if (!(authorNode.id in booksOfAuthors)) {
            booksOfAuthors[authorNode.id] = []
          }
          // add book to this author
          booksOfAuthors[authorNode.id].push(node.id)
        }
      }
    })

  Object.entries(booksOfAuthors).forEach(([authorNodeId, bookIds]) => {
    createNodeField({
      node: getNode(authorNodeId),
      name: `books`,
      value: bookIds,
    })
  })
}

and in your gatsby-config.js use this mapping config:

  mapping: {
    'MarkdownRemark.fields.author': `MarkdownRemark`,
    'MarkdownRemark.fields.books': `MarkdownRemark`,
  },

and example query:

{
  markdownRemark(frontmatter: {title: {eq: "New Beginnings"}}) {
    id
    frontmatter {
      title
    }
    # author 
    fields {
      author {
        frontmatter {
          title
        }
        # all books of author
        fields {
          books {
            frontmatter {
              title
            }
          }
        }
      }
    }
  }
}

[pieh]

There’s always room for improvement for sure. I’m currently working on schema related things and will add this to my list (why that list is only growing and not getting smaller 😠 ).

Way to to be able to specify on what field to we should link nodes would indeed be great as current mapping is best suited for json/yaml data (where we define id ourselves) or for programmatic solution (like one I pasted above). It would be great to do something like:

'MarkdownRemark.fields.author': {
  type: `MarkdownRemark`,
  fieldToJoinOn: 'frontmatter.title'
}