Fixing 'Cannot Query Field site' In Gatsby & WP GraphQL
Hey there, fellow developers! Ever hit that frustrating wall when you're working with Gatsby and WordPress, trying to query your site data, only to be slapped with a big, fat error message saying, "Cannot query field 'site' on type 'RootQuery'"? Yeah, it's a super common head-scratcher, especially when you're just getting started or diving deep into integrating these two powerful platforms. You're probably scratching your head, thinking, "But wait, I use site all the time in Gatsby! Why isn't it working now?" Well, guys, you're not alone, and today we're going to demystify this error, break down exactly why it happens, and most importantly, show you the right way to get that precious site data in your Gatsby projects, even when WordPress is in the mix. So, let's dive in and clear up this confusion once and for all, making your Gatsby + WordPress development a whole lot smoother!
Understanding the 'Cannot Query Field "site"' Error: A Tale of Two GraphQLs
Alright, let's kick things off by really understanding what that gnarly error message, "Cannot query field "site" on type "RootQuery".", actually means when you see it. When you're working with Gatsby and WordPress, you're essentially dealing with two distinct GraphQL layers, and this is where the confusion often originates. Think of it like this: Gatsby has its own internal GraphQL schema, which is incredibly powerful. This is the schema that gives you access to all sorts of Gatsby-specific data, including file system nodes, images processed by gatsby-plugin-image, and crucially, the site object. The site object is where Gatsby stores its own metadata, like your site's title, description, and other configurations you've defined in your gatsby-config.js file under siteMetadata. It's a core part of the Gatsby ecosystem, and querying it is fundamental to building a Gatsby site.
Now, on the other side of the fence, we have your WordPress site. When you install a GraphQL plugin for WordPress (like WPGraphQL, which is super popular for this kind of integration), it exposes a GraphQL API for your WordPress data. This API is designed to query posts, pages, custom post types, menus, media, and all the other goodies that live within your WordPress database. It creates its own RootQuery type, which is essentially the entry point for all queries related to your WordPress content. This RootQuery is fantastic for fetching wpMenu items, wpGatsby information (if you have a custom field for it), and all your content nodes. However, and this is the crucial distinction, this WordPress GraphQL RootQuery does not know anything about Gatsby's internal site object. It simply doesn't expose it, because it's not part of WordPress's data model. The WordPress GraphQL plugin's job is to give you access to WordPress data, not to mirror Gatsby's internal structure. So, when you try to run a query like site { siteMetadata { title } } within your WordPress GraphQL IDE, the WordPress server sees site, looks at its RootQuery type, and rightfully says, "Hey, I don't have a field called site here!" It's like asking for a screwdriver at a bakery – they might have tools, but not that specific tool for that specific job. This fundamental difference is often overlooked, leading to that pesky error. Understanding that these are separate (though interconnected via gatsby-source-wordpress) GraphQL environments is the first big step to resolving this common issue and becoming a Gatsby + WordPress pro. We’re talking about two separate worlds, guys, and they have their own rules!
Why You're Seeing This in Your WordPress GraphQL IDE: The Context Mismatch
So, let's dig a bit deeper into why you're specifically encountering this error when you're in your local WordPress site's GraphQL IDE, like GraphiQL or the GraphQL IDE plugin. It all boils down to a context mismatch. Imagine you're in a library, but you're asking for directions to a specific shop in a different city. The librarian might know a lot about books, but they won't have the map for that shop! Similarly, your WordPress GraphQL IDE is designed to interact solely with the GraphQL API exposed by your WordPress installation. It's purpose-built to let you explore and query the data that your WordPress site natively provides. This includes all your posts, pages, taxonomies, menus, and any custom data types you've set up within WordPress itself. It's a fantastic tool for validating and testing your WordPress data queries before you even bring Gatsby into the picture.
The critical point here, my friends, is that the site field, which contains siteMetadata and other Gatsby-specific configurations, is an integral part of Gatsby's own GraphQL schema. This schema is dynamically generated by Gatsby during its build or development process, pulling together data from all its various sources and plugins. When you include gatsby-source-wordpress in your Gatsby project, what it does is pull data from your WordPress GraphQL API, process it, and then integrate that WordPress data into Gatsby's larger GraphQL schema. It doesn't, however, somehow inject Gatsby's own site object back into your WordPress GraphQL API. That's not how the data flow works. The WordPress GraphQL server, and by extension its IDE, has no idea about the site object because it doesn't originate from WordPress content. It's a construct created and managed entirely by Gatsby itself.
So, when you type query HeaderQuery { site { siteMetadata { title } } } into your WordPress GraphQL IDE, the IDE sends that query to your WordPress GraphQL endpoint. That endpoint then tries to resolve site against its own schema, which, as we've discussed, is a RootQuery type focused purely on WordPress data. Since site is not a recognized field on WordPress's RootQuery type, the WordPress GraphQL server throws that error: "Cannot query field site on type RootQuery." It's essentially telling you, "Hey, you're asking for something I don't provide within my data model." This separation is by design and is actually quite logical once you grasp the distinct roles of each GraphQL layer. You're trying to access Gatsby-specific data from a WordPress-specific context, and that's the core of the problem. Remember, the WordPress GraphQL IDE is for WordPress data, while Gatsby's GraphQL playground (localhost:8000/__graphql) is for Gatsby's aggregated data, which includes both WordPress and Gatsby's internal nodes. Keep these contexts straight, and you'll save yourself a lot of debugging headaches!
The Right Way to Query Site Data in Gatsby: Using Gatsby's GraphQL Playground
Alright, now that we've properly understood why you're hitting that brick wall in the WordPress GraphQL IDE, let's pivot to the correct and effective way to query your site data. The solution, my friends, is surprisingly straightforward: you must query the site object within your Gatsby project's own GraphQL environment. This means running your Gatsby development server and using its built-in GraphQL playground, typically found at http://localhost:8000/__graphql (assuming you're running Gatsby locally on port 8000). This is the magical place where Gatsby's entire aggregated schema lives, including all your WordPress data (pulled in by gatsby-source-wordpress) and all the Gatsby-specific nodes, like site, allFile, allImageSharp, and so on.
When you open localhost:8000/__graphql in your browser, you'll see a robust GraphQL IDE that looks very similar to the one you might be using for WordPress. The key difference, however, is the schema it's querying. This IDE is directly connected to Gatsby's GraphQL server, which has meticulously built a unified schema from all your data sources. So, when you enter a query there, it knows exactly how to resolve site because it's part of its own native schema. Here’s how you'd correctly structure that query:
query HeaderQuery {
site {
siteMetadata {
title
description
author
}
}
}
This query, when executed in Gatsby's GraphQL playground, will successfully return your site's title, description, and author (or whatever fields you've defined in siteMetadata within your gatsby-config.js). It will work perfectly because you're asking the right GraphQL server for the right data. You can even expand this to include other Gatsby-specific data, such as querying for images or file nodes.
Furthermore, when you're building your Gatsby components, you'll use this exact query structure within either a StaticQuery (for non-page components that don't need props) or a page query (for pages that might also need dynamic data based on their path). For example, in a React component in Gatsby, you might do something like this:
import React from "react"
import { useStaticQuery, graphql } from "gatsby"
const Header = () => {
const data = useStaticQuery(graphql`
query SiteTitleQuery {
site {
siteMetadata {
title
}
}
}
`)
return (
<header>
<h1>{data.site.siteMetadata.title}</h1>
</header>
)
}
export default Header
This pattern is the standard and expected way to access Gatsby's site data within your project. Remember, the WordPress GraphQL IDE is for testing what WordPress offers directly, while Gatsby's GraphQL IDE is for testing what Gatsby itself offers, which includes both its own native data and all the external data it has successfully sourced. By shifting your querying context to Gatsby's playground, you're aligning with the correct architecture and making site data readily available for your Gatsby builds. It’s all about putting your queries in the right place, guys!
Integrating WordPress Data with Gatsby Site Data: The Unified Query
Now that we've nailed down how to correctly query Gatsby's site data, let's talk about the real magic: combining your WordPress data with your Gatsby site data in a single, unified query. This is where gatsby-source-wordpress truly shines, and it's the core reason why many of us choose this powerful stack. The beauty of Gatsby is its ability to pull data from multiple sources – whether it's Markdown files, APIs, local JSON, or in our case, a WordPress installation – and then stitch it all together into one cohesive GraphQL schema. This means you don't have to run separate queries from different GraphQL endpoints; you can get everything you need with one efficient request, from Gatsby's GraphQL layer.
Think about it: for your HeaderQuery, you initially wanted site { siteMetadata { title } } and `wpMenu(name: {eq: