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Gatsby Node APIs

Gatsby gives plugins and site builders many APIs for controlling your site.

Async plugins

If your plugin performs async operations (disk I/O, database access, calling remote APIs, etc.) you must either return a promise or use the callback passed to the 3rd argument. Gatsby needs to know when plugins are finished as some APIs, to work correctly, require previous APIs to be complete first. See Debugging Async Lifecycles for more info.

// Promise API
exports.createPages = () => {
  return new Promise((resolve, reject) => {
    // do async work
  })
}

// Callback API
exports.createPages = (_, pluginOptions, cb) => {
  // do Async work
  cb()
}

If your plugin does not do async work, you can just return directly.

Usage

Implement any of these APIs by exporting them from a file named gatsby-node.js in the root of your project.

APIs


Reference

createPages
Source
12

Tell plugins to add pages. This extension point is called only after the initial sourcing and transformation of nodes plus creation of the GraphQL schema are complete so you can query your data in order to create pages.

See also the documentation for the action createPage.

Example

const path = require(`path`)

exports.createPages = ({ graphql, actions }) => {
  const { createPage } = actions
  const blogPostTemplate = path.resolve(`src/templates/blog-post.js`)
  // Query for markdown nodes to use in creating pages.
  // You can query for whatever data you want to create pages for e.g.
  // products, portfolio items, landing pages, etc.
  // Variables can be added as the second function parameter
  return graphql(`
    query loadPagesQuery ($limit: Int!) {
      allMarkdownRemark(limit: $limit) {
        edges {
          node {
            frontmatter {
              slug
            }
          }
        }
      }
    }
  `, { limit: 1000 }).then(result => {
    if (result.errors) {
      throw result.errors
    }

    // Create blog post pages.
    result.data.allMarkdownRemark.edges.forEach(edge => {
      createPage({
        // Path for this page — required
        path: `${edge.node.frontmatter.slug}`,
        component: blogPostTemplate,
        context: {
          // Add optional context data to be inserted
          // as props into the page component..
          //
          // The context data can also be used as
          // arguments to the page GraphQL query.
          //
          // The page "path" is always available as a GraphQL
          // argument.
        },
      })
    })
  })
}

createPagesStatefully
Source

Like createPages but for plugins who want to manage creating and removing pages themselves in response to changes in data not managed by Gatsby. Plugins implementing createPages will get called regularly to recompute page information as Gatsby’s data changes but those implementing createPagesStatefully will not.

An example of a plugin that uses this extension point is the plugin gatsby-plugin-page-creator which monitors the src/pages directory for the adding and removal of JS pages. As its source of truth, files in the pages directory, is not known by Gatsby, it needs to keep its own state about its world to know when to add and remove pages.

createResolvers
Source

Add custom field resolvers to the GraphQL schema.

Allows adding new fields to types by providing field configs, or adding resolver functions to existing fields.

Things to note:

  • Overriding field types is disallowed, instead use the createTypes action. In case of types added from third-party schemas, where this is not possible, overriding field types is allowed.
  • New fields will not be available on filter and sort input types. Extend types defined with createTypes if you need this.
  • In field configs, types can be referenced as strings.
  • When extending a field with an existing field resolver, the original resolver function is available from info.originalResolver.
  • The createResolvers API is called as the last step in schema generation. Thus, an intermediate schema is made available on the schema property. In resolver functions themselves, it is recommended to access the final built schema from info.schema.
  • Gatsby’s data layer, including all internal query capabilities, is exposed on context.nodeModel. The node store can be queried directly with getAllNodes, getNodeById and getNodesByIds, while more advanced queries can be composed with runQuery. Note that runQuery will call field resolvers before querying, so e.g. foreign-key fields will be expanded to full nodes. The other methods on nodeModel don’t do this.
  • It is possible to add fields to the root Query type.
  • When using the first resolver argument (source in the example below, often also called parent or root), take care of the fact that field resolvers can be called more than once in a query, e.g. when the field is present both in the input filter and in the selection set. This means that foreign-key fields on source can be either resolved or not-resolved.

For fuller examples, see using-type-definitions.

Parameters

  • destructured object
    • schema GraphQLSchema

      Current GraphQL schema

    • createResolvers function

      Add custom resolvers to GraphQL field configs

  • $1 object
    • resolvers object

      Resolvers from plugin options in gatsby-config.js.

Example

exports.createResolvers = ({ createResolvers }) => {
  const resolvers = {
    Author: {
      fullName: {
        resolve: (source, args, context, info) => {
          return source.firstName + source.lastName
        }
      },
    },
    Query: {
      allRecentPosts: {
        type: [`BlogPost`],
        resolve: (source, args, context, info) => {
          const posts = context.nodeModel.getAllNodes({ type: `BlogPost` })
          const recentPosts = posts.filter(
            post => post.publishedAt > Date.UTC(2018, 0, 1)
          )
          return recentPosts
        }
      }
    }
  }
  createResolvers(resolvers)
}

generateSideEffects

Tell plugins with expensive “side effects” from queries to start running those now. This is a soon-to-be-replaced API only currently in use by gatsby-plugin-sharp.

onCreateBabelConfig
Source
1234

Let plugins extend/mutate the site’s Babel configuration. This API will change before 2.0 as it needs still to be converted to use Redux actions.

onCreateDevServer
Source

Run when gatsby develop server is started, its useful to add proxy and middleware to the dev server app

Parameters

  • destructured object

Example

exports.onCreateDevServer = ({ app }) => {
  app.get('/hello', function (req, res) {
    res.send('hello world')
  })
}

onCreateNode
Source

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

Example

exports.onCreateNode = ({ node, actions }) => {
  const { createNode, createNodeField } = actions
  // Transform the new node here and create a new node or
  // create a new node field.
}

onCreatePage
Source

Called when a new page is created. This extension API is useful for programmatically manipulating pages created by other plugins e.g. if you want paths without trailing slashes.

See the guide Creating and Modifying Pages for more on this API.

onCreateWebpackConfig
Source

Let plugins extend/mutate the site’s webpack configuration.

See also the documentation for setWebpackConfig.

Parameters

  • destructured object
    • stage string

      The current build stage. One of ‘develop’, ‘develop-html’, ‘build-javascript’, or ‘build-html’

    • getConfig function

      Returns the current webpack config

    • rules object

      A set of preconfigured webpack config rules

    • loaders object

      A set of preconfigured webpack config loaders

    • plugins object

      A set of preconfigured webpack config plugins

    • actions object

Example

exports.onCreateWebpackConfig = ({
 stage, getConfig, rules, loaders, actions
}) => {
  actions.setWebpackConfig({
    module: {
      rules: [
        {
          test: 'my-css',
          use: [loaders.style(), loaders.css()]
        },
      ],
    },
  });
}

onPostBootstrap
Source

Called at the end of the bootstrap process after all other extension APIs have been called.

onPostBuild
Source

The last extension point called after all other parts of the build process are complete.

onPreBootstrap
Source

Called once Gatsby has initialized itself and is ready to bootstrap your site.

onPreBuild
Source

The first extension point called during the build process. Called after the bootstrap has completed but before the build steps start.

onPreExtractQueries
Source

Run before GraphQL queries/fragments are extracted from JavaScript files. Useful for plugins to add more JavaScript files with queries/fragments e.g. from node_modules.

See gatsby-transformer-sharp and gatsby-source-contentful for examples.

onPreInit
Source

The first API called during Gatsby execution, runs as soon as plugins are loaded, before cache initialization and bootstrap preparation.

preprocessSource
Source

Ask compile-to-js plugins to process source to JavaScript so the query runner can extract out GraphQL queries for running.

resolvableExtensions
Source

Lets plugins implementing support for other compile-to-js add to the list of “resolvable” file extensions. Gatsby supports .js and .jsx by default.

Return value

string[]

array of extensions

setFieldsOnGraphQLNodeType
Source

Called during the creation of the GraphQL schema. Allows plugins to add new fields to the types created from data nodes. It will be called separately for each type.

This function should return an object in the shape of GraphQLFieldConfigMap which will be appended to fields inferred by Gatsby from data nodes.

Note: Import GraphQL types from gatsby/graphql and don’t add the graphql package to your project/plugin dependencies to avoid Schema must contain unique named types but contains multiple types named errors. gatsby/graphql exports all builtin GraphQL types as well as the graphQLJSON type.

Many transformer plugins use this to add fields that take arguments.

Parameters

  • destructured object
    • type object

      Object containing name and nodes

Example

import { GraphQLString } from "gatsby/graphql"

exports.setFieldsOnGraphQLNodeType = ({ type }) => {
  if (type.name === `File`) {
    return {
      newField: {
        type: GraphQLString,
        args: {
          myArgument: {
            type: GraphQLString,
          }
        },
        resolve: (source, fieldArgs) => {
          return `Id of this node is ${source.id}.
                  Field was called with argument: ${fieldArgs.myArgument}`
        }
      }
    }
  }

  // by default return empty object
  return {}
}

sourceNodes
Source

Extension point to tell plugins to source nodes. This API is called during the Gatsby bootstrap sequence. Source plugins use this hook to create nodes. This API is called exactly once per plugin (and once for your site’s gatsby-config.js file). If you define this hook in gatsby-node.js it will be called exactly once after all of your source plugins have finished creating nodes.

See also the documentation for createNode.

Example

exports.sourceNodes = ({ actions, createNodeId, createContentDigest }) => {
  const { createNode } = actions

  // Data can come from anywhere, but for now create it manually
  const myData = {
    key: 123,
    foo: `The foo field of my node`,
    bar: `Baz`
  }

  const nodeContent = JSON.stringify(myData)

  const nodeMeta = {
    id: createNodeId(`my-data-${myData.key}`),
    parent: null,
    children: [],
    internal: {
      type: `MyNodeType`,
      mediaType: `text/html`,
      content: nodeContent,
      contentDigest: createContentDigest(myData)
    }
  }

  const node = Object.assign({}, myData, nodeMeta)
  createNode(node)
}
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