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Gatsby Node APIs | Gatsby

Introduction

Gatsby gives plugins and site builders many APIs for building your site. Code in the file gatsby-node.js/gatsby-node.ts is run once in the process of building your site. You can use its APIs to create pages dynamically, add data into GraphQL, or respond to events during the build lifecycle. To use the Gatsby Node APIs, create a file named gatsby-node.js/gatsby-node.ts in the root of your site. Export any of the APIs you wish to use in this file.

You can author the file in JavaScript (CommonJS or ES Modules (ESM) syntax) or TypeScript.

Every Gatsby Node API gets passed a set of helper functions. These let you access several methods like reporting, or perform actions like creating new pages.

An example gatsby-node.js file that implements two APIs, onPostBuild, and createPages.

The TypeScript and Gatsby documentation shows how to set up a gatsby-node file in TypeScript.

Read the ES Modules (ESM) and Gatsby documentation if you don’t want to use CommonJS syntax.

Async vs. sync work

If your plugin performs async operations (disk I/O, database access, calling remote APIs, etc.) you must either return a promise (explicitly using Promise API or implicitly using async/await syntax) 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.

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

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APIs

Create pages dynamically. 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.

You can also fetch data from remote or local sources to create pages.

See also the documentation for the action createPage.

Parameters Return value

Promise<void>

No return value required, but the caller will await any promise that’s returned

Example
const path = require(`path`)

exports.createPages = ({ graphql, actions }) => {
  const { createPage } = actions
  const blogPostTemplate = path.resolve(`src/templates/blog-post.js`)
  
  
  
  
  return graphql(`
    query loadPagesQuery ($limit: Int!) {
      allMarkdownRemark(limit: $limit) {
        edges {
          node {
            frontmatter {
              slug
            }
          }
        }
      }
    }
  `, { limit: 1000 }).then(result => {
    if (result.errors) {
      throw result.errors
    }

    
    result.data.allMarkdownRemark.edges.forEach(edge => {
      createPage({
        
        path: `${edge.node.frontmatter.slug}`,
        component: blogPostTemplate,
        context: {
          
          
          
          
          
          
          
          
        },
      })
    })
  })
}

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.

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:

For fuller examples, see using-type-definitions.

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

Customize Gatsby’s GraphQL schema by creating type definitions, field extensions or adding third-party schemas.

The createTypes, createFieldExtension and addThirdPartySchema actions are only available in this API. For details on their usage please refer to the actions documentation.

This API runs immediately before schema generation. For modifications of the generated schema, e.g. to customize added third-party types, use the createResolvers API.

Parameters Example
exports.createSchemaCustomization = ({ actions }) => {
  const { createTypes, createFieldExtension } = actions

  createFieldExtension({
    name: 'shout',
    extend: () => ({
      resolve(source, args, context, info) {
        return String(source[info.fieldName]).toUpperCase()
      }
    })
  })

  const typeDefs = `
    type MarkdownRemark implements Node @dontInfer {
      frontmatter: Frontmatter
    }
    type Frontmatter {
      title: String!
      tagline: String @shout
      date: Date @dateformat
      image: File @fileByRelativePath
    }
  `
  createTypes(typeDefs)
}

Let plugins extend/mutate the site’s Babel configuration by calling setBabelPlugin or setBabelPreset.

Parameters Example
exports.onCreateBabelConfig = ({ actions }) => {
  actions.setBabelPlugin({
    name: `babel-plugin-that-i-like`,
    options: {}
  })
}

Run when the gatsby develop server is started. It can be used for adding proxies and Express middleware to the server.

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

The Creating a Source Plugin tutorial demonstrates a way a plugin or site might use this API.

Example
exports.onCreateNode = ({ node, actions }) => {
  const { createNode, createNodeField } = actions
  
  
}

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.

There is a mechanism in Gatsby to prevent calling onCreatePage for pages created by the same gatsby-node.js to avoid infinite loops/callback.

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

Source

Let plugins extend/mutate the site’s webpack configuration. This method can be used by any Gatsby site, app, or plugin, not just plugins.

See also the documentation for setWebpackConfig.

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

Lifecycle executed in each process (one time per process). Used to store actions etc for later use.

Example
let createJobV2
exports.onPluginInit = ({ actions }) => {
  
  createJobV2 = actions.createJobV2
}

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

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

Example
exports.onPostBuild = ({ reporter, basePath, pathPrefix }) => {
 reporter.info(
  `Site was built with basePath: ${basePath} & pathPrefix: ${pathPrefix}`
 );
};

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

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

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

Parameters Example
exports.onPreInit = ({ actions }) => {

}

Run during the bootstrap phase. Plugins can use this to define a schema for their options using Joi to validate the options users pass to the plugin.

Parameters Example
exports.pluginOptionsSchema = ({ Joi }) => {
  return Joi.object({
    
    anonymize: Joi.boolean().required(),
  })
}

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

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

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.

adds an “excerpt” field where the user when writing their query can specify how many characters to prune the markdown source to.

many image transformation options as GraphQL fields.

Parameters 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}`
        }
      }
    }
  }

  
  return {}
}

Called before scheduling a onCreateNode callback for a plugin. If it returns falsy then Gatsby will not schedule the onCreateNode callback for this node for this plugin. Note: this API does not receive the regular api that other callbacks get as first arg.

Example
exports.shouldOnCreateNode = ({node}, pluginOptions) => node.internal.type === 'Image'

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.

The Creating a Source Plugin tutorial demonstrates a way a plugin or site might use this API.

See also the documentation for createNode.

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

  
  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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