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Gatsby Typescript Plugin

An alternative to the official typescript plugin, with ts-loader & automatic type generation for your graphql queries (using graphql-code-generator)


Installation

yarn add typescript gatsby-plugin-ts

Add this to your gatsby config like any other plugins:

// gatsby-config.js
module.exports = {
  plugins: [
    `gatsby-plugin-ts`,
  ]
}

Unlike the official plugin, you’d have to bring your own tsconfig.json.

# generate a tsconfig if you have none
tsc --init

In order for this plugin to work right, you’d need to set your compile options like the following:

  "compilerOptions": {
    "target": "ESNext",    /* or at least ES2015 */
    "module": "ESNext",    /* or at least ES2015 */
    "lib": ["dom"],             /* <-- required! */
    "jsx": "preserve",          /* <-- required! */
    "moduleResolution": "node", /* <-- required! */

    /* for mixed ts/js codebase */
    "allowJS": true,
    "outDir": "./build"    /* this won't be used by ts-loader */
    /* other options... */
  }

Options

key default value
typecheck options
options.tsLoader {} option to be passed into ts-loader. transpileOnly is always true, since typechecking is handled by fork-ts-checker-webpack-plugin. See ts-loader docs for more
options.alwaysCheck false ⚠️deprecated
By default type checking is disabled in production mode (during gatsby build). Set this to true to enable type checking in production as well
options.typeCheck true Enable / disable type checking with fork-ts-checker-webpack-plugin.
options.forkTsCheckerPlugin {} Options that’ll be passed to fork-ts-checker-webpack-plugin. For all options, please see their docs
codegen options
options.codegen true enable / disable generating definitions for graphql queries
options.documentPaths
[’./src/**/*.{ts,tsx}‘,
’./.cache/fragments/*.js’,
’./node_modules/gatsby-*/**/*.js’]
The paths to files containing graphql queries.
⚠️ The default paths will be overwritten by the documentPaths you pass in, so please make sure to include all necessary paths ⚠️
options.fileName graphql-type.ts path to the generated file. By default, it’s placed at the project root directory & it should not be placed into src, since this will create an infinite loop
options.codegenDelay 200 amount of delay from file change to codegen

An example setup:

// gatsby-config.js
{
  resolve: `gatsby-plugin-ts`,
  options: {
    tsLoader: {
      logLevel: 'warn',
    },
    forkTsCheckerPlugin: {
      eslint: true,
    },
    fileName: `types/graphql-types.ts`,
    codegen: true,
    codegenDelay: 250,
    alwaysCheck: false,
  }
},

Gatsby files

  • gatsby-config has to be a .js file
  • gatsby-node is run directly by node, so it has to be a .js file as well. It is a shame, because in a complicated Gatsby app it is where a lot of logic live & will benefit from ts. As a work around, it can be built with tsc independently, in a script in package.json or somehow in gatsby’s pre-init hook.
  • Gatsby’s global variable like __PATH_PREFIX__ can be handled by declaring this code somewhere:
// src/global.d.ts
declare const __PATH_PREFIX__: string

Code generation

By default, this plugin will build typing for your queries automatically to graphql-types.d.ts on every edit. Please note that the definition file should not be placed inside src since this triggers a never ending loop during development.

In order to take advantage of the generated code, user needs to name their query:

// src/pages/index.tsx

  export const pageQuery = graphql`
-   query {
+   query BlogIndex {
      site {
        siteMetadata {
          title
        }
      }
  ...

…and import it from the generated type file:

// src/pages/index.tsx

import { BlogIndexQuery } from '../graphqlTypes'

interface IBlogIndexProps {
  data: BlogIndexQuery;
  location: Location;
}

const BlogIndex: React.FC<IBlogIndexProps> = ({ data, location }) => {
  ...
}

Disable type checking in production

Previously this plugin disable type checking in production by default, which can be changed by setting alwaysCheck to true. Since 2.0.0 it no longer does this. If you want to preseve the previous behavior, please set the typeCheck option like below:

{
  resolve: 'gatsby-plugin-ts',
  options: {
    // Disable type checking in production
    typeCheck: process.env.NODE_ENV !== 'production',
  }
}

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