mercurius-codegen

mercurius-codegen

Get full type-safety and autocompletion for Mercurius using TypeScript and GraphQL Code Generator seamlessly while you code.

pnpm add mercurius-codegen
# or
yarn add mercurius-codegen
# or
npm install mercurius-codegen

Usage

For convenience, this package also exports a fake gql tag that gives tooling support for "prettier formatting" and "IDE syntax highlighting". It's completely optional.

import Fastify from 'fastify'
import mercurius from 'mercurius'
import mercuriusCodegen, { gql } from 'mercurius-codegen'

const app = Fastify()

app.register(mercurius, {
  schema: gql`
    type Query {
      hello(greetings: String!): String!
    }
  `,
  resolvers: {
    Query: {
      hello(_root, { greetings }) {
        // greetings ~ string
        return 'Hello World'
      },
    },
  },
})

mercuriusCodegen(app, {
  targetPath: './src/graphql/generated.ts',
}).catch(console.error)

// Then it will automatically generate the file,
// and without doing anything special,
// the resolvers are going to be typed,
// or if your resolvers are in different files...

app.listen(8000)

import { IResolvers } from 'mercurius'

// Fully typed!
export const resolvers: IResolvers = {
  Query: {
    hello(_root, { greetings }) {
      // greetings ~ string
      return 'Hello World'
    },
  },
}

It also gives type-safety for Mercurius Loaders:

import { MercuriusLoaders } from 'mercurius'

// Fully typed!
export const loaders: MercuriusLoaders = {
  Dog: {
    async owner(queries, ctx) {
      // queries & ctx are typed accordingly
      return queries.map(({ obj, params }) => {
        // obj & params are typed accordingly
        return owners[obj.name]
      })
    },
  },
}

By default it disables itself if NODE_ENV is 'production'

It automatically uses prettier resolving the most nearby config for you.

Operations

mercurius-codegen also supports giving it GraphQL Operation files, basically client queries, mutations or subscriptions, and it creates Typed Document Nodes, that later can be used by other libraries, like for example mercurius-integration-testing (that has native support for typed document nodes), and then be able to have end-to-end type-safety and auto-completion.

You might need to install @graphql-typed-document-node/core manually in your project.

import mercuriusCodegen from 'mercurius-codegen'

mercuriusCodegen(app, {
  targetPath: './src/graphql/generated.ts',
  // You can also specify an array of globs
  operationsGlob: './src/graphql/operations/*.gql',
}).catch(console.error)

/your-project/src/graphql/operations/example.gql

query hello {
  HelloWorld
}

Then, for example, in your tests:

import { createMercuriusTestClient } from 'mercurius-integration-testing'

import { helloDocument } from '../src/graphql/generated'
import { app } from '../src/server'

// ...

const client = createMercuriusTestClient(app)

const response = await client.query(helloDocument)

// response is completely typed!

Keep in mind that you can always call mercuriusCodegen multiple times for different environments and different paths if you prefer to keep the production code as light as possible (which is generally a good practice).

Options

There are a couple extra options that can be specified:

interface CodegenMercuriusOptions {
  /**
   * Specify the target path of the code generation.
   *
   * Relative to the directory of the executed script if targetPath isn't absolute
   * @example './src/graphql/generated.ts'
   */
  targetPath: string
  /**
   * Disable the code generation manually, by default it's `process.env.NODE_ENV === 'production'`
   */
  disable?: boolean
  /**
   * Don't notify to the console
   */
  silent?: boolean
  /**
   * Specify GraphQL Code Generator configuration
   * @example
   * codegenConfig: {
   *    scalars: {
   *        DateTime: "Date",
   *    },
   *    defaultMapper: "DeepPartial<{T}>"
   * }
   * @default
   * codegenConfig: {
   *    defaultMapper: "DeepPartial<{T}>"
   * }
   */
  codegenConfig?: CodegenPluginsConfig
  /**
   * Add code in the beginning of the generated code
   */
  preImportCode?: string
  /**
   * Operations glob patterns
   */
  operationsGlob?: string[] | string
}

mercuriusCodegen(app, {
  targetPath: './src/graphql/generated.ts',
  operationsGlob: ['./src/graphql/operations/*.gql'],
  disable: false,
  silent: true,
  codegenConfig: {
    scalars: {
      DateTime: 'Date',
    },
    defaultMapper: 'DeepPartial<{T}>',
  },
  preImportCode: `
  // Here you can put any code and it will be added at very beginning of the file
  `,
}).catch(console.error)

License

MIT