GraphQL TypeScript - w/ GraphQL-Modules and GraphQL-Code-Generator

This article was published on Tuesday, December 4, 2018 by Arda Tanrikulu @ The Guild Blog

Last year we've released GraphQL-Modules — which applies modular
approach to large scale, GraphQL-based applications.

We've also released a new version of GraphQL Code Generator
which generates server-side typings and signatures for resolvers from GraphQL Schemas.

Those are two separate projects, but because we use both in production across many different
applications, we wanted to write about the benefits of the tight integration of those projects and
how it provides us with great development experience while implementing our projects in TypeScript.

GraphQL Code Generator can take a JS/TS export from GraphQL-Modules to generate server-side typings
(or anything else that its plugins can generate). So,
let's export typeDefs without any business logic that includes resolvers, DI, providers etc…

You can create a schema.ts file to expose typeDefs to GraphQL Code Generator:

```ts filename="schema.ts"
import { AppModule } from './modules/app'

export default AppModule.typeDefs

// If your module needs a configuration

export default AppModule.forRoot({ ...dummyConfiguration }).typeDefs

Create a `codegen.yml` config file, including `schema.ts` as a schema source, and generate
[common](https://graphql-code-generator.com/docs/plugins/typescript-common) and
[server](https://graphql-code-generator.com/docs/plugins/typescript-server) typings for TypeScript.
We use `transpile-only` to prevent errors related to TypeScript on typing generation phase to let
`ts-node` handle this on running the actual application.



```yaml filename="codegen.yml"
overwrite: true
schema: ./src/schema.ts
require:
  - ts-node/register/transpile-only
generates:
  ./src/generated-models.ts:
    plugins:
      - typescript
      - typescript-resolvers
    config:
      contextType: @graphql-modules/core#ModuleContext

We can add a script to package.json to run:

{
  //...
 "scripts": {
   //...
    "generate": "gql-gen",
    // You can use nodemon to watch changes on graphql files
    "generate:watch": "nodemon --exec yarn generate -e graphql",
   //...
 //...
}

Then, we can use these typings in our project. This example shows a resolvers handler that
implements resolvers for Query type with generated types.

import { IResolvers } from '../../generated-models'
import { UsersProvider } from '../providers/users.provider'

export default <IResolvers>{
  Query: {
    // all parameters and return value are typed
    users: (root, args, context, info) => context.injector.get(UsersProvider).getUsers(args)
  }
}

At the end, we have a strictly-typed backend project, based of separate feature modules, and each of
those modules uses GraphQL and TypeScript.

You can check our working example that is created by using this approach;
https://github.com/darkbasic/graphql-modules-seed

All Posts about GraphQL Modules

• GraphQL Modules — Feature based GraphQL Modules at scale
• Why is True Modular Encapsulation So Important in Large-Scale GraphQL Projects?
• Why did we implement our own Dependency Injection library for GraphQL-Modules?
• Scoped Providers in GraphQL-Modules Dependency Injection
• Writing a GraphQL TypeScript project w/ GraphQL-Modules and GraphQL-Code-Generator
• Authentication and Authorization in GraphQL (and how GraphQL-Modules can help)
• Authentication with AccountsJS & GraphQL Modules
• Manage Circular Imports Hell with GraphQL-Modules