TypeGraphQL reflection (PoC)

Proof of concept of an enhanced reflection system for TypeScript.

How it works?

I uses a custom transform plugin and TS compiler API with a bit of help from ts-morph to read deeply nested generic types info for GraphQL schema making purposes.

What does it do?

It can read type definitions of this class declaration:

@ObjectType
export class Sample {
  @Field
  dateField!: Date;

  @Field
  optionalStringField?: string;

  @Field
  optionalStringArrayField?: string[];

  @Field
  nullableStringArrayField!: Array<string | null>;

  @Field
  nullableStringPromiseField!: Promise<string | null>;

  @Field
  nullableStringNullableArrayPromiseField!: Promise<Array<string | null> | null>;
}

And emit that metadata, which then allows to read and transform them into this GraphQL type definition (SDL):

type Sample {
  dateField: Date!
  optionalStringField: String
  optionalStringArrayField: [String!]
  nullableStringArrayField: [String]!
  nullableStringPromiseField: String
  nullableStringNullableArrayPromiseField: [String]
}

How to run it?

You can run the example by npm start - it will run a ts-node with a special ttypescript compiler flag (ts-node -C ttypescript src/example/index.ts) that allows to apply the plugins defined in tsconfig.json during the TS files transpilation.

The transform plugin files are located in src/transformer directory. The example code (class source file and reading the metadata) are in src/example folder and the related supporting code is in src/helpers dir. In src/sdl you can find some simple helpers for creating GraphQL type SDL string for this demo purposes.

Further work

This proof of concept supports only basic subset of types - primitive types, array, nullability.

There is a lot of work to do next, both on the reflection plugin side and the TypeGraphQL core side.

If you like this idea of making TypeGraphQL easier to use without all the additional boilerplate, please consider supporting the project and our development efforts!