README.md

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.