Typescript Codegen

A Graphql-Codegen inspired approach to generate runtime code based on static types.

Usage

• Initialize: npx typescript-codegen init
• Run: npx typescript-codegen

Config

TBD, see initialized config file for now

Plugins

typeguards

The goal of this plugin is to write user defined type guards that duck type if an unknown is of a type.

Input:

type AmbigiousString = string | boolean;

interface Post {
  title: string;
  content: string;
  isFeatured: AmbigiousString;
  numberOfComments: number;
}
interface PostResponsePayload {
  timestamp?: string;
  items: Post[];
}

interface ApiResponse<T> {
  success: boolean;
  data: T;
}

// @ts-gen typeguards
type PostApiResponse = ApiResponse<PostResponsePayload>;

Output:

import { PostApiResponse } from "/path/to/src";
export function isPostApiResponse(data: unknown): data is PostApiResponse {
  return (
    typeof data === "object" &&
    typeof data.success === "boolean" &&
    typeof data.data === "object" &&
    (data.data.timestamp === undefined ||
      data.data.timestamp === null ||
      typeof data.data.timestamp === "string") &&
    data.data.items instanceof Array &&
    data.data.items.every(
      item =>
        typeof item.title === "string" &&
        typeof item.content === "string" &&
        (typeof item.isFeatured === "string" ||
          typeof item.isFeatured === "boolean") &&
        typeof item.numberOfComments === "number"
    )
  );
}

Plugin Development Guide

TBD

Roadmap

• Init generates a config file
• Embedded Plugin: duck-typing
• Embedded Plugin: decoder
• Documented plugin interface
• Watch mode
• Incremental buulds / caching