Object Mapping

Zero-cost compile-time object mapping and transformation. Inspired by Scala's Chimney.

Quick Start

npm install @typesugar/mapper

import { transformInto } from "@typesugar/mapper";

interface User {
  first_name: string;
  last_name: string;
  age: number;
}

interface UserDTO {
  firstName: string;
  lastName: string;
  age: number;
  role: string;
}

const user: User = { first_name: "John", last_name: "Doe", age: 30 };

const dto = transformInto<User, UserDTO>(user, {
  rename: {
    firstName: "first_name",
    lastName: "last_name",
  },
  const: {
    role: "user",
  },
});

// dto is { firstName: "John", lastName: "Doe", age: 30, role: "user" }

Features

• Zero-cost — All transformations are evaluated at compile time and inlined
• Type-safe — Compile-time validation. Fails build if a target field is not mapped
• No decorators needed — Works with plain interfaces and types

How It Works

The macro analyzes source and target types at compile time:

1. Fields with matching names are copied automatically
2. rename maps target field names to source field names
3. const provides constant values for fields not in the source
4. Missing mappings cause compile-time errors

Learn More

• API Reference
• Package README