Rust Setup

Create a new Rust crate that will contain your custom macros. It compiles to WebAssembly, packaged as an npm package that Macroforge loads.

Prerequisites

A Rust toolchain with the WebAssembly target: rustup target add wasm32-unknown-unknown
The Macroforge CLI: cargo install macroforge_ts
wasm-bindgen-cli at the version of the wasm-bindgen crate your macro crate builds with. After adding macroforge_ts below, cargo tree -i wasm-bindgen --depth 0 prints it; install that version with cargo install wasm-bindgen-cli --version <version> --locked.

Create the Project

Bash

cargo new --lib my-macros
cd my-macros

Configure Cargo.toml

Cargo.toml

[package]
name = "my-macros"
version = "0.1.0"
edition = "2024"

[lib]
crate-type = ["cdylib", "rlib"]

[dependencies]
macroforge_ts = "0.4"

[profile.release]
lto = true
strip = true

Create src/lib.rs

src/lib.rs

use macroforge_ts::macros::{ts_macro_derive, ts_template};
use macroforge_ts::ts_syn::{
    Data, DeriveInput, MacroforgeError, TsStream, parse_ts_macro_input,
};

#[ts_macro_derive(
    JSON,
    description = "Generates toJSON() returning a plain object"
)]
pub fn derive_json(mut input: TsStream) -> Result<TsStream, MacroforgeError> {
    let input = parse_ts_macro_input!(input as DeriveInput);

    match &input.data {
        Data::Class(class) => {
            Ok(ts_template!(Within {
                toJSON(): Record<string, unknown> {
                    return {
                        {#for field in class.field_names()}
                            @{field}: this.@{field},
                        {/for}
                    };
                }
            }))
        }
        _ => Err(MacroforgeError::new(
            input.decorator_span(),
            "@derive(JSON) only works on classes",
        )),
    }
}

Create package.json

macroforge build writes the package into pkg/, named after the library target: my_macros for this crate.

package.json

{
  "name": "@my-org/macros",
  "version": "0.1.0",
  "main": "pkg/my_macros.js",
  "types": "pkg/my_macros.d.ts",
  "files": ["pkg"],
  "scripts": {
    "build": "macroforge build . --out pkg"
  }
}

Build the Package