@spilne/perfect-swc-plugin

SWC WASM plugin that desugars Perfect's eff(($) => ...) syntax to .flatMap chains at compile time, with source maps.

Build

From the repo root:

bun run build:swc

The build compiles crates/swc-plugin-perfect/ to WebAssembly and copies the output to dist/plugin.wasm in this package.

Usage

The WASM file lives at packages/swc-plugin/dist/plugin.wasm after bun run build:swc.

Inside this repo (file path)

Point directly at the built file — no npm install needed:

// next.config.js / vite.config.ts / etc.
const PLUGIN = new URL("./packages/swc-plugin/dist/plugin.wasm", import.meta.url).pathname;

After publishing or npm link (package import)

Once this package is on npm or linked into node_modules/@spilne/perfect-swc-plugin:

// Next.js
import { createRequire } from "module";
const require = createRequire(import.meta.url);

export default {
  experimental: {
    swcPlugins: [[require.resolve("@spilne/perfect-swc-plugin"), {}]],
  },
};

// Vite
import swc from "unplugin-swc";
import { createRequire } from "module";
const require = createRequire(import.meta.url);

export default {
  plugins: [
    swc.vite({
      jsc: {
        experimental: {
          plugins: [[require.resolve("@spilne/perfect-swc-plugin"), {}]],
        },
      },
    }),
  ],
};

Local link (between projects on your machine)

cd packages/swc-plugin && npm link
cd /path/to/your-other-project && npm link @spilne/perfect-swc-plugin

What it handles

• eff(($) => { const x = $(e); return x }) → e.flatMap((x) => succeed(x))
• Object & array destructuring in binds: const { a, b } = $(e), const [x, y] = $(e)
• if/else branches containing $() become a ternary between two effect branches
• Expression-body shorthand: eff(($) => $(e)) and eff(($) => 42)
• Non-$ statements wrapped in sync() automatically
• Source maps preserved — spans flow from the driving statements to generated nodes

What it does not handle

• for { x <- e } yield expr — this is source-text rewriting, not AST. Use @spilne/perfect-transform (the Bun plugin / preload) for that.

See docs/transform-pipeline.md at the repo root for the full picture.