@cassida/swc-plugin

SWC plugin (WASM) for Cassida. Detects cas() chains in JSX spreads, walks them into an Op[] IR, and emits the IR as a comment annotation that @cassida/next-plugin picks up and compiles against @cassida/compiler in a Node post-pass.

Status: Phase 1 scaffold. The current build ships a no-op transform. Subsequent releases will fill in the chain walker, modifier scopes, .set() / .unsafe() escape hatches, and JSX rewrite. See .claude/plans/swc-port-phase-1.md (local to maintainers) for the full design.

Why a SWC plugin

@cassida/parser (Babel-based) and @cassida/vite-plugin together give Vite users the full zero-runtime experience. Next.js's transform pipeline is SWC; injecting a Babel pass adds significant build cost. This package mirrors the Babel parser's behaviour in Rust so Next.js (Webpack + Turbopack) users get the same output without paying a Babel tax.

Architecture

The plugin emits an IR-as-comment, not a finished class name. A companion Node loader in @cassida/next-plugin reads the comment, calls compileOps() from @cassida/compiler, and substitutes the resulting cas-XXXXXXXX class. This keeps the compiler and hash function single-sourced in JS — Babel-parsed and SWC-parsed files always produce identical class names for the same chain.

Install

pnpm add -D @cassida/swc-plugin @cassida/next-plugin

Then in next.config.js:

import { withCassida } from '@cassida/next-plugin';

export default withCassida({ /* normal next config */ }, {
  /* cassida options */
});

You do not register @cassida/swc-plugin directly — withCassida() wires it into experimental.swcPlugins for you.

If you need the WASM path from JS (custom build setup, SWC CLI usage, esbuild, etc.):

// ESM
import { wasmPath } from '@cassida/swc-plugin/loader';

// CJS
const { wasmPath } = require('@cassida/swc-plugin/loader');

The package's main field also points at the WASM directly for SWC's built-in require.resolve() lookup of swcPlugins: [['@cassida/swc-plugin', ...]] shorthand.

Development

Requires Rust 1.91+ (rust-toolchain.toml at the repo root pins this) and the wasm32-wasip1 target.

pnpm build       # cargo build --release --target wasm32-wasip1
pnpm test        # cargo test (native target)
pnpm lint        # cargo clippy
pnpm fmt         # cargo fmt --check

License

MIT