README.md

vite-plugin-zig

Import WebAssembly modules compiled from Zig files.

Prerequisites

• Install the Zig compiler: the binary can be downloaded from downloads page, or built from source by following the GitHub Wiki instructions, or using the zig-bootstrap scripts. As an alternative, the @ziglang/cli npm package can be added as a dependency, useful in a CI environment for instance.

Usage

Install with npm i -D vite-plugin-zig (or pnpm i -D or yarn i -D), then add the plugin to your vite.config.js:

// vite.config.js
import zig from 'vite-plugin-zig';

/** @type {import('vite').UserConfig} */
export default {
  plugins: [zig()],
  build: { target: 'esnext' },
};

Write your Zig code and export any symbol to be used in JS code:

// src/main.zig
export fn add(a: i32, b: i32) i32 {
    return a + b;
}

If available, top-level await can be used so that importing the module feels similar to importing a regular JS module:

// example.js
import { instantiate } from './src/main.zig';

// pass any custom importObject here, functions should be declared
// as extern in the Zig file
const importObject = {
  // ...
};
// instantiate the compiled WebAssembly module, can also be moved
// to a Worker for instantiation in another thread
const { exports, instance } = await instantiate(importObject);
// call exported functions from the exports object
console.log(exports.add(5, 37)); // 42

As a shorthand to avoid having to manually call await instantiate(), the ?instantiate query parameter can be specified in the module import to both compile and instantiate the module at import time, allowing access to instance and exports:

import { exports, instance, module } from './src/main.zig?instantiate';

// call exported functions from the exports object
console.log(exports.add(5, 37)); // 42

If your Vite config does not allow for top-level await (by setting build: { target: 'esnext' }, e.g. if the framework you're using enforces a specific target value), an alternative API is provided which instead exposes Promises (compiled and instantiated respectively depending on whether ?instantiate is used) which resolve when the compilation or instantiation of the module are complete:

// example.js
import { compiled, instantiate, module } from './src/main.zig';

(async () => {
  // `await compiled` can be used to populate the `module` import
  // manually before instantiation if necessary

  // pass any custom importObject here, functions should be declared
  // as extern in the Zig file
  const importObject = {
    // ...
  };
  // instantiate the compiled WebAssembly module, can also be moved
  // to a Worker for instantiation in another thread
  const { exports, instance } = await instantiate(importObject);
  // call exported functions from the exports object
  console.log(exports.add(5, 37)); // 42
})();

// example.js
import {
  exports,
  instance,
  instantiated,
  module,
} from './src/main.zig?instantiate';

(async () => {
  // manually await to populate the imports
  await instantiated;
  // call exported functions from the exports object
  console.log(exports.add(5, 37)); // 42
})();

To integrate with SSR frameworks such as SvelteKit, use a dynamic import:

<script>
  import { onMount } from 'svelte';

  onMount(async () => {
    const wasm = await import('$lib/main.zig?instantiate');
    await wasm.instantiated;
    console.log(wasm.exports.add(5, 37)); // 42
  });
</script>

Notes and TODOs

• It would be great to have something similar to Rust's wasm-bindgen to generate JS glue code and type definitions

License

MIT