lib.rs

#[no_mangle]
pub fn add(a: i32, b: i32) -> i32 {
    a + b
}

index.js

import wasm from "lib.rs";

export async function increment(a) {
  const { instance } = await wasm;
  return instance.exports.add(1, a);
}

How wasm code would be exported. This options is identical with option export in webassembly-loader. (see examples)

{
  "globals": {
    "rs-jest": {
      "export": "instance"
    }
  },
  "transform": {
    "^.+\\.rs$": "rs-jest"
  }
}

• Type: String
• Default: wasm32-unknown-unknown
• Expected value: see supported platform

The Rust target to use. Currently it only support wasm related target

{
  "globals": {
    "rs-jest": {
      "target": "wasm32-unknown-emscripten"
    }
  },
  "transform": {
    "^.+\\.rs$": "rs-jest"
  }
}

• Type: Boolean
• Default: true

Whether to compile the Rust code in debug or release mode.

{
  "globals": {
    "rs-jest": {
      "release": false
    }
  },
  "transform": {
    "^.+\\.rs$": "rs-jest"
  }
}

Given this Rust code

lib.rs

#[no_mangle]
pub fn add(a: i32, b: i32) -> i32 {
    a + b
}

Cargo.toml

[package]
name = "adder"
version = "0.1.0"
authors = ["Full Name <[email protected]>"]

[lib]
crate-type = ["cdylib"]
path = "lib.rs"

With options

{export: 'buffer'}

import wasmCode from "./lib.rs";

WebAssembly.compile(wasmCode).then(module => {
  const instance = new WebAssembly.Instance(module);
  console(instance.exports.add(1, 2)); // 3
});

{export: 'module'}

import wasmModule from "./lib.rs";

const instance = new WebAssembly.Instance(wasmModule);
console(instance.exports.add(1, 2)); // 3

{export: 'instance'}

import wasm from "./lib.rs";

console(wasm.exports.add(1, 2)); // 3

{export: 'async'}

extern {
    fn hook(c: i32);
}

#[no_mangle]
pub fn add(a: i32, b: i32) -> i32 {
    hook(a + b)
}

import wasmInstantiate from "./lib.rs";

wasmInstantiate(importObject | undefined).then(({ instance, module }) => {
  console(instance.exports.add(1, 2)); // 3

  // create different instance, extra will be called in different environment
  const differentInstance = new WebAssembly.Instance(module, {
    env: {
      hook: result => result * 2
    }
  });
  console(differentInstance.exports.add(1, 2)); // 6
});

{export: 'async-instance'}

import wasmInstantiate from "./lib.rs";

wasmInstantiate(importObject | undefined).then(instance => {
  console(instance.exports.add(1, 2)); // 3
});

{export: 'async-module'}

import wasmInstantiate from "./lib.rs";

wasmCompile(importObject | undefined).then(module => {
  const differentInstance = new WebAssembly.Instance(module);
  console(differentInstance.exports.add(1, 2)); // 3
});