Testing jwt-compact Crate in WASM

This simple crate tests that jwt-compact builds and can be used in WASM.

Note that chrono and getrandom crates need to be configured in Cargo.toml in order to work with the WASM target:

[dependencies]
chrono = { version = "0.4.22", features = ["wasmbind"] }
getrandom = { version = "0.2", features = ["js"] }

Usage

1. Install WASM target for Rust via rustup: rustup target add wasm32-unknown-unknown.
2. Install wasm-pack.
3. Install Node.
4. Switch to the directory with this README and run wasm-pack build --target bundler.
5. Run the testing script: node test.js.

:::note

If you are using wasm-bindgen without workers-rs / worker-build, then you will need to patch the JavaScript that it emits. This is because when you import a wasm file in Workers, you get a WebAssembly.Module instead of a WebAssembly.Instance for performance and security reasons.

To patch the JavaScript that wasm-bindgen emits:

1. Run wasm-pack build --target bundler as you normally would.
2. Patch the JavaScript file that it produces (the following code block assumes the file is called mywasmlib.js):

import * as imports from "./mywasmlib_bg.js";

// switch between both syntax for node and for workerd
import wkmod from "./mywasmlib_bg.wasm";
import * as nodemod from "./mywasmlib_bg.wasm";
if (typeof process !== "undefined" && process.release.name === "node") {
	imports.__wbg_set_wasm(nodemod);
} else {
	const instance = new WebAssembly.Instance(wkmod, {
		"./mywasmlib_bg.js": imports,
	});
	imports.__wbg_set_wasm(instance.exports);
}

export * from "./mywasmlib_bg.js";

3. In your Worker entrypoint, import the function and use it directly:

import { myFunction } from "path/to/mylib.js";

:::

src: https://github.com/cloudflare/cloudflare-docs/blob/95aacf2eee782e3a89525b0f0855f02959367536/src/content/docs/workers/languages/rust/index.mdx?plain=1#L154