71 / wasm-bindgen-switch

Replace functions, structs and more in Rust with `wasm_bindgen`-imported JS values.

wasm-bindgen-switch

Switch between a pure-Rust implementation and a #[wasm_bindgen]-backed implementation based on whether your code is compiled for WebAssembly.

See tests/person.rs (which uses tests/person.js in wasm builds) for an example. Both cargo test and cargo test --target wasm32-unknown-unknown test the same code and succeed.

The goal is to be able to write Rust code that is used the exact same way, no matter the actual implementation (JS or Rust). Ideally, such a project would not be needed: the Rust core would be Rust-only and a separate, clearly defined layer would glue Rust and JavaScript together. However, if your project is designed to work in the browser and uses many browser APIs, separating all code in such a way might be counterproductive. This is why this package exists.

My initial approach was to use traits with a macro that would generate a

#[wasm_bindgen]
extern "C" {
    // ...
}

block which imports functions and implements that trait for a JS value, but this forces all relevant APIs to be generic on that interface. With dozens of shared types and hundreds of functions, this is too much work.

More work needed:

• More tests.
• Better documentation.
• extends, js_namespace.
• Shims for JsValue, JsError, JsCast, and other types in js_sys and web_sys.
• Probably a better name?