c35d6f4b0a
Reported in #1191 the fix requires us to get a bit creative I think. The general gist is that a block like this: #[wasm_bindgen] impl Foo { pub fn foo() {} } was previously expanded all in one go. Now, however, it's expanded into: impl Foo { #[__wasm_bindgen_class_marker(Foo = "Foo")] pub fn foo() {} } // goop generated by orginal #[wasm_bindgen] This method of expansion takes advantage of rustc's recursive expansion feature. It also allows us to expand `impl` blocks and allow inner items to not be fully expanded yet, such as still having `#[cfg]` attributes (like in the original bug report). We use theinternal `__wasm_bindgen_class_marker` to indicate that we're parsing an `ImplItemMethod` unconditionally, and then generation proceeds as usual. The only final catch is that when we're expanding in an `impl` block we have to generate tokens for the `Program` (wasm-bindgen injected goop like the custom section) inside the body of the function itself instead of next to it. Otherwise we'd get syntax errors inside of impl blocks! Closes #1191
wasm-bindgen
Facilitating high-level interactions between wasm modules and JavaScript.
Import JavaScript things into Rust and export Rust things to JavaScript.
extern crate wasm_bindgen;
use wasm_bindgen::prelude::*;
// Import the `window.alert` function from the Web.
#[wasm_bindgen]
extern "C" {
fn alert(s: &str);
}
// Export a `greet` function from Rust to JavaScript, that alerts a
// hello message.
#[wasm_bindgen]
pub fn greet(name: &str) {
alert(&format!("Hello, {}!", name));
}
Use exported Rust things from JavaScript with ECMAScript modules!
import { greet } from "./hello_world";
greet("World!");
Features
-
Lightweight. Only pay for what you use.
wasm-bindgenonly generates bindings and glue for the JavaScript imports you actually use and Rust functionality that you export. For example, importing and using thedocument.querySelectormethod doesn't causeNode.prototype.appendChildorwindow.alertto be included in the bindings as well. -
ECMAScript modules. Just import WebAssembly modules the same way you would import JavaScript modules. Future compatible with WebAssembly modules and ECMAScript modules integration.
-
Designed with the "host bindings" proposal in mind. Eventually, there won't be any JavaScript shims between Rust-generated wasm functions and native DOM methods. Because the wasm functions are statically type checked, some of those native methods' dynamic type checks should become unnecessary, promising to unlock even-faster-than-JavaScript DOM access.
Guide
📚 Read the wasm-bindgen guide here! 📚
API Docs
License
This project is licensed under either of
- Apache License, Version 2.0, (LICENSE-APACHE or http://www.apache.org/licenses/LICENSE-2.0)
- MIT license (LICENSE-MIT or http://opensource.org/licenses/MIT)
at your option.
Contribution
See the "Contributing" section of the guide for information on
hacking on wasm-bindgen!
Unless you explicitly state otherwise, any contribution intentionally submitted for inclusion in this project by you, as defined in the Apache-2.0 license, shall be dual licensed as above, without any additional terms or conditions.