web-sys
APIs on activated features (#790)
* Gate `web-sys` APIs on activated features Currently the compile times of `web-sys` are unfortunately prohibitive, increasing the barrier to using it. This commit updates the crate to instead have all APIs gated by a set of Cargo features which affect what bindings are generated at compile time (and which are then compiled by rustc). It's significantly faster to activate only a handful of features vs all thousand of them! A magical env var is added to print the list of all features that should be generated, and then necessary logic is added to ferry features from the build script to the webidl crate which then uses that as a filter to remove items after parsing. Currently parsing is pretty speedy so we'll unconditionally parse all WebIDL files, but this may change in the future! For now this will make the `web-sys` crate a bit less ergonomic to use as lots of features will need to be specified, but it should make it much more approachable in terms of first-user experience with compile times. * Fix AppVeyor testing web-sys * FIx a typo * Udpate feature listings from rebase conflicts * Add some crate docs and such
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 {
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-bindgen
only generates bindings and glue for the JavaScript imports you actually use and Rust functionality that you export. For example, importing and using thedocument.querySelector
method doesn't causeNode.prototype.appendChild
orwindow.alert
to 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! 📚
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.