integrating wasm-bindgen

[ashleygwilliams]

there are several steps to using wasm-bindgen that i'd like to discuss here:

1. rustup target add wasm32-unknown-unknown

2. add wasm-bindgen as a dep to Cargo.toml:

    [lib]
    crate-type = ["cdylib"]
   
    [dependencies]
    wasm-bindgen = { git = 'https://github.com/alexcrichton/wasm-bindgen' }

3. add the following code to your src/lib.rs:

   #![feature(proc_macro)]
   
   extern crate wasm_bindgen;
   
   use wasm_bindgen::prelude::*;
   
   #[wasm_bindgen]
   extern {
       fn alert(s: &str);
   }

4. add this annotation to each publicly exported function:

   #[wasm_bindgen]
   #[no_mangle]

5. cargo build --release --target wasm32-unknown-unknown

6. cargo install --git https://github.com/alexcrichton/wasm-bindgen (this seems redundant with 2??? https://github.com/alexcrichton/wasm-bindgen/issues/44)

7. wasm-bindgen target/wasm32-unknown-unknown/release/<name of lib>.wasm \ --out-dir . (ergonomics ask: https://github.com/alexcrichton/wasm-bindgen/issues/45)

i can see clear ways to integrate 1, 2, 5, 6, 7. 3 and 4 will need to be done manually by the user. @alexcrichton do you have any thoughts on this?

[ashleygwilliams]

also curious for @linclark, @yoshuawuyts, @sendilkumarn's thoughts on the ergonomics of this all.

i am leaning toward integrating steps 1 and 5-7 into the tool. leaving 3 and 4 to the user. check out @alexcrichton's issue on how the ergonomics of this should work here: https://github.com/alexcrichton/wasm-bindgen/issues/46

[alexcrichton]

FWIW the code for this example in wasm-bindgen will one day be:

use wasm_bindgen::prelude::*;

#[wasm_bindgen]
#[no_mangle]
pub extern fn foo() {
    webabi_sys::alert("hello!");
}

in that #![feature] will eventually get stabilized (procedural macros), extern crate annotations will no longer be necessary (an epoch change), and the extern block won't be necessary with WebIDL-generated binding crates. It may also be reasonable to not require #[no_mangle] and extern functions for the #[wasm_bindgen] macro when exporting functions as well!

[sendilkumarn]

@ashleygwilliams I haven't played enough with bindgen (which I will hopefully do it in next week) But having a quick look. I too find adding 1,5 and 7 and leaving 3 & 4 makes super sense. OTOH, would love to add a sample repo to how to do 3&4 would be cool 😎 WDYT?

[ashleygwilliams]

@sendilkumarn done! totally agree :) see #17