How to read template literals from js?

[oovm]

https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Template_literals

• rs side

#[wasm_bindgen]
pub fn parsing(template: ?) -> Result<Self, JsError> {
    // some parsing progress
}

• js side

parsing`template {raw} text`

[Liamolucko]

Looking at that MDN page, the signature of a tag functions seems to be:

function tag(strings: string[] & { raw: string[] }, ...args: unknown[]): unknown;

The variadic args argument is the tricky part, since exporting functions with variadic arguments isn't supported as of wasm-bindgen 0.2.81. However, support was added in #2954, and will be there in the next release.

So, using a git version of wasm-bindgen, a tag function can be written like this:

use js_sys::Array;
use wasm_bindgen::prelude::*;

#[wasm_bindgen(variadic)]
pub fn tag(strings: Array, args: Array) -> Array {
    // ...
}

#[wasm_bindgen(variadic)] makes the last argument of the function an array of all the arguments passed after all the non-variadic arguments (in this case, args).

And, if you need to access the raw property of the first argument, you can define a subtype of Array which includes it:

use js_sys::Array;
use wasm_bindgen::prelude::*;

#[wasm_bindgen]
extern "C" {
    #[wasm_bindgen(extends = Array)]
    pub type Strings;

    #[wasm_bindgen(method, getter)]
    pub fn raw(this: &Strings) -> Array;
}

#[wasm_bindgen(variadic)]
pub fn tag(strings: Strings, args: Array) -> Array {
    // ...
}

Again though, this support hasn't been released yet, so to use it you'll need a git version of wasm-bindgen.

To do that, you have to add this to your Cargo.toml:

[patch.crates-io]
wasm-bindgen = { git = "https://github.com/rustwasm/wasm-bindgen" }

And install the git version of the CLI (note that this will be incompatible with anything compiled with non-git versions of wasm-bindgen):

cargo install --git=https://github.com/rustwasm/wasm-bindgen