Wasming a Rust Package for Fun


Whilst getting interested in Library.JSON and building my own library, one of the issues I continually run into is slight variations between slugifying in javascript and rust (which the static site generator I use is written in). Eventually I reached the point where I decided it was easier to compile whatever Zola was using for slugs to web assembly than trying to get it exactly the same in javascript.

With some spelunking, I found https://github.com/Stebalien/slug-rs.

I git pull'd it added to the Cargo.toml

crate-type = ["cdylib", "rlib"] # cdylib is for web assembly and rlib is a normal rust library
# ...

[target.'cfg(target_family = "wasm")'.dependencies]
wasm-bindgen = "0.2"

Threw a #[wasm_bindgen] on slugify() function and ran wasm-pack build --target web which provides a wonderfully descriptive error

error: can't #[wasm_bindgen] functions with lifetime or type parameters
  --> src/lib.rs:42:15
42 | pub fn slugify<S: AsRef<str>>(s: S) -> String {
   |               ^^^^^^^^^^^^^^^

error: could not compile `slug` due to previous error

I replaced S with String and Voila! A pkg folder was generated.

This pkg folder was then copied to the static assets folder and in JS, it's called by

<script defer type="module">
import init, { slugify } from '/pkg/slug.js';
// ...

async function run() {
	await init();
	// ...
	slugify("My Test String!!!1!1");


For the search bar on library, my template sets the id for a 'book'

<div class="book" id="{{list.name ~ "-" ~ book.title | slugify}}">

And the dynamic elements in the search dropdown use the exact same slugifying logic!

Was this unnecessary? Probably. But it works and it was a neat exercise.

See the code