Improve worker.js reliability

[RReverser]

While it doesn't happen right now in this particular example, lastPtr can be potentially overridden several times before the module is fully initialised.

Rather than having a boolean and a storage for one last argument, await a promise returned from wasm_bindgen itself in the new onmessage handler before executing actual command.

This way all the potential tasks will queue up naturally, wait for the initialisation, and then execute in a correct order.

[alexcrichton]

Nice!

[RReverser]

@alexcrichton Thanks for merging!

By the way, I found this published crate that pretty much extracted code from this example in a reusable fashion: https://crates.io/crates/web_worker.

I believe it's slightly out of sync and misses e.g. this worker.js, but otherwise it seems like quite a good idea to have a ready-to-use adapter for other people (like me) playing with multithreading in Rust + Wasm on their own.

I wonder if you'd want to coordinate with author and maybe help to make sure that their code is up-to-date, or make your own crate, and then switch this example to use it as a dependency?

[alexcrichton]

Sure yeah, refactorings here seem reasonable to me! When I made this example afaik it was the only thing that could work, so it was the minimal thing I got working quickly. If there's more official ways to do it nowadays seems good!

[RReverser]

@alexcrichton Oh, I don't think there are more official ways - as I said, that crate is basically an extracted version of your code here.

What I'm asking is if you'd want to make that crate the official way and sync your code to it, or publish your own crate for others to use.

[alexcrichton]

I think we probably don't want to farm this out just yet, I don't have the time to maintain a separate crate and the threads spec is volatile enough I think we want to retain the ability to make changes here if necessary.

[RReverser]

Fair enough. I think I'll publish some small wrapper myself then, but for now am hitting some Chromium bugs that need to be fixed before it's released.