Test TypeScript output on CI

[alexcrichton]

There have been a number of TypeScript-related regressions recently like #917, and while we used to test TypeScript on CI we no longer do! We should figure out how to set up a dedicated builder focused on testing the TypeScript output of wasm-bindgen!

[emk]

A great idea!

The following issue contains some instructions on how to get async loading working with TypeScript and Webpack, which would allow testing the entire compilation process from end-to-end: rustwasm/rust-webpack-template#43

[emk]

And as mentioned in that issue, if you'd like, I can try to take a look at setting up an example TypeScript+Rust+Webpack project which can be built using npm run something sometime this coming weekend.

[alexcrichton]

A nice idea! I think it's good to have a test like that but for this repository we can probably just stick to the vanilla typescript compiler and a sample project

I'd be wary of coupling to too many things outside of wasm bindgens control

[emk]

My recent experience is that if I just check run wasm-bindgen and tsc, there's still a really impressive number of ways that everything can silently produce broken output. (And it feels like I've hit most of them getting this to work.) In particular, the async module loading code requires cooperation from all 3 of wasm-bindgen, tsc's esnext support, and webpack, and it's easy for one tool to be silently out of alignment with the other 2.

In a perfect world, something would run webpack and make sure that everything all hooks up together. Basically, my goal here is to be able to upgrade wasm-bindgen and expect everything to still work. But there's an excellent argument to be made that this is an "integration" or "acceptance" test, and that as such, maybe it belongs in a new rust-webpack-typescript-template repository somewhere.

Still, I'd love for wasm-bindgen to "just work" with TypeScript. And I suspect that it may be hard to guarantee that without a good end-to-end test somewhere.

What would be the most useful way for me to approach this goal?

[alexcrichton]

Oh well I think the priority here is getting something tested, so I'm fine getting that done however and then we can tweak it as necessary!