[WIP] Add explicit wasm extension

[pd4d10]

For the case that wasm is not specified at webpack resolve.extensions

[alexcrichton]

Thanks for the PR! Unfortunately though it looks like CI has discovered that we rely on the convention that if you omit the extension it'll find the file via the first extension that matches. The theory is that the actual extension behind that import doesn't matter, and while it could be a wasm file tools like wasm2es6js will replace it with a JS file.

We may be able to fix this directly though with the tests? It seems like this may be worthwhile fixing in the wild!

[Pauan]

@alexcrichton I think we should fix it to use .wasm, because when ES6 modules are supported natively in browsers it will need the .wasm extension.

That's because when you import something, the browser does not add any extension, it just makes a direct HTTP GET request.

So if you import "/foo", then the browser will make a GET request to /foo. So it will return a 404, since /foo doesn't exist.

That can be fixed by configuring the web server to automatically rewrite /foo requests to /foo.wasm, but we probably shouldn't require everybody to do that.

[alexcrichton]

Indeed and I agree! This doesn't pass CI though and that needs fixing before we can land it.

[alexcrichton]

Ok I'm gonna close this to help clear out our PR list for now, but we can always land this with working tests!