Support #[should_panic] in tests

[d-e-s-o]

I think it would be great to have support for the #[should_panic] attribute on tests. That is, the following works as expected when compiling natively:

#[test]
#[should_panic]
fn foo() {
  panic!("foo")
}

But if I am doing the same in WASM:

#[wasm_bindgen_test::wasm_bindgen_test]
#[should_panic]
fn foo() {
  panic!("foo")
}

I see warning: unused attribute and a panic:

panicked at 'foo', src/XXX:YYY:ZZ

Stack:

Error
    at target/wasm32-unknown-unknown/wbg-tmp/wasm-bindgen-test.js:751:15
   ...

[d-e-s-o]

Oh, well, do we have no unwinding support in WASM at all?

#[test]
fn foo() {
  use std::panic::catch_unwind;

  let _ = catch_unwind(|| {
    panic!("test");
  });
}

Even that panics.

[alexcrichton]

Unfortunately this is not possible to easily support today because wasm does not have catchable exceptions, this will work once that proposal stabilizes, though!

[Tamschi]

I just tripped across this but had noticed earlier that the test runner now trampolines through JS to run the individual tests, which if I'm not mistaken gives it an interface to observe and handle the error.

Is it feasible to implement this feature on that basis now or is there another blocker?