mbt-error-in-test.md

///|
extern "js" fn ffi_request_animation_frame(f : () -> Unit) -> Unit =
  #|(f) => {
  #|  if (globalThis.requestAnimationFrame) {
  #|    requestAnimationFrame(f)
  #|  } else {
  #|    setTimeout(f, 0) // fallback
  #|  }
  #|}

///|
pub async fn request_animation_frame(f : () -> Unit noraise) -> Unit noraise {
  suspend(fn(resume_ok, _resume_err) {
    ffi_request_animation_frame(() => {
      f()
      resume_ok(())
    })
  }) catch {
    _ => ()
  }
}

///|
test "raf mainloop" {
  let mut f : (async () -> Unit noraise)? = None
  let mut cnt = 0
  f = Some(fn() {
    let _ = request_animation_frame(() => match f {
      Some(next) => {
        println("Animation frame \{cnt + 1}")
        if cnt >= 5 {
          f = None
          println("Completed 5 animation frames.")
          return
        }
        cnt += 1
        run_async(next)
      }
      None => ()
    })

  })
  run_async(() => match f {
    Some(f) => f()
    None => ()
  })
}

Error Message

✦ $ moon test --target js
Animation frame 1
Animation frame 2
Animation frame 3
Animation frame 4
Animation frame 5
Animation frame 6
Completed 5 animation frames.

test dom/raf.mbt:24 ("js") failed: TypeError: Cannot read properties of undefined (reading '$tag')
    at mizchi$jslib$dom$$moonbit_test_driver_internal_do_execute

Error Line

target/js/debug/test/dom/dom.internal_test.js

in moonbit_test_driver_internal_do_execute()

const on_err = (err) => {
    let e;
    _L$2: {
      let e$2;
      _L$3: {
        switch (err.$tag) { // <= this line
          case 0: {
            const _Failure = err;
            const _e = _Failure._0;