[chenyan2002]

Problem

A sync component runs under JSPI and calls an import that rejects or throws. The guest stays suspended forever, and the export's promise never settles.

Imports from sync components that JSPI suspends go through the CallInterface trampoline in crates/js-component-bindgen/src/function_bindgen.rs. When the import throws, the async error branch rejects and exits the task, then returns task.completionPromise() to the suspended guest.

That promise settles only after #completionReady is set. The flag is set only for tasks that are isAsync or isManualAsync. A JSPI-only import task is created with isAsync: false and no isManualAsync, so the promise never settles.

Fix

In the async error branch of CallInterface, end with throw err; unless the function is async in the component-model sense (*async_). For those functions, keep return task.completionPromise();. Throwing rejects the promise that WebAssembly.Suspending is waiting on, so the guest traps and the export rejects, the same as in the sync path.

[vados-cosmonic]

LGTM 🚀

Thanks @chenyan2002 , this looks good to me in general, I'm a little worried about throwing early but I think with the fix for the async function that maybe won't be a problem?

Also I'll have to change the commits a little bit.