Bug 297134 – Exception (JS value) thrown inside WebAssembly using WebAssembly.JSTag is wrapped into WebAssembly.Exception immediately

• Component: WebAssembly
• Status: RESOLVED DUPLICATE

So as a result, 
1. It's observable inside a wasm module as an instance of WebAssembly.Exception instead of thrown JS value.
2. It's not unwrapped when it crosses wasm-js border, so in JS it is also visible as an instance of WebAssembly.Exception instead of thrown JS value.

[Yusuke Suzuki]

Thanks! This will be fixed in bug 297127

[Yusuke Suzuki]

*** This bug has been marked as a duplicate of bug 297127 ***

[Radar WebKit Bug Importer]

<rdar://problem/157875232>

[Keith Miller]

Are you sure 2 is the case? https://webassembly.github.io/exception-handling/js-api/#call-an-exported-function says it is unwrapped back to the underlying JS value when propagating back through JS. I'm pretty sure the bug in https://github.com/WebKit/WebKit/pull/49130 was due to the opposite; we weren't unwrapping the `WebAssembly.Exception` if it had a JSTag for exported functions if it was created and thrown from wasm i.e. `(throw $JSTag someExternref)`

What's the case you're seeing 1 in?

> we weren't unwrapping the `WebAssembly.Exception`
(2) is basically saying the same thing

BTW, I don't see any test for (1) in the PR. Could you please check if it's fixed?

> What's the case you're seeing 1 in?

Case: an exception is thrown inside wasm using JSTag and caught with JSTag inside wasm.
Actual: in the catch block, we receive an instance of WebAssembly.Exception wrapping the original JS value, e,g, JS Error.
Expected: in the catch block, we receive the original JS value.