Failures when decoding the input cause a memory leak.

[utdemir]

When tsify fails to parse the argument passed, it throws an error which causes a memory leak on Rust side. Which eventually causes a memory access out of bounds to be thrown, irrecoverably killing the WASM instance.

Reproducer here: https://github.com/utdemir/tsify-leak-repro

I dug in a bit and here's what I think happens: #[tsify(from_wasm_abi)] generates a FromWasmABI implementation which uses throw_str when parsing fails. Which has a note in docs:

Note that it is very easy to leak memory with this function because this function, unlike panic! on other platforms, will not run destructors. It’s recommended to return a Result where possible to avoid the worry of leaks.

From a cursory look - I don't think FromWasmABI is meant to be used with fallible conversions. So unsure what the proper fix would be other than significantly changing the tsify interface. Or coordinating with wasm_bindgen folks to allow partial FromWasmABI implementations.

[siefkenj]

Good find. What would happen if instead of using wasm_bindgen::throw_str(err.to_string().as_ref()); we propagated the Err to the caller? I presume that throws a JS error but with a confusing error message?

[madonoharu]

This issue also seems to be related:
#47