Wasm-bindgen does not pass String from Rust to JS

[wdanilo]

Describe the Bug

Hi, I've got such a code:

#[wasm_bindgen]
pub fn test() -> String {
    "hello".to_string()
}

When compiling it with wasm-pack --target=web and calling it from JS, I've got undefined as a result. It seems that I'm not the only one facing this issue and it seems that compiling everything with --target=nodejs makes it working: https://stackoverflow.com/questions/70079979/how-do-i-return-a-string-from-a-rust-function-in-nodejs-webassembly-using-wasm-b

I'm not sure whether this issue is connected more with wasm-pack or wasm-bindgen, but as wam-pack is not very actively maintained, I prefer to ask here first for any help / guidance. Thank you :)

[Liamolucko]

It's hard to say what exactly the issue is without seeing how you're instantiating the wasm module on the JS side, as well as where you're running the JS, etc.

If you're doing the same thing as the Stack Overflow question you linked, using WebAssembly.instantiate on the raw wasm file, the problem is that you should be importing the JS wrapper around it instead. The API exported by the raw wasm isn't meant to be used directly, which is why it returns undefined instead of the string you expect.

[wdanilo]

You are right, the Stack Overflow code is wrong and I didn't notice it. I am using the JS wrapper. The setup here is pretty complex. Let me clean it a little bit and I link it with a proper description in a few days. Thank you for the help.