Passing i64 around always fails with the js feature

[kajacx]

Passing i64 to and from a module on the web always fails with the js feature

When compiling wasmer itself to WASM using the js feature so that it can run in the browser, there is an error when you then load another plugin from wasmer and try to pass i64 values around.

Steps to reproduce

1. Clone this repo at the add-i64-result-error tag.
2. Run the build.sh script (after reading the entire source code, of course).
3. Open the webpage and see the result.

Expected behavior

i64 values should be added correctly inside the plugin and the values should be passed between the plugin and wasmer without a problem.

Actual behavior

Calling the add_i64 exported function always returns a runtime error, example:

RuntimeError { source: Js(JsValue(TypeError: can't convert 5 to BigInt
getImports/imports.wbg.__wbg_apply_aedce30790c00792/<@http://127.0.0.1:8094/hello_wasmer_u64.js:414:37
handleError@http://127.0.0.1:8094/hello_wasmer_u64.js:224:18
getImports/imports.wbg.__wbg_apply_aedce30790c00792@http://127.0.0.1:8094/hello_wasmer_u64.js:413:68
@http://127.0.0.1:8094/hello_wasmer_u64_bg.wasm:wasm-function[199]:0x21883
@http://127.0.0.1:8094/hello_wasmer_u64_bg.wasm:wasm-function[43]:0x2b1e
test_add_i64@http://127.0.0.1:8094/hello_wasmer_u64.js:212:14
@http://127.0.0.1:8094/:13:15
promise callback*@http://127.0.0.1:8094/:11:14
)) }

Additional context

This was discovered when I was doing testing for #3763. Although this is a different error than I was experiencing there. That might be because I was using wasmer from source in that PR, whereas here I am using the currently released version 3.1.1.

Also, I followed this example by Mozilla on how to run Rust on the browser using wasm-pack, if that's relevant.

[ptitSeb]

Can you try again with current master, mainy things have changed on the Js part so it might just work now.

[kajacx]

Can you try again with current master, many things have changed on the Js part so it might just work now.

Ok, I have tried just that, and it is giving me a different error. This time, calling the add_i64 panics inside the library code instead of returning an error value, which is even worse.

You can clone this repo again, this time at the add-i64-source-panic tag for a minimal(-ish) reproducible example.

This is the new error:

panicked at 'called `Result::unwrap()` on an `Err` value: --1', C:\Programs\Cargo\bin\git\checkouts\wasmer-f11f30e62739aa29\8a343d0\lib\api\src\js\as_js.rs:43:41

Stack:

getImports/imports.wbg.__wbg_new_abda76e883ba8a5f@http://127.0.0.1:8094/hello_wasmer_u64.js:356:21
@http://127.0.0.1:8094/hello_wasmer_u64_bg.wasm:wasm-function[344]:0x261a2
@http://127.0.0.1:8094/hello_wasmer_u64_bg.wasm:wasm-function[138]:0x20a04
@http://127.0.0.1:8094/hello_wasmer_u64_bg.wasm:wasm-function[229]:0x23a95
@http://127.0.0.1:8094/hello_wasmer_u64_bg.wasm:wasm-function[159]:0x21df2
@http://127.0.0.1:8094/hello_wasmer_u64_bg.wasm:wasm-function[67]:0x19b10
@http://127.0.0.1:8094/hello_wasmer_u64_bg.wasm:wasm-function[54]:0x31be
test_add_i64@http://127.0.0.1:8094/hello_wasmer_u64.js:221:14
@http://127.0.0.1:8094/:14:17
promise callback*@http://127.0.0.1:8094/:11:14

This is the line that throws the error:

#[inline]
pub fn param_from_js(ty: &Type, js_val: &JsValue) -> Value {
    match ty {
        Type::I32 => Value::I32(js_val.as_f64().unwrap() as _),
        Type::I64 => {
            let number = js_val.as_f64().map(|f| f as i64).unwrap_or_else(|| {
                if js_val.is_bigint() {
                    // To support BigInt
                    let big_num: u128 = js_sys::BigInt::from(js_val.clone()).try_into().unwrap(); // <-- HERE
                    big_num as i64
                } else {
                    (js_sys::Number::from(js_val.clone()).as_f64().unwrap()) as i64
                }
            });
            Value::I64(number)
        }
        Type::F32 => Value::F32(js_val.as_f64().unwrap() as _),
        Type::F64 => Value::F64(js_val.as_f64().unwrap()),
        Type::V128 => {
            let big_num: u128 = js_sys::BigInt::from(js_val.clone()).try_into().unwrap();
            Value::V128(big_num)
        }
        Type::ExternRef | Type::FuncRef => unimplemented!(
            "The type `{:?}` is not yet supported in the JS Function API",
            ty
        ),
    }
}

Clearly, something is wrong with the BigInt values. I will investigate further.

[kajacx]

Ok, passing any i64 values into the wasm module is ok, but returning any negative i64 value causes the problem. Also, I have verified that it is indeed the communication between wasmer and the plugin module that is the problem, and not the communication between the web host and the wasmer wasm plugin.

You can check out this repo again at the return-negative-i64-is-the-problem tag.