TypeError: WebAssembly __wbg_init expects a string, object passed

[dgasparri]

Description of the bug

On load in the web browser it raises the following Javascript exception:

TypeError: WebAssembly.instantiate(): Argument 0 must be a buffer source
pkg/my_project.js 523:44  __wbg_load
pkg/my_project.js 872:40  __wbg_init

My machine:

• Windows 11
• flutter_rust_bridge_codegen 2.11.1

The code is generated with wasm-pack called through flutter_rust_bridge_codegen with the build-web call.

The Rust and Dart source code is irrelevant, as it's giving me the same error even with the provided example.

What I found so far

__wbg_init (in pkg/my_project.js) is called with a {module_or_path: 'pkg/my_project_bg.wasm'} Object, the wasm file exists and it is accessible.

What it is expected

As far as I can tell from reading __wbg_init, it expects a simple string (or a Response or URL object), not a object.

Possible patch

I am not a Dart developer so unfortunately I can only offer guesses for a solution.

From the stack trace and source map, __wbg_init is called from _web.dart:18 (which in turns is called from async_patch.dart:623).

From frb_dart/lib/src/wasm_module/_web.dart:

await wasmBindgen({"module_or_path": '${root}_bg.wasm'}.jsify()).toDart;

should probably be:

await wasmBindgen('${root}_bg.wasm'.jsify()).toDart;

[dgasparri]

Forgot to mention, I'm using flutter_rust_bridge: ^2.11.1

[dgasparri]

Updating Rust solved the issue

cd rust
cargo update
cd ..

@fzyzcjy Should we put the cargo update as a suggested step in the Quickstart guide and/or in the website/docs/manual/troubleshooting.md ?

[fzyzcjy]

Great fix!

Should we put the cargo update as a suggested step in the Quickstart guide and/or in the website/docs/manual/troubleshooting.md ?

Yes, feel free to add it in troubleshooting.md :)