Panic when trying to run with dependencies

[nappa85]

wasm-bindgen panics on my application with this message:

wasm-bindgen --target web --out-dir . target/wasm32-wasi/release/my_project.wasm 
thread 'main' panicked at 'assertion failed: `(left == right)`
  left: `3`,
 right: `1`', ~/.cargo/registry/src/index.crates.io-6f17d22bba15001f/wasm-bindgen-cli-support-0.2.87/src/js/binding.rs:172:9
note: run with `RUST_BACKTRACE=1` environment variable to display a backtrace

From what I've been able to understand, this is due the fact my application generates more than one wasm file in target/wasm32-wasi/release/deps/, where the second one is called wasm_streams-4a21c93a06539d08.wasm.

If I remove the proc-macro and manually export my methods as extern "C" (thus removing all the describing code), wasm-bindgen starts working and exports what I think are methods from the other wasm file.

What's the solution in this situation?

[Liamolucko]

From what I've been able to understand, this is due the fact my application generates more than one wasm file in target/wasm32-wasi/release/deps/, where the second one is called wasm_streams-4a21c93a06539d08.wasm.

I don't think that's the issue. target/release/deps is just an internal folder where cargo keeps the results of building your Rust dependencies, and it's not actually referenced by the final wasm file: the last step of compiling is to merge all those dependencies into a single wasm file. (Usually it's mostly rlib files for dependencies though, not wasm files, so I'm not too sure what's going on there.)

It might be because you're using wasm32-wasi, which often doesn't work properly with wasm-bindgen, and was actually disabled in #3233 (not released yet). Is there any particular reason why you're using wasm32-wasi? Does this issue still happen when you use wasm32-unknown-unknown?

[nappa85]

In facts it was a test I didn't do, building with wasm32-wasi an example crate gives the same problems.

I'm building with wasm32-wasi because I don't have full control over the deps, and many of the crates in my deps tree works on wasi but not on wasm (e.g. https://crates.io/crates/im)

I see that with #3233 everything will stop working, I'll have to find another approach...

[hamza1311]

You don't need to use wasm-bindgen if you want to use WASI. If a dependency can't be compiled to wasm32-unknown-unknown, it can't be run in browser anyway.

I suggest you look into WASI runtimes such as wasmtime for running your app as WASM

[nappa85]

As far as I know, to return an object froma wasi exposed method you'll need the same approach used by wasm-bindgen. Anyway I've filled the codebase of conditional compilation to exclude non-wasm compatible crates when building for wasm, that is inelegant but solved the problem. You can close the issue (I can't right now) Il mer 4 ott 2023, 17:57 Muhammad Hamza ***@***.***> ha scritto:

…

You don't need to use wasm-bindgen if you want to use WASI. If a dependency can't be compiled to wasm32-unknown-unknown, it can't be run in browser anyway. I suggest you look into WASI runtimes such as wasmtime for running your app as WASM — Reply to this email directly, view it on GitHub <#3640 (comment)>, or unsubscribe <https://github.com/notifications/unsubscribe-auth/ABZXINLW6LFBMY437E3QXALX5WBNNAVCNFSM6AAAAAA5RIF5OOVHI2DSMVQWIX3LMV43OSLTON2WKQ3PNVWWK3TUHMYTONBXGE3TENJUHE> . You are receiving this because you authored the thread.Message ID: ***@***.***>