WASM cannot build for wasm32-wasi

[schtauffen]

Bevy version

0.7

What you did

Cargo.toml

<snip>

[target.'cfg(target_arch="wasm32")'.dependencies]
lunatic = "0.9"
bevy = { version = "0.7", default-features = false }

.cargo/config.toml

[target.wasm32-wasi]
runner = "lunatic"

ran cargo run --bin server --target wasm32-wasi

What went wrong

I expect bevy to compile for use inside wasm. Instead, it gives errors:

error[E0463]: can't find crate for `js_sys`
 --> C:\Users\Zach and Andrea\.cargo\registry\src\github.com-1ecc6299db9ec823\cpal-0.13.5\src\host\webaudio\mod.rs:1:1
  |
1 | extern crate js_sys;
  | ^^^^^^^^^^^^^^^^^^^^ can't find crate

error[E0463]: can't find crate for `wasm_bindgen`
 --> C:\Users\Zach and Andrea\.cargo\registry\src\github.com-1ecc6299db9ec823\cpal-0.13.5\src\host\webaudio\mod.rs:2:1
  |
2 | extern crate wasm_bindgen;
  | ^^^^^^^^^^^^^^^^^^^^^^^^^^ can't find crate

error[E0463]: can't find crate for `web_sys`
 --> C:\Users\Zach and Andrea\.cargo\registry\src\github.com-1ecc6299db9ec823\cpal-0.13.5\src\host\webaudio\mod.rs:3:1
  |
3 | extern crate web_sys;
  | ^^^^^^^^^^^^^^^^^^^^^ can't find crate

   Compiling image v0.23.14
error[E0433]: failed to resolve: use of undeclared type `AudioContextOptions`
   --> C:\Users\Zach and Andrea\.cargo\registry\src\github.com-1ecc6299db9ec823\cpal-0.13.5\src\host\webaudio\mod.rs:218:31    
    |
218 |         let mut stream_opts = AudioContextOptions::new();
    |                               ^^^^^^^^^^^^^^^^^^^ use of undeclared type `AudioContextOptions`

error[E0433]: failed to resolve: use of undeclared type `AudioContext`
   --> C:\Users\Zach and Andrea\.cargo\registry\src\github.com-1ecc6299db9ec823\cpal-0.13.5\src\host\webaudio\mod.rs:221:13    
    |
221 |             AudioContext::new_with_context_options(&stream_opts).map_err(
    |             ^^^^^^^^^^^^ use of undeclared type `AudioContext`

error[E0433]: failed to resolve: use of undeclared type `Closure`
   --> C:\Users\Zach and Andrea\.cargo\registry\src\github.com-1ecc6299db9ec823\cpal-0.13.5\src\host\webaudio\mod.rs:269:26
    |
269 |                 .replace(Closure::wrap(Box::new(move || {
    |                          ^^^^^^^ use of undeclared type `Closure`

error[E0412]: cannot find type `AudioContext` in this scope
  --> C:\Users\Zach and Andrea\.cargo\registry\src\github.com-1ecc6299db9ec823\cpal-0.13.5\src\host\webaudio\mod.rs:28:14      
   |
27 | pub struct Stream {
   |                  - help: you might be missing a type parameter: `<AudioContext>`
28 |     ctx: Arc<AudioContext>,
   |              ^^^^^^^^^^^^ not found in this scope

error[E0412]: cannot find type `Closure` in this scope
  --> C:\Users\Zach and Andrea\.cargo\registry\src\github.com-1ecc6299db9ec823\cpal-0.13.5\src\host\webaudio\mod.rs:29:46      
   |
29 |     on_ended_closures: Vec<Arc<RwLock<Option<Closure<dyn FnMut()>>>>>,
   |                                              ^^^^^^^ not found in this scope

error[E0412]: cannot find type `Closure` in this scope
   --> C:\Users\Zach and Andrea\.cargo\registry\src\github.com-1ecc6299db9ec823\cpal-0.13.5\src\host\webaudio\mod.rs:231:58    
    |
231 |         let mut on_ended_closures: Vec<Arc<RwLock<Option<Closure<dyn FnMut()>>>>> = Vec::new();
    |                                                          ^^^^^^^ not found in this scope

error[E0412]: cannot find type `Closure` in this scope
   --> C:\Users\Zach and Andrea\.cargo\registry\src\github.com-1ecc6299db9ec823\cpal-0.13.5\src\host\webaudio\mod.rs:262:53    
    |
262 |             let on_ended_closure: Arc<RwLock<Option<Closure<dyn FnMut()>>>> =
    |                                                     ^^^^^^^ not found in this scope

error[E0425]: cannot find function `eval` in this scope
   --> C:\Users\Zach and Andrea\.cargo\registry\src\github.com-1ecc6299db9ec823\cpal-0.13.5\src\host\webaudio\mod.rs:444:43    
    |
444 |     if let Ok(audio_context_is_defined) = eval("typeof AudioContext !== 'undefined'") {
    |                                           ^^^^ not found in this scope

error[E0599]: no method named `clone` found for struct `Arc<_>` in the current scope
   --> C:\Users\Zach and Andrea\.cargo\registry\src\github.com-1ecc6299db9ec823\cpal-0.13.5\src\host\webaudio\mod.rs:241:34    
    |
241 |             let ctx_handle = ctx.clone();
    |                                  ^^^^^ method not found in `Arc<_>`

error[E0599]: no method named `create_buffer` found for struct `Arc<_>` in the current scope
   --> C:\Users\Zach and Andrea\.cargo\registry\src\github.com-1ecc6299db9ec823\cpal-0.13.5\src\host\webaudio\mod.rs:250:18    
    |
250 |                 .create_buffer(
    |                  ^^^^^^^^^^^^^ method not found in `Arc<_>`
Some errors have detailed explanations: E0412, E0425, E0433, E0463, E0599.
For more information about an error, try `rustc --explain E0412`.
error: could not compile `cpal` due to 13 previous errors
warning: build failed, waiting for other jobs to finish...

Additional information

I would not expect javascript/browser (js-sys, web-sys) interop to be required to compile to wasm.

[infmagic2047]

Do you have bevy listed elsewhere in your Cargo.toml? Cargo features are additive, so all places where bevy is added as a dependency should have default-features = false. Audio is controlled by the bevy_audio feature, so it can be turned off.

However, I don't think wasm32-wasi will work right now, as our bevy_asset crate currently forces a web-based implementation for wasm32. You can try to get the filesystem-based implementation work on wasi (and a pull request for this is welcome). Alternatively, if you don't need asset loading, you can use bevy subcrates directly (bevy_ecs + bevy_app + whatever else you need).

[jakobhellermann]

Audio is indeed behind a feature flag, just one that that is enabled by default: https://github.com/bevyengine/bevy/blob/main/docs/cargo_features.md.
If you run cargo check --no-default-features --target wasm32-wasi it checks without errors.

EDIT: yeah what @infmagic2047 said

[schtauffen]

I looked at just pulling the pieces I need but wasm_bindgen is utilized throughout the code, such as:

bevy/crates/bevy_app/src/schedule_runner.rs

Lines 116 to 155 in f907d67

	#[cfg(not(target_arch = "wasm32"))]
	{
	while let Ok(delay) = tick(&mut app, wait) {
	if let Some(delay) = delay {
	std::thread::sleep(delay);
	}
	}
	}
	#[cfg(target_arch = "wasm32")]
	{
	fn set_timeout(f: &Closure<dyn FnMut()>, dur: Duration) {
	web_sys::window()
	.unwrap()
	.set_timeout_with_callback_and_timeout_and_arguments_0(
	f.as_ref().unchecked_ref(),
	dur.as_millis() as i32,
	)
	.expect("Should register `setTimeout`.");
	}
	let asap = Duration::from_millis(1);
	let mut rc = Rc::new(app);
	let f = Rc::new(RefCell::new(None));
	let g = f.clone();
	let c = move || {
	let mut app = Rc::get_mut(&mut rc).unwrap();
	let delay = tick(&mut app, wait);
	match delay {
	Ok(delay) => {
	set_timeout(f.borrow().as_ref().unwrap(), delay.unwrap_or(asap))
	}
	Err(_) => {}
	}
	};
	*g.borrow_mut() = Some(Closure::wrap(Box::new(c) as Box<dyn FnMut()>));
	set_timeout(g.borrow().as_ref().unwrap(), asap);
	};
	}

It seems the engine authors equate the wasm32 target with being run in a browser which does not fit my use case. I would like the code to stay lean and mean and not attempt to punt to javascript at all (the code in the not wasm32 branch would suffice for me). I will explore writing patches but worry it is going to be a huge undertaking. Probably less of a burden than writing my own engine, however :P

[expenses]

You can't use wgpu with wasm32-wasi because it pretty heavily ties into wasm-bindgen (including js-sys and web-sys). See rustwasm/wasm-bindgen#2471.

[pedronasser]

The problem here goes way further than just audio, if I am not mistaken. Like @schtauffen mentioned bevy currently uses wasm-bindgen even on non graphical/audio related functionalities. So for example even if try to build just a bevy App() without any default-features or the default plugins, it will try to build with wasm-bindgen which is currently breaking on wasm32-wasi targets.

[schtauffen]

To recap: the initial errors were user error but the ticket itself is valid and is related to the use of wasm-bindgen as mentioned by @pedronasser . I initially forked and began working towards a wasm32-wasi friendly version with 0.7 but wasn't successful. I plan to attempt again from scratch with 0.8;

[schtauffen]

I cannot seem to remove labels, can S-User-Error be removed? @jakobhellermann

[bakcxoj]

This is also a huge issue for my work on the bevy_wasm crate. Bevy generates a huge amount of unnecessary wasm-bindgen calls that I have had to manually stub out. I really think the wasm-bindgen functionality should be gated behind a web or browser feature flag.