Enable wasm-bindgen feature with target wasm32-unknown-emscripten - #1349
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DouglasDwyer wants to merge 1 commit into
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Enable wasm-bindgen feature with target wasm32-unknown-emscripten#1349DouglasDwyer wants to merge 1 commit into
DouglasDwyer wants to merge 1 commit into
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The WebAudio host and its `wasm-bindgen`/`js-sys`/`web-sys` dependencies were gated on `all(target_arch = "wasm32", target_os = "unknown", feature = "wasm-bindgen")`. Nothing in the host needs `target_os = "unknown"` -- only `wasm32` and the browser Web APIs `feature = "wasm-bindgen"` pulls in -- so on `wasm32-unknown-emscripten` cpal silently fell back to the `null` host. Drop the `target_os = "unknown"` clause from the WebAudio gates (host/mod.rs, platform/mod.rs, lib.rs, sample_format.rs, Cargo.toml). `wasm32-unknown-unknown` still matches unchanged. The AudioWorklet host stays `wasm32-unknown-unknown`-only: its `worklet.js` bootstrap re-instantiates the module through wasm-bindgen's ESM `initSync`, which only exists in the `bundler`/`web` output that `target_os = "unknown"` implies. Its module gate, its `platform_impl` entry, and `frames_to_duration` (its sole wasm consumer) keep the constraint. Switch the WebAudio host's three JS event closures to `Closure::wrap_aborting`. `Closure::wrap` requires the closure to be `UnwindSafe` under `panic = "unwind"`, which is the default only on `wasm32-unknown-emscripten`; `wrap_aborting` selects the non-catching invoke shim on every target, identical to what `wrap` already did on the `panic = "abort"` wasm targets. Raises the minimum `wasm-bindgen` to 0.2.110, where `wrap_aborting` was added. Add a `wasm-emscripten` job to the platform matrix and a `WASM-emscripten` clippy entry, mirroring the existing `wasm-bindgen` coverage. Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>
roderickvd
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Sep 1, 2026
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That's great! Not so long ago we removed the old Emscripten host that had become defunct. This seems like a light-weight manner to get Emscripten support back.
Beyond the changes requested in the review points, please also consider updating README.md with Emscripten support.
| }) | ||
| as Box<dyn FnMut(AudioProcessingEvent)>); | ||
| as Box<dyn FnMut(AudioProcessingEvent)>; | ||
| let on_audio_process = Closure::wrap_aborting(on_audio_process_fn); |
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wrap_abort instead of wrap would abort the whole WASM instance for regular WebAudio users, where currently they just get a JS exception.
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| [target.'cfg(all(target_arch = "wasm32", target_os = "unknown"))'.dependencies] | ||
| wasm-bindgen = { version = "0.2", optional = true } | ||
| [target.'cfg(target_arch = "wasm32")'.dependencies] |
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This is not necessary for wasm32-wasip1/wasip2.
| - `InputCallbackInfo`/`OutputCallbackInfo` merged into `CallbackInfo`. | ||
| - `InputStreamTimestamp`/`OutputStreamTimestamp` merged into `StreamTimestamp`; `capture`/`playback` renamed `device`. | ||
| - Renamed the `wasm-beep` and `audioworklet-beep` examples to `webaudio` and `audioworklet`. | ||
| - **WebAudio**: the host and its `wasm-bindgen`/`js-sys`/`web-sys` dependencies are now gated on `target_arch = "wasm32"` rather than `all(target_arch = "wasm32", target_os = "unknown")`, so the WebAudio host works under `wasm32-unknown-emscripten` (previously it fell back to the `null` host). The AudioWorklet host stays `wasm32-unknown-unknown`-only. Raises the minimum `wasm-bindgen` to 0.2.110. |
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Please make this consistent with the other lines: short and observable behavior, not implementation details.
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Summary
The
wasm-bindgentool is finally getting support for integration with Emscripten. The feature is still quite new, but this means that most of Rust's web ecosystem can now work with the Emscripten target. I'd like to usecpalin a WASM/Emscripten project, but right now thewasm32-unknown-emscriptentarget is hard-coded to use the null backend. This PR eliminates the feature gate to make thewasm-bindgenfeature work withwasm32-unknown-emscriptentoo.This PR exposes the
webaudiobackend but not theaudioworkletbackend. That backend relies on re-instantiating the WASM module, but the way Emscripten modules get instantiated is different, so it wouldn't work without more changes.Changes
#[cfg(all(target_arch = "wasm32", target_os = "unknown", feature = "wasm-bindgen"))]with#[cfg(all(target_arch = "wasm32", feature = "wasm-bindgen"))]for thewebaudiobackendClosure::wrap_abortinginstead ofClosure::wrapso that the code properly compiles on WASM targets withpanic=unwindwasm-bindgendependency to0.2.110in order to useClosure::wrap_abortingTesting
In my own project, I have gotten
cpalaudio working with a Rust/Emscripten WASM module in Chrome. This PR also adds CI checks to ensure that compilation is successful.Related issues
#92 #413 #810