Fix wasm32 compile errors

.github/workflows/ci.yml

@@ -37,12 +37,14 @@ jobs:
       - uses: actions/checkout@v4
       - name: Install Rust
         run: rustup update ${{ matrix.rust }} && rustup default ${{ matrix.rust }}
+      - run: rustup target add wasm32-unknown-unknown
       - run: cargo build --all --all-features --all-targets
         if: startsWith(matrix.rust, 'nightly')
       - name: Run cargo check (without dev-dependencies to catch missing feature flags)
         if: startsWith(matrix.rust, 'nightly')
         run: cargo check -Z features=dev_dep
       - run: cargo test
+      - run: cargo check --all --all-features --target wasm32-unknown-unknown
 
   msrv:
     runs-on: ubuntu-latest

Cargo.toml

@@ -22,6 +22,10 @@ fastrand = "2.0.0"
 futures-lite = { version = "2.0.0", default-features = false }
 slab = "0.4.4"
 
+[target.'cfg(target_family = "wasm")'.dependencies]
+js-sys = "0.3.65"
+wasm-bindgen = "0.2.88"
+
 [dev-dependencies]
 async-channel = "2.0.0"
 async-io = "2.1.0"

src/lib.rs

@@ -263,7 +263,18 @@ impl<'a> Executor<'a> {
 
     /// Returns a reference to the inner state.
     fn state(&self) -> &Arc<State> {
-        self.state.get_or_init_blocking(|| Arc::new(State::new()))
+        #[cfg(not(target_family = "wasm"))]
+        {
+            return self.state.get_or_init_blocking(|| Arc::new(State::new()));
+        }
+
+        // Some projects use this on WASM for some reason. In this case get_or_init_blocking
+        // doesn't work. Just poll the future once and panic if there is contention.
+        #[cfg(target_family = "wasm")]
+        future::block_on(future::poll_once(
+            self.state.get_or_init(|| async { Arc::new(State::new()) }),
+        ))
+        .expect("encountered contention on WASM")
     }
 }
 

src/wasm.rs

@@ -0,0 +1,33 @@
+//! WebAssembly implementation of the executor.
+
+use std::collections::VecDeque;
+use std::sync::{Arc, Mutex};
+
+use async_task::{Runnable, Task};
+use js_sys::Promise;
+use wasm_bindgen::prelude::*;
+
+/// The state of the executor.
+pub(super) struct State {
+
+}
+
+impl State {
+    /// Create a new, empty executor state.
+    #[inline]
+    pub(crate) fn new() -> Self {
+
+    }
+}
+
+#[wasm_bindgen]
+extern "C" {
+    #[wasm_bindgen]
+    fn queueMicrotask(closure: &Closure<dyn FnMut(JsValue)>);
+
+    type Global;
+
+    #[wasm_bindgen(method, getter, js_name = queueMicrotask)]
+    fn hasQueueMicrotask(this: &Global) -> JsValue;
+}
+