tests: enable running wasm32-unknown-unknown tests (#4421)

* Several of tokio's features (e.g. the channel implementation) do not
  need a runtime to work, and can be compiled and used for
  wasm32-unknown-unknown targets
* This change enables running tests for the `sync` and `macros` features
  so that we can note any regressions there

Author: ipetkov

.github/workflows/ci.yml

@@ -36,6 +36,7 @@ jobs:
       - loom-compile
       - check-readme
       - test-hyper
+      - wasm32-unknown-unknown
     steps:
       - run: exit 0
 
@@ -391,3 +392,17 @@ jobs:
           echo 'tokio-test = { path = "../tokio-test" }' >>Cargo.toml
           git diff
           cargo test --features full
+
+  wasm32-unknown-unknown:
+    name: test tokio for wasm32-unknown-unknown
+    runs-on: ubuntu-latest
+    steps:
+      - uses: actions/checkout@v2
+      - name: Install Rust
+        run: rustup update stable
+      - uses: Swatinem/rust-cache@v1
+      - name: Install wasm-pack
+        run: curl https://rustwasm.github.io/wasm-pack/installer/init.sh -sSf | sh
+      - name: test tokio
+        run: wasm-pack test --node -- --features "macros sync"
+        working-directory: tokio

tokio/Cargo.toml

@@ -128,12 +128,17 @@ tokio-test = { version = "0.4.0", path = "../tokio-test" }
 tokio-stream = { version = "0.1", path = "../tokio-stream" }
 futures = { version = "0.3.0", features = ["async-await"] }
 mockall = "0.10.2"
-proptest = "1"
-rand = "0.8.0"
 tempfile = "3.1.0"
 async-stream = "0.3"
+
+[target.'cfg(not(target_arch = "wasm32"))'.dev-dependencies]
+proptest = "1"
+rand = "0.8.0"
 socket2 = "0.4"
 
+[target.'cfg(target_arch = "wasm32")'.dev-dependencies]
+wasm-bindgen-test = "0.3.0"
+
 [target.'cfg(target_os = "freebsd")'.dev-dependencies]
 mio-aio = { version = "0.6.0", features = ["tokio"] }
 

tokio/src/coop.rs

@@ -207,6 +207,9 @@ cfg_coop! {
 mod test {
     use super::*;
 
+    #[cfg(target_arch = "wasm32")]
+    use wasm_bindgen_test::wasm_bindgen_test as test;
+
     fn get() -> Budget {
         CURRENT.with(|cell| cell.get())
     }

tokio/src/runtime/mod.rs

@@ -174,6 +174,7 @@
 
 // At the top due to macros
 #[cfg(test)]
+#[cfg(not(target_arch = "wasm32"))]
 #[macro_use]
 mod tests;
 

tokio/src/runtime/task/mod.rs

@@ -347,6 +347,7 @@ impl<S: Schedule> LocalNotified<S> {
 impl<S: Schedule> UnownedTask<S> {
     // Used in test of the inject queue.
     #[cfg(test)]
+    #[cfg_attr(target_arch = "wasm32", allow(dead_code))]
     pub(super) fn into_notified(self) -> Notified<S> {
         Notified(self.into_task())
     }

tokio/src/sync/tests/atomic_waker.rs

@@ -12,6 +12,9 @@ impl AssertSync for AtomicWaker {}
 impl AssertSend for Waker {}
 impl AssertSync for Waker {}
 
+#[cfg(target_arch = "wasm32")]
+use wasm_bindgen_test::wasm_bindgen_test as test;
+
 #[test]
 fn basic_usage() {
     let mut waker = task::spawn(AtomicWaker::new());
@@ -34,6 +37,7 @@ fn wake_without_register() {
 }
 
 #[test]
+#[cfg(not(target_arch = "wasm32"))] // wasm currently doesn't support unwinding
 fn atomic_waker_panic_safe() {
     use std::panic;
     use std::ptr;

tokio/src/sync/tests/notify.rs

@@ -4,6 +4,9 @@ use std::mem::ManuallyDrop;
 use std::sync::Arc;
 use std::task::{Context, RawWaker, RawWakerVTable, Waker};
 
+#[cfg(target_arch = "wasm32")]
+use wasm_bindgen_test::wasm_bindgen_test as test;
+
 #[test]
 fn notify_clones_waker_before_lock() {
     const VTABLE: &RawWakerVTable = &RawWakerVTable::new(clone_w, wake, wake_by_ref, drop_w);

tokio/src/sync/tests/semaphore_batch.rs

@@ -1,6 +1,9 @@
 use crate::sync::batch_semaphore::Semaphore;
 use tokio_test::*;
 
+#[cfg(target_arch = "wasm32")]
+use wasm_bindgen_test::wasm_bindgen_test as test;
+
 #[test]
 fn poll_acquire_one_available() {
     let s = Semaphore::new(100);
@@ -167,6 +170,7 @@ fn poll_acquire_one_zero_permits() {
 
 #[test]
 #[should_panic]
+#[cfg(not(target_arch = "wasm32"))] // wasm currently doesn't support unwinding
 fn validates_max_permits() {
     use std::usize;
     Semaphore::new((usize::MAX >> 2) + 1);

tokio/src/util/linked_list.rs

@@ -614,6 +614,7 @@ mod tests {
         }
     }
 
+    #[cfg(not(target_arch = "wasm32"))]
     proptest::proptest! {
         #[test]
         fn fuzz_linked_list(ops: Vec<usize>) {

tokio/tests/_require_full.rs

@@ -1,2 +1,2 @@
-#![cfg(not(feature = "full"))]
+#![cfg(not(any(feature = "full", target_arch = "wasm32")))]
 compile_error!("run main Tokio tests with `--features full`");