fix issues running component-async-tests under miri

crates/misc/component-async-tests/src/round_trip.rs

@@ -25,7 +25,7 @@ pub mod non_concurrent_export_bindings {
 
 impl bindings::local::local::baz::HostConcurrent for Ctx {
     async fn foo<T>(_: &mut Accessor<T, Self>, s: String) -> wasmtime::Result<String> {
-        tokio::time::sleep(Duration::from_millis(10)).await;
+        crate::util::sleep(Duration::from_millis(10)).await;
         Ok(format!("{s} - entered host - exited host"))
     }
 }

crates/misc/component-async-tests/src/round_trip_direct.rs

@@ -15,7 +15,7 @@ pub mod bindings {
 
 impl bindings::RoundTripDirectImportsConcurrent for Ctx {
     async fn foo<T>(_: &mut Accessor<T, Self>, s: String) -> wasmtime::Result<String> {
-        tokio::time::sleep(Duration::from_millis(10)).await;
+        crate::util::sleep(Duration::from_millis(10)).await;
         Ok(format!("{s} - entered host - exited host"))
     }
 }

crates/misc/component-async-tests/src/round_trip_many.rs

@@ -47,7 +47,7 @@ impl bindings::local::local::many::HostConcurrent for Ctx {
         Option<Stuff>,
         Result<Stuff, ()>,
     )> {
-        tokio::time::sleep(Duration::from_millis(10)).await;
+        crate::util::sleep(Duration::from_millis(10)).await;
         Ok((
             format!("{a} - entered host - exited host"),
             b,

crates/misc/component-async-tests/src/sleep.rs

@@ -16,7 +16,7 @@ wasmtime::component::bindgen!({
 
 impl local::local::sleep::HostConcurrent for Ctx {
     async fn sleep_millis<T>(_: &mut Accessor<T, Self>, time_in_millis: u64) {
-        tokio::time::sleep(Duration::from_millis(time_in_millis)).await;
+        crate::util::sleep(Duration::from_millis(time_in_millis)).await;
     }
 }
 

crates/misc/component-async-tests/src/util.rs

@@ -42,6 +42,60 @@ pub fn config() -> Config {
     config
 }
 
+pub async fn sleep(duration: std::time::Duration) {
+    if cfg!(miri) {
+        // TODO: We should be able to use `tokio::time::sleep` here, but as of
+        // this writing the miri-compatible version of `wasmtime-fiber` uses
+        // threads behind the scenes, which means thread-local storage is not
+        // preserved when we switch fibers, and that confuses Tokio.  If we ever
+        // fix that we can stop using our own, special version of `sleep` and
+        // switch back to the Tokio version.
+
+        use std::{
+            future,
+            sync::{
+                Arc, Mutex,
+                atomic::{AtomicU32, Ordering::SeqCst},
+            },
+            task::Poll,
+            thread,
+        };
+
+        let state = Arc::new(AtomicU32::new(0));
+        let waker = Arc::new(Mutex::new(None));
+        let mut join_handle = None;
+        future::poll_fn(move |cx| match state.load(SeqCst) {
+            0 => {
+                state.store(1, SeqCst);
+                let state = state.clone();
+                *waker.lock().unwrap() = Some(cx.waker().clone());
+                let waker = waker.clone();
+                join_handle = Some(thread::spawn(move || {
+                    thread::sleep(duration);
+                    state.store(2, SeqCst);
+                    let waker = waker.lock().unwrap().clone().unwrap();
+                    waker.wake();
+                }));
+                Poll::Pending
+            }
+            1 => {
+                *waker.lock().unwrap() = Some(cx.waker().clone());
+                Poll::Pending
+            }
+            2 => {
+                if let Some(handle) = join_handle.take() {
+                    _ = handle.join();
+                }
+                Poll::Ready(())
+            }
+            _ => unreachable!(),
+        })
+        .await;
+    } else {
+        tokio::time::sleep(duration).await;
+    }
+}
+
 /// Compose two components
 ///
 /// a is the "root" component, and b is composed into it
@@ -166,7 +220,11 @@ pub async fn test_run(components: &[&str]) -> Result<()> {
 
 pub async fn test_run_with_count(components: &[&str], count: usize) -> Result<()> {
     let mut config = config();
-    config.epoch_interruption(true);
+    // As of this writing, miri/pulley/epochs is a problematic combination, so
+    // we don't test it.
+    if env::var_os("MIRI_TEST_CWASM_DIR").is_none() {
+        config.epoch_interruption(true);
+    }
 
     let engine = Engine::new(&config)?;
 
@@ -198,12 +256,15 @@ pub async fn test_run_with_count(components: &[&str], count: usize) -> Result<()
             wakers: Arc::new(std::sync::Mutex::new(None)),
         },
     );
-    store.set_epoch_deadline(1);
 
-    std::thread::spawn(move || {
-        std::thread::sleep(Duration::from_secs(10));
-        engine.increment_epoch();
-    });
+    if env::var_os("MIRI_TEST_CWASM_DIR").is_none() {
+        store.set_epoch_deadline(1);
+
+        std::thread::spawn(move || {
+            std::thread::sleep(Duration::from_secs(10));
+            engine.increment_epoch();
+        });
+    }
 
     let instance = linker.instantiate_async(&mut store, &component).await?;
     let yield_host = super::yield_host::bindings::YieldHost::new(&mut store, &instance)?;

crates/misc/component-async-tests/tests/scenario/borrowing.rs

@@ -1,3 +1,4 @@
+use std::env;
 use std::sync::{Arc, Mutex};
 use std::time::Duration;
 
@@ -65,7 +66,11 @@ pub async fn async_borrowing_callee() -> Result<()> {
 
 pub async fn test_run_bool(components: &[&str], v: bool) -> Result<()> {
     let mut config = config();
-    config.epoch_interruption(true);
+    // As of this writing, miri/pulley/epochs is a problematic combination, so
+    // we don't test it.
+    if env::var_os("MIRI_TEST_CWASM_DIR").is_none() {
+        config.epoch_interruption(true);
+    }
 
     let engine = Engine::new(&config)?;
 
@@ -88,12 +93,15 @@ pub async fn test_run_bool(components: &[&str], v: bool) -> Result<()> {
             wakers: Arc::new(Mutex::new(None)),
         },
     );
-    store.set_epoch_deadline(1);
 
-    std::thread::spawn(move || {
-        std::thread::sleep(Duration::from_secs(10));
-        engine.increment_epoch();
-    });
+    if env::var_os("MIRI_TEST_CWASM_DIR").is_none() {
+        store.set_epoch_deadline(1);
+
+        std::thread::spawn(move || {
+            std::thread::sleep(Duration::from_secs(10));
+            engine.increment_epoch();
+        });
+    }
 
     let instance = linker.instantiate_async(&mut store, &component).await?;
     let borrowing_host =

crates/misc/component-async-tests/tests/scenario/common.rs

@@ -49,7 +49,11 @@ pub async fn compose(a: &[u8], b: &[u8]) -> Result<Vec<u8>> {
 #[allow(unused)]
 pub async fn test_run(component: &[u8]) -> Result<()> {
     let mut config = config();
-    config.epoch_interruption(true);
+    // As of this writing, miri/pulley/epochs is a problematic combination, so
+    // we don't test it.
+    if env::var_os("MIRI_TEST_CWASM_DIR").is_none() {
+        config.epoch_interruption(true);
+    }
 
     let engine = Engine::new(&config)?;
 
@@ -80,12 +84,15 @@ pub async fn test_run(component: &[u8]) -> Result<()> {
             wakers: Arc::new(Mutex::new(None)),
         },
     );
-    store.set_epoch_deadline(1);
 
-    std::thread::spawn(move || {
-        std::thread::sleep(Duration::from_secs(10));
-        engine.increment_epoch();
-    });
+    if env::var_os("MIRI_TEST_CWASM_DIR").is_none() {
+        store.set_epoch_deadline(1);
+
+        std::thread::spawn(move || {
+            std::thread::sleep(Duration::from_secs(10));
+            engine.increment_epoch();
+        });
+    }
 
     let yield_host = component_async_tests::yield_host::bindings::YieldHost::instantiate_async(
         &mut store, &component, &linker,

crates/misc/component-async-tests/tests/scenario/error_context.rs

@@ -7,10 +7,12 @@ pub async fn async_error_context() -> Result<()> {
     test_run(&[test_programs_artifacts::ASYNC_ERROR_CONTEXT_COMPONENT]).await
 }
 
-#[tokio::test]
-pub async fn async_error_context_callee() -> Result<()> {
-    test_run(&[test_programs_artifacts::ASYNC_ERROR_CONTEXT_COMPONENT]).await
-}
+// No-op function; we only test this by composing it in `async_error_context_caller`
+#[allow(
+    dead_code,
+    reason = "here only to make the `assert_test_exists` macro happy"
+)]
+pub fn async_error_context_callee() {}
 
 #[tokio::test]
 pub async fn async_error_context_caller() -> Result<()> {