Release 2.5.0

CHANGELOG.md

@@ -1,3 +1,7 @@
+# Version 2.5.0
+
+- Fix an issue where the future returned by `Mutex::lock_arc`/`Semaphore::acquire_arc` holds a reference to `self`. (#20, #21)
+
 # Version 2.4.0
 
 - Add WASM support. (#14)

Cargo.toml

@@ -3,15 +3,13 @@ name = "async-lock"
 # When publishing a new version:
 # - Update CHANGELOG.md
 # - Create "v2.x.y" git tag
-version = "2.4.0"
+version = "2.5.0"
 authors = ["Stjepan Glavina <stjepang@gmail.com>"]
 edition = "2018"
 rust-version = "1.43"
 description = "Async synchronization primitives"
 license = "Apache-2.0 OR MIT"
 repository = "https://github.com/smol-rs/async-lock"
-homepage = "https://github.com/smol-rs/async-lock"
-documentation = "https://docs.rs/async-lock"
 keywords = ["lock", "mutex", "rwlock", "semaphore", "barrier"]
 categories = ["asynchronous", "concurrency"]
 exclude = ["/.*"]

src/semaphore.rs

@@ -1,3 +1,4 @@
+use std::future::Future;
 use std::sync::atomic::{AtomicUsize, Ordering};
 use std::sync::Arc;
 
@@ -135,6 +136,21 @@ impl Semaphore {
         }
     }
 
+    async fn acquire_arc_impl(self: Arc<Self>) -> SemaphoreGuardArc {
+        let mut listener = None;
+
+        loop {
+            if let Some(guard) = self.try_acquire_arc() {
+                return guard;
+            }
+
+            match listener.take() {
+                None => listener = Some(self.event.listen()),
+                Some(l) => l.await,
+            }
+        }
+    }
+
     /// Waits for an owned permit for a concurrent operation.
     ///
     /// Returns a guard that releases the permit when dropped.
@@ -150,19 +166,8 @@ impl Semaphore {
     /// let guard = s.acquire_arc().await;
     /// # });
     /// ```
-    pub async fn acquire_arc(self: &Arc<Self>) -> SemaphoreGuardArc {
-        let mut listener = None;
-
-        loop {
-            if let Some(guard) = self.try_acquire_arc() {
-                return guard;
-            }
-
-            match listener.take() {
-                None => listener = Some(self.event.listen()),
-                Some(l) => l.await,
-            }
-        }
+    pub fn acquire_arc(self: &Arc<Self>) -> impl Future<Output = SemaphoreGuardArc> {
+        self.clone().acquire_arc_impl()
     }
 }
 

tests/semaphore.rs

@@ -81,3 +81,12 @@ fn multi_resource() {
         rx1.recv().unwrap();
     });
 }
+
+#[test]
+fn lifetime() {
+    // Show that the future keeps the semaphore alive.
+    let _fut = {
+        let mutex = Arc::new(Semaphore::new(2));
+        mutex.acquire_arc()
+    };
+}