Allow non-sync futures (#18)

* tests: run async tests only when "async" feature is enabled

Signed-off-by: Eliad Peller <eliad.peller@wiz.io>

* async_cron: don't require Future to be Sync

Signed-off-by: Eliad Peller <eliad.peller@wiz.io>

---------

Signed-off-by: Eliad Peller <eliad.peller@wiz.io>

Cargo.toml

@@ -25,5 +25,10 @@ chrono = "0.4"
 cron = "0.12"
 thiserror = "1.0"
 crossbeam-channel = "0.5"
-tokio = { version = "1.25", optional = true , features = ["sync", "rt-multi-thread", "time", "macros"] }
+tokio = { version = "1.25", optional = true, features = ["sync", "rt-multi-thread", "time", "macros"] }
 futures = { version = "0.3.26", optional = true }
+
+[[example]]
+name = "async_simple"
+path = "examples/async_simple.rs"
+required-features = ["async"]

src/async_cron.rs

@@ -53,7 +53,7 @@ where
     pub async fn add_fn<F, T>(&mut self, spec: &str, f: F) -> Result<usize>
     where
         F: 'static + Fn() -> T + Send + Sync,
-        T: 'static + Future<Output = ()> + Send + Sync,
+        T: 'static + Future<Output = ()> + Send,
     {
         let schedule = cron::Schedule::from_str(spec)?;
         self.schedule(schedule, f).await
@@ -184,7 +184,7 @@ where
     async fn schedule<F, T>(&mut self, schedule: cron::Schedule, f: F) -> Result<usize>
     where
         F: 'static + Fn() -> T + Send + Sync,
-        T: 'static + Future<Output = ()> + Send + Sync,
+        T: 'static + Future<Output = ()> + Send,
     {
         let next_id = self.next_id.fetch_add(1, Ordering::SeqCst);
 

tests/async.rs

@@ -1,5 +1,7 @@
+#[cfg(feature = "async")]
 #[cfg(test)]
 mod tests {
+    use std::cell::UnsafeCell;
     use std::sync::Arc;
 
     use chrono::{FixedOffset, Local, TimeZone};
@@ -28,9 +30,14 @@ mod tests {
 
         cron.add_fn("* * * * * *", move || {
             let counter1 = Arc::clone(&counter1);
+
+            // use UnsafeCell to make sure we can still use non-Sync types
+            let mut inc: UnsafeCell<usize> = 1.into();
+
             async move {
                 let mut value = counter1.lock().await;
-                *value += 1;
+                let inc = *inc.get_mut();
+                *value += inc;
             }
         })
         .await