feat: add a side_effect waiter which takes a function

And call that function every tick.

Author: hansl

delay/Cargo.toml

@@ -1,6 +1,6 @@
 [package]
 name = "delay"
-version = "0.2.0"
+version = "0.3.0"
 authors = ["Hans Larsen <[email protected]>"]
 edition = "2018"
 description = "A collection of trait and classes to make your thread wait (and timeout)."

delay/src/lib.rs

@@ -96,6 +96,15 @@ impl Delay {
         Self::exponential_backoff_capped(initial, multiplier, Duration::from_secs(std::u64::MAX))
     }
 
+    /// Call a function every tick, expecting some kind of side effect (e.g. a progress
+    /// bar).
+    pub fn side_effect<F>(function: F) -> Self
+    where
+        F: 'static + Sync + Send + Clone + Fn() -> Result<(), WaiterError>,
+    {
+        Self::from(Box::new(SideEffectWaiter::new(function)))
+    }
+
     pub fn builder() -> DelayBuilder {
         DelayBuilder { inner: None }
     }
@@ -142,6 +151,12 @@ impl DelayBuilder {
     ) -> Self {
         self.with(Delay::exponential_backoff_capped(initial, multiplier, cap))
     }
+    pub fn side_effect<F>(self, function: F) -> Self
+    where
+        F: 'static + Sync + Send + Clone + Fn() -> Result<(), WaiterError>,
+    {
+        self.with(Delay::side_effect(function))
+    }
     pub fn build(mut self) -> Delay {
         self.inner.take().unwrap_or_else(Delay::instant)
     }
@@ -289,3 +304,28 @@ impl Waiter for ExponentialBackoffWaiter {
         Ok(())
     }
 }
+
+#[derive(Clone)]
+struct SideEffectWaiter<F>
+where
+    F: 'static + Sync + Send + Clone + Fn() -> Result<(), WaiterError>,
+{
+    function: F,
+}
+
+impl<F> SideEffectWaiter<F>
+where
+    F: 'static + Sync + Send + Clone + Fn() -> Result<(), WaiterError>,
+{
+    pub fn new(function: F) -> Self {
+        Self { function }
+    }
+}
+impl<F> Waiter for SideEffectWaiter<F>
+where
+    F: 'static + Sync + Send + Clone + Fn() -> Result<(), WaiterError>,
+{
+    fn wait(&self) -> Result<(), WaiterError> {
+        (self.function)()
+    }
+}