Add Handler trait

lib/src/handler.rs

@@ -0,0 +1,42 @@
+// it would be good to have an async handle here but it's not clear how to do it
+
+/// A callable that can be used to hook into watchexec.
+pub trait Handler<T> {
+	type Error: std::error::Error;
+
+	fn handle(&mut self, _data: T) -> Result<(), Self::Error>;
+}
+
+impl<F, T, E> Handler<T> for F
+where
+	E: std::error::Error,
+	F: FnMut(T) -> Result<(), E> + Send + 'static,
+{
+	type Error = E;
+
+	fn handle(&mut self, data: T) -> Result<(), Self::Error> {
+		(self)(data)
+	}
+}
+
+impl<T> Handler<T> for std::sync::mpsc::Sender<T>
+where
+	T: Send,
+{
+	type Error = std::sync::mpsc::SendError<T>;
+
+	fn handle(&mut self, data: T) -> Result<(), Self::Error> {
+		self.send(data)
+	}
+}
+
+impl<T> Handler<T> for tokio::sync::mpsc::Sender<T>
+where
+	T: std::fmt::Debug,
+{
+	type Error = tokio::sync::mpsc::error::TrySendError<T>;
+
+	fn handle(&mut self, data: T) -> Result<(), Self::Error> {
+		self.try_send(data)
+	}
+}

lib/src/lib.rs

@@ -24,11 +24,14 @@ pub mod signal;
 
 // the core experience
 mod config;
+mod handler;
 mod watchexec;
 
 #[doc(inline)]
 pub use config::Config;
 #[doc(inline)]
+pub use handler::Handler;
+#[doc(inline)]
 pub use watchexec::Watchexec;
 
 // the *action* is debounced, not the events