Relax T: Clone bound to only apply to static values

Cargo.toml

@@ -17,6 +17,7 @@ exclude = ["flake.nix", "flake.lock", ".envrc", "cliff.toml", "release-plz.toml"
 thiserror = "2.0"
 flume = { version = "0.11", optional = true }
 crossbeam-channel = { version = "0.5", optional = true }
+arc-swap = "1.7.1"
 
 [features]
 default = ["all"]

flake.nix

@@ -20,11 +20,17 @@
     flake-utils.lib.eachDefaultSystem (system: let
       overlays = [(import rust-overlay)];
       pkgs = import nixpkgs {inherit system overlays;};
-      rustToolchain = pkgs.pkgsBuildHost.rust-bin.stable.latest.default;
+      rustToolchain = pkgs.pkgsBuildHost.rust-bin.fromRustupToolchainFile ./rust-toolchain.toml;
+      rustToolchainNightly = pkgs.pkgsBuildHost.rust-bin.nightly.latest.default;
       tools = with pkgs; [cargo-nextest];
-      nativeBuildInputs = with pkgs; [rustToolchain pkg-config] ++ tools;
+      nativeBuildInputs = with pkgs; [rustToolchain rustToolchainNightly pkg-config] ++ tools;
     in
       with pkgs; {
-        devShells.default = mkShell {inherit nativeBuildInputs;};
+        devShells.default = mkShell {
+          inherit nativeBuildInputs;
+          shellHook = ''
+            export CARGO_NIGHTLY="${rustToolchainNightly}/bin/cargo"
+          '';
+        };
       });
 }

src/channel.rs

@@ -1,3 +1,4 @@
+use std::sync::atomic::{AtomicBool, Ordering};
 use std::sync::{Arc, Mutex};
 
 use crate::error::Error;
@@ -10,10 +11,26 @@ where
     ST: ChannelSender<Request>,
     SR: ChannelReceiver<Response<T>>,
 {
-    pub(crate) request_tx: ST,
+    request_tx: ST,
-    pub(crate) response_rx: SR,
+    response_rx: SR,
-    pub(crate) closed: Mutex<bool>,
+    closed: AtomicBool,
-    pub(crate) _phantom: std::marker::PhantomData<T>,
+    _phantom: std::marker::PhantomData<T>,
+}
+
+impl<T, ST, SR> Sucker<T, ST, SR>
+where
+    ST: ChannelSender<Request>,
+    SR: ChannelReceiver<Response<T>>,
+{
+    /// Create a new Sucker instance
+    pub(crate) fn new(request_tx: ST, response_rx: SR) -> Self {
+        Self {
+            request_tx,
+            response_rx,
+            closed: AtomicBool::new(false),
+            _phantom: std::marker::PhantomData,
+        }
+    }
 }
 
 /// The producer side of the channel that provides values
@@ -22,46 +39,71 @@ where
     SR: ChannelReceiver<Request>,
     ST: ChannelSender<Response<T>>,
 {
-    pub(crate) request_rx: SR,
+    request_rx: SR,
-    pub(crate) response_tx: ST,
+    response_tx: ST,
-    pub(crate) state: Arc<Mutex<ChannelState<T>>>,
+    state: ChannelState<T>,
-    pub(crate) _phantom: std::marker::PhantomData<T>,
+    _phantom: std::marker::PhantomData<T>,
 }
 
 impl<T, SR, ST> Sourcer<T, SR, ST>
 where
-    T: Clone + Send + 'static,
+    SR: ChannelReceiver<Request>,
+    ST: ChannelSender<Response<T>>,
+{
+    /// Create a new Sourcer instance
+    pub(crate) fn new(request_rx: SR, response_tx: ST, state: ChannelState<T>) -> Self {
+        Self {
+            request_rx,
+            response_tx,
+            state,
+            _phantom: std::marker::PhantomData,
+        }
+    }
+}
+
+impl<T, SR, ST> Sourcer<T, SR, ST>
+where
+    T: Send + 'static,
     SR: ChannelReceiver<Request>,
     ST: ChannelSender<Response<T>>,
 {
     /// Set a fixed value
-    pub fn set_static(&self, value: T) -> Result<(), Error> {
+    pub fn set_static(&self, val: T) -> Result<(), Error>
-        let mut state = self.state.lock().map_err(|_| Error::InternalError)?;
+    where
-        if state.closed {
+        T: Clone,
-            return Err(Error::ChannelClosed);
+    {
-        }
+        self.state.swap(Arc::new(ValueSource::Static {
-        state.source = ValueSource::Static(value);
+            val,
+            clone: T::clone,
+        }));
         Ok(())
     }
 
-    /// Set a closure
+    /// Set a closure that implements [Fn]
     pub fn set<F>(&self, closure: F) -> Result<(), Error>
     where
         F: Fn() -> T + Send + Sync + 'static,
     {
-        let mut state = self.state.lock().map_err(|_| Error::InternalError)?;
+        self.state
-        if state.closed {
+            .swap(Arc::new(ValueSource::Dynamic(Box::new(closure))));
-            return Err(Error::ChannelClosed);
+        Ok(())
     }
-        state.source = ValueSource::Dynamic(Box::new(closure));
+
+    /// Set a closure that implements [FnMut]
+    pub fn set_mut<F>(&self, closure: F) -> Result<(), Error>
+    where
+        F: FnMut() -> T + Send + Sync + 'static,
+    {
+        self.state
+            .swap(Arc::new(ValueSource::DynamicMut(Mutex::new(Box::new(
+                closure,
+            )))));
         Ok(())
     }
 
     /// Close the channel
     pub fn close(&self) -> Result<(), Error> {
-        let mut state = self.state.lock().map_err(|_| Error::InternalError)?;
+        self.state.swap(Arc::new(ValueSource::Cleared));
-        state.closed = true;
-        state.source = ValueSource::None;
         Ok(())
     }
 
@@ -78,9 +120,7 @@ where
                 }
                 Ok(Request::Close) => {
                     // Close channel
-                    let mut state = self.state.lock().map_err(|_| Error::InternalError)?;
+                    self.close()?;
-                    state.closed = true;
-                    state.source = ValueSource::None;
                     break;
                 }
                 Err(_) => {
@@ -93,27 +133,39 @@ where
     }
 
     fn handle_get_value(&self) -> Result<Response<T>, Error> {
-        let state = self.state.lock().map_err(|_| Error::InternalError)?;
+        let state = self.state.load();
-        if state.closed {
-            return Ok(Response::Closed);
-        }
 
-        match &state.source {
+        match &**state {
-            ValueSource::Static(value) => Ok(Response::Value(value.clone())),
+            ValueSource::Static { val, clone } => {
-            ValueSource::Dynamic(closure) => {
+                let value = self.execute_closure_safely(&mut || clone(val));
-                let value = self.execute_closure_safely(closure);
                 match value {
                     Ok(v) => Ok(Response::Value(v)),
                     Err(_) => Ok(Response::NoSource), // Closure execution failed
                 }
             }
-            ValueSource::None => Ok(Response::NoSource),
+            ValueSource::Dynamic(closure) => {
+                let value = self.execute_closure_safely(&mut || closure());
+                match value {
+                    Ok(v) => Ok(Response::Value(v)),
+                    Err(_) => Ok(Response::NoSource), // Closure execution failed
+                }
+            }
+            ValueSource::DynamicMut(closure) => {
+                let mut closure = closure.lock().unwrap();
+                let value = self.execute_closure_safely(&mut *closure);
+                match value {
+                    Ok(v) => Ok(Response::Value(v)),
+                    Err(_) => Ok(Response::NoSource), // Closure execution failed
+                }
+            }
+            ValueSource::None => Ok(Response::NoSource), // No source was ever set
+            ValueSource::Cleared => Ok(Response::Closed), // Channel was closed (source was set then cleared)
         }
     }
 
     fn execute_closure_safely(
         &self,
-        closure: &dyn Fn() -> T,
+        closure: &mut dyn FnMut() -> T,
     ) -> Result<T, Box<dyn std::any::Any + Send>> {
         std::panic::catch_unwind(std::panic::AssertUnwindSafe(closure))
     }
@@ -127,7 +179,7 @@ where
     /// Get the current value from the producer
     pub fn get(&self) -> Result<T, Error> {
         // Check if locally marked as closed
-        if *self.closed.lock().unwrap() {
+        if self.closed.load(Ordering::Acquire) {
             return Err(Error::ChannelClosed);
         }
 
@@ -152,7 +204,7 @@ where
     /// Close the channel from the consumer side
     pub fn close(&self) -> Result<(), Error> {
         // Mark locally as closed
-        *self.closed.lock().unwrap() = true;
+        self.closed.store(true, Ordering::Release);
 
         // Send close request
         self.request_tx

src/sync/crossbeam.rs

@@ -1,6 +1,9 @@
+use std::sync::Arc;
+
 #[cfg(feature = "sync-crossbeam")]
 use crate::sync::traits::{ChannelError, ChannelReceiver, ChannelSender, ChannelType};
 use crate::types;
+use arc_swap::ArcSwap;
 use crossbeam_channel;
 
 type CrossbeamSucker<T> =
@@ -62,24 +65,10 @@ impl<T> CrossbeamSuck<T> {
         let (request_tx, request_rx) = CrossbeamChannel::create_request_channel();
         let (response_tx, response_rx) = CrossbeamChannel::create_response_channel::<T>();
 
-        let state = std::sync::Arc::new(std::sync::Mutex::new(crate::types::ChannelState {
+        let state = ArcSwap::new(Arc::new(crate::types::ValueSource::None));
-            source: crate::types::ValueSource::None,
-            closed: false,
-        }));
 
-        let sucker = crate::Sucker {
+        let sucker = crate::Sucker::new(request_tx, response_rx);
-            request_tx,
+        let sourcer = crate::Sourcer::new(request_rx, response_tx, state);
-            response_rx,
-            closed: std::sync::Mutex::new(false),
-            _phantom: std::marker::PhantomData,
-        };
-
-        let sourcer = crate::Sourcer {
-            request_rx,
-            response_tx,
-            state: std::sync::Arc::clone(&state),
-            _phantom: std::marker::PhantomData,
-        };
 
         (sucker, sourcer)
     }

src/sync/flume.rs

@@ -1,6 +1,9 @@
+use std::sync::Arc;
+
 #[cfg(feature = "sync-flume")]
 use crate::sync::traits::{ChannelError, ChannelReceiver, ChannelSender, ChannelType};
 use crate::types;
+use arc_swap::ArcSwap;
 use flume;
 
 type FlumeSucker<T> =
@@ -62,24 +65,11 @@ impl<T> FlumeSuck<T> {
         let (request_tx, request_rx) = FlumeChannel::create_request_channel();
         let (response_tx, response_rx) = FlumeChannel::create_response_channel::<T>();
 
-        let state = std::sync::Arc::new(std::sync::Mutex::new(crate::types::ChannelState {
+        let state = Arc::new(crate::types::ValueSource::None);
-            source: crate::types::ValueSource::None,
+        let state = ArcSwap::new(state);
-            closed: false,
-        }));
 
-        let sucker = crate::Sucker {
+        let sucker = crate::Sucker::new(request_tx, response_rx);
-            request_tx,
+        let sourcer = crate::Sourcer::new(request_rx, response_tx, state);
-            response_rx,
-            closed: std::sync::Mutex::new(false),
-            _phantom: std::marker::PhantomData,
-        };
-
-        let sourcer = crate::Sourcer {
-            request_rx,
-            response_tx,
-            state: std::sync::Arc::clone(&state),
-            _phantom: std::marker::PhantomData,
-        };
 
         (sucker, sourcer)
     }

src/sync/std.rs

@@ -1,5 +1,8 @@
+use arc_swap::ArcSwap;
+
 use crate::sync::traits::{ChannelError, ChannelReceiver, ChannelSender, ChannelType};
 use crate::types;
+use std::sync::Arc;
 #[cfg(feature = "sync-std")]
 use std::sync::mpsc;
 
@@ -60,24 +63,11 @@ impl<T> StdSuck<T> {
         let (request_tx, request_rx) = StdChannel::create_request_channel();
         let (response_tx, response_rx) = StdChannel::create_response_channel::<T>();
 
-        let state = std::sync::Arc::new(std::sync::Mutex::new(crate::types::ChannelState {
+        let state = Arc::new(crate::types::ValueSource::None);
-            source: crate::types::ValueSource::None,
+        let state = ArcSwap::new(state);
-            closed: false,
-        }));
 
-        let sucker = crate::Sucker {
+        let sucker = crate::Sucker::new(request_tx, response_rx);
-            request_tx,
+        let sourcer = crate::Sourcer::new(request_rx, response_tx, state);
-            response_rx,
-            closed: std::sync::Mutex::new(false),
-            _phantom: std::marker::PhantomData,
-        };
-
-        let sourcer = crate::Sourcer {
-            request_rx,
-            response_tx,
-            state: std::sync::Arc::clone(&state),
-            _phantom: std::marker::PhantomData,
-        };
 
         (sucker, sourcer)
     }

src/types.rs

@@ -1,3 +1,7 @@
+use std::sync::Mutex;
+
+use arc_swap::ArcSwap;
+
 /// Request messages sent from consumer to producer
 pub enum Request {
     GetValue,
@@ -13,13 +17,12 @@ pub enum Response<T> {
 
 /// Represents the source of values: either static or dynamic
 pub(crate) enum ValueSource<T> {
-    Static(T),
+    Static { val: T, clone: fn(&T) -> T },
+    DynamicMut(Mutex<Box<dyn FnMut() -> T + Send + Sync + 'static>>),
     Dynamic(Box<dyn Fn() -> T + Send + Sync + 'static>),
-    None,
+    None,    // Never set
+    Cleared, // Was set but cleared (closed)
 }
 
 /// Internal channel state shared between producer and consumer
-pub(crate) struct ChannelState<T> {
+pub(crate) type ChannelState<T> = ArcSwap<ValueSource<T>>;
-    pub(crate) source: ValueSource<T>,
-    pub(crate) closed: bool,
-}