feat: emit chain notifications (#9732)

crates/chain-state/src/in_memory.rs

@@ -1,6 +1,8 @@
 //! Types for tracking the canonical chain state in memory.
 
-use crate::{CanonStateNotificationSender, CanonStateNotifications, ChainInfoTracker};
+use crate::{
+    CanonStateNotification, CanonStateNotificationSender, CanonStateNotifications, ChainInfoTracker,
+};
 use parking_lot::RwLock;
 use reth_chainspec::ChainInfo;
 use reth_execution_types::ExecutionOutcome;
@@ -251,6 +253,11 @@ impl CanonicalInMemoryState {
     pub fn subscribe_canon_state(&self) -> CanonStateNotifications {
         self.inner.canon_state_notification_sender.subscribe()
     }
+
+    /// Attempts to send a new [`CanonStateNotification`] to all active Receiver handles.
+    pub fn notify_canon_state(&self, event: CanonStateNotification) {
+        self.inner.canon_state_notification_sender.send(event).ok();
+    }
 }
 
 /// State after applying the given block.

crates/engine/tree/src/tree/mod.rs

@@ -1380,7 +1380,9 @@ where
             // TODO
             //  update inmemory state
             //  update trackers
-            //  emit notification
+
+            // sends an event to all active listeners about the new canonical chain
+            self.canonical_in_memory_state.notify_canon_state(update.to_chain_notification());
 
             if let Some(attr) = attrs {
                 let updated = self.process_payload_attributes(attr, &update.tip().header, state);