feat: make EngineApiRequestHandler generic over request

crates/engine/tree/src/engine.rs

@@ -6,8 +6,7 @@ use crate::{
     download::{BlockDownloader, DownloadAction, DownloadOutcome},
 };
 use futures::{Stream, StreamExt};
-use reth_beacon_consensus::{BeaconConsensusEngineEvent, BeaconEngineMessage};
-use reth_engine_primitives::EngineTypes;
+use reth_beacon_consensus::BeaconConsensusEngineEvent;
 use reth_primitives::{SealedBlockWithSenders, B256};
 use std::{
     collections::HashSet,
@@ -54,12 +53,18 @@ impl<T, S, D> EngineHandler<T, S, D> {
     {
         Self { handler, incoming_requests, downloader }
     }
+
+    /// Returns a mutable reference to the request handler.
+    pub fn handler_mut(&mut self) -> &mut T {
+        &mut self.handler
+    }
 }
 
 impl<T, S, D> ChainHandler for EngineHandler<T, S, D>
 where
     T: EngineRequestHandler,
-    S: Stream<Item = T::Request> + Send + Sync + Unpin + 'static,
+    S: Stream + Send + Sync + Unpin + 'static,
+    <S as Stream>::Item: Into<T::Request>,
     D: BlockDownloader,
 {
     type Event = T::Event;
@@ -98,7 +103,7 @@ where
             // pop the next incoming request
             if let Poll::Ready(Some(req)) = self.incoming_requests.poll_next_unpin(cx) {
                 // and delegate the request to the handler
-                self.handler.on_event(FromEngine::Request(req));
+                self.handler.on_event(FromEngine::Request(req.into()));
                 // skip downloading in this iteration to allow the handler to process the request
                 continue
             }
@@ -156,32 +161,29 @@ pub trait EngineRequestHandler: Send + Sync {
 /// In case required blocks are missing, the handler will request them from the network, by emitting
 /// a download request upstream.
 #[derive(Debug)]
-pub struct EngineApiRequestHandler<T: EngineTypes> {
+pub struct EngineApiRequestHandler<Request> {
     /// channel to send messages to the tree to execute the payload.
-    to_tree: Sender<FromEngine<BeaconEngineMessage<T>>>,
+    to_tree: Sender<FromEngine<Request>>,
     /// channel to receive messages from the tree.
     from_tree: UnboundedReceiver<EngineApiEvent>,
 }
 
-impl<T> EngineApiRequestHandler<T>
-where
-    T: EngineTypes,
-{
+impl<Request> EngineApiRequestHandler<Request> {
     /// Creates a new `EngineApiRequestHandler`.
     pub const fn new(
-        to_tree: Sender<FromEngine<BeaconEngineMessage<T>>>,
+        to_tree: Sender<FromEngine<Request>>,
         from_tree: UnboundedReceiver<EngineApiEvent>,
     ) -> Self {
         Self { to_tree, from_tree }
     }
 }
 
-impl<T> EngineRequestHandler for EngineApiRequestHandler<T>
+impl<Request> EngineRequestHandler for EngineApiRequestHandler<Request>
 where
-    T: EngineTypes,
+    Request: Send,
 {
     type Event = BeaconConsensusEngineEvent;
-    type Request = BeaconEngineMessage<T>;
+    type Request = Request;
 
     fn on_event(&mut self, event: FromEngine<Self::Request>) {
         // delegate to the tree

crates/ethereum/engine/src/service.rs

@@ -33,7 +33,7 @@ use tokio_stream::wrappers::UnboundedReceiverStream;
 /// Alias for Ethereum chain orchestrator.
 type EthServiceType<DB, Client> = ChainOrchestrator<
     EngineHandler<
-        EngineApiRequestHandler<EthEngineTypes>,
+        EngineApiRequestHandler<BeaconEngineMessage<EthEngineTypes>>,
         UnboundedReceiverStream<BeaconEngineMessage<EthEngineTypes>>,
         BasicBlockDownloader<Client>,
     >,