fix(engine): Prevent instant miner from creating empty blocks

crates/engine/local/src/miner.rs

@@ -24,12 +24,14 @@ use tracing::error;
 
 /// A mining mode for the local dev engine.
 #[derive(Debug)]
-pub enum MiningMode {
+pub enum MiningMode<Pool: TransactionPool + Unpin> {
     /// In this mode a block is built as soon as
     /// a valid transaction reaches the pool.
     /// If `max_transactions` is set, a block is built when that many transactions have
     /// accumulated.
     Instant {
+        /// The transaction pool.
+        pool: Pool,
         /// Stream of transaction notifications.
         rx: Fuse<ReceiverStream<TxHash>>,
         /// Maximum number of transactions to accumulate before mining a block.
@@ -42,11 +44,11 @@ pub enum MiningMode {
     Interval(Interval),
 }
 
-impl MiningMode {
+impl<Pool: TransactionPool + Unpin> MiningMode<Pool> {
     /// Constructor for a [`MiningMode::Instant`]
-    pub fn instant<Pool: TransactionPool>(pool: Pool, max_transactions: Option<usize>) -> Self {
+    pub fn instant(pool: Pool, max_transactions: Option<usize>) -> Self {
         let rx = pool.pending_transactions_listener();
-        Self::Instant { rx: ReceiverStream::new(rx).fuse(), max_transactions, accumulated: 0 }
+        Self::Instant { pool, rx: ReceiverStream::new(rx).fuse(), max_transactions, accumulated: 0 }
     }
 
     /// Constructor for a [`MiningMode::Interval`]
@@ -56,15 +58,18 @@ impl MiningMode {
     }
 }
 
-impl Future for MiningMode {
+impl<Pool: TransactionPool + Unpin> Future for MiningMode<Pool> {
     type Output = ();
 
     fn poll(self: Pin<&mut Self>, cx: &mut Context<'_>) -> Poll<Self::Output> {
         let this = self.get_mut();
         match this {
-            Self::Instant { rx, max_transactions, accumulated } => {
+            Self::Instant { pool, rx, max_transactions, accumulated } => {
                 // Poll for new transaction notifications
                 while let Poll::Ready(Some(_)) = rx.poll_next_unpin(cx) {
+                    if pool.pending_and_queued_txn_count().0 == 0 {
+                        continue;
+                    }
                     if let Some(max_tx) = max_transactions {
                         *accumulated += 1;
                         // If we've reached the max transactions threshold, mine a block
@@ -91,13 +96,13 @@ impl Future for MiningMode {
 
 /// Local miner advancing the chain
 #[derive(Debug)]
-pub struct LocalMiner<T: PayloadTypes, B> {
+pub struct LocalMiner<T: PayloadTypes, B, Pool: TransactionPool + Unpin> {
     /// The payload attribute builder for the engine
     payload_attributes_builder: B,
     /// Sender for events to engine.
     to_engine: ConsensusEngineHandle<T>,
     /// The mining mode for the engine
-    mode: MiningMode,
+    mode: MiningMode<Pool>,
     /// The payload builder for the engine
     payload_builder: PayloadBuilderHandle<T>,
     /// Timestamp for the next block.
@@ -106,17 +111,18 @@ pub struct LocalMiner<T: PayloadTypes, B> {
     last_block_hashes: Vec<B256>,
 }
 
-impl<T, B> LocalMiner<T, B>
+impl<T, B, Pool> LocalMiner<T, B, Pool>
 where
     T: PayloadTypes,
     B: PayloadAttributesBuilder<<T as PayloadTypes>::PayloadAttributes>,
+    Pool: TransactionPool + Unpin,
 {
     /// Spawns a new [`LocalMiner`] with the given parameters.
     pub fn new(
         provider: impl BlockReader,
         payload_attributes_builder: B,
         to_engine: ConsensusEngineHandle<T>,
-        mode: MiningMode,
+        mode: MiningMode<Pool>,
         payload_builder: PayloadBuilderHandle<T>,
     ) -> Self {
         let latest_header =

crates/node/builder/src/launch/common.rs

@@ -442,7 +442,10 @@ impl<R, ChainSpec: EthChainSpec> LaunchContextWith<Attached<WithConfigs<ChainSpe
     }
 
     /// Returns the [`MiningMode`] intended for --dev mode.
-    pub fn dev_mining_mode(&self, pool: impl TransactionPool) -> MiningMode {
+    pub fn dev_mining_mode<Pool>(&self, pool: Pool) -> MiningMode<Pool>
+    where
+        Pool: TransactionPool + Unpin,
+    {
         if let Some(interval) = self.node_config().dev.block_time {
             MiningMode::interval(interval)
         } else {

crates/node/core/src/node_config.rs

@@ -494,7 +494,10 @@ impl<ChainSpec> NodeConfig<ChainSpec> {
     }
 
     /// Returns the [`MiningMode`] intended for --dev mode.
-    pub fn dev_mining_mode(&self, pool: impl TransactionPool) -> MiningMode {
+    pub fn dev_mining_mode<Pool>(&self, pool: Pool) -> MiningMode<Pool>
+    where
+        Pool: TransactionPool + Unpin,
+    {
         if let Some(interval) = self.dev.block_time {
             MiningMode::interval(interval)
         } else {