fix: return zero latestValidHash pre-merge (#1677)

crates/rpc/rpc-engine-api/src/engine_api.rs

@@ -4,7 +4,7 @@ use reth_interfaces::consensus::ForkchoiceState;
 use reth_primitives::{
     proofs::{self, EMPTY_LIST_HASH},
     BlockHash, BlockId, BlockNumber, ChainSpec, Hardfork, Header, SealedBlock, TransactionSigned,
-    H64, U256,
+    H256, H64, U256,
 };
 use reth_provider::{
     BlockExecutor, BlockProvider, EvmEnvProvider, ExecutorFactory, HeaderProvider,
@@ -257,6 +257,9 @@ impl<Client: HeaderProvider + BlockProvider + StateProviderFactory + EvmEnvProvi
     /// state in the block header, then passes validation data back to Consensus layer, that
     /// adds the block to the head of its own blockchain and attests to it. The block is then
     /// broadcasted over the consensus p2p network in the form of a "Beacon block".
+    ///
+    /// These responses should adhere to the [Engine API Spec for
+    /// `engine_newPayload`](https://github.com/ethereum/execution-apis/blob/main/src/engine/paris.md#specification).
     pub fn new_payload(&mut self, payload: ExecutionPayload) -> EngineApiResult<PayloadStatus> {
         let block = match self.try_construct_block(payload) {
             Ok(b) => b,
@@ -289,9 +292,22 @@ impl<Client: HeaderProvider + BlockProvider + StateProviderFactory + EvmEnvProvi
 
         // Short circuit the check by passing parent total difficulty.
         if !self.chain_spec.fork(Hardfork::Paris).active_at_ttd(parent_td, U256::ZERO) {
+            // This case returns a `latestValidHash` of zero because it is required by the engine
+            // api spec:
+            //
+            // Client software MUST respond to this method call in the following way:
+            // {
+            //     status: INVALID,
+            //     latestValidHash:
+            // 0x0000000000000000000000000000000000000000000000000000000000000000,
+            //     validationError: errorMessage | null
+            // }
+            //
+            // if terminal block conditions are not satisfied
             return Ok(PayloadStatus::from_status(PayloadStatusEnum::Invalid {
                 validation_error: EngineApiError::PayloadPreMerge.to_string(),
-            }))
+            })
+            .with_latest_valid_hash(H256::zero()))
         }
 
         if block.timestamp <= parent.timestamp {
@@ -646,7 +662,8 @@ mod tests {
 
             let expected_result = PayloadStatus::from_status(PayloadStatusEnum::Invalid {
                 validation_error: EngineApiError::PayloadPreMerge.to_string(),
-            });
+            })
+            .with_latest_valid_hash(H256::zero());
             assert_matches!(result_rx.await, Ok(Ok(result)) => assert_eq!(result, expected_result));
         }
 

crates/rpc/rpc-types/src/eth/engine.rs

@@ -145,6 +145,11 @@ impl PayloadStatus {
     pub fn from_status(status: PayloadStatusEnum) -> Self {
         Self { status, latest_valid_hash: None }
     }
+
+    pub fn with_latest_valid_hash(mut self, latest_valid_hash: H256) -> Self {
+        self.latest_valid_hash = Some(latest_valid_hash);
+        self
+    }
 }
 
 #[derive(Clone, Debug, PartialEq, Eq, Serialize, Deserialize)]