Use cached header for latest eth_getBlockByNumber (hyperledger#5292)

While syncing, it is possible that we access the cached header's number before the block itself has had chance to be imported. In other words there is a mismatch between cached blockNumber and non-cached blockHeader that is being retrieved for the RPC.
Signed-off-by: Simon Dudley <simon.dudley@consensys.net>

CHANGELOG.md

@@ -13,8 +13,8 @@
 - Upgrade RocksDB version from 7.7.3 to 8.0.0. Besu Team [contributed](https://github.com/facebook/rocksdb/pull/11099) to this release to make disabling checksum verification work. 
 
 ### Bug Fixes
+- Fix eth_getBlockByNumber cache error for latest block when called during syncing [#5292](https://github.com/hyperledger/besu/pull/5292)
 - Fix QBFT and IBFT unable to propose blocks on London when zeroBaseFee is used [#5276](https://github.com/hyperledger/besu/pull/5276) 
-
 - Make QBFT validator smart contract mode work with london fork [#5249](https://github.com/hyperledger/besu/issues/5249)
 
 ### Download Links

ethereum/api/src/main/java/org/hyperledger/besu/ethereum/api/jsonrpc/internal/methods/EthGetBlockByNumber.java

@@ -21,7 +21,6 @@
 import org.hyperledger.besu.ethereum.api.jsonrpc.internal.results.BlockResult;
 import org.hyperledger.besu.ethereum.api.jsonrpc.internal.results.BlockResultFactory;
 import org.hyperledger.besu.ethereum.api.query.BlockchainQueries;
-import org.hyperledger.besu.ethereum.chain.Blockchain;
 import org.hyperledger.besu.ethereum.core.BlockHeader;
 import org.hyperledger.besu.ethereum.core.Synchronizer;
 
@@ -80,8 +79,7 @@ protected Object resultByBlockNumber(
   protected Object latestResult(final JsonRpcRequestContext request) {
 
     final long headBlockNumber = blockchainQueriesSupplier.get().headBlockNumber();
-    Blockchain chain = blockchainQueriesSupplier.get().getBlockchain();
-    BlockHeader headHeader = chain.getBlockHeader(headBlockNumber).orElse(null);
+    BlockHeader headHeader = blockchainQueriesSupplier.get().headBlockHeader();
 
     Hash block = headHeader.getHash();
     Hash stateRoot = headHeader.getStateRoot();

ethereum/api/src/test/java/org/hyperledger/besu/ethereum/api/jsonrpc/JsonRpcHttpServiceTest.java

@@ -1063,10 +1063,7 @@ public void getBlockByNumberForLatest() throws Exception {
     final BlockWithMetadata<TransactionWithMetadata, Hash> blockWithMetadata =
         blockWithMetadata(block);
     when(blockchainQueries.headBlockNumber()).thenReturn(0L);
-    when(blockchainQueries.blockByNumber(eq(0L))).thenReturn(Optional.of(blockWithMetadata));
-    when(blockchainQueries.getBlockchain()).thenReturn(blockchain);
-    when(blockchain.getBlockHeader(blockchainQueries.headBlockNumber()))
-        .thenReturn(Optional.of(block.getHeader()));
+    when(blockchainQueries.headBlockHeader()).thenReturn(block.getHeader());
     WorldStateArchive state = mock(WorldStateArchive.class);
     when(state.isWorldStateAvailable(any(Hash.class), any(Hash.class))).thenReturn(true);
     when(blockchainQueries.getWorldStateArchive()).thenReturn(state);
@@ -1097,11 +1094,8 @@ public void getBlockByNumberForPending() throws Exception {
     final Block block = gen.genesisBlock();
     final BlockWithMetadata<TransactionWithMetadata, Hash> blockWithMetadata =
         blockWithMetadata(block);
-    when(blockchainQueries.headBlockNumber()).thenReturn(0L);
     when(blockchainQueries.blockByNumber(eq(0L))).thenReturn(Optional.of(blockWithMetadata));
-    when(blockchainQueries.getBlockchain()).thenReturn(blockchain);
-    when(blockchain.getBlockHeader(blockchainQueries.headBlockNumber()))
-        .thenReturn(Optional.of(block.getHeader()));
+    when(blockchainQueries.headBlockHeader()).thenReturn(block.getHeader());
     WorldStateArchive state = mock(WorldStateArchive.class);
     when(state.isWorldStateAvailable(any(Hash.class), any(Hash.class))).thenReturn(true);
     when(blockchainQueries.getWorldStateArchive()).thenReturn(state);