Withdrawals processor to clear empty accounts (#4995)

Signed-off-by: Jason Frame <jason.frame@consensys.net>

ethereum/core/src/main/java/org/hyperledger/besu/ethereum/mainnet/MainnetTransactionProcessor.java

@@ -45,7 +45,6 @@ import org.hyperledger.besu.evm.tracing.OperationTracer;
 import org.hyperledger.besu.evm.worldstate.WorldUpdater;
 
 import java.util.ArrayDeque;
-import java.util.ArrayList;
 import java.util.Deque;
 import java.util.HashSet;
 import java.util.List;
@@ -463,7 +462,7 @@ public class MainnetTransactionProcessor {
       initialFrame.getSelfDestructs().forEach(worldState::deleteAccount);
 
       if (clearEmptyAccounts) {
-        clearAccountsThatAreEmpty(worldState);
+        worldState.clearAccountsThatAreEmpty();
       }
 
       if (initialFrame.getState() == MessageFrame.State.COMPLETED_SUCCESS) {
@@ -489,11 +488,6 @@ public class MainnetTransactionProcessor {
     return transactionValidator;
   }
 
-  private static void clearAccountsThatAreEmpty(final WorldUpdater worldState) {
-    new ArrayList<>(worldState.getTouchedAccounts())
-        .stream().filter(Account::isEmpty).forEach(a -> worldState.deleteAccount(a.getAddress()));
-  }
-
   protected void process(final MessageFrame frame, final OperationTracer operationTracer) {
     final AbstractMessageProcessor executor = getMessageProcessor(frame.getType());
 

ethereum/core/src/main/java/org/hyperledger/besu/ethereum/mainnet/WithdrawalsProcessor.java

@@ -28,6 +28,7 @@ public class WithdrawalsProcessor {
       final EvmAccount account = worldUpdater.getOrCreate(withdrawal.getAddress());
       account.getMutable().incrementBalance(withdrawal.getAmount().getAsWei());
     }
+    worldUpdater.clearAccountsThatAreEmpty();
     worldUpdater.commit();
   }
 }

ethereum/core/src/test/java/org/hyperledger/besu/ethereum/mainnet/WithdrawalsProcessorTest.java

@@ -35,7 +35,7 @@ import org.junit.jupiter.api.Test;
 class WithdrawalsProcessorTest {
 
   @Test
-  void defaultProcessor_shouldProcessEmptyWithdrawalsWithoutChangingWorldState() {
+  void shouldProcessEmptyWithdrawalsWithoutChangingWorldState() {
     final MutableWorldState worldState =
         createWorldStateWithAccounts(List.of(entry("0x1", 1), entry("0x2", 2), entry("0x3", 3)));
     final MutableWorldState originalState = worldState.copy();
@@ -51,7 +51,7 @@ class WithdrawalsProcessorTest {
   }
 
   @Test
-  void defaultProcessor_shouldProcessWithdrawalsUpdatingExistingAccountsBalance() {
+  void shouldProcessWithdrawalsUpdatingExistingAccountsBalance() {
     final MutableWorldState worldState =
         createWorldStateWithAccounts(List.of(entry("0x1", 1), entry("0x2", 2), entry("0x3", 3)));
     final WorldUpdater updater = worldState.updater();
@@ -79,7 +79,7 @@ class WithdrawalsProcessorTest {
   }
 
   @Test
-  void defaultProcessor_shouldProcessWithdrawalsUpdatingEmptyAccountsBalance() {
+  void shouldProcessWithdrawalsUpdatingEmptyAccountsBalance() {
     final MutableWorldState worldState = createWorldStateWithAccounts(Collections.emptyList());
     final WorldUpdater updater = worldState.updater();
 
@@ -104,6 +104,27 @@ class WithdrawalsProcessorTest {
         .isEqualTo(GWei.of(200).getAsWei());
   }
 
+  @Test
+  void shouldDeleteEmptyAccounts() {
+    final MutableWorldState worldState = createWorldStateWithAccounts(List.of(entry("0x1", 0)));
+    final WorldUpdater updater = worldState.updater();
+
+    final List<Withdrawal> withdrawals =
+        List.of(
+            new Withdrawal(
+                UInt64.valueOf(100), UInt64.valueOf(1000), Address.fromHexString("0x1"), GWei.ZERO),
+            new Withdrawal(
+                UInt64.valueOf(200),
+                UInt64.valueOf(2000),
+                Address.fromHexString("0x2"),
+                GWei.ZERO));
+    final WithdrawalsProcessor withdrawalsProcessor = new WithdrawalsProcessor();
+    withdrawalsProcessor.processWithdrawals(withdrawals, updater);
+
+    assertThat(worldState.get(Address.fromHexString("0x1"))).isNull();
+    assertThat(worldState.get(Address.fromHexString("0x2"))).isNull();
+  }
+
   private MutableWorldState createWorldStateWithAccounts(
       final List<Map.Entry<String, Integer>> accountBalances) {
     final MutableWorldState worldState = InMemoryKeyValueStorageProvider.createInMemoryWorldState();
@@ -111,7 +132,7 @@ class WithdrawalsProcessorTest {
     accountBalances.forEach(
         entry ->
             updater.createAccount(
-                Address.fromHexString(entry.getKey()), 1, Wei.of(entry.getValue())));
+                Address.fromHexString(entry.getKey()), 0, Wei.of(entry.getValue())));
     updater.commit();
     return worldState;
   }

evm/src/main/java/org/hyperledger/besu/evm/worldstate/WorldUpdater.java

@@ -21,6 +21,7 @@ import org.hyperledger.besu.evm.account.EvmAccount;
 import org.hyperledger.besu.evm.account.MutableAccount;
 import org.hyperledger.besu.evm.frame.MessageFrame;
 
+import java.util.ArrayList;
 import java.util.Collection;
 import java.util.Optional;
 
@@ -145,4 +146,10 @@ public interface WorldUpdater extends MutableWorldView {
    * @return The parent WorldUpdater if this wraps another one, empty otherwise
    */
   Optional<WorldUpdater> parentUpdater();
+
+  /** Clears any accounts that are empty */
+  default void clearAccountsThatAreEmpty() {
+    new ArrayList<>(getTouchedAccounts())
+        .stream().filter(Account::isEmpty).forEach(a -> deleteAccount(a.getAddress()));
+  }
 }