Implement "pending" for qbft_getValidatorsByBlockNumber (#6436)

* Implement 'pending' for qbft_getValidatorsByBlockNumber

Signed-off-by: Matthew Whitehead <matthew1001@gmail.com>

* Update change log

Signed-off-by: Matthew Whitehead <matthew1001@gmail.com>

* Update consensus/qbft/src/main/java/org/hyperledger/besu/consensus/qbft/jsonrpc/methods/QbftGetValidatorsByBlockNumber.java

Co-authored-by: Jason Frame <jasonwframe@gmail.com>
Signed-off-by: Matt Whitehead <matthew1001@hotmail.com>

* Refactoring

Signed-off-by: Matthew Whitehead <matthew1001@gmail.com>

---------

Signed-off-by: Matthew Whitehead <matthew1001@gmail.com>
Signed-off-by: Matt Whitehead <matthew1001@hotmail.com>
Co-authored-by: Jason Frame <jasonwframe@gmail.com>

CHANGELOG.md

@@ -46,6 +46,7 @@
 - Upgrade Mockito [#6397](https://github.com/hyperledger/besu/pull/6397)
 - Upgrade `tech.pegasys.discovery:discovery` [#6414](https://github.com/hyperledger/besu/pull/6414)
 - Options to tune the max allowed time that can be spent selecting transactions during block creation are now stable [#6423](https://github.com/hyperledger/besu/pull/6423)
+- Support for "pending" in `qbft_getValidatorsByBlockNumber` [#6436](https://github.com/hyperledger/besu/pull/6436)
 
 ### Bug fixes
 - INTERNAL_ERROR from `eth_estimateGas` JSON/RPC calls [#6344](https://github.com/hyperledger/besu/issues/6344)

consensus/qbft/src/main/java/org/hyperledger/besu/consensus/qbft/jsonrpc/methods/QbftGetValidatorsByBlockNumber.java

@@ -53,6 +53,15 @@ public class QbftGetValidatorsByBlockNumber extends AbstractBlockParameterMethod
     return request.getRequiredParameter(0, BlockParameter.class);
   }
 
+  @Override
+  protected Object pendingResult(final JsonRpcRequestContext request) {
+    final BlockHeader blockHeader = getBlockchainQueries().headBlockHeader();
+    LOG.trace("Received RPC rpcName={} block={}", getName(), blockHeader.getNumber());
+    return validatorProvider.getValidatorsAfterBlock(blockHeader).stream()
+        .map(Address::toString)
+        .collect(Collectors.toList());
+  }
+
   @Override
   protected Object resultByBlockNumber(
       final JsonRpcRequestContext request, final long blockNumber) {

consensus/qbft/src/test/java/org/hyperledger/besu/consensus/qbft/jsonrpc/methods/QbftGetValidatorsByBlockNumberTest.java

@@ -23,6 +23,7 @@ import org.hyperledger.besu.datatypes.Address;
 import org.hyperledger.besu.ethereum.api.jsonrpc.internal.JsonRpcRequest;
 import org.hyperledger.besu.ethereum.api.jsonrpc.internal.JsonRpcRequestContext;
 import org.hyperledger.besu.ethereum.api.jsonrpc.internal.parameters.BlockParameter;
+import org.hyperledger.besu.ethereum.api.jsonrpc.internal.response.JsonRpcSuccessResponse;
 import org.hyperledger.besu.ethereum.api.query.BlockchainQueries;
 import org.hyperledger.besu.ethereum.core.BlockHeader;
 
@@ -73,4 +74,33 @@ public class QbftGetValidatorsByBlockNumberTest {
     Object result = method.resultByBlockNumber(request, 12);
     assertThat(result).isEqualTo(expectedOutput);
   }
+
+  @Test
+  public void shouldReturnListOfValidatorsFromLatestBlock() {
+    request =
+        new JsonRpcRequestContext(
+            new JsonRpcRequest("2.0", "qbft_getValidatorsByBlockNumber", new String[] {"latest"}));
+    when(blockchainQueries.headBlockNumber()).thenReturn(12L);
+    when(blockchainQueries.getBlockHeaderByNumber(12)).thenReturn(Optional.of(blockHeader));
+    final List<Address> addresses = Collections.singletonList(Address.ID);
+    final List<String> expectedOutput = Collections.singletonList(Address.ID.toString());
+    when(validatorProvider.getValidatorsForBlock(any())).thenReturn(addresses);
+    Object result = method.response(request);
+    assertThat(result).isInstanceOf(JsonRpcSuccessResponse.class);
+    assertThat(((JsonRpcSuccessResponse) result).getResult()).isEqualTo(expectedOutput);
+  }
+
+  @Test
+  public void shouldReturnListOfValidatorsFromPendingBlock() {
+    request =
+        new JsonRpcRequestContext(
+            new JsonRpcRequest("2.0", "qbft_getValidatorsByBlockNumber", new String[] {"pending"}));
+    when(blockchainQueries.headBlockHeader()).thenReturn(blockHeader);
+    final List<Address> addresses = Collections.singletonList(Address.ID);
+    final List<String> expectedOutput = Collections.singletonList(Address.ID.toString());
+    when(validatorProvider.getValidatorsAfterBlock(any())).thenReturn(addresses);
+    Object result = method.response(request);
+    assertThat(result).isInstanceOf(JsonRpcSuccessResponse.class);
+    assertThat(((JsonRpcSuccessResponse) result).getResult()).isEqualTo(expectedOutput);
+  }
 }