debug_traceCallMany: strip filler blocks from overrides result

src/Nethermind/Nethermind.Evm/BlockOverrideExtensions.cs

@@ -0,0 +1,10 @@
+// SPDX-FileCopyrightText: 2025 Demerzel Solutions Limited
+// SPDX-License-Identifier: LGPL-3.0-only
+
+namespace Nethermind.Evm;
+
+public static class BlockOverrideExtensions
+{
+    public static ulong GetBlockNumber(this BlockOverride? blockOverride, long lastBlockNumber)
+        => blockOverride?.Number ?? (ulong)lastBlockNumber + 1;
+}

src/Nethermind/Nethermind.JsonRpc.Test/Modules/DebugRpcModuleTests.TraceCallMany.cs

@@ -180,6 +180,26 @@ public async Task Debug_traceCallMany_mixed_bundles_preserves_order()
         result.Data.Select(r => r.Count()).Should().BeEquivalentTo([1, 1]);
     }
 
+    [TestCase(3, TestName = "Debug_traceCallMany_with_minimum_block_number_gap_returns_one_entry_per_bundle")]
+    [TestCase(5, TestName = "Debug_traceCallMany_with_block_number_gap_returns_one_entry_per_bundle")]
+    public async Task Debug_traceCallMany_with_block_number_gap_returns_one_entry_per_bundle(int secondBundleOffset)
+    {
+        using Context ctx = await CreateContext();
+        long headNumber = ctx.Blockchain.BlockTree.Head!.Number;
+
+        TransactionBundle first = CreateBundle(CreateTransaction());
+        first.BlockOverride = new BlockOverride { Number = (ulong)(headNumber + 1) };
+
+        TransactionBundle second = CreateBundle(CreateTransaction(to: TestItem.AddressD));
+        second.BlockOverride = new BlockOverride { Number = (ulong)(headNumber + secondBundleOffset) };
+
+        ResultWrapper<IEnumerable<IEnumerable<GethLikeTxTrace>>> result =
+            ctx.DebugRpcModule.debug_traceCallMany([first, second], BlockParameter.Latest);
+
+        result.Data.Should().HaveCount(2);
+        result.Data.Select(r => r.Count()).Should().BeEquivalentTo([1, 1]);
+    }
+
     [Test]
     public async Task Debug_traceCallMany_caps_gas_to_gas_cap()
     {

src/Nethermind/Nethermind.JsonRpc/Modules/DebugModule/DebugRpcModule.cs

@@ -10,6 +10,7 @@
 using Nethermind.Core;
 using Nethermind.Core.Crypto;
 using Nethermind.Core.Extensions;
+using Nethermind.Evm;
 using Nethermind.Blockchain.Tracing.GethStyle;
 using Nethermind.JsonRpc.Data;
 using Nethermind.Logging;
@@ -482,6 +483,18 @@ private ResultWrapper<IEnumerable<IEnumerable<GethLikeTxTrace>>> TraceCallManyWi
             }).ToList()
         };
 
+        // SimulateTxExecutor inserts filler blocks between bundles when BlockOverride.Number has gaps.
+        // Pre-compute the block number each bundle targets so we can drop fillers from the result and
+        // keep a 1:1 mapping to the input bundles.
+        HashSet<long> bundleBlockNumbers = new(bundles.Length);
+        long lastBlockNumber = header.Number;
+        foreach (TransactionBundle bundle in bundles)
+        {
+            long number = (long)bundle.BlockOverride.GetBlockNumber(lastBlockNumber);
+            bundleBlockNumbers.Add(number);
+            lastBlockNumber = number;
+        }
+
         BlockParameter concreteBlockParameter = new(header.Number);
 
         using CancellationTokenSource timeout = BuildTimeoutCancellationTokenSource();
@@ -503,7 +516,9 @@ private ResultWrapper<IEnumerable<IEnumerable<GethLikeTxTrace>>> TraceCallManyWi
             return ResultWrapper<IEnumerable<IEnumerable<GethLikeTxTrace>>>.Fail(errorMessage, simulationResult.ErrorCode);
         }
 
-        IEnumerable<IEnumerable<GethLikeTxTrace>> bundleTraces = simulationResult.Data.Select(blockResult => blockResult.Traces);
+        IEnumerable<IEnumerable<GethLikeTxTrace>> bundleTraces = simulationResult.Data
+            .Where(blockResult => blockResult.Number is long n && bundleBlockNumbers.Contains(n))
+            .Select(blockResult => blockResult.Traces);
 
         return ResultWrapper<IEnumerable<IEnumerable<GethLikeTxTrace>>>.Success(bundleTraces);
     }

src/Nethermind/Nethermind.JsonRpc/Modules/Eth/SimulateTxExecutor.cs

@@ -128,7 +128,7 @@ public override ResultWrapper<IReadOnlyList<SimulateBlockResult<TTrace>>> Execut
             foreach (BlockStateCall<TransactionForRpc>? blockToSimulate in call.BlockStateCalls)
             {
                 blockToSimulate.BlockOverrides ??= new BlockOverride();
-                ulong givenNumber = blockToSimulate.BlockOverrides.Number ?? (ulong)lastBlockNumber + 1;
+                ulong givenNumber = blockToSimulate.BlockOverrides.GetBlockNumber(lastBlockNumber);
 
                 if (givenNumber > long.MaxValue)
                     return ResultWrapper<IReadOnlyList<SimulateBlockResult<TTrace>>>.Fail($"Block number too big {givenNumber}!", ErrorCodes.InvalidParams);