From 419343123a51ff5b76e54617a3ef0048c254b629 Mon Sep 17 00:00:00 2001
From: terence tsao <terence@prysmaticlabs.com>
Date: Fri, 8 May 2020 21:56:51 -0700
Subject: [PATCH] Fix e2e flakynes for new state mgmt (#5790)

---
 beacon-chain/blockchain/process_block_helpers.go | 12 ++++++++++++
 shared/featureconfig/flags.go                    |  1 +
 2 files changed, 13 insertions(+)

diff --git a/beacon-chain/blockchain/process_block_helpers.go b/beacon-chain/blockchain/process_block_helpers.go
index a81ca14c3..835c8e5bf 100644
--- a/beacon-chain/blockchain/process_block_helpers.go
+++ b/beacon-chain/blockchain/process_block_helpers.go
@@ -43,6 +43,18 @@ func (s *Service) getBlockPreState(ctx context.Context, b *ethpb.BeaconBlock) (*
 		return nil, err
 	}
 
+	//  For new state management, this ensures the state does not get mutated since initial syncing
+	//  uses verifyBlkPreState.
+	if featureconfig.Get().NewStateMgmt {
+		preState, err = s.stateGen.StateByRoot(ctx, bytesutil.ToBytes32(b.ParentRoot))
+		if err != nil {
+			return nil, errors.Wrapf(err, "could not get pre state for slot %d", b.Slot)
+		}
+		if preState == nil {
+			return nil, errors.Wrapf(err, "nil pre state for slot %d", b.Slot)
+		}
+	}
+
 	// Verify block slot time is not from the feature.
 	if err := helpers.VerifySlotTime(preState.GenesisTime(), b.Slot, helpers.TimeShiftTolerance); err != nil {
 		return nil, err
diff --git a/shared/featureconfig/flags.go b/shared/featureconfig/flags.go
index 5774f0e83..686d28ac4 100644
--- a/shared/featureconfig/flags.go
+++ b/shared/featureconfig/flags.go
@@ -433,4 +433,5 @@ var E2EBeaconChainFlags = []string{
 	"--check-head-state",
 	"--enable-state-field-trie",
 	"--enable-state-ref-copy",
+	"--enable-new-state-mgmt",
 }