Fix Justified and Finalized Retrieval in Genesis (#6861)

* fix
* fix tests
* add test

beacon-chain/blockchain/service.go

@@ -176,7 +176,7 @@ func (s *Service) Start() {
 
 		// Resume fork choice.
 		s.justifiedCheckpt = stateTrie.CopyCheckpoint(justifiedCheckpoint)
-		if err := s.cacheJustifiedStateBalances(s.ctx, bytesutil.ToBytes32(s.justifiedCheckpt.Root)); err != nil {
+		if err := s.cacheJustifiedStateBalances(s.ctx, s.ensureRootNotZeros(bytesutil.ToBytes32(s.justifiedCheckpt.Root))); err != nil {
 			log.Fatalf("Could not cache justified state balances: %v", err)
 		}
 		s.prevJustifiedCheckpt = stateTrie.CopyCheckpoint(justifiedCheckpoint)

beacon-chain/blockchain/service_test.go

@@ -198,6 +198,31 @@ func TestChainService_InitializeBeaconChain(t *testing.T) {
 	}
 }
 
+func TestChainService_CorrectGenesisRoots(t *testing.T) {
+	ctx := context.Background()
+	db, sc := testDB.SetupDB(t)
+
+	chainService := setupBeaconChain(t, db, sc)
+
+	genesisBlk := testutil.NewBeaconBlock()
+	blkRoot, err := stateutil.BlockRoot(genesisBlk.Block)
+	require.NoError(t, err)
+	require.NoError(t, db.SaveBlock(ctx, genesisBlk))
+	s := testutil.NewBeaconState()
+	require.NoError(t, s.SetSlot(0))
+	require.NoError(t, db.SaveState(ctx, s, blkRoot))
+	require.NoError(t, db.SaveHeadBlockRoot(ctx, blkRoot))
+	require.NoError(t, db.SaveGenesisBlockRoot(ctx, blkRoot))
+	// Test the start function.
+	chainService.Start()
+
+	require.DeepEqual(t, params.BeaconConfig().ZeroHash[:], chainService.finalizedCheckpt.Root, "Finalize Checkpoint root is incorrect")
+	require.DeepEqual(t, params.BeaconConfig().ZeroHash[:], chainService.justifiedCheckpt.Root, "Justified Checkpoint root is incorrect")
+
+	require.NoError(t, chainService.Stop(), "Unable to stop chain service")
+
+}
+
 func TestChainService_InitializeChainInfo(t *testing.T) {
 	db, sc := testDB.SetupDB(t)
 	ctx := context.Background()

beacon-chain/db/kv/checkpoint.go

@@ -6,6 +6,7 @@ import (
 
 	ethpb "github.com/prysmaticlabs/ethereumapis/eth/v1alpha1"
 	"github.com/prysmaticlabs/prysm/shared/bytesutil"
+	"github.com/prysmaticlabs/prysm/shared/params"
 	bolt "go.etcd.io/bbolt"
 	"go.opencensus.io/trace"
 )
@@ -21,9 +22,7 @@ func (kv *Store) JustifiedCheckpoint(ctx context.Context) (*ethpb.Checkpoint, er
 		bkt := tx.Bucket(checkpointBucket)
 		enc := bkt.Get(justifiedCheckpointKey)
 		if enc == nil {
-			blockBucket := tx.Bucket(blocksBucket)
+			checkpoint = &ethpb.Checkpoint{Root: params.BeaconConfig().ZeroHash[:]}
-			genesisRoot := blockBucket.Get(genesisBlockRootKey)
-			checkpoint = &ethpb.Checkpoint{Root: genesisRoot}
 			return nil
 		}
 		checkpoint = &ethpb.Checkpoint{}
@@ -41,9 +40,7 @@ func (kv *Store) FinalizedCheckpoint(ctx context.Context) (*ethpb.Checkpoint, er
 		bkt := tx.Bucket(checkpointBucket)
 		enc := bkt.Get(finalizedCheckpointKey)
 		if enc == nil {
-			blockBucket := tx.Bucket(blocksBucket)
+			checkpoint = &ethpb.Checkpoint{Root: params.BeaconConfig().ZeroHash[:]}
-			genesisRoot := blockBucket.Get(genesisBlockRootKey)
-			checkpoint = &ethpb.Checkpoint{Root: genesisRoot}
 			return nil
 		}
 		checkpoint = &ethpb.Checkpoint{}

beacon-chain/db/kv/checkpoint_test.go

@@ -9,6 +9,7 @@ import (
 	ethpb "github.com/prysmaticlabs/ethereumapis/eth/v1alpha1"
 	"github.com/prysmaticlabs/prysm/beacon-chain/state/stateutil"
 	"github.com/prysmaticlabs/prysm/shared/bytesutil"
+	"github.com/prysmaticlabs/prysm/shared/params"
 	"github.com/prysmaticlabs/prysm/shared/testutil"
 )
 
@@ -94,16 +95,11 @@ func TestStore_FinalizedCheckpoint_CanSaveRetrieve(t *testing.T) {
 	}
 }
 
-func TestStore_JustifiedCheckpoint_DefaultCantBeNil(t *testing.T) {
+func TestStore_JustifiedCheckpoint_DefaultIsZeroHash(t *testing.T) {
 	db := setupDB(t)
 	ctx := context.Background()
 
-	genesisRoot := [32]byte{'A'}
+	cp := &ethpb.Checkpoint{Root: params.BeaconConfig().ZeroHash[:]}
-	if err := db.SaveGenesisBlockRoot(ctx, genesisRoot); err != nil {
-		t.Fatal(err)
-	}
-
-	cp := &ethpb.Checkpoint{Root: genesisRoot[:]}
 	retrieved, err := db.JustifiedCheckpoint(ctx)
 	if err != nil {
 		t.Fatal(err)
@@ -113,16 +109,11 @@ func TestStore_JustifiedCheckpoint_DefaultCantBeNil(t *testing.T) {
 	}
 }
 
-func TestStore_FinalizedCheckpoint_DefaultCantBeNil(t *testing.T) {
+func TestStore_FinalizedCheckpoint_DefaultIsZeroHash(t *testing.T) {
 	db := setupDB(t)
 	ctx := context.Background()
 
-	genesisRoot := [32]byte{'B'}
+	cp := &ethpb.Checkpoint{Root: params.BeaconConfig().ZeroHash[:]}
-	if err := db.SaveGenesisBlockRoot(ctx, genesisRoot); err != nil {
-		t.Fatal(err)
-	}
-
-	cp := &ethpb.Checkpoint{Root: genesisRoot[:]}
 	retrieved, err := db.FinalizedCheckpoint(ctx)
 	if err != nil {
 		t.Fatal(err)