Fix Fork Copying (prysmaticlabs#4922)

* add fix and reg test

* goimports

beacon-chain/state/BUILD.bazel

@@ -46,5 +46,6 @@ go_test(
         "//shared/stateutil:go_default_library",
         "@com_github_gogo_protobuf//proto:go_default_library",
         "@com_github_prysmaticlabs_ethereumapis//eth/v1alpha1:go_default_library",
+        "@com_github_prysmaticlabs_go_ssz//:go_default_library",
     ],
 )

beacon-chain/state/getters.go

@@ -135,8 +135,8 @@ func (b *BeaconState) Fork() *pbp2p.Fork {
 
 	prevVersion := make([]byte, len(b.state.Fork.PreviousVersion))
 	copy(prevVersion, b.state.Fork.PreviousVersion)
-	currVersion := make([]byte, len(b.state.Fork.PreviousVersion))
-	copy(currVersion, b.state.Fork.PreviousVersion)
+	currVersion := make([]byte, len(b.state.Fork.CurrentVersion))
+	copy(currVersion, b.state.Fork.CurrentVersion)
 	return &pbp2p.Fork{
 		PreviousVersion: prevVersion,
 		CurrentVersion:  currVersion,

beacon-chain/state/types_test.go

@@ -7,6 +7,7 @@ import (
 
 	"github.com/gogo/protobuf/proto"
 	ethpb "github.com/prysmaticlabs/ethereumapis/eth/v1alpha1"
+	"github.com/prysmaticlabs/go-ssz"
 	stateTrie "github.com/prysmaticlabs/prysm/beacon-chain/state"
 	pb "github.com/prysmaticlabs/prysm/proto/beacon/p2p/v1"
 	"github.com/prysmaticlabs/prysm/shared/bytesutil"
@@ -226,3 +227,24 @@ func TestBeaconState_ImmutabilityWithSharedResources(t *testing.T) {
 		t.Fatal("Expected a.BlockRoots() to be different from b.BlockRoots()")
 	}
 }
+
+func TestForkManualCopy_OK(t *testing.T) {
+	params.UseMinimalConfig()
+	genesis := setupGenesisState(t, 64)
+	a, err := stateTrie.InitializeFromProto(genesis)
+	if err != nil {
+		t.Fatal(err)
+	}
+	wantedFork := &pb.Fork{
+		PreviousVersion: []byte{'a', 'b', 'c'},
+		CurrentVersion:  []byte{'d', 'e', 'f'},
+		Epoch:           0,
+	}
+	a.SetFork(wantedFork)
+
+	newState := a.CloneInnerState()
+	if !ssz.DeepEqual(newState.Fork, wantedFork) {
+		t.Errorf("Wanted %v but got %v", wantedFork, newState.Fork)
+	}
+
+}