Add REST implementation for validator's GetSyncMessageBlockRoot (#11824)

* add REST implementation for GetSyncMessageBlockRoot

* improve sync_message_block_root_test.go to handle errors

* include context

* fix unit tests

validator/client/beacon-api/BUILD.bazel

@@ -21,6 +21,7 @@ go_library(
         "state_validators.go",
         "status.go",
         "sync_committee.go",
+        "sync_message_block_root.go",
     ],
     importpath = "github.com/prysmaticlabs/prysm/v3/validator/client/beacon-api",
     visibility = ["//validator:__subpackages__"],
@@ -72,6 +73,7 @@ go_test(
         "state_validators_test.go",
         "status_test.go",
         "sync_committee_test.go",
+        "sync_message_block_root_test.go",
         "wait_for_chain_start_test.go",
     ],
     embed = [":go_default_library"],

validator/client/beacon-api/beacon_api_validator_client.go

@@ -95,13 +95,8 @@ func (c *beaconApiValidatorClient) GetSyncCommitteeContribution(ctx context.Cont
 	panic("beaconApiValidatorClient.GetSyncCommitteeContribution is not implemented. To use a fallback client, create this validator with NewBeaconApiValidatorClientWithFallback instead.")
 }
 
-func (c *beaconApiValidatorClient) GetSyncMessageBlockRoot(ctx context.Context, in *empty.Empty) (*ethpb.SyncMessageBlockRootResponse, error) {
-	if c.fallbackClient != nil {
-		return c.fallbackClient.GetSyncMessageBlockRoot(ctx, in)
-	}
-
-	// TODO: Implement me
-	panic("beaconApiValidatorClient.GetSyncMessageBlockRoot is not implemented. To use a fallback client, create this validator with NewBeaconApiValidatorClientWithFallback instead.")
+func (c *beaconApiValidatorClient) GetSyncMessageBlockRoot(ctx context.Context, _ *empty.Empty) (*ethpb.SyncMessageBlockRootResponse, error) {
+	return c.getSyncMessageBlockRoot(ctx)
 }
 
 func (c *beaconApiValidatorClient) GetSyncSubcommitteeIndex(ctx context.Context, in *ethpb.SyncSubcommitteeIndexRequest) (*ethpb.SyncSubcommitteeIndexResponse, error) {

validator/client/beacon-api/sync_message_block_root.go

@@ -0,0 +1,41 @@
+package beacon_api
+
+import (
+	"context"
+
+	"github.com/ethereum/go-ethereum/common/hexutil"
+	"github.com/pkg/errors"
+	"github.com/prysmaticlabs/prysm/v3/beacon-chain/rpc/apimiddleware"
+	ethpb "github.com/prysmaticlabs/prysm/v3/proto/prysm/v1alpha1"
+)
+
+func (c *beaconApiValidatorClient) getSyncMessageBlockRoot(ctx context.Context) (*ethpb.SyncMessageBlockRootResponse, error) {
+	// Get head beacon block root.
+	var resp apimiddleware.BlockRootResponseJson
+	if _, err := c.jsonRestHandler.GetRestJsonResponse(ctx, "/eth/v1/beacon/blocks/head/root", &resp); err != nil {
+		return nil, errors.Wrap(err, "failed to query GET REST endpoint")
+	}
+
+	// An optimistic validator MUST NOT participate in sync committees
+	// (i.e., sign across the DOMAIN_SYNC_COMMITTEE, DOMAIN_SYNC_COMMITTEE_SELECTION_PROOF or DOMAIN_CONTRIBUTION_AND_PROOF domains).
+	if resp.ExecutionOptimistic {
+		return nil, errors.New("the node is currently optimistic and cannot serve validators")
+	}
+
+	if resp.Data == nil {
+		return nil, errors.New("no data returned")
+	}
+
+	if resp.Data.Root == "" {
+		return nil, errors.New("no root returned")
+	}
+
+	blockRoot, err := hexutil.Decode(resp.Data.Root)
+	if err != nil {
+		return nil, errors.Wrap(err, "failed to decode beacon block root")
+	}
+
+	return &ethpb.SyncMessageBlockRootResponse{
+		Root: blockRoot,
+	}, nil
+}

validator/client/beacon-api/sync_message_block_root_test.go

@@ -0,0 +1,92 @@
+package beacon_api
+
+import (
+	"context"
+	"errors"
+	"testing"
+
+	"github.com/ethereum/go-ethereum/common/hexutil"
+	"github.com/golang/mock/gomock"
+	"github.com/prysmaticlabs/prysm/v3/beacon-chain/rpc/apimiddleware"
+	"github.com/prysmaticlabs/prysm/v3/testing/require"
+	"github.com/prysmaticlabs/prysm/v3/validator/client/beacon-api/mock"
+)
+
+func TestGetSyncMessageBlockRoot(t *testing.T) {
+	ctrl := gomock.NewController(t)
+	defer ctrl.Finish()
+
+	const blockRoot = "0xcf8e0d4e9587369b2301d0790347320302cc0943d5a1884560367e8208d920f2"
+	tests := []struct {
+		name                 string
+		endpointError        error
+		expectedErrorMessage string
+		expectedResponse     apimiddleware.BlockRootResponseJson
+	}{
+		{
+			name: "valid request",
+			expectedResponse: apimiddleware.BlockRootResponseJson{
+				Data: &apimiddleware.BlockRootContainerJson{
+					Root: blockRoot,
+				},
+			},
+		},
+		{
+			name:                 "internal server error",
+			expectedErrorMessage: "internal server error",
+			endpointError:        errors.New("internal server error"),
+		},
+		{
+			name: "execution optimistic",
+			expectedResponse: apimiddleware.BlockRootResponseJson{
+				ExecutionOptimistic: true,
+			},
+			expectedErrorMessage: "the node is currently optimistic and cannot serve validators",
+		},
+		{
+			name:                 "no data",
+			expectedResponse:     apimiddleware.BlockRootResponseJson{},
+			expectedErrorMessage: "no data returned",
+		},
+		{
+			name: "no root",
+			expectedResponse: apimiddleware.BlockRootResponseJson{
+				Data: new(apimiddleware.BlockRootContainerJson),
+			},
+			expectedErrorMessage: "no root returned",
+		},
+	}
+
+	for _, test := range tests {
+		t.Run(test.name, func(t *testing.T) {
+			ctx := context.Background()
+			jsonRestHandler := mock.NewMockjsonRestHandler(ctrl)
+			jsonRestHandler.EXPECT().GetRestJsonResponse(
+				ctx,
+				"/eth/v1/beacon/blocks/head/root",
+				&apimiddleware.BlockRootResponseJson{},
+			).SetArg(
+				2,
+				test.expectedResponse,
+			).Return(
+				nil,
+				test.endpointError,
+			).Times(1)
+
+			validatorClient := &beaconApiValidatorClient{jsonRestHandler: jsonRestHandler}
+			actualResponse, err := validatorClient.getSyncMessageBlockRoot(ctx)
+			if test.expectedErrorMessage != "" {
+				require.ErrorContains(t, test.expectedErrorMessage, err)
+				return
+			}
+
+			require.NoError(t, err)
+
+			expectedRootBytes, err := hexutil.Decode(test.expectedResponse.Data.Root)
+			require.NoError(t, err)
+
+			require.NoError(t, err)
+			require.DeepEqual(t, expectedRootBytes, actualResponse.Root)
+		})
+	}
+}