Update API to return empty next page token on last page response (#4176)

* Update API to return empty next page token on last page response
* Update tests
* Merge branch 'master' into api-return-empty-page-token-on-last-page

beacon-chain/rpc/beacon/assignments_test.go

@@ -513,7 +513,7 @@ func TestServer_ListAssignments_CanFilterPubkeysIndices_WithPagination(t *testin
 	wantedRes = &ethpb.ValidatorAssignments{
 		Assignments:   assignments,
 		TotalSize:     int32(len(req.Indices)),
-		NextPageToken: "2",
+		NextPageToken: "",
 	}
 
 	if !reflect.DeepEqual(res, wantedRes) {

beacon-chain/rpc/beacon/attestations_test.go

@@ -93,7 +93,7 @@ func TestServer_ListAttestations_Genesis(t *testing.T) {
 	}
 	wanted := &ethpb.ListAttestationsResponse{
 		Attestations:  []*ethpb.Attestation{att},
-		NextPageToken: "1",
+		NextPageToken: "",
 		TotalSize:     1,
 	}
 
@@ -398,7 +398,7 @@ func TestServer_ListAttestations_Pagination_CustomPageParameters(t *testing.T) {
 						AggregationBits: bitfield.Bitlist{0b11},
 						CustodyBits:     bitfield.NewBitlist(1)},
 				},
-				NextPageToken: strconv.Itoa(34),
+				NextPageToken: "",
 				TotalSize:     int32(count)}},
 		{
 			req: &ethpb.ListAttestationsRequest{

beacon-chain/rpc/beacon/blocks_test.go

@@ -174,7 +174,7 @@ func TestServer_ListBlocks_Pagination(t *testing.T) {
 			PageSize:    3},
 			res: &ethpb.ListBlocksResponse{
 				BlockContainers: []*ethpb.BeaconBlockContainer{{Block: &ethpb.BeaconBlock{Slot: 5}, BlockRoot: blkContainers[5].BlockRoot}},
-				NextPageToken:   strconv.Itoa(1),
+				NextPageToken:   "",
 				TotalSize:       1}},
 		{req: &ethpb.ListBlocksRequest{
 			PageToken:   strconv.Itoa(0),
@@ -193,7 +193,7 @@ func TestServer_ListBlocks_Pagination(t *testing.T) {
 			PageSize:    100},
 			res: &ethpb.ListBlocksResponse{
 				BlockContainers: blkContainers[0:params.BeaconConfig().SlotsPerEpoch],
-				NextPageToken:   strconv.Itoa(1),
+				NextPageToken:   "",
 				TotalSize:       int32(params.BeaconConfig().SlotsPerEpoch)}},
 		{req: &ethpb.ListBlocksRequest{
 			PageToken:   strconv.Itoa(1),
@@ -201,7 +201,7 @@ func TestServer_ListBlocks_Pagination(t *testing.T) {
 			PageSize:    3},
 			res: &ethpb.ListBlocksResponse{
 				BlockContainers: blkContainers[43:46],
-				NextPageToken:   strconv.Itoa(2),
+				NextPageToken:   "2",
 				TotalSize:       int32(params.BeaconConfig().SlotsPerEpoch)}},
 		{req: &ethpb.ListBlocksRequest{
 			PageToken:   strconv.Itoa(1),
@@ -209,7 +209,7 @@ func TestServer_ListBlocks_Pagination(t *testing.T) {
 			PageSize:    7},
 			res: &ethpb.ListBlocksResponse{
 				BlockContainers: blkContainers[95:96],
-				NextPageToken:   strconv.Itoa(2),
+				NextPageToken:   "",
 				TotalSize:       int32(params.BeaconConfig().SlotsPerEpoch)}},
 		{req: &ethpb.ListBlocksRequest{
 			PageToken:   strconv.Itoa(0),
@@ -217,7 +217,7 @@ func TestServer_ListBlocks_Pagination(t *testing.T) {
 			PageSize:    4},
 			res: &ethpb.ListBlocksResponse{
 				BlockContainers: blkContainers[96:100],
-				NextPageToken:   strconv.Itoa(1),
+				NextPageToken:   "1",
 				TotalSize:       int32(params.BeaconConfig().SlotsPerEpoch / 2)}},
 	}
 
@@ -227,7 +227,7 @@ func TestServer_ListBlocks_Pagination(t *testing.T) {
 			t.Fatal(err)
 		}
 		if !proto.Equal(res, test.res) {
-			t.Errorf("Incorrect blocks response, wanted %d, received %d", len(test.res.BlockContainers), len(res.BlockContainers))
+			t.Errorf("Incorrect blocks response, wanted %v, received %v", test.res, res)
 		}
 	}
 }

beacon-chain/rpc/beacon/committees_test.go

@@ -252,7 +252,7 @@ func TestServer_ListBeaconCommittees_FromArchive(t *testing.T) {
 		Epoch:                0,
 		Committees:           wanted,
 		ActiveValidatorCount: uint64(numValidators),
-		NextPageToken:        strconv.Itoa(1),
+		NextPageToken:        "",
 		TotalSize:            int32(len(wanted)),
 	}
 	if !reflect.DeepEqual(wantedRes, res1) {

beacon-chain/rpc/beacon/validators_test.go

@@ -248,7 +248,7 @@ func TestServer_ListValidatorBalances_Pagination_Default(t *testing.T) {
 				Balances: []*ethpb.ValidatorBalances_Balance{
 					{Index: 99, PublicKey: []byte{99}, Balance: 99},
 				},
-				NextPageToken: strconv.Itoa(1),
+				NextPageToken: "",
 				TotalSize:     1,
 			},
 		},
@@ -259,7 +259,7 @@ func TestServer_ListValidatorBalances_Pagination_Default(t *testing.T) {
 					{Index: 2, PublicKey: []byte{2}, Balance: 2},
 					{Index: 3, PublicKey: []byte{3}, Balance: 3},
 				},
-				NextPageToken: strconv.Itoa(1),
+				NextPageToken: "",
 				TotalSize:     3,
 			},
 		},
@@ -270,7 +270,7 @@ func TestServer_ListValidatorBalances_Pagination_Default(t *testing.T) {
 					{Index: 11, PublicKey: []byte{11}, Balance: 11},
 					{Index: 12, PublicKey: []byte{12}, Balance: 12},
 				},
-				NextPageToken: strconv.Itoa(1),
+				NextPageToken: "",
 				TotalSize:     3,
 			}},
 		{req: &ethpb.ListValidatorBalancesRequest{PublicKeys: [][]byte{{2}, {3}}, Indices: []uint64{3, 4}}, // Duplication
@@ -280,7 +280,7 @@ func TestServer_ListValidatorBalances_Pagination_Default(t *testing.T) {
 					{Index: 3, PublicKey: []byte{3}, Balance: 3},
 					{Index: 4, PublicKey: []byte{4}, Balance: 4},
 				},
-				NextPageToken: strconv.Itoa(1),
+				NextPageToken: "",
 				TotalSize:     3,
 			}},
 		{req: &ethpb.ListValidatorBalancesRequest{PublicKeys: [][]byte{{}}, Indices: []uint64{3, 4}}, // Public key has a blank value
@@ -289,7 +289,7 @@ func TestServer_ListValidatorBalances_Pagination_Default(t *testing.T) {
 					{Index: 3, PublicKey: []byte{3}, Balance: 3},
 					{Index: 4, PublicKey: []byte{4}, Balance: 4},
 				},
-				NextPageToken: strconv.Itoa(1),
+				NextPageToken: "",
 				TotalSize:     2,
 			}},
 	}
@@ -351,7 +351,7 @@ func TestServer_ListValidatorBalances_Pagination_CustomPageSizes(t *testing.T) {
 					{PublicKey: []byte{100}, Index: 100, Balance: uint64(100)},
 					{PublicKey: []byte{101}, Index: 101, Balance: uint64(101)},
 				},
-				NextPageToken: strconv.Itoa(34),
+				NextPageToken: "34",
 				TotalSize:     int32(count)}},
 		{req: &ethpb.ListValidatorBalancesRequest{PageSize: 2},
 			res: &ethpb.ValidatorBalances{
@@ -663,7 +663,7 @@ func TestServer_ListValidators_Pagination(t *testing.T) {
 			res: &ethpb.Validators{
 				Validators: []*ethpb.Validator{
 					{PublicKey: []byte{99}}},
-				NextPageToken: strconv.Itoa(34),
+				NextPageToken: "",
 				TotalSize:     int32(count)}},
 		{req: &ethpb.ListValidatorsRequest{PageSize: 2},
 			res: &ethpb.Validators{
@@ -679,7 +679,7 @@ func TestServer_ListValidators_Pagination(t *testing.T) {
 			t.Fatal(err)
 		}
 		if !proto.Equal(res, test.res) {
-			t.Error("Incorrect respond of validators")
+			t.Errorf("Incorrect validator response, wanted %v, received %v", test.res, res)
 		}
 	}
 }

shared/pagination/pagination.go

@@ -23,7 +23,7 @@ func StartAndEndPage(pageToken string, pageSize int, totalSize int) (int, int, s
 		return 0, 0, "", errors.Wrap(err, "could not convert page token")
 	}
 
-	// Start page can not be greater than validator size.
+	// Start page can not be greater than set size.
 	start := token * pageSize
 	if start >= totalSize {
 		return 0, 0, "", fmt.Errorf("page start %d >= list %d", start, totalSize)
@@ -31,10 +31,12 @@ func StartAndEndPage(pageToken string, pageSize int, totalSize int) (int, int, s
 
 	// End page can not go out of bound.
 	end := start + pageSize
+	nextPageToken := strconv.Itoa(token + 1)
+
 	if end > totalSize {
 		end = totalSize
+		nextPageToken = "" // Return an empty next page token for the last page of a set
 	}
 
-	nextPageToken := strconv.Itoa(token + 1)
 	return start, end, nextPageToken, nil
 }

shared/pagination/pagination_test.go

@@ -44,7 +44,7 @@ func TestStartAndEndPage(t *testing.T) {
 			token:     "3",
 			pageSize:  33,
 			totalSize: 100,
-			nextToken: "4",
+			nextToken: "",
 			start:     99,
 			end:       100,
 		},