Prevent deprecation of AppServerOrSAMLIdPServiceProvider from being a breaking change

lib/auth/assist/assistv1/service.go

@@ -374,7 +374,7 @@ func assembleSearchResponse(ctx context.Context, a *Service, documents []*ai.Doc
 		resources = append(resources, resource)
 	}
 
-	paginated, err := services.MakePaginatedResources(types.KindUnifiedResource, resources, nil /* requestable map */)
+	paginated, err := services.MakePaginatedResources(ctx, types.KindUnifiedResource, resources, nil /* requestable map */)
 	if err != nil {
 		return nil, trace.Wrap(err)
 	}

lib/auth/auth_with_roles.go

@@ -1423,7 +1423,7 @@ func (a *ServerWithRoles) ListUnifiedResources(ctx context.Context, req *proto.L
 		}
 	}
 
-	paginatedResources, err := services.MakePaginatedResources(types.KindUnifiedResource, unifiedResources, resourceAccess.requestableMap)
+	paginatedResources, err := services.MakePaginatedResources(ctx, types.KindUnifiedResource, unifiedResources, resourceAccess.requestableMap)
 	if err != nil {
 		return nil, trace.Wrap(err, "making paginated unified resources")
 	}

lib/auth/grpcserver.go

@@ -4310,7 +4310,7 @@ func (g *GRPCServer) ListResources(ctx context.Context, req *authpb.ListResource
 		return nil, trace.Wrap(err)
 	}
 
-	paginatedResources, err := services.MakePaginatedResources(req.ResourceType, resp.Resources, nil /* requestable map */)
+	paginatedResources, err := services.MakePaginatedResources(ctx, req.ResourceType, resp.Resources, nil /* requestable map */)
 	if err != nil {
 		return nil, trace.Wrap(err, "making paginated resources")
 	}

lib/services/unified_resource.go

@@ -25,6 +25,7 @@ import (
 	"sync"
 	"time"
 
+	"github.com/coreos/go-semver/semver"
 	"github.com/google/btree"
 	"github.com/gravitational/trace"
 	"github.com/jonboulle/clockwork"
@@ -33,6 +34,7 @@ import (
 	"github.com/gravitational/teleport"
 	"github.com/gravitational/teleport/api/client/proto"
 	apidefaults "github.com/gravitational/teleport/api/defaults"
+	"github.com/gravitational/teleport/api/metadata"
 	"github.com/gravitational/teleport/api/types"
 	"github.com/gravitational/teleport/lib/backend"
 	"github.com/gravitational/teleport/lib/utils"
@@ -742,7 +744,7 @@ const (
 )
 
 // MakePaginatedResource converts a resource into a paginated proto representation.
-func MakePaginatedResource(requestType string, r types.ResourceWithLabels, requiresRequest bool) (*proto.PaginatedResource, error) {
+func MakePaginatedResource(ctx context.Context, requestType string, r types.ResourceWithLabels, requiresRequest bool) (*proto.PaginatedResource, error) {
 	var protoResource *proto.PaginatedResource
 	resourceKind := requestType
 	if requestType == types.KindUnifiedResource {
@@ -850,7 +852,37 @@ func MakePaginatedResource(requestType string, r types.ResourceWithLabels, requi
 			return nil, trace.BadParameter("%s has invalid type %T", resourceKind, resource)
 		}
 
-		protoResource = &proto.PaginatedResource{Resource: &proto.PaginatedResource_SAMLIdPServiceProvider{SAMLIdPServiceProvider: serviceProvider}, RequiresRequest: requiresRequest}
+		// TODO(gzdunek): DELETE IN 17.0
+		// This is needed to maintain backward compatibility between v16 server and v15 client.
+		clientVersion, versionExists := metadata.ClientVersionFromContext(ctx)
+		isClientNotSupportingSAMLIdPServiceProviderResource := false
+		if versionExists {
+			version, err := semver.NewVersion(clientVersion)
+			if err == nil && version.Major < 16 {
+				isClientNotSupportingSAMLIdPServiceProviderResource = true
+			}
+		}
+
+		if isClientNotSupportingSAMLIdPServiceProviderResource {
+			protoResource = &proto.PaginatedResource{
+				Resource: &proto.PaginatedResource_AppServerOrSAMLIdPServiceProvider{
+					//nolint:staticcheck // SA1019. TODO(gzdunek): DELETE IN 17.0
+					AppServerOrSAMLIdPServiceProvider: &types.AppServerOrSAMLIdPServiceProviderV1{
+						Resource: &types.AppServerOrSAMLIdPServiceProviderV1_SAMLIdPServiceProvider{
+							SAMLIdPServiceProvider: serviceProvider,
+						},
+					},
+				},
+				RequiresRequest: requiresRequest,
+			}
+		} else {
+			protoResource = &proto.PaginatedResource{
+				Resource: &proto.PaginatedResource_SAMLIdPServiceProvider{
+					SAMLIdPServiceProvider: serviceProvider,
+				},
+				RequiresRequest: requiresRequest,
+			}
+		}
 	default:
 		return nil, trace.NotImplemented("resource type %s doesn't support pagination", resource.GetKind())
 	}
@@ -859,11 +891,11 @@ func MakePaginatedResource(requestType string, r types.ResourceWithLabels, requi
 }
 
 // MakePaginatedResources converts a list of resources into a list of paginated proto representations.
-func MakePaginatedResources(requestType string, resources []types.ResourceWithLabels, requestableMap map[string]struct{}) ([]*proto.PaginatedResource, error) {
+func MakePaginatedResources(ctx context.Context, requestType string, resources []types.ResourceWithLabels, requestableMap map[string]struct{}) ([]*proto.PaginatedResource, error) {
 	paginatedResources := make([]*proto.PaginatedResource, 0, len(resources))
 	for _, r := range resources {
 		_, requiresRequest := requestableMap[r.GetName()]
-		protoResource, err := MakePaginatedResource(requestType, r, requiresRequest)
+		protoResource, err := MakePaginatedResource(ctx, requestType, r, requiresRequest)
 		if err != nil {
 			return nil, trace.Wrap(err)
 		}

lib/services/unified_resource_test.go

@@ -30,9 +30,12 @@ import (
 	"github.com/google/uuid"
 	"github.com/stretchr/testify/assert"
 	"github.com/stretchr/testify/require"
+	"google.golang.org/grpc/metadata"
 
 	"github.com/gravitational/teleport"
+	"github.com/gravitational/teleport/api/client/proto"
 	"github.com/gravitational/teleport/api/defaults"
+	apimetadata "github.com/gravitational/teleport/api/metadata"
 	"github.com/gravitational/teleport/api/types"
 	"github.com/gravitational/teleport/api/types/header"
 	"github.com/gravitational/teleport/lib/backend/memory"
@@ -382,6 +385,47 @@ func TestUnifiedResourceWatcher_DeleteEvent(t *testing.T) {
 	}, 5*time.Second, 10*time.Millisecond, "Timed out waiting for unified resources to be deleted")
 }
 
+func Test_PaginatedResourcesSAMLIdPServiceProviderCompatibility(t *testing.T) {
+	samlApp, err := types.NewSAMLIdPServiceProvider(
+		types.Metadata{
+			Name: "sp1",
+		},
+		types.SAMLIdPServiceProviderSpecV1{
+			EntityDescriptor: newTestEntityDescriptor("sp1"),
+			EntityID:         "sp1",
+		},
+	)
+	require.NoError(t, err)
+
+	// for a v15 client, expect AppServerOrSAMLIdPServiceProvider response
+	v15ctx := metadata.NewIncomingContext(context.Background(), metadata.New(map[string]string{apimetadata.VersionKey: "15.0.0"}))
+	v15response, err := services.MakePaginatedResources(v15ctx, types.KindUnifiedResource, []types.ResourceWithLabels{samlApp}, map[string]struct{}{})
+	require.NoError(t, err)
+	require.Equal(t,
+		&proto.PaginatedResource{
+			Resource: &proto.PaginatedResource_AppServerOrSAMLIdPServiceProvider{
+				//nolint:staticcheck // SA1019. TODO(gzdunek): DELETE IN 17.0 (with the entire test)
+				AppServerOrSAMLIdPServiceProvider: &types.AppServerOrSAMLIdPServiceProviderV1{
+					Resource: &types.AppServerOrSAMLIdPServiceProviderV1_SAMLIdPServiceProvider{
+						SAMLIdPServiceProvider: samlApp.(*types.SAMLIdPServiceProviderV1),
+					},
+				}}},
+		v15response[0],
+	)
+
+	// for a v16 client, expect SAMLIdPServiceProvider response
+	v16ctx := metadata.NewIncomingContext(context.Background(), metadata.New(map[string]string{apimetadata.VersionKey: "16.0.0"}))
+	v16response, err := services.MakePaginatedResources(v16ctx, types.KindUnifiedResource, []types.ResourceWithLabels{samlApp}, map[string]struct{}{})
+	require.NoError(t, err)
+	require.Equal(t,
+		&proto.PaginatedResource{
+			Resource: &proto.PaginatedResource_SAMLIdPServiceProvider{
+				SAMLIdPServiceProvider: samlApp.(*types.SAMLIdPServiceProviderV1),
+			}},
+		v16response[0],
+	)
+}
+
 func newTestEntityDescriptor(entityID string) string {
 	return fmt.Sprintf(testEntityDescriptor, entityID)
 }