Fix lint warnings in storage group package

Signed-off-by: Alex Vanin <alexey@nspcc.ru>

v2/storagegroup/convert.go

@@ -6,6 +6,7 @@ import (
 	sg "github.com/nspcc-dev/neofs-api-go/v2/storagegroup/grpc"
 )
 
+// StorageGroupToGRPCMessage converts unified proto structure into grpc structure.
 func StorageGroupToGRPCMessage(s *StorageGroup) *sg.StorageGroup {
 	if s == nil {
 		return nil
@@ -29,6 +30,7 @@ func StorageGroupToGRPCMessage(s *StorageGroup) *sg.StorageGroup {
 	return m
 }
 
+// StorageGroupFromGRPCMessage converts grpc structure into unified proto structure.
 func StorageGroupFromGRPCMessage(m *sg.StorageGroup) *StorageGroup {
 	if m == nil {
 		return nil

v2/storagegroup/marshal.go

@@ -7,12 +7,18 @@ import (
 )
 
 const (
-	SizeField       = 1
+	// SizeField order number from storage group proto definition.
-	HashField       = 2
+	SizeField = 1
+	// HashField order number from storage group proto definition.
+	HashField = 2
+	// ExpirationField order number from storage group proto definition.
 	ExpirationField = 3
-	ObjectIDsField  = 4
+	// ObjectIDsField order number from storage group proto definition.
+	ObjectIDsField = 4
 )
 
+// StableMarshal marshals unified storage group structure in a protobuf
+// compatible way without field order shuffle.
 func (s *StorageGroup) StableMarshal(buf []byte) ([]byte, error) {
 	if s == nil {
 		return []byte{}, nil
@@ -32,21 +38,25 @@ func (s *StorageGroup) StableMarshal(buf []byte) ([]byte, error) {
 	if err != nil {
 		return nil, err
 	}
+
 	offset += n
 
 	n, err = proto.BytesMarshal(HashField, buf[offset:], s.hash)
 	if err != nil {
 		return nil, err
 	}
+
 	offset += n
 
 	n, err = proto.UInt64Marshal(ExpirationField, buf[offset:], s.exp)
 	if err != nil {
 		return nil, err
 	}
+
 	offset += n
 
 	prefix, _ = proto.NestedStructurePrefix(ObjectIDsField)
+
 	for i := range s.members {
 		offset += binary.PutUvarint(buf[offset:], prefix)
 
@@ -64,6 +74,7 @@ func (s *StorageGroup) StableMarshal(buf []byte) ([]byte, error) {
 	return buf, nil
 }
 
+// StableSize of storage group structure marshalled by StableMarshal function.
 func (s *StorageGroup) StableSize() (size int) {
 	if s == nil {
 		return 0
@@ -74,6 +85,7 @@ func (s *StorageGroup) StableSize() (size int) {
 	size += proto.UInt64Size(ExpirationField, s.exp)
 
 	_, ln := proto.NestedStructurePrefix(ObjectIDsField)
+
 	for i := range s.members {
 		n := s.members[i].StableSize()
 		size += ln + proto.VarUIntSize(uint64(n)) + n

v2/storagegroup/marshal_test.go

@@ -12,6 +12,7 @@ import (
 func TestStorageGroup_StableMarshal(t *testing.T) {
 	ownerID1 := new(refs.ObjectID)
 	ownerID1.SetValue([]byte("Object ID 1"))
+
 	ownerID2 := new(refs.ObjectID)
 	ownerID2.SetValue([]byte("Object ID 2"))
 

v2/storagegroup/types.go

@@ -4,6 +4,8 @@ import (
 	"github.com/nspcc-dev/neofs-api-go/v2/refs"
 )
 
+// StorageGroup is a unified structure of StorageGroup
+// message from proto definition.
 type StorageGroup struct {
 	size uint64
 
@@ -14,6 +16,7 @@ type StorageGroup struct {
 	members []*refs.ObjectID
 }
 
+// GetValidationDataSize of unified storage group structure.
 func (s *StorageGroup) GetValidationDataSize() uint64 {
 	if s != nil {
 		return s.size
@@ -22,12 +25,14 @@ func (s *StorageGroup) GetValidationDataSize() uint64 {
 	return 0
 }
 
+// SetValidationDataSize into unified storage group structure.
 func (s *StorageGroup) SetValidationDataSize(v uint64) {
 	if s != nil {
 		s.size = v
 	}
 }
 
+// GetValidationHash of unified storage group structure.
 func (s *StorageGroup) GetValidationHash() []byte {
 	if s != nil {
 		return s.hash
@@ -36,12 +41,14 @@ func (s *StorageGroup) GetValidationHash() []byte {
 	return nil
 }
 
+// SetValidationHash into unified storage group structure.
 func (s *StorageGroup) SetValidationHash(v []byte) {
 	if s != nil {
 		s.hash = v
 	}
 }
 
+// GetExpirationEpoch of unified storage group structure.
 func (s *StorageGroup) GetExpirationEpoch() uint64 {
 	if s != nil {
 		return s.exp
@@ -50,12 +57,15 @@ func (s *StorageGroup) GetExpirationEpoch() uint64 {
 	return 0
 }
 
+// SetExpirationEpoch into unified storage group structure.
 func (s *StorageGroup) SetExpirationEpoch(v uint64) {
 	if s != nil {
 		s.exp = v
 	}
 }
 
+// GetMembers of unified storage group structure. Members are objects of
+// storage group.
 func (s *StorageGroup) GetMembers() []*refs.ObjectID {
 	if s != nil {
 		return s.members
@@ -64,6 +74,8 @@ func (s *StorageGroup) GetMembers() []*refs.ObjectID {
 	return nil
 }
 
+// SetMembers into unified storage group structure. Members are objects of
+// storage group.
 func (s *StorageGroup) SetMembers(v []*refs.ObjectID) {
 	if s != nil {
 		s.members = v