From b50697063693708f9ff37232d73cf42b39a35c5d Mon Sep 17 00:00:00 2001
From: Pavel Karpy <carpawell@nspcc.ru>
Date: Tue, 8 Jun 2021 21:12:17 +0300
Subject: [PATCH] [#302] pkg/signature: Convert nil `Signature` to nil message

Document that `Signature.ToV2` method return `nil`
when called on `nil`. Document that `NewSignatureFromV2`
function return `nil` when called on `nil`. Write
corresponding unit tests.

Signed-off-by: Pavel Karpy <carpawell@nspcc.ru>
---
 pkg/signature.go      |  5 +++++
 pkg/signature_test.go | 17 +++++++++++++++++
 2 files changed, 22 insertions(+)

diff --git a/pkg/signature.go b/pkg/signature.go
index 7cf318d..1847dcd 100644
--- a/pkg/signature.go
+++ b/pkg/signature.go
@@ -8,6 +8,8 @@ import (
 type Signature refs.Signature
 
 // NewSignatureFromV2 wraps v2 Signature message to Signature.
+//
+// Nil refs.Signature converts to nil.
 func NewSignatureFromV2(sV2 *refs.Signature) *Signature {
 	return (*Signature)(sV2)
 }
@@ -39,6 +41,9 @@ func (s *Signature) SetSign(v []byte) {
 	(*refs.Signature)(s).SetSign(v)
 }
 
+// ToV2 converts Signature to v2 Signature message.
+//
+// Nil Signature converts to nil.
 func (s *Signature) ToV2() *refs.Signature {
 	return (*refs.Signature)(s)
 }
diff --git a/pkg/signature_test.go b/pkg/signature_test.go
index 72196c8..5b8c32f 100644
--- a/pkg/signature_test.go
+++ b/pkg/signature_test.go
@@ -1,6 +1,7 @@
 package pkg
 
 import (
+	"github.com/nspcc-dev/neofs-api-go/v2/refs"
 	"testing"
 
 	"github.com/stretchr/testify/require"
@@ -31,3 +32,19 @@ func TestSignatureEncoding(t *testing.T) {
 		require.Equal(t, s, s2)
 	})
 }
+
+func TestNewSignatureFromV2(t *testing.T) {
+	t.Run("from nil", func(t *testing.T) {
+		var x *refs.Signature
+
+		require.Nil(t, NewSignatureFromV2(x))
+	})
+}
+
+func TestSignature_ToV2(t *testing.T) {
+	t.Run("nil", func(t *testing.T) {
+		var x *Signature
+
+		require.Nil(t, x.ToV2())
+	})
+}