[#474] Use appropriate null version during listing

Signed-off-by: Denis Kirillov <denis@nspcc.ru>

api/handler/object_list_test.go

@@ -1,8 +1,12 @@
 package handler
 
 import (
+	"bytes"
+	"context"
+	"net/http"
 	"testing"
 
+	"github.com/nspcc-dev/neofs-s3-gw/api/layer"
 	"github.com/stretchr/testify/require"
 )
 
@@ -35,3 +39,37 @@ func TestParseContinuationToken(t *testing.T) {
 		require.Equal(t, tokenStr, token)
 	})
 }
+
+func TestListObjectNullVersions(t *testing.T) {
+	ctx := context.Background()
+	hc := prepareHandlerContext(t)
+
+	bktName := "bucket-versioning-enabled"
+	createTestBucket(ctx, t, hc, bktName)
+
+	objName := "object"
+
+	body := bytes.NewReader([]byte("content"))
+	w, r := prepareTestPayloadRequest(bktName, objName, body)
+	hc.Handler().PutObjectHandler(w, r)
+	assertStatus(t, w, http.StatusOK)
+
+	versioning := &VersioningConfiguration{Status: "Enabled"}
+	w, r = prepareTestRequest(t, bktName, objName, versioning)
+	hc.Handler().PutBucketVersioningHandler(w, r)
+	assertStatus(t, w, http.StatusOK)
+
+	body2 := bytes.NewReader([]byte("content2"))
+	w, r = prepareTestPayloadRequest(bktName, objName, body2)
+	hc.Handler().PutObjectHandler(w, r)
+	assertStatus(t, w, http.StatusOK)
+
+	w, r = prepareTestRequest(t, bktName, objName, nil)
+	hc.Handler().ListBucketObjectVersionsHandler(w, r)
+
+	result := &ListObjectsVersionsResponse{}
+	parseTestResponse(t, w, result)
+
+	require.Len(t, result.Version, 2)
+	require.Equal(t, layer.UnversionedObjectVersionID, result.Version[1].VersionID)
+}