From fb6151f556756808539857280c37c37f1953b2ec Mon Sep 17 00:00:00 2001
From: Masaaki Goshima <goccy54@gmail.com>
Date: Sun, 2 May 2021 15:26:36 +0900
Subject: [PATCH] Fix decoding of null value to []byte by json.Unmarshal

---
 decode_bytes.go | 16 +++-------------
 decode_test.go  | 29 +++++++++++++++++++++++++++++
 2 files changed, 32 insertions(+), 13 deletions(-)

diff --git a/decode_bytes.go b/decode_bytes.go
index 0babe82..b5e34a3 100644
--- a/decode_bytes.go
+++ b/decode_bytes.go
@@ -160,21 +160,11 @@ func (d *bytesDecoder) decodeBinary(buf []byte, cursor, depth int64, p unsafe.Po
 			}
 			return nil, c, nil
 		case 'n':
-			buflen := int64(len(buf))
-			if cursor+3 >= buflen {
-				return nil, 0, errUnexpectedEndOfJSON("null", cursor)
-			}
-			if buf[cursor+1] != 'u' {
-				return nil, 0, errInvalidCharacter(buf[cursor+1], "null", cursor)
-			}
-			if buf[cursor+2] != 'l' {
-				return nil, 0, errInvalidCharacter(buf[cursor+2], "null", cursor)
-			}
-			if buf[cursor+3] != 'l' {
-				return nil, 0, errInvalidCharacter(buf[cursor+3], "null", cursor)
+			if err := validateNull(buf, cursor); err != nil {
+				return nil, 0, err
 			}
 			cursor += 4
-			return []byte{}, cursor, nil
+			return nil, cursor, nil
 		default:
 			goto ERROR
 		}
diff --git a/decode_test.go b/decode_test.go
index c057add..cfc6df3 100644
--- a/decode_test.go
+++ b/decode_test.go
@@ -3388,3 +3388,32 @@ func TestDecodeUnknownInterface(t *testing.T) {
 		}
 	})
 }
+
+func TestDecodeByteSliceNull(t *testing.T) {
+	t.Run("unmarshal", func(t *testing.T) {
+		var v1 []byte
+		if err := stdjson.Unmarshal([]byte(`null`), &v1); err != nil {
+			t.Fatal(err)
+		}
+		var v2 []byte
+		if err := json.Unmarshal([]byte(`null`), &v2); err != nil {
+			t.Fatal(err)
+		}
+		if v1 == nil && v2 != nil || len(v1) != len(v2) {
+			t.Fatalf("failed to decode null to []byte. expected:%#v but got %#v", v1, v2)
+		}
+	})
+	t.Run("stream", func(t *testing.T) {
+		var v1 []byte
+		if err := stdjson.NewDecoder(strings.NewReader(`null`)).Decode(&v1); err != nil {
+			t.Fatal(err)
+		}
+		var v2 []byte
+		if err := json.NewDecoder(strings.NewReader(`null`)).Decode(&v2); err != nil {
+			t.Fatal(err)
+		}
+		if v1 == nil && v2 != nil || len(v1) != len(v2) {
+			t.Fatalf("failed to decode null to []byte. expected:%#v but got %#v", v1, v2)
+		}
+	})
+}