From ae909aeb7242f3c26b4c5870821ab8abe35ce5a1 Mon Sep 17 00:00:00 2001
From: Marten Seemann <martenseemann@gmail.com>
Date: Sat, 11 Oct 2025 13:08:06 +0800
Subject: [PATCH] jsontext: add support for encoding null (#5371)

---
 qlogwriter/jsontext/encoder.go      | 10 ++++++++++
 qlogwriter/jsontext/encoder_test.go | 24 +++++++++++++++++++++++-
 2 files changed, 33 insertions(+), 1 deletion(-)

diff --git a/qlogwriter/jsontext/encoder.go b/qlogwriter/jsontext/encoder.go
index b838e2fb..4f715bbd 100644
--- a/qlogwriter/jsontext/encoder.go
+++ b/qlogwriter/jsontext/encoder.go
@@ -19,6 +19,7 @@ const (
 	kindUint
 	kindFloat
 	kindBool
+	kindNull
 	kindObjectStart
 	kindObjectEnd
 	kindArrayStart
@@ -60,6 +61,9 @@ func Bool(b bool) Token {
 	return Token{kind: kindBool, b: b}
 }
 
+// Null is a null token.
+var Null Token = Token{kind: kindNull}
+
 // BeginObject is the begin object token.
 var BeginObject Token = Token{kind: kindObjectStart}
 
@@ -86,6 +90,7 @@ var (
 	colonByte       = []byte(":")
 	trueByte        = []byte("true")
 	falseByte       = []byte("false")
+	nullByte        = []byte("null")
 	openObjectByte  = []byte("{")
 	closeObjectByte = []byte("}")
 	openArrayByte   = []byte("[")
@@ -256,6 +261,11 @@ func (e *Encoder) WriteToken(t Token) error {
 			}
 		}
 		e.afterValue()
+	case kindNull:
+		if _, err = e.w.Write(nullByte); err != nil {
+			return err
+		}
+		e.afterValue()
 	case kindObjectStart:
 		if _, err = e.w.Write(openObjectByte); err != nil {
 			return err
diff --git a/qlogwriter/jsontext/encoder_test.go b/qlogwriter/jsontext/encoder_test.go
index d684e994..f580cfaa 100644
--- a/qlogwriter/jsontext/encoder_test.go
+++ b/qlogwriter/jsontext/encoder_test.go
@@ -88,6 +88,8 @@ func TestEncoderNumbersAndBool(t *testing.T) {
 	enc.WriteToken(jsontext.True)
 	enc.WriteToken(jsontext.String("false"))
 	enc.WriteToken(jsontext.False)
+	enc.WriteToken(jsontext.String("nullv"))
+	enc.WriteToken(jsontext.Null)
 	enc.WriteToken(jsontext.EndObject)
 	output := buf.String()
 
@@ -99,6 +101,7 @@ func TestEncoderNumbersAndBool(t *testing.T) {
 		"float": 3.14,
 		"true":  true,
 		"false": false,
+		"nullv": nil,
 	}, got)
 }
 
@@ -126,6 +129,21 @@ func TestEncoderEmptyArray(t *testing.T) {
 	require.Equal(t, []any{}, got)
 }
 
+func TestEncoderArrayWithNulls(t *testing.T) {
+	buf := bytes.NewBuffer(nil)
+	enc := jsontext.NewEncoder(buf)
+	enc.WriteToken(jsontext.BeginArray)
+	enc.WriteToken(jsontext.Null)
+	enc.WriteToken(jsontext.String("x"))
+	enc.WriteToken(jsontext.Null)
+	enc.WriteToken(jsontext.EndArray)
+	output := buf.String()
+
+	var got []any
+	require.NoError(t, json.Unmarshal([]byte(output), &got))
+	require.Equal(t, []any{nil, "x", nil}, got)
+}
+
 func TestEncoderEscapedStrings(t *testing.T) {
 	t.Run("no escapes", func(t *testing.T) {
 		testEncoderEscapedStrings(t, "simplekey", "simplevalue")
@@ -210,6 +228,9 @@ func encodeValue(t testing.TB, enc *jsontext.Encoder, v any) (isSupported bool)
 	case bool:
 		require.NoError(t, enc.WriteToken(jsontext.Bool(val)))
 		return true
+	case nil:
+		require.NoError(t, enc.WriteToken(jsontext.Null))
+		return true
 	default:
 		return false
 	}
@@ -326,12 +347,13 @@ func FuzzEncoder(f *testing.F) {
 	examples := []string{
 		`{"hello": "world"}`,
 		`{"foo": 123, "bar": [1, 2, 3]}`,
-		`{"nested": {"a": 1, "b": [true, false, "foobar"]}}`,
+		`{"nested": {"a": 1, "b": [true, false, "foobar", null]}}`,
 		`[{"x": 1}, {"y": "foo"}]`,
 		`["foo", "bar"]`,
 		`["a", {"b": [1, 2, {"c": "d"}]}, 3]`,
 		`{"emptyObj": {}, "emptyArr": []}`,
 		`{"mixed": [1, "two", {"three": 3}]}`,
+		`[null]`,
 	}
 	for _, tc := range examples {
 		// first test that