Fix ParseMode.MarshalJSON

types.go

@@ -1,6 +1,7 @@
-//go:generate python keyboards.py
 package telegram
 
+//go:generate python keyboards.py
+
 import (
 	"encoding/json"
 	"io"
@@ -209,23 +210,27 @@ type InputFile interface {
 
 // Parse modes.
 const (
-	ModeDefault ParseMode = iota
-	ModeMarkdown
-	ModeHTML
+	ModeDefault  ParseMode = 0
+	ModeMarkdown           = 1
+	ModeHTML               = 2
 )
 
 type ParseMode int
 
 // MarshalJSON implements json.Marshaler interface.
-func (m *ParseMode) MarshalJSON() ([]byte, error) {
-	var s string
-	switch *m {
+func (m ParseMode) MarshalJSON() (b []byte, err error) {
+	switch m {
+	case ModeDefault:
+		// ModeDefault should be evaluated as empty by json package and skipped
+		// in message marshalling. But empty string was a simplest solution to
+		// leave ParseMode a simple type.
+		b = []byte(`""`)
 	case ModeMarkdown:
-		s = "Markdown"
+		b = []byte(`"Markdown"`)
 	case ModeHTML:
-		s = "HTML"
+		b = []byte(`"HTML"`)
 	}
-	return []byte(s), nil
+	return
 }
 
 type NewMessage struct {

types_test.go

@@ -1,6 +1,7 @@
 package telegram
 
 import (
+	"bytes"
 	"encoding/json"
 	"testing"
 )
@@ -29,3 +30,23 @@ func TestReplyKeyboardMarkup_UnmarshalJSON(t *testing.T) {
 		t.Fatalf("button: want %q, got %q", "test", s)
 	}
 }
+
+var parseModeTests = []struct {
+	Name  string
+	Mode  ParseMode
+	Bytes []byte
+}{
+	{"default", ModeDefault, []byte(`""`)},
+	{"markdown", ModeMarkdown, []byte(`"Markdown"`)},
+	{"html", ModeHTML, []byte(`"HTML"`)},
+}
+
+func TestParseMode_MarshalJSON(t *testing.T) {
+	for _, tt := range parseModeTests {
+		if b, err := json.Marshal(tt.Mode); err != nil {
+			t.Fatalf("%s: %s", tt.Name, err)
+		} else if !bytes.Equal(b, tt.Bytes) {
+			t.Fatalf("%s: want %v, got %v", tt.Name, tt.Bytes, b)
+		}
+	}
+}