Fix encoding of string that contains "- " (#657)

* fix encoding of string that contains "- "

* fix test case

Author: goccy

encode_test.go

@@ -171,7 +171,7 @@ func TestEncoder(t *testing.T) {
 			},
 		},
 		{
-			"a: -\n",
+			"a: \"-\"\n",
 			map[string]string{"a": "-"},
 			nil,
 		},

token/token.go

@@ -679,6 +679,9 @@ func IsNeedQuoted(value string) bool {
 	if isNumber(value) {
 		return true
 	}
+	if value == "-" {
+		return true
+	}
 	first := value[0]
 	switch first {
 	case '*', '&', '[', '{', '}', ']', ',', '!', '|', '>', '%', '\'', '"', '@', ' ', '`':
@@ -696,7 +699,7 @@ func IsNeedQuoted(value string) bool {
 		switch c {
 		case '#', '\\':
 			return true
-		case ':':
+		case ':', '-':
 			if i+1 < len(value) && value[i+1] == ' ' {
 				return true
 			}

token/token_test.go

@@ -133,6 +133,8 @@ func TestIsNeedQuoted(t *testing.T) {
 		"Null",
 		"NULL",
 		"~",
+		"-",
+		"- --foo",
 	}
 	for i, test := range needQuotedTests {
 		if !token.IsNeedQuoted(test) {