Fix snake_case parser for an input ending in an idle state (remove delimiter)

Author: VojtechVitek

camel.go

@@ -11,12 +11,12 @@ import (
 func CamelCase(input string) string {
 	var b strings.Builder
 
-	stateMachine := idle
+	state := idle
 	for i := 0; i < len(input); {
 		r, size := utf8.DecodeRuneInString(input[i:])
 		i += size
-		stateMachine = stateMachine.next(r)
-		switch stateMachine {
+		state = state.next(r)
+		switch state {
 		case firstAlphaNum:
 			if b.Len() > 0 {
 				b.WriteRune(unicode.ToUpper(r))

parser.go

@@ -4,16 +4,17 @@ import (
 	"unicode"
 )
 
-type stateMachine int
+type parserStateMachine int
 
 const (
-	idle          stateMachine = iota // 0 _$$_This is some text, OK?!
-	firstAlphaNum                     // 1     ↑    ↑  ↑    ↑     ↑
-	alphaNum                          // 2      ↑↑↑  ↑  ↑↑↑  ↑↑↑   ↑
-	delimiter                         // 3         ↑  ↑    ↑    ↑   ↑
+	_             parserStateMachine = iota //   _$$_This is some text, OK?!
+	idle                                    // 1 ↑↑↑↑                  ↑   ↑
+	firstAlphaNum                           // 2     ↑    ↑  ↑    ↑     ↑
+	alphaNum                                // 3      ↑↑↑  ↑  ↑↑↑  ↑↑↑   ↑
+	delimiter                               // 4         ↑  ↑    ↑    ↑   ↑
 )
 
-func (s stateMachine) next(r rune) stateMachine {
+func (s parserStateMachine) next(r rune) parserStateMachine {
 	switch s {
 	case idle:
 		if isAlphaNum(r) {

pascal.go

@@ -11,12 +11,12 @@ import (
 func PascalCase(input string) string {
 	var b strings.Builder
 
-	stateMachine := idle
+	state := idle
 	for i := 0; i < len(input); {
 		r, size := utf8.DecodeRuneInString(input[i:])
 		i += size
-		stateMachine = stateMachine.next(r)
-		switch stateMachine {
+		state = state.next(r)
+		switch state {
 		case firstAlphaNum:
 			b.WriteRune(unicode.ToUpper(r))
 		case alphaNum:

snake.go

@@ -11,20 +11,21 @@ import (
 func SnakeCase(str string) string {
 	var b bytes.Buffer
 
-	stateMachine := idle
+	state := idle
 	for i := 0; i < len(str); {
 		r, size := utf8.DecodeRuneInString(str[i:])
 		i += size
-		stateMachine = stateMachine.next(r)
-		switch stateMachine {
+		state = state.next(r)
+		switch state {
 		case firstAlphaNum, alphaNum:
 			b.WriteRune(unicode.ToLower(r))
 		case delimiter:
 			b.WriteByte('_')
 		}
 	}
-	if stateMachine == idle {
-		return string(bytes.TrimSuffix(b.Bytes(), []byte{'_'}))
+	if (state == idle || state == delimiter) && b.Len() > 0 {
+		b.Truncate(b.Len() - 1)
 	}
+
 	return b.String()
 }

textcase_test.go

@@ -24,6 +24,7 @@ func TestTextCases(t *testing.T) {
 		{in: "a___", camel: "a", snake: "a"},
 		{in: "a___b", camel: "aB", snake: "a_b"},
 		{in: "ax___by", camel: "axBy", snake: "ax_by"},
+		{in: "Háčky, čárky. Příliš žluťoučký kůň úpěl ďábelské ódy.", camel: "háčkyČárkyPřílišŽluťoučkýKůňÚpělĎábelskéÓdy", snake: "háčky_čárky_příliš_žluťoučký_kůň_úpěl_ďábelské_ódy"},
 	}
 
 	for _, test := range tt {