refactor color parsing and environ loader using strings.Cut

cli/color.go

@@ -41,32 +41,21 @@ func validColor(x string) bool {
 			return false
 		}
 	}
-	return num || x == ""
+	return num
 }
 
 func setColors(colors string) error {
-	var i int
 	var color string
 	for _, target := range []*[]byte{
 		&nullColor, &falseColor, &trueColor, &numberColor,
 		&stringColor, &objectKeyColor, &arrayColor, &objectColor,
 	} {
-		if i < len(colors) {
-			if j := strings.IndexByte(colors[i:], ':'); j >= 0 {
-				color = colors[i : i+j]
-				i += j + 1
-			} else {
-				color = colors[i:]
-				i = len(colors)
-			}
+		color, colors, _ = strings.Cut(colors, ":")
+		if color != "" {
 			if !validColor(color) {
 				return fmt.Errorf("invalid color: %q", color)
 			}
-			if color == "" {
-				*target = nil
-			} else {
-				*target = newColor(color)
-			}
+			*target = newColor(color)
 		} else {
 			*target = nil
 		}

cli/error.go

@@ -125,13 +125,11 @@ func (err *yamlParseError) Error() string {
 	msg := strings.TrimPrefix(
 		strings.TrimPrefix(err.err.Error(), "yaml: "),
 		"unmarshal errors:\n  ")
-	if fmt.Sscanf(msg, "line %d: ", &line); line == 0 {
+	if _, e := fmt.Sscanf(msg, "line %d: ", &line); e != nil {
 		return "invalid yaml: " + err.fname
 	}
-	msg = msg[strings.Index(msg, ": ")+2:]
-	if i := strings.IndexByte(msg, '\n'); i >= 0 {
-		msg = msg[:i]
-	}
+	_, msg, _ = strings.Cut(msg, ": ")
+	msg, _, _ = strings.Cut(msg, "\n")
 	linestr := getLineByLine(err.contents, line)
 	return fmt.Sprintf("invalid yaml: %s:%d\n%s  %s",
 		err.fname, line, formatLineInfo(linestr, line, 0), msg)

compiler.go

@@ -913,8 +913,8 @@ func (c *compiler) compileFunc(e *Func) error {
 			env := make(map[string]any)
 			if c.environLoader != nil {
 				for _, kv := range c.environLoader() {
-					if i := strings.IndexByte(kv, '='); i > 0 {
-						env[kv[:i]] = kv[i+1:]
+					if k, v, ok := strings.Cut(kv, "="); ok && k != "" {
+						env[k] = v
 					}
 				}
 			}