Add new x/errors/validation package to make your life even more easier (using Generics)

x/errors/validation/string.go

@@ -0,0 +1,69 @@
+package validation
+
+import (
+	"fmt"
+	"strings"
+)
+
+// StringError describes a string field validation error.
+type StringError struct{ *FieldError[string] }
+
+// String returns a new string validation error.
+func String(field string, value string) *StringError {
+	return &StringError{Field(field, value)}
+}
+
+// NotEmpty adds an error if the string is empty.
+func (e *StringError) NotEmpty() *StringError {
+	e.Func(NotEmpty)
+	return e
+}
+
+// Fullname adds an error if the string is not a full name.
+func (e *StringError) Fullname() *StringError {
+	e.Func(Fullname)
+	return e
+}
+
+// Length adds an error if the string length is not in the given range.
+func (e *StringError) Length(min, max int) *StringError {
+	e.Func(StringLength(min, max))
+	return e
+}
+
+// NotEmpty accepts any string and returns a message if the value is empty.
+func NotEmpty(s string) string {
+	if s == "" {
+		return "must not be empty"
+	}
+
+	return ""
+}
+
+// Fullname accepts any string and returns a message if the value is not a full name.
+func Fullname(s string) string {
+	if len(strings.Split(s, " ")) < 2 {
+		return "must contain first and last name"
+	}
+
+	return ""
+}
+
+// StringLength accepts any string and returns a message if the length is not in the given range.
+func StringLength(min, max int) func(s string) string {
+	return func(s string) string {
+		n := len(s)
+
+		if min == max {
+			if n != min {
+				return fmt.Sprintf("must be %d characters", min)
+			}
+		}
+
+		if n < min || n > max {
+			return fmt.Sprintf("must be between %d and %d characters", min, max)
+		}
+
+		return ""
+	}
+}