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

x/errors/validation/slice.go

@@ -0,0 +1,57 @@
+package validation
+
+import "fmt"
+
+type SliceValue[T any] interface {
+	~[]T
+}
+
+// SliceError describes a slice field validation error.
+type SliceError[T any, V SliceValue[T]] struct{ *FieldError[V] }
+
+// Slice returns a new slice validation error.
+func Slice[T any, V SliceValue[T]](field string, value V) *SliceError[T, V] {
+	return &SliceError[T, V]{Field(field, value)}
+}
+
+// NotEmpty adds an error if the slice is empty.
+func (e *SliceError[T, V]) NotEmpty() *SliceError[T, V] {
+	e.Func(NotEmptySlice)
+	return e
+}
+
+// Length adds an error if the slice length is not in the given range.
+func (e *SliceError[T, V]) Length(min, max int) *SliceError[T, V] {
+	e.Func(SliceLength[T, V](min, max))
+	return e
+}
+
+// NotEmptySlice accepts any slice and returns a message if the value is empty.
+func NotEmptySlice[T any, V SliceValue[T]](s V) string {
+	if len(s) == 0 {
+		return "must not be empty"
+	}
+
+	return ""
+}
+
+// SliceLength accepts any slice and returns a message if the length is not in the given range.
+func SliceLength[T any, V SliceValue[T]](min, max int) func(s V) string {
+	return func(s V) string {
+		n := len(s)
+
+		if min == max {
+			if n != min {
+				return fmt.Sprintf("must be %d elements", min)
+			}
+
+			return ""
+		}
+
+		if n < min || n > max {
+			return fmt.Sprintf("must be between %d and %d elements", min, max)
+		}
+
+		return ""
+	}
+}