Validation: fix distinct fail if array is empty

validation/distinct.go

@@ -8,6 +8,11 @@ type DistinctValidator[T comparable] struct {
 
 // Validate checks the field under validation satisfies this validator's criteria.
 func (v *DistinctValidator[T]) Validate(ctx *Context) bool {
+	if empty, ok := ctx.Value.([]any); ok && len(empty) == 0 {
+		// The array will stay `[]any` even after recursive validation if it's empty.
+		// We don't want to check distinct elements for empty arrays.
+		return true
+	}
 	list, ok := ctx.Value.([]T)
 	if !ok {
 		return false

validation/distinct_test.go

@@ -22,6 +22,7 @@ func TestDistinctValidator(t *testing.T) {
 		validator Validator
 		want      bool
 	}{
+		{value: []any{}, validator: Distinct[string](), want: true},
 		{value: []string{}, validator: Distinct[string](), want: true},
 		{value: []string{"a", "b"}, validator: Distinct[string](), want: true},
 		{value: []string{"a", "b", "a"}, validator: Distinct[string](), want: false},