make 'or' validator immutable

Author: ArturAssisComp

lib/src/form_builder_validators.dart

@@ -1827,7 +1827,6 @@ final class Validators {
   /// - [ArgumentError] if `validators` is empty
   /// {@endtemplate}
   static Validator<T> or<T extends Object>(
-    // TODO(ArturAssisComp): refactor to make this input immutable.
     List<Validator<T>> validators, {
     String prefix = '',
     String suffix = '',

lib/src/validators/core_validators/compose_validators.dart

@@ -46,9 +46,11 @@ Validator<T> or<T extends Object>(
     throw ArgumentError.value(
         '[]', 'validators', 'The list of validators must not be empty');
   }
+  final List<Validator<T>> immutableValidators =
+      List<Validator<T>>.unmodifiable(validators);
   return (T value) {
     final List<String> errorMessageBuilder = <String>[];
-    for (final Validator<T> validator in validators) {
+    for (final Validator<T> validator in immutableValidators) {
       final String? errorMessage = validator(value);
       if (errorMessage == null) {
         return null;

test/src/validators/core_validators/composition_validators/or_validator_test.dart

@@ -104,5 +104,26 @@ void main() {
     test('Should throw AssertionError when the validators input is empty', () {
       expect(() => or(<Validator<Object?>>[]), throwsArgumentError);
     });
+
+    test('should be immutable even when input validators change', () {
+      final List<String? Function(double)> validators =
+          <String? Function(double)>[ltE(10), gt(17)];
+
+      final Validator<double> v = or(validators);
+      expect(v(12), stringContainsInOrder(<String>[errorLtE, errorGt]));
+      expect(v(10), isNull);
+      expect(v(19.0), isNull);
+
+      validators.add(gt(11));
+      expect(v(12), stringContainsInOrder(<String>[errorLtE, errorGt]));
+      expect(v(10), isNull);
+      expect(v(19.0), isNull);
+
+      validators.removeLast();
+      validators.removeLast();
+      expect(v(12), stringContainsInOrder(<String>[errorLtE, errorGt]));
+      expect(v(10), isNull);
+      expect(v(19.0), isNull);
+    });
   });
 }