From bdcd5295d4ad1bb52e54e1e38b6866d7da516174 Mon Sep 17 00:00:00 2001
From: Lukas Klingsbo <lukas.klingsbo@gmail.com>
Date: Wed, 22 Jul 2026 00:17:58 +0200
Subject: [PATCH] fix: Mark the reversed() cache as valid after rebuilding it

---
 lib/comparing_ordered_set.dart       |  1 +
 lib/mapping_ordered_set.dart         |  1 +
 test/comparing_ordered_set_test.dart | 19 +++++++++++++++++++
 test/priority_ordered_set_test.dart  | 19 +++++++++++++++++++
 4 files changed, 40 insertions(+)

diff --git a/lib/comparing_ordered_set.dart b/lib/comparing_ordered_set.dart
index 809be7d..4e77a87 100644
--- a/lib/comparing_ordered_set.dart
+++ b/lib/comparing_ordered_set.dart
@@ -62,6 +62,7 @@ class ComparingOrderedSet<E> extends OrderedSet<E>
   Iterable<E> reversed() {
     if (!_validReverseCache) {
       _reverseCache = toList(growable: false).reversed;
+      _validReverseCache = true;
     }
     return _reverseCache;
   }
diff --git a/lib/mapping_ordered_set.dart b/lib/mapping_ordered_set.dart
index 59441af..c5ee899 100644
--- a/lib/mapping_ordered_set.dart
+++ b/lib/mapping_ordered_set.dart
@@ -40,6 +40,7 @@ class MappingOrderedSet<K extends Comparable<K>, E> extends OrderedSet<E>
   Iterable<E> reversed() {
     if (!_validReverseCache) {
       _reverseCache = toList(growable: false).reversed;
+      _validReverseCache = true;
     }
     return _reverseCache;
   }
diff --git a/test/comparing_ordered_set_test.dart b/test/comparing_ordered_set_test.dart
index 11e48b6..4f8891c 100644
--- a/test/comparing_ordered_set_test.dart
+++ b/test/comparing_ordered_set_test.dart
@@ -425,6 +425,25 @@ void main() {
         orderedSet.addAll([a, b]);
         expect(orderedSet.reversed().join(), 'badc');
       });
+
+      test('reversed result is cached between calls without mutations', () {
+        final orderedSet = OrderedSet.comparing<ComparableObject>(
+          compare: Comparing.on((e) => e.priority),
+        );
+        orderedSet.addAll([
+          ComparableObject(0, 'a'),
+          ComparableObject(1, 'b'),
+        ]);
+
+        final firstCall = orderedSet.reversed();
+        expect(identical(firstCall, orderedSet.reversed()), isTrue);
+
+        orderedSet.add(ComparableObject(2, 'c'));
+        final afterMutation = orderedSet.reversed();
+        expect(identical(firstCall, afterMutation), isFalse);
+        expect(afterMutation.join(), 'cba');
+        expect(identical(afterMutation, orderedSet.reversed()), isTrue);
+      });
     });
   });
 }
diff --git a/test/priority_ordered_set_test.dart b/test/priority_ordered_set_test.dart
index 85d66f5..49b7a1c 100644
--- a/test/priority_ordered_set_test.dart
+++ b/test/priority_ordered_set_test.dart
@@ -479,6 +479,25 @@ void main() {
         orderedSet.addAll([a, b]);
         expect(orderedSet.reversed().join(), 'badc');
       });
+
+      test('reversed result is cached between calls without mutations', () {
+        final orderedSet = OrderedSet.mapping<num, ComparableObject>(
+          (e) => e.priority,
+        );
+        orderedSet.addAll([
+          ComparableObject(0, 'a'),
+          ComparableObject(1, 'b'),
+        ]);
+
+        final firstCall = orderedSet.reversed();
+        expect(identical(firstCall, orderedSet.reversed()), isTrue);
+
+        orderedSet.add(ComparableObject(2, 'c'));
+        final afterMutation = orderedSet.reversed();
+        expect(identical(firstCall, afterMutation), isFalse);
+        expect(afterMutation.join(), 'cba');
+        expect(identical(afterMutation, orderedSet.reversed()), isTrue);
+      });
     });
   });
 }