fix: method "keys" return an immutable copy of the cache keys

CHANGELOG.md

@@ -7,35 +7,44 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 
 ## [Unreleased]
 
+### Added
+
+- Method "keys" for listing all cache keys —
+  [152](https://github.com/dartoos-dev/json_cache/issues/152)
+
 ### Changed
 
-- update linting rules —
+- Mehtod "keys" returns an immutable copy of the underlying cache keys —
+  [165](https://github.com/dartoos-dev/json_cache/issues/152)
+
+- Update linting rules —
   [162](https://github.com/dartoos-dev/json_cache/issues/154).
 
-
 ## [3.0.2] - 2024-08-19
 
 ### Changed
 
-- Bump up dependencies —
+- Updated dependencies —
   [154](https://github.com/dartoos-dev/json_cache/issues/154).
 
 ### Fixed
 
-- Removed code warnings and upgraded dart SDK range and each dependency to latest resolvable version available - [148](https://github.com/dartoos-dev/json_cache/issues/148).
+- Remove code warnings and upgrade the dart SDK range. In addition, 
+  dependencies were updated to the latest resolvable version —
+  [148](https://github.com/dartoos-dev/json_cache/issues/148).
 
 ## [3.0.1] - 2023-08-10
 
 ### Fixed
 
-- removed unused package 'cross_local_storage' from pubspec —
+- Removed unused package 'cross_local_storage' from pubspec —
   [144](https://github.com/dartoos-dev/json_cache/issues/144). 
 
 ## [3.0.0] - 2023-08-10
 
 ### Removed
 
-- support for the 'cross_local_storage' package — **BREAKING CHANGE** —
+- Support for the 'cross_local_storage' package — **BREAKING CHANGE** —
   [140](https://github.com/dartoos-dev/json_cache/issues/140).
 
 ### Fixed

lib/src/json_cache.dart

@@ -28,8 +28,8 @@ abstract class JsonCache {
   /// Returns `true` if there is cached data at [key]; `false` otherwise.
   Future<bool> contains(String key);
 
-  /// Lists all keys.
+  /// The cache keys.
   ///
-  /// Returns an **unmodifiable** list of cache keys without duplicates.
+  /// Returns an **unmodifiable** list of all cache keys without duplicates.
   Future<UnmodifiableListView<String>> keys();
 }

lib/src/json_cache_fake.dart

@@ -55,6 +55,6 @@ class JsonCacheFake implements JsonCache {
 
   @override
   Future<UnmodifiableListView<String>> keys() async {
-    return UnmodifiableListView(_memory.keys);
+    return UnmodifiableListView(List.unmodifiable(_memory.keys));
   }
 }

lib/src/json_cache_hive.dart

@@ -41,6 +41,8 @@ class JsonCacheHive implements JsonCache {
 
   @override
   Future<UnmodifiableListView<String>> keys() async {
-    return UnmodifiableListView(_box.keys.map((k) => k as String));
+    return UnmodifiableListView(
+      _box.keys.map((k) => k as String).toList(growable: false),
+    );
   }
 }

lib/src/json_cache_mem.dart

@@ -161,7 +161,7 @@ class JsonCacheMem implements JsonCache {
   @override
   Future<UnmodifiableListView<String>> keys() {
     return _mutex.protectRead(() async {
-      return UnmodifiableListView(_memory.keys);
+      return UnmodifiableListView(_memory.keys.toList(growable: false));
     });
   }
 }

lib/src/json_cache_safe_local_storage.dart

@@ -47,9 +47,8 @@ class JsonCacheSafeLocalStorage implements JsonCache {
 
   @override
   Future<UnmodifiableListView<String>> keys() async {
-    final data = await _cachedData;
     return UnmodifiableListView(
-      data.keys.map((k) => k as String),
+      (await _cachedData).keys.map((k) => k as String),
     );
   }
 

test/json_cache_fake_test.dart

@@ -2,7 +2,7 @@ import 'package:flutter_test/flutter_test.dart';
 import 'package:json_cache/json_cache.dart';
 
 void main() {
-  group('JsonCacheFake', () {
+  group('JsonCacheFake:', () {
     const profKey = 'profile';
     const prefKey = 'preferences';
     const profData = <String, dynamic>{'id': 1, 'name': 'John Due'};
@@ -65,13 +65,24 @@ void main() {
       expect(await fake.contains(prefKey), false);
       expect(await fake.contains('a key'), false);
     });
-    test('keys', () async {
-      final fake = JsonCacheFake();
-      // update data
-      await fake.refresh(profKey, profData);
-      await fake.refresh(prefKey, prefData);
-
-      expect(await fake.keys(), [profKey, prefKey]);
+    group('method "keys"', () {
+      late JsonCacheFake fakeCache;
+      setUp(() async {
+        fakeCache = JsonCacheFake();
+        // update data
+        await fakeCache.refresh(profKey, profData);
+        await fakeCache.refresh(prefKey, prefData);
+      });
+      test('should return the inserted keys', () async {
+        expect(await fakeCache.keys(), [profKey, prefKey]);
+      });
+      test('should keep the returned keys immutable', () async {
+        final keys = await fakeCache.keys();
+        // This should not change the 'keys' variable.
+        await fakeCache
+            .refresh('info', {'This is very important information.': true});
+        expect(keys, [profKey, prefKey]);
+      });
     });
     group('remove', () {
       test('default ctor', () async {

test/json_cache_flutter_secure_storage_test.dart

@@ -4,7 +4,7 @@ import 'package:json_cache/json_cache.dart';
 import 'flutter_secure_storage_mock.dart';
 
 void main() {
-  group('JsonCacheFlutterSecureStorage', () {
+  group('JsonCacheFlutterSecureStorage:', () {
     const profKey = 'profile';
     const prefKey = 'preferences';
     const profData = <String, dynamic>{'id': 1, 'name': 'John Due'};
@@ -50,15 +50,26 @@ void main() {
       await flutterSecureCache.remove(prefKey);
       expect(await flutterSecureCache.contains(prefKey), false);
     });
-    test('keys', () async {
-      final secStorageMock = FlutterSecureStorageMock();
-      final JsonCacheFlutterSecureStorage flutterSecureCache =
-          JsonCacheFlutterSecureStorage(secStorageMock);
-      // update data
-      await flutterSecureCache.refresh(profKey, profData);
-      await flutterSecureCache.refresh(prefKey, prefData);
 
-      expect(await flutterSecureCache.keys(), [profKey, prefKey]);
+    group('method "keys"', () {
+      late JsonCacheFlutterSecureStorage flutterSecureCache;
+      setUp(() async {
+        flutterSecureCache =
+            JsonCacheFlutterSecureStorage(FlutterSecureStorageMock());
+        // update data
+        await flutterSecureCache.refresh(profKey, profData);
+        await flutterSecureCache.refresh(prefKey, prefData);
+      });
+      test('should return the inserted keys', () async {
+        expect(await flutterSecureCache.keys(), [profKey, prefKey]);
+      });
+      test('should keep the returned keys immutable', () async {
+        final keys = await flutterSecureCache.keys();
+        // This should not change the 'keys' variable.
+        await flutterSecureCache
+            .refresh('info', {'This is very important information.': true});
+        expect(keys, [profKey, prefKey]);
+      });
     });
     test('remove', () async {
       final secStorageMock = FlutterSecureStorageMock();

test/json_cache_hive_test.dart

@@ -10,7 +10,7 @@ void main() {
   tearDown(() async {
     await tearDownTestHive();
   });
-  group('JsonCacheHive', () {
+  group('JsonCacheHive:', () {
     const profKey = 'profile';
     const prefKey = 'preferences';
     const profData = <String, dynamic>{'id': 1, 'name': 'John Due'};
@@ -47,15 +47,25 @@ void main() {
       await hiveCache.remove(prefKey);
       expect(await hiveCache.contains(prefKey), false);
     });
-
-    test('keys', () async {
-      final box = await Hive.openBox<String>('test-contains-method');
-      final JsonCacheHive hiveCache = JsonCacheHive(box);
-      // update data
-      await hiveCache.refresh(profKey, profData);
-      await hiveCache.refresh(prefKey, prefData);
-
-      expect(await hiveCache.keys(), [prefKey, profKey]);
+    group('method "keys"', () {
+      late JsonCacheHive hiveCache;
+      setUp(() async {
+        final box = await Hive.openBox<String>('test-keys-method');
+        hiveCache = JsonCacheHive(box);
+        // update data
+        await hiveCache.refresh(profKey, profData);
+        await hiveCache.refresh(prefKey, prefData);
+      });
+      test('should return the inserted keys', () async {
+        expect(await hiveCache.keys(), [prefKey, profKey]);
+      });
+      test('should keep the returned keys immutable', () async {
+        final keys = await hiveCache.keys();
+        // This should not change the 'keys' variable.
+        await hiveCache
+            .refresh('info', {'This is very important information.': true});
+        expect(keys, [prefKey, profKey]);
+      });
     });
     test('remove', () async {
       final box = await Hive.openBox<String>('test-remove');

test/json_cache_hollow_test.dart

@@ -2,7 +2,7 @@ import 'package:flutter_test/flutter_test.dart';
 import 'package:json_cache/json_cache.dart';
 
 void main() {
-  group('JsonCacheHollow', () {
+  group('JsonCacheHollow:', () {
     const profKey = 'profile';
     const prefKey = 'preferences';
     const profData = <String, dynamic>{'id': 1, 'name': 'John Due'};
@@ -36,11 +36,17 @@ void main() {
       expect(await fake.contains('a key'), false);
     });
     test('keys', () async {
-      const fake = JsonCacheHollow();
-      await fake.refresh(profKey, profData);
-      await fake.refresh(prefKey, prefData);
+      const hollowCache = JsonCacheHollow();
+      await hollowCache.refresh(profKey, profData);
+      await hollowCache.refresh(prefKey, prefData);
+
+      final keys = await hollowCache.keys();
+      expect(keys, const []);
 
-      expect(await fake.keys(), const []);
+      // This should not change the 'keys' variable.
+      await hollowCache
+          .refresh('info', {'This is very important information.': true});
+      expect(keys, const []);
     });
     test('remove', () async {
       const JsonCacheHollow hollowCache = JsonCacheHollow();

test/json_cache_local_storage_test.dart

@@ -4,8 +4,9 @@ import 'package:json_cache/json_cache.dart';
 import 'fake_local_storage.dart';
 
 void main() {
-  group('JsonCacheLocalStorage', () {
+  group('JsonCacheLocalStorage:', () {
     const profKey = 'profile';
+    const prefKey = 'preferences';
     const profData = <String, Object>{'id': 1, 'name': 'John Due'};
     const prefData = <String, dynamic>{
       'theme': 'dark',
@@ -40,14 +41,24 @@ void main() {
       expect(await jsonCache.contains(prefKey), false);
     });
 
-    test('keys', () async {
-      const prefKey = 'preferences';
-      final JsonCacheLocalStorage jsonCache = _fakeInstance;
-      // update data
-      await jsonCache.refresh(profKey, profData);
-      await jsonCache.refresh(prefKey, prefData);
-
-      expect(await jsonCache.keys(), [profKey, prefKey]);
+    group('method "keys"', () {
+      late JsonCacheLocalStorage localStorageCache;
+      setUp(() async {
+        localStorageCache = JsonCacheLocalStorage(FakeLocalStorage());
+        // update data
+        await localStorageCache.refresh(profKey, profData);
+        await localStorageCache.refresh(prefKey, prefData);
+      });
+      test('should return the inserted keys', () async {
+        expect(await localStorageCache.keys(), [profKey, prefKey]);
+      });
+      test('should keep the returned keys immutable', () async {
+        final keys = await localStorageCache.keys();
+        // This should not change the 'keys' variable.
+        await localStorageCache
+            .refresh('info', {'This is very important information.': true});
+        expect(keys, [profKey, prefKey]);
+      });
     });
     test('remove', () async {
       const prefKey = 'preferences';