fix(hydrated_cubit): retain data during migration (#61)

Author: felangel

packages/hydrated_cubit/CHANGELOG.md

@@ -1,3 +1,7 @@
+# 0.1.2
+
+- fix: reintroduce migration code to ensure no data loss ([#67](https://github.com/felangel/hydrated_bloc/issues/67))
+
 # 0.1.1
 
 - fix: support use alongside hive ([#53](https://github.com/felangel/cubit/pull/53))

packages/hydrated_cubit/lib/src/hydrated_storage.dart

@@ -1,4 +1,5 @@
 import 'dart:async';
+import 'dart:convert';
 import 'dart:io';
 import 'package:flutter/foundation.dart';
 import 'package:hive/hive.dart';
@@ -62,10 +63,32 @@ class HydratedStorage implements Storage {
         'hydrated_box',
         encryptionCipher: encryptionCipher,
       );
+
+      await _migrate(directory, box);
+
       return _instance = HydratedStorage(box);
     });
   }
 
+  static Future _migrate(Directory directory, Box box) async {
+    final file = File('${directory.path}/.hydrated_bloc.json');
+    if (await file.exists()) {
+      try {
+        final dynamic storageJson = json.decode(await file.readAsString());
+        final cache = (storageJson as Map).cast<String, String>();
+        for (final key in cache.keys) {
+          try {
+            final string = cache[key];
+            final dynamic object = json.decode(string);
+            await box.put(key, object);
+          } on dynamic catch (_) {}
+        }
+      } on dynamic catch (_) {} finally {
+        await file.delete();
+      }
+    }
+  }
+
   /// Internal instance of [HiveImpl].
   /// It should only be used for testing.
   @visibleForTesting

packages/hydrated_cubit/pubspec.yaml

@@ -1,6 +1,6 @@
 name: hydrated_cubit
 description: An extension to the cubit state management library which automatically persists and restores cubit states.
-version: 0.1.1
+version: 0.1.2
 homepage: https://github.com/felangel/cubit
 
 environment:

packages/hydrated_cubit/test/hydrated_storage_test.dart

@@ -1,3 +1,4 @@
+import 'dart:convert';
 import 'dart:io';
 
 import 'package:flutter/services.dart';
@@ -33,6 +34,18 @@ void main() {
       await storage?.clear();
     });
 
+    group('migration', () {
+      test('returns correct value when file exists', () async {
+        final directory = await getTemporaryDirectory();
+        File('${directory.path}/.hydrated_bloc.json')
+          ..writeAsStringSync(json.encode({
+            'CounterBloc': json.encode({'value': 4})
+          }));
+        storage = await HydratedStorage.build();
+        expect(storage.read('CounterBloc')['value'] as int, 4);
+      });
+    });
+
     group('build', () {
       setUp(() async {
         await (await HydratedStorage.build()).clear();