[shared_preferences] Fix JSON parsing issue with _decodeValue (flutter#8211)

[shared_preferences] Fix JSON parsing issue with getAllWithParameters

this is a restored PR flutter#5813
Fixes flutter/flutter#156574

https://github.com/flutter/flutter/blob/master/docs/ecosystem/contributing/README.md#changelog-style

Author: Dan-Crane

packages/shared_preferences/shared_preferences_web/CHANGELOG.md

@@ -1,3 +1,7 @@
+## 2.4.3
+
+* Fixes issue where non-JSON formatted strings cause parsing errors.
+
 ## 2.4.2
 
 * Fixes `getStringList` returning immutable list.

packages/shared_preferences/shared_preferences_web/example/integration_test/shared_preferences_web_test.dart

@@ -382,6 +382,24 @@ void main() {
       );
       expect(values['Int'], writeCount);
     });
+
+    testWidgets('returns all valid JSON data', (WidgetTester _) async {
+      const String value = 'value';
+      const String invalidJsonDataKey = 'invalidJsonData';
+      const String validJsonDataKey = 'validJsonData';
+      html.window.localStorage.setItem(invalidJsonDataKey, value);
+      html.window.localStorage.setItem(validJsonDataKey, '"$value"');
+
+      final Map<String, Object> values = await preferences.getAllWithParameters(
+        GetAllParameters(
+          filter: PreferencesFilter(prefix: ''),
+        ),
+      );
+
+      expect(values.containsKey(invalidJsonDataKey), isFalse);
+      expect(values.containsKey(validJsonDataKey), isTrue);
+      expect(values[validJsonDataKey], equals(value));
+    });
   });
 
   group('shared_preferences_async', () {
@@ -454,6 +472,29 @@ void main() {
       expect(list?.length, testList.length + 1);
     });
 
+    testWidgets(
+      'returns null when reading invalid JSON value',
+      (WidgetTester _) async {
+        const String value = 'value';
+        const String invalidJsonDataKey = 'invalidJsonData';
+        const String validJsonDataKey = 'validJsonData';
+        final SharedPreferencesAsyncPlatform preferences =
+            await getPreferences();
+
+        html.window.localStorage.setItem(invalidJsonDataKey, value);
+        html.window.localStorage.setItem(validJsonDataKey, '"$value"');
+
+        expect(
+          await preferences.getString(invalidJsonDataKey, emptyOptions),
+          isNull,
+        );
+        expect(
+          await preferences.getString(validJsonDataKey, emptyOptions),
+          equals(value),
+        );
+      },
+    );
+
     testWidgets('getPreferences', (WidgetTester _) async {
       final SharedPreferencesAsyncPlatform preferences = await getPreferences();
       await Future.wait(<Future<void>>[

packages/shared_preferences/shared_preferences_web/lib/shared_preferences_web.dart

@@ -73,7 +73,11 @@ class SharedPreferencesPlugin extends SharedPreferencesStorePlatform {
     final Map<String, Object> allData = <String, Object>{};
     for (final String key
         in _getPrefixedKeys(filter.prefix, allowList: filter.allowList)) {
-      allData[key] = _decodeValue(html.window.localStorage.getItem(key)!);
+      final Object? value =
+          _decodeValue(html.window.localStorage.getItem(key)!);
+      if (value != null) {
+        allData[key] = value;
+      }
     }
     return allData;
   }
@@ -132,7 +136,11 @@ base class SharedPreferencesAsyncWeb extends SharedPreferencesAsyncPlatform {
   ) async {
     final Map<String, Object> allData = <String, Object>{};
     for (final String key in _getAllowedKeys(allowList: allowList)) {
-      allData[key] = _decodeValue(html.window.localStorage.getItem(key)!);
+      final Object? value =
+          _decodeValue(html.window.localStorage.getItem(key)!);
+      if (value != null) {
+        allData[key] = value;
+      }
     }
     return allData;
   }
@@ -258,8 +266,13 @@ String _encodeValue(Object? value) {
   return json.encode(value);
 }
 
-Object _decodeValue(String encodedValue) {
-  final Object? decodedValue = json.decode(encodedValue);
+Object? _decodeValue(String encodedValue) {
+  final Object? decodedValue;
+  try {
+    decodedValue = json.decode(encodedValue);
+  } on FormatException catch (_) {
+    return null;
+  }
 
   if (decodedValue is List) {
     // JSON does not preserve generics. The encode/decode roundtrip is
@@ -268,7 +281,7 @@ Object _decodeValue(String encodedValue) {
     return decodedValue.cast<String>();
   }
 
-  return decodedValue!;
+  return decodedValue;
 }
 
 /// Web specific SharedPreferences Options.

packages/shared_preferences/shared_preferences_web/pubspec.yaml

@@ -2,7 +2,7 @@ name: shared_preferences_web
 description: Web platform implementation of shared_preferences
 repository: https://github.com/flutter/packages/tree/main/packages/shared_preferences/shared_preferences_web
 issue_tracker: https://github.com/flutter/flutter/issues?q=is%3Aissue+is%3Aopen+label%3A%22p%3A+shared_preferences%22
-version: 2.4.2
+version: 2.4.3
 
 environment:
   sdk: ^3.4.0