[shared_preferences] Fix Android type mismatch regression

`getStringList` should throw a `TypeError` if the stored value is of a
different type, but the recent change to use JSON-encoded string lists
regression that behavior if the stored type was a string, causing it to
instead return null.

This restores the previous behavior by passing extra information from
Kotlin to Dart when attempting to get an enecoded string list, so that
if a non-encoded-list string is found, a TypeError can be created on the
Dart side.

Since extra information is now being passed, the case of a
legacy-encoded value is now communicated as well, so that we only have
to request the legacy value if it's there, rather than always trying
(which was not worth the complexity of adding extra data just for that
initially, but now that we need extra data anyway, it's easy to
distinguish that case).

Fixes OOB regression in `shared_preferences` tests that has closed the
tree.

packages/shared_preferences/shared_preferences_android/CHANGELOG.md

@@ -1,3 +1,8 @@
+## 2.4.4
+
+* Restores the behavior of throwing a `TypeError` when calling `getStringList`
+  on a value stored with `setString`.
+
 ## 2.4.3
 
 * Migrates `List<String>` value encoding to JSON.

packages/shared_preferences/shared_preferences_android/android/src/main/kotlin/io/flutter/plugins/sharedpreferences/MessagesAsync.g.kt

@@ -1,7 +1,7 @@
 // Copyright 2013 The Flutter Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
-// Autogenerated from Pigeon (v22.7.2), do not edit directly.
+// Autogenerated from Pigeon (v22.7.4), do not edit directly.
 // See also: https://pub.dev/packages/pigeon
 @file:Suppress("UNCHECKED_CAST", "ArrayInDataClass")
 
@@ -61,6 +61,39 @@ data class SharedPreferencesPigeonOptions(val fileName: String? = null, val useD
   }
 }
 
+/** Generated class from Pigeon that represents data sent in messages. */
+data class StringListResult(
+    /**
+     * The JSON-encoded stored value, or null if there isn't one.
+     *
+     * This will be null if either there is no store value (in which case
+     * [foundPlatformEncodedValue] will be false), or if there was a platform-encoded value.
+     */
+    val jsonEncodedValue: String? = null,
+    /**
+     * Whether value using the legacy platform-side encoding was found.
+     *
+     * If this is true, [jsonEncodedValue] will be null, and the value should be fetched with
+     * getPlatformEncodedStringList(...) instead.
+     */
+    val foundPlatformEncodedValue: Boolean
+) {
+  companion object {
+    fun fromList(pigeonVar_list: List<Any?>): StringListResult {
+      val jsonEncodedValue = pigeonVar_list[0] as String?
+      val foundPlatformEncodedValue = pigeonVar_list[1] as Boolean
+      return StringListResult(jsonEncodedValue, foundPlatformEncodedValue)
+    }
+  }
+
+  fun toList(): List<Any?> {
+    return listOf(
+        jsonEncodedValue,
+        foundPlatformEncodedValue,
+    )
+  }
+}
+
 private open class MessagesAsyncPigeonCodec : StandardMessageCodec() {
   override fun readValueOfType(type: Byte, buffer: ByteBuffer): Any? {
     return when (type) {
@@ -69,6 +102,9 @@ private open class MessagesAsyncPigeonCodec : StandardMessageCodec() {
           SharedPreferencesPigeonOptions.fromList(it)
         }
       }
+      130.toByte() -> {
+        return (readValue(buffer) as? List<Any?>)?.let { StringListResult.fromList(it) }
+      }
       else -> super.readValueOfType(type, buffer)
     }
   }
@@ -79,6 +115,10 @@ private open class MessagesAsyncPigeonCodec : StandardMessageCodec() {
         stream.write(129)
         writeValue(stream, value.toList())
       }
+      is StringListResult -> {
+        stream.write(130)
+        writeValue(stream, value.toList())
+      }
       else -> super.writeValue(stream, value)
     }
   }
@@ -119,8 +159,8 @@ interface SharedPreferencesAsyncApi {
       key: String,
       options: SharedPreferencesPigeonOptions
   ): List<String>?
-  /** Gets individual List<String> value stored with [key], if any. */
-  fun getStringList(key: String, options: SharedPreferencesPigeonOptions): String?
+  /** Gets the JSON-encoded List<String> value stored with [key], if any. */
+  fun getStringList(key: String, options: SharedPreferencesPigeonOptions): StringListResult?
   /** Removes all properties from shared preferences data set with matching prefix. */
   fun clear(allowList: List<String>?, options: SharedPreferencesPigeonOptions)
   /** Gets all properties from shared preferences data set with matching prefix. */

packages/shared_preferences/shared_preferences_android/android/src/main/kotlin/io/flutter/plugins/sharedpreferences/SharedPreferencesPlugin.kt

@@ -203,13 +203,20 @@ class SharedPreferencesPlugin() : FlutterPlugin, SharedPreferencesAsyncApi {
   }
 
   /** Gets StringList at [key] from data store. */
-  override fun getStringList(key: String, options: SharedPreferencesPigeonOptions): String? {
+  override fun getStringList(
+      key: String,
+      options: SharedPreferencesPigeonOptions
+  ): StringListResult? {
     val stringValue = getString(key, options)
     stringValue?.let {
       // The JSON-encoded lists use an extended prefix to distinguish them from
       // lists that using listEncoder.
-      if (stringValue.startsWith(JSON_LIST_PREFIX)) {
-        return stringValue
+      return if (stringValue.startsWith(JSON_LIST_PREFIX)) {
+        StringListResult(stringValue, foundPlatformEncodedValue = false)
+      } else if (stringValue.startsWith(LIST_PREFIX)) {
+        StringListResult(null, foundPlatformEncodedValue = true)
+      } else {
+        StringListResult(null, foundPlatformEncodedValue = false)
       }
     }
     return null
@@ -408,12 +415,21 @@ class SharedPreferencesBackend(
   }
 
   /** Gets StringList at [key] from data store. */
-  override fun getStringList(key: String, options: SharedPreferencesPigeonOptions): String? {
+  override fun getStringList(
+      key: String,
+      options: SharedPreferencesPigeonOptions
+  ): StringListResult? {
     val preferences = createSharedPreferences(options)
     if (preferences.contains(key)) {
       val value = preferences.getString(key, "")
-      if (value!!.startsWith(JSON_LIST_PREFIX)) {
-        return value
+      // The JSON-encoded lists use an extended prefix to distinguish them from
+      // lists that using listEncoder.
+      return if (value!!.startsWith(JSON_LIST_PREFIX)) {
+        StringListResult(value, foundPlatformEncodedValue = false)
+      } else if (value.startsWith(LIST_PREFIX)) {
+        StringListResult(null, foundPlatformEncodedValue = true)
+      } else {
+        StringListResult(null, foundPlatformEncodedValue = false)
       }
     }
     return null

packages/shared_preferences/shared_preferences_android/android/src/test/kotlin/io/flutter/plugins/sharedpreferences/SharedPreferencesTest.kt

@@ -96,7 +96,26 @@ internal class SharedPreferencesTest {
   fun testSetAndGetStringListWithDataStore() {
     val plugin = pluginSetup(dataStoreOptions)
     plugin.setEncodedStringList(listKey, testList, dataStoreOptions)
-    Assert.assertEquals(plugin.getStringList(listKey, dataStoreOptions), testList)
+    val result = plugin.getStringList(listKey, dataStoreOptions)
+    Assert.assertEquals(result?.jsonEncodedValue, testList)
+  }
+
+  @Test
+  fun testSetAndGetStringListWithDataStoreRedirectsForLegacy() {
+    val plugin = pluginSetup(dataStoreOptions)
+    plugin.setDeprecatedStringList(listKey, listOf(""), dataStoreOptions)
+    val result = plugin.getStringList(listKey, dataStoreOptions)
+    Assert.assertEquals(result?.jsonEncodedValue, null)
+    Assert.assertEquals(result?.foundPlatformEncodedValue, true)
+  }
+
+  @Test
+  fun testSetAndGetStringListWithDataStoreReportsRawString() {
+    val plugin = pluginSetup(dataStoreOptions)
+    plugin.setString(listKey, testString, dataStoreOptions)
+    val result = plugin.getStringList(listKey, dataStoreOptions)
+    Assert.assertEquals(result?.jsonEncodedValue, null)
+    Assert.assertEquals(result?.foundPlatformEncodedValue, false)
   }
 
   @Test
@@ -217,7 +236,26 @@ internal class SharedPreferencesTest {
   fun testSetAndGetStringListWithSharedPreferences() {
     val plugin = pluginSetup(sharedPreferencesOptions)
     plugin.setEncodedStringList(listKey, testList, sharedPreferencesOptions)
-    Assert.assertEquals(plugin.getStringList(listKey, sharedPreferencesOptions), testList)
+    val result = plugin.getStringList(listKey, sharedPreferencesOptions)
+    Assert.assertEquals(result?.jsonEncodedValue, testList)
+  }
+
+  @Test
+  fun testSetAndGetStringListWithSharedPreferencesRedirectsForLegacy() {
+    val plugin = pluginSetup(sharedPreferencesOptions)
+    plugin.setDeprecatedStringList(listKey, listOf(""), sharedPreferencesOptions)
+    val result = plugin.getStringList(listKey, sharedPreferencesOptions)
+    Assert.assertEquals(result?.jsonEncodedValue, null)
+    Assert.assertEquals(result?.foundPlatformEncodedValue, true)
+  }
+
+  @Test
+  fun testSetAndGetStringListWithSharedPreferencesReportsRawString() {
+    val plugin = pluginSetup(sharedPreferencesOptions)
+    plugin.setString(listKey, testString, sharedPreferencesOptions)
+    val result = plugin.getStringList(listKey, sharedPreferencesOptions)
+    Assert.assertEquals(result?.jsonEncodedValue, null)
+    Assert.assertEquals(result?.foundPlatformEncodedValue, false)
   }
 
   @Test

packages/shared_preferences/shared_preferences_android/example/integration_test/shared_preferences_test.dart

@@ -639,6 +639,22 @@ void main() {
         expect(list?.length, testList.length + 1);
       });
 
+      testWidgets('getStringList throws type error for String with $backend',
+          (WidgetTester _) async {
+        final SharedPreferencesAsyncAndroidOptions options =
+            getOptions(useDataStore: useDataStore, fileName: 'notDefault');
+        final SharedPreferencesAsyncPlatform preferences = getPreferences();
+        await clearPreferences(preferences, options);
+
+        await preferences.setString(listKey, testString, options);
+
+        // Internally, List<String> is stored as a String on Android, but that
+        // implementation detail shouldn't leak to clients; getting the wrong
+        // type should still throw.
+        expect(preferences.getStringList(listKey, options),
+            throwsA(isA<TypeError>()));
+      });
+
       testWidgets('getPreferences with $backend', (WidgetTester _) async {
         final SharedPreferencesAsyncAndroidOptions options =
             getOptions(useDataStore: useDataStore, fileName: 'notDefault');

packages/shared_preferences/shared_preferences_android/lib/src/messages_async.g.dart

@@ -1,7 +1,7 @@
 // Copyright 2013 The Flutter Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
-// Autogenerated from Pigeon (v22.7.2), do not edit directly.
+// Autogenerated from Pigeon (v22.7.4), do not edit directly.
 // See also: https://pub.dev/packages/pigeon
 // ignore_for_file: public_member_api_docs, non_constant_identifier_names, avoid_as, unused_import, unnecessary_parenthesis, prefer_null_aware_operators, omit_local_variable_types, unused_shown_name, unnecessary_import, no_leading_underscores_for_local_identifiers
 
@@ -44,6 +44,41 @@ class SharedPreferencesPigeonOptions {
   }
 }
 
+class StringListResult {
+  StringListResult({
+    this.jsonEncodedValue,
+    required this.foundPlatformEncodedValue,
+  });
+
+  /// The JSON-encoded stored value, or null if there isn't one.
+  ///
+  /// This will be null if either there is no store value (in which case
+  /// [foundPlatformEncodedValue] will be false), or if there was a
+  /// platform-encoded value.
+  String? jsonEncodedValue;
+
+  /// Whether value using the legacy platform-side encoding was found.
+  ///
+  /// If this is true, [jsonEncodedValue] will be null, and the value should be
+  /// fetched with getPlatformEncodedStringList(...) instead.
+  bool foundPlatformEncodedValue;
+
+  Object encode() {
+    return <Object?>[
+      jsonEncodedValue,
+      foundPlatformEncodedValue,
+    ];
+  }
+
+  static StringListResult decode(Object result) {
+    result as List<Object?>;
+    return StringListResult(
+      jsonEncodedValue: result[0] as String?,
+      foundPlatformEncodedValue: result[1]! as bool,
+    );
+  }
+}
+
 class _PigeonCodec extends StandardMessageCodec {
   const _PigeonCodec();
   @override
@@ -54,6 +89,9 @@ class _PigeonCodec extends StandardMessageCodec {
     } else if (value is SharedPreferencesPigeonOptions) {
       buffer.putUint8(129);
       writeValue(buffer, value.encode());
+    } else if (value is StringListResult) {
+      buffer.putUint8(130);
+      writeValue(buffer, value.encode());
     } else {
       super.writeValue(buffer, value);
     }
@@ -64,6 +102,8 @@ class _PigeonCodec extends StandardMessageCodec {
     switch (type) {
       case 129:
         return SharedPreferencesPigeonOptions.decode(readValue(buffer)!);
+      case 130:
+        return StringListResult.decode(readValue(buffer)!);
       default:
         return super.readValueOfType(type, buffer);
     }
@@ -373,8 +413,8 @@ class SharedPreferencesAsyncApi {
     }
   }
 
-  /// Gets individual List<String> value stored with [key], if any.
-  Future<String?> getStringList(
+  /// Gets the JSON-encoded List<String> value stored with [key], if any.
+  Future<StringListResult?> getStringList(
       String key, SharedPreferencesPigeonOptions options) async {
     final String pigeonVar_channelName =
         'dev.flutter.pigeon.shared_preferences_android.SharedPreferencesAsyncApi.getStringList$pigeonVar_messageChannelSuffix';
@@ -395,7 +435,7 @@ class SharedPreferencesAsyncApi {
         details: pigeonVar_replyList[2],
       );
     } else {
-      return (pigeonVar_replyList[0] as String?);
+      return (pigeonVar_replyList[0] as StringListResult?);
     }
   }
 

packages/shared_preferences/shared_preferences_android/lib/src/shared_preferences_async_android.dart

@@ -198,9 +198,13 @@ base class SharedPreferencesAsyncAndroid
         convertOptionsToPigeonOptions(options);
     final SharedPreferencesAsyncApi api = getApiForBackend(pigeonOptions);
     // Request JSON encoded string list.
-    final String? jsonEncodedStringList =
-        await _convertKnownExceptions<String?>(
+    final StringListResult? result =
+        await _convertKnownExceptions<StringListResult?>(
             () async => api.getStringList(key, pigeonOptions));
+    if (result == null) {
+      return null;
+    }
+    final String? jsonEncodedStringList = result.jsonEncodedValue;
     if (jsonEncodedStringList != null) {
       final String jsonEncodedString =
           jsonEncodedStringList.substring(jsonListPrefix.length);
@@ -213,10 +217,16 @@ base class SharedPreferencesAsyncAndroid
       }
     }
     // If no JSON encoded string list exists, check for platform encoded value.
-    final List<String>? stringList =
-        await _convertKnownExceptions<List<String>?>(
-            () async => api.getPlatformEncodedStringList(key, pigeonOptions));
-    return stringList?.cast<String>().toList();
+    if (result.foundPlatformEncodedValue) {
+      final List<String>? stringList =
+          await _convertKnownExceptions<List<String>?>(
+              () async => api.getPlatformEncodedStringList(key, pigeonOptions));
+      return stringList?.cast<String>().toList();
+    } else {
+      // A non-null result where foundPlatformEncodedValue is false means there
+      // was a raw string result, so the client is fetching the wrong type.
+      throw TypeError();
+    }
   }
 
   Future<T?> _convertKnownExceptions<T>(Future<T?> Function() method) async {

packages/shared_preferences/shared_preferences_android/pigeons/messages_async.dart

@@ -24,6 +24,27 @@ class SharedPreferencesPigeonOptions {
   bool useDataStore;
 }
 
+class StringListResult {
+  StringListResult({
+    required this.jsonEncodedValue,
+    required this.foundPlatformEncodedValue,
+  });
+
+  /// The JSON-encoded stored value, or null if something else was found, in
+  /// which case [foundPlatformEncodedValue] will indicate its type.
+  String? jsonEncodedValue;
+
+  /// Whether value using the legacy platform-side encoding was found.
+  ///
+  /// This value is only meaningful if [jsonEncodedValue] is null.
+  /// - If true, the value should be fetched with
+  ///   getPlatformEncodedStringList(...) instead.
+  /// - If false, an unexpected string (one without any encoding prefix) was
+  ///   found. This will happen if a client uses getStringList with a key that
+  ///   was used with setString.
+  bool foundPlatformEncodedValue;
+}
+
 @HostApi(dartHostTestHandler: 'TestSharedPreferencesAsyncApi')
 abstract class SharedPreferencesAsyncApi {
   /// Adds property to shared preferences data set of type bool.
@@ -107,9 +128,9 @@ abstract class SharedPreferencesAsyncApi {
     SharedPreferencesPigeonOptions options,
   );
 
-  /// Gets individual List<String> value stored with [key], if any.
+  /// Gets the JSON-encoded List<String> value stored with [key], if any.
   @TaskQueue(type: TaskQueueType.serialBackgroundThread)
-  String? getStringList(
+  StringListResult? getStringList(
     String key,
     SharedPreferencesPigeonOptions options,
   );

packages/shared_preferences/shared_preferences_android/pubspec.yaml

@@ -2,7 +2,7 @@ name: shared_preferences_android
 description: Android implementation of the shared_preferences plugin
 repository: https://github.com/flutter/packages/tree/main/packages/shared_preferences/shared_preferences_android
 issue_tracker: https://github.com/flutter/flutter/issues?q=is%3Aissue+is%3Aopen+label%3A%22p%3A+shared_preferences%22
-version: 2.4.3
+version: 2.4.4
 
 environment:
   sdk: ^3.5.0