fix(database,android): fix an issue where setPersistenceEnabled needed to be called first (#18259)

Author: Lyokone

packages/firebase_database/firebase_database/android/src/main/kotlin/io/flutter/plugins/firebase/database/FirebaseDatabasePlugin.kt

@@ -516,7 +516,9 @@ class FirebaseDatabasePlugin :
   override fun setPersistenceEnabled(app: DatabasePigeonFirebaseApp, enabled: Boolean, callback: (KotlinResult<Unit>) -> Unit) {
     try {
       val database = getDatabaseFromPigeonApp(app)
-      database.setPersistenceEnabled(enabled)
+      if (app.settings.persistenceEnabled == null) {
+        database.setPersistenceEnabled(enabled)
+      }
       callback(KotlinResult.success(Unit))
     } catch (e: Exception) {
       callback(KotlinResult.failure(e))
@@ -526,7 +528,9 @@ class FirebaseDatabasePlugin :
   override fun setPersistenceCacheSizeBytes(app: DatabasePigeonFirebaseApp, cacheSize: Long, callback: (KotlinResult<Unit>) -> Unit) {
     try {
       val database = getDatabaseFromPigeonApp(app)
-      database.setPersistenceCacheSizeBytes(cacheSize)
+      if (app.settings.cacheSizeBytes == null) {
+        database.setPersistenceCacheSizeBytes(cacheSize)
+      }
       callback(KotlinResult.success(Unit))
     } catch (e: Exception) {
       callback(KotlinResult.failure(e))

tests/integration_test/firebase_database/firebase_database_configuration_e2e.dart

@@ -2,8 +2,11 @@
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 
+import 'package:firebase_core/firebase_core.dart';
+import 'package:firebase_database/firebase_database.dart';
 import 'package:flutter/foundation.dart';
 import 'package:flutter_test/flutter_test.dart';
+import 'package:tests/firebase_options.dart';
 
 import 'firebase_database_e2e_test.dart';
 
@@ -37,5 +40,31 @@ void setupConfigurationTests() {
     test('setLoggingEnabled to false', () {
       database.setLoggingEnabled(false);
     });
+
+    test(
+      'setPersistenceEnabled can be followed immediately by goOnline',
+      () async {
+        for (var i = 0; i < 5; i++) {
+          final app = await Firebase.initializeApp(
+            name:
+                'firebase-database-persistence-${DateTime.now().microsecondsSinceEpoch}-$i',
+            options: DefaultFirebaseOptions.currentPlatform,
+          );
+          addTearDown(app.delete);
+
+          final database = FirebaseDatabase.instanceFor(app: app);
+
+          database.setPersistenceEnabled(true);
+          await database.goOnline();
+
+          await database.ref('persistence-enabled-regression').keepSynced(true);
+          await database
+              .ref('persistence-enabled-regression')
+              .keepSynced(false);
+          await database.goOffline();
+        }
+      },
+      skip: kIsWeb || defaultTargetPlatform != TargetPlatform.android,
+    );
   });
 }