Migrate database if prefered option is available

drift/lib/wasm.dart

@@ -8,12 +8,12 @@ library;
 
 import 'dart:async';
 import 'dart:js_interop';
-import 'dart:typed_data';
 
 import 'package:collection/collection.dart';
+import 'package:drift/drift.dart';
+import 'package:sqlite3/wasm.dart';
 import 'package:web/web.dart'
     show DedicatedWorkerGlobalScope, SharedWorkerGlobalScope;
-import 'package:sqlite3/wasm.dart';
 
 import 'backends.dart';
 import 'src/sqlite3/database.dart';
@@ -138,13 +138,17 @@ class WasmDatabase extends DelegatedDatabase {
   /// When [enableMigrations] is set to `false`, drift will not check the
   /// `user_version` pragma when opening the database or run migrations.
   ///
+  /// If a [preferedImplemetation] is defined and available in the browser the
+  /// data will automatically be migrated to it.
+  ///
   /// For more detailed information, see https://drift.simonbinder.eu/web.
   static Future<WasmDatabaseResult> open({
     required String databaseName,
     required Uri sqlite3Uri,
     required Uri driftWorkerUri,
     FutureOr<Uint8List?> Function()? initializeDatabase,
     WasmDatabaseSetup? localSetup,
+    WasmStorageImplementation? preferedImplemetation,
     bool enableMigrations = true,
   }) async {
     final probed = await probe(
@@ -159,6 +163,14 @@ class WasmDatabase extends DelegatedDatabase {
     // to consider migrating between storage implementations as well.
     final availableImplementations = probed.availableStorages.toList();
 
+    // Enum values are ordered by preferrability, so just pick the best option
+    // left.
+    availableImplementations.sortBy<num>((element) => element.index);
+
+    final preferedAvailable =
+        availableImplementations.contains(preferedImplemetation);
+    ExistingDatabase? currentDatabase;
+
     checkExisting:
     for (final (location, name) in probed.existingDatabases) {
       if (name == databaseName) {
@@ -178,22 +190,26 @@ class WasmDatabase extends DelegatedDatabase {
         if (implementationsForStorage.any(availableImplementations.contains)) {
           availableImplementations
               .removeWhere((i) => !implementationsForStorage.contains(i));
+          currentDatabase = (location, name);
           break checkExisting;
         }
       }
     }
 
-    // Enum values are ordered by preferrability, so just pick the best option
-    // left.
-    availableImplementations.sortBy<num>((element) => element.index);
-
     final bestImplementation = availableImplementations.firstOrNull ??
         WasmStorageImplementation.inMemory;
+
+    final needsMigration = preferedAvailable &&
+        currentDatabase != null &&
+        bestImplementation != preferedImplemetation;
+
     final connection = await probed.open(
-      bestImplementation,
+      needsMigration ? preferedImplemetation! : bestImplementation,
       databaseName,
       localSetup: localSetup,
-      initializeDatabase: initializeDatabase,
+      initializeDatabase: needsMigration
+          ? () => probed.exportDatabase(currentDatabase!)
+          : initializeDatabase,
       enableMigrations: enableMigrations,
     );
 

extras/integration_tests/web_wasm/README.md

@@ -5,3 +5,5 @@ To run the tests automatically (with us managing a browser driver), just run `da
 To manually debug issues, it might make sense to trigger some functionality manually.
 You can run `dart run tool/serve_manually.dart` to start a web server hosting the test
 content on <http://localhost:8080>.
+
+Make sure to install [chromedriver](https://googlechromelabs.github.io/chrome-for-testing) and [geckodriver](https://github.com/mozilla/geckodriver/releases) for the test to use.

extras/integration_tests/web_wasm/lib/driver.dart

@@ -7,14 +7,14 @@ import 'package:build_daemon/constants.dart';
 import 'package:build_daemon/data/build_status.dart';
 import 'package:build_daemon/data/build_target.dart';
 import 'package:collection/collection.dart';
+// ignore: implementation_imports
+import 'package:drift/src/web/wasm_setup/types.dart';
 import 'package:package_config/package_config.dart';
 import 'package:path/path.dart' as p;
 import 'package:shelf/shelf_io.dart';
 import 'package:shelf_proxy/shelf_proxy.dart';
 import 'package:web_wasm/initialization_mode.dart';
 import 'package:webdriver/async_io.dart';
-// ignore: implementation_imports
-import 'package:drift/src/web/wasm_setup/types.dart';
 import 'package:webdriver/support/async.dart';
 
 class TestAssetServer {
@@ -36,7 +36,7 @@ class TestAssetServer {
         await loadPackageConfigUri((await Isolate.packageConfig)!);
     final ownPackage = packageConfig['web_wasm']!.root;
     var packageDir = ownPackage.toFilePath(windows: Platform.isWindows);
-    if (packageDir.endsWith('/')) {
+    if (packageDir.endsWith('/') || packageDir.endsWith('\\')) {
       packageDir = packageDir.substring(0, packageDir.length - 1);
     }
 
@@ -146,9 +146,12 @@ class DriftWebDriver {
     );
   }
 
-  Future<void> openDatabase([WasmStorageImplementation? implementation]) async {
-    await driver.executeAsync(
-        'open(arguments[0], arguments[1])', [implementation?.name]);
+  Future<void> openDatabase(
+      [WasmStorageImplementation? implementation,
+      WasmStorageImplementation? preferedImplemetation]) async {
+    await driver.executeAsync('open(arguments[0], arguments[1])', [
+      json.encode([implementation?.name, preferedImplemetation?.name])
+    ]);
   }
 
   Future<void> closeDatabase() async {

extras/integration_tests/web_wasm/test/drift_wasm_test.dart

@@ -351,6 +351,29 @@ final class _TestConfiguration {
         },
       );
 
+      test(
+        'switch from IndexedDB database to OPFS if it is the prefered implementation',
+        () async {
+          // Open an IndexedDB database first
+          await driver.openDatabase(WasmStorageImplementation.unsafeIndexedDb);
+          await driver.insertIntoDatabase();
+          await Future.delayed(const Duration(seconds: 2));
+          await driver.driver.refresh(); // Reset JS state
+          await driver.waitReady();
+
+          // Open the database again, this time specifying opfs as the
+          // preferred implementation.
+          await driver.openDatabase(null, WasmStorageImplementation.opfsLocks);
+          expect(await driver.amountOfRows, 1);
+          await Future.delayed(const Duration(seconds: 2));
+          await driver.driver.refresh(); // Reset JS state
+          await driver.waitReady();
+
+          await driver.openDatabase(WasmStorageImplementation.opfsLocks);
+          expect(await driver.amountOfRows, 1);
+        },
+      );
+
       if (!browser.supports(WasmStorageImplementation.opfsShared)) {
         test('uses indexeddb after OPFS becomes unavailable', () async {
           // This browser only supports OPFS with the right headers. If they

extras/integration_tests/web_wasm/web/main.dart

@@ -6,11 +6,11 @@ import 'package:async/async.dart';
 import 'package:drift/drift.dart';
 import 'package:drift/wasm.dart';
 import 'package:http/http.dart' as http;
+import 'package:sqlite3/wasm.dart';
 import 'package:web/web.dart'
     show document, EventStreamProviders, HTMLDivElement;
 import 'package:web_wasm/initialization_mode.dart';
 import 'package:web_wasm/src/database.dart';
-import 'package:sqlite3/wasm.dart';
 
 const dbName = 'drift_test';
 final sqlite3WasmUri = Uri.parse('sqlite3.wasm');
@@ -32,7 +32,10 @@ void main() {
     driftWorkerUri = Uri.parse('wrong.js');
     return _detectImplementations(arg);
   });
-  _addCallbackForWebDriver('open', _open);
+  _addCallbackForWebDriver('open', (arg) {
+    final decoded = json.decode(arg!);
+    return _open(decoded[0] as String?, decoded[1] as String?);
+  });
   _addCallbackForWebDriver('close', (arg) async {
     await tableUpdates?.cancel();
     await openedDatabase?.close();
@@ -178,7 +181,8 @@ Future<JSString> _detectImplementations(String? _) async {
   }).toJS;
 }
 
-Future<JSAny?> _open(String? implementationName) async {
+Future<JSAny?> _open(
+    String? implementationName, String? preferedImplemetationName) async {
   DatabaseConnection connection;
 
   if (implementationName != null) {
@@ -201,6 +205,8 @@ Future<JSAny?> _open(String? implementationName) async {
       initializeDatabase: _initializeDatabase,
       enableMigrations:
           initializationMode != InitializationMode.noneAndDisableMigrations,
+      preferedImplemetation: WasmStorageImplementation.values
+          .asNameMap()[preferedImplemetationName],
       localSetup: (db) {
         // The worker has a similar setup call that will make database_host
         // return `worker` instead.