drift_sqflite: Support nested transactions

drift_sqflite/lib/drift_sqflite.dart

@@ -17,8 +17,7 @@ import 'package:sqflite/sqflite.dart' as s;
 /// doesn't exist.
 typedef DatabaseCreator = FutureOr<void> Function(File file);
 
-class _SqfliteDelegate extends DatabaseDelegate with _SqfliteExecutor {
-  @override
+class _SqfliteDelegate extends DatabaseDelegate {
   late s.Database db;
   bool _isOpen = false;
 
@@ -35,8 +34,7 @@ class _SqfliteDelegate extends DatabaseDelegate with _SqfliteExecutor {
   late final DbVersionDelegate versionDelegate = _SqfliteVersionDelegate(db);
 
   @override
-  TransactionDelegate get transactionDelegate =>
-      _SqfliteTransactionDelegate(this);
+  TransactionDelegate get transactionDelegate => const NoTransactionDelegate();
 
   @override
   bool get isOpen => _isOpen;
@@ -67,48 +65,6 @@ class _SqfliteDelegate extends DatabaseDelegate with _SqfliteExecutor {
   Future<void> close() {
     return db.close();
   }
-}
-
-class _SqfliteVersionDelegate extends DynamicVersionDelegate {
-  final s.Database _db;
-
-  _SqfliteVersionDelegate(this._db);
-
-  @override
-  Future<int> get schemaVersion async {
-    final result = await _db.rawQuery('PRAGMA user_version;');
-    return result.single.values.first as int;
-  }
-
-  @override
-  Future<void> setSchemaVersion(int version) async {
-    await _db.rawUpdate('PRAGMA user_version = $version;');
-  }
-}
-
-class _SqfliteTransactionDelegate extends SupportedTransactionDelegate {
-  final _SqfliteDelegate delegate;
-
-  _SqfliteTransactionDelegate(this.delegate);
-
-  @override
-  Future<void> startTransaction(Future<void> Function(QueryDelegate) run) {
-    return delegate.db.transaction((transaction) async {
-      final executor = _SqfliteTransactionExecutor(transaction);
-      await run(executor);
-    });
-  }
-}
-
-class _SqfliteTransactionExecutor extends QueryDelegate with _SqfliteExecutor {
-  @override
-  final s.DatabaseExecutor db;
-
-  _SqfliteTransactionExecutor(this.db);
-}
-
-mixin _SqfliteExecutor on QueryDelegate {
-  s.DatabaseExecutor get db;
 
   @override
   Future<void> runBatched(BatchedStatements statements) async {
@@ -143,6 +99,23 @@ mixin _SqfliteExecutor on QueryDelegate {
   }
 }
 
+class _SqfliteVersionDelegate extends DynamicVersionDelegate {
+  final s.Database _db;
+
+  _SqfliteVersionDelegate(this._db);
+
+  @override
+  Future<int> get schemaVersion async {
+    final result = await _db.rawQuery('PRAGMA user_version;');
+    return result.single.values.first as int;
+  }
+
+  @override
+  Future<void> setSchemaVersion(int version) async {
+    await _db.rawUpdate('PRAGMA user_version = $version;');
+  }
+}
+
 /// A query executor that uses sqflite internally.
 class SqfliteQueryExecutor extends DelegatedDatabase {
   /// A query executor that will store the database in the file declared by
@@ -154,7 +127,7 @@ class SqfliteQueryExecutor extends DelegatedDatabase {
   /// migrations might behave differently when populating the database this way.
   /// For instance, a database created by an [creator] will not receive the
   /// [MigrationStrategy.onCreate] callback because it hasn't been created by
-  /// moor.
+  /// drift.
   SqfliteQueryExecutor(
       {required String path,
       bool? logStatements,
@@ -175,7 +148,7 @@ class SqfliteQueryExecutor extends DelegatedDatabase {
   /// migrations might behave differently when populating the database this way.
   /// For instance, a database created by an [creator] will not receive the
   /// [MigrationStrategy.onCreate] callback because it hasn't been created by
-  /// moor.
+  /// drift.
   SqfliteQueryExecutor.inDatabaseFolder(
       {required String path,
       bool? logStatements,
@@ -186,17 +159,18 @@ class SqfliteQueryExecutor extends DelegatedDatabase {
                 singleInstance: singleInstance, creator: creator),
             logStatements: logStatements);
 
-  /// The underlying sqflite [s.Database] object used by moor to send queries.
+  /// The underlying sqflite [s.Database] object used by drift to send queries.
   ///
-  /// Using the sqflite database can cause unexpected behavior in moor. For
+  /// Using the sqflite database can cause unexpected behavior in drift. For
   /// instance, stream queries won't update for updates sent to the [s.Database]
-  /// directly.
+  /// directly. Further, drift assumes full control over the database for its
+  /// internal connection management.
   /// For this reason, projects shouldn't use this getter unless they absolutely
-  /// need to. The database is exposed to make migrating from sqflite to moor
+  /// need to. The database is exposed to make migrating from sqflite to drift
   /// easier.
   ///
-  /// Note that this returns null until the moor database has been opened.
-  /// A moor database is opened lazily when the first query runs.
+  /// Note that this returns null until the drifft database has been opened.
+  /// A drift database is opened lazily when the first query runs.
   s.Database? get sqfliteDb {
     final sqfliteDelegate = delegate as _SqfliteDelegate;
     return sqfliteDelegate.isOpen ? sqfliteDelegate.db : null;
@@ -205,7 +179,7 @@ class SqfliteQueryExecutor extends DelegatedDatabase {
   @override
   // We're not really required to be sequential since sqflite has an internal
   // lock to bring statements into a sequential order.
-  // Setting isSequential here helps with moor cancellations in stream queries
+  // Setting isSequential here helps with cancellations in stream queries
   // though.
   bool get isSequential => true;
 }

drift_sqflite/pubspec.yaml

@@ -1,6 +1,6 @@
 name: drift_sqflite
 description: A Flutter-only implementation of a drift database, based on the `sqflite` package.
-version: 1.0.0
+version: 2.0.0
 repository: https://github.com/simolus3/drift
 homepage: https://drift.simonbinder.eu/
 issue_tracker: https://github.com/simolus3/drift/issues
@@ -9,7 +9,7 @@ environment:
   sdk: '>=2.12.0 <3.0.0'
 
 dependencies:
-  drift: ^1.8.0-dev
+  drift: ^2.0.0
   sqflite: ^2.0.0+3
   path: ^1.8.0
   flutter:

extras/integration_tests/ffi_on_flutter/lib/moor_ffi.dart

@@ -14,6 +14,9 @@ class FfiExecutor extends TestExecutor {
 
   FfiExecutor(this.dbPath);
 
+  @override
+  bool get supportsNestedTransactions => true;
+
   @override
   DatabaseConnection createConnection() {
     return DatabaseConnection.fromExecutor(

extras/integration_tests/sqflite/lib/drift_sqflite.dart

@@ -4,11 +4,14 @@ import 'package:drift_sqflite/drift_sqflite.dart';
 import 'package:flutter/services.dart';
 import 'package:flutter/widgets.dart' show WidgetsFlutterBinding;
 import 'package:path/path.dart';
-import 'package:sqflite/sqflite.dart' show getDatabasesPath, DatabaseException;
+import 'package:sqflite/sqflite.dart' show getDatabasesPath;
 import 'package:test/test.dart';
 import 'package:tests/tests.dart';
 
 class SqfliteExecutor extends TestExecutor {
+  @override
+  bool get supportsNestedTransactions => true;
+
   @override
   DatabaseConnection createConnection() {
     return DatabaseConnection.fromExecutor(
@@ -100,7 +103,7 @@ Future<void> main() async {
       database.transaction(() async {
         await database.customStatement('INSERT INTO y VALUES (2);');
       }),
-      throwsA(isA<DatabaseException>()),
+      throwsA(isA<CouldNotRollBackException>()),
     );
   });
 }

extras/integration_tests/tests/lib/suite/suite.dart

@@ -10,6 +10,7 @@ abstract class TestExecutor {
   DatabaseConnection createConnection();
 
   bool get supportsReturning => false;
+  bool get supportsNestedTransactions => false;
 
   /// Delete the data that would be written by the executor.
   Future deleteData();

extras/integration_tests/tests/lib/suite/transactions.dart

@@ -1,3 +1,4 @@
+import 'package:drift/drift.dart';
 import 'package:test/test.dart';
 import 'package:tests/data/sample_data.dart' as people;
 import 'package:tests/database/database.dart';
@@ -59,4 +60,40 @@ void transactionTests(TestExecutor executor) {
     await db.transaction(() => Future.value(null));
     await executor.clearDatabaseAndClose(db);
   });
+
+  test(
+    'nested transactions',
+    () async {
+      final db = Database(executor.createConnection());
+      await db.users.delete().go();
+
+      await db.transaction(() async {
+        expect(await db.select(db.users).get(), isEmpty);
+
+        await db.transaction(() async {
+          await db.users.insertOne(UsersCompanion.insert(
+              name: 'first user', birthDate: DateTime.now()));
+          expect(await db.select(db.users).get(), hasLength(1));
+        });
+
+        expect(await db.select(db.users).get(), hasLength(1));
+
+        final rollback = Exception('rollback');
+        await expectLater(db.transaction(() async {
+          await db.users.insertOne(UsersCompanion.insert(
+              name: 'second user', birthDate: DateTime.now()));
+          expect(await db.select(db.users).get(), hasLength(2));
+
+          throw rollback;
+        }), throwsA(rollback));
+
+        expect(await db.select(db.users).get(), hasLength(1));
+      });
+
+      expect(await db.select(db.users).get(), hasLength(1));
+    },
+    skip: executor.supportsNestedTransactions
+        ? false
+        : 'Tested implementation does not support nested transactions',
+  );
 }

extras/integration_tests/vm/test/vm_test.dart

@@ -9,6 +9,9 @@ class VmExecutor extends TestExecutor {
   static String fileName = 'moor-vm-tests-${DateTime.now().toIso8601String()}';
   final File file = File(join(Directory.systemTemp.path, fileName));
 
+  @override
+  bool get supportsNestedTransactions => true;
+
   @override
   bool get supportsReturning {
     final version = sqlite3.version;