Migrate VM database to use the new delegate api

moor/lib/moor_vm.dart

@@ -7,7 +7,7 @@ import 'dart:async';
 import 'dart:io';
 
 import 'package:meta/meta.dart';
-import 'package:synchronized/synchronized.dart';
+import 'backends.dart';
 import 'moor.dart';
 
 import 'src/vm/api/database.dart';

moor/lib/src/runtime/database.dart

@@ -321,4 +321,10 @@ abstract class GeneratedDatabase extends DatabaseConnectionUser
       });
     }
   }
+
+  /// Closes this database instance and released the resources associated with
+  /// it.
+  void close() {
+    executor.close();
+  }
 }

moor/lib/src/runtime/executor/executor.dart

@@ -89,28 +89,8 @@ class BatchedStatement {
 }
 
 /// A [QueryExecutor] that runs multiple queries atomically.
-mixin TransactionExecutor on QueryExecutor {
+abstract class TransactionExecutor extends QueryExecutor {
   /// Completes the transaction. No further queries may be sent to to this
   /// [QueryExecutor] after this method was called.
   Future<void> send();
-
-  @override
-  TransactionExecutor beginTransaction() {
-    throw UnsupportedError(
-        'Transactions cannot be created inside a transaction');
-  }
-}
-
-/// Used internally by moor. Responsible for executing the `beforeOpen`
-/// callback.
-mixin BeforeOpenMixin on QueryExecutor {
-  @override
-  Future<bool> ensureOpen() {
-    return Future.value(true);
-  }
-
-  @override
-  TransactionExecutor beginTransaction() {
-    throw UnsupportedError('Transactions cannot be created inside beforeOpen!');
-  }
 }

moor/lib/src/runtime/executor/helpers/engines.dart

@@ -217,6 +217,12 @@ class DelegatedDatabase extends QueryExecutor with _ExecutorWithQueryDelegate {
     final alreadyOpen = await delegate.isOpen;
     if (alreadyOpen) return true;
 
+    // could have changed already, see https://github.com/dart-lang/linter/issues/1384
+    // ignore: invariant_booleans
+    if (_openingCompleter != null) {
+      return _openingCompleter.future;
+    }
+
     // not already open or opening. Open the database now!
     _openingCompleter = Completer();
     await delegate.open(databaseInfo);

moor/lib/src/vm/api/result.dart

@@ -6,9 +6,9 @@ class Result extends Iterable<Row> {
   // a result set can have multiple columns with the same name, but that's rare
   // and users usually use a name as index. So we cache that for O(1) lookups
   Map<String, int> _calculatedIndexes;
-  final List<List<dynamic>> _rows;
+  final List<List<dynamic>> rows;
 
-  Result(this.columnNames, this._rows) {
+  Result(this.columnNames, this.rows) {
     _calculatedIndexes = {
       for (var column in columnNames) column: columnNames.lastIndexOf(column),
     };
@@ -28,7 +28,7 @@ class Row extends MapMixin<String, dynamic>
 
   /// Returns the value stored in the [i]-th column in this row (zero-indexed).
   dynamic columnAt(int i) {
-    return _result._rows[_rowIndex][i];
+    return _result.rows[_rowIndex][i];
   }
 
   @override
@@ -57,6 +57,6 @@ class _ResultIterator extends Iterator<Row> {
   @override
   bool moveNext() {
     index++;
-    return index < result._rows.length;
+    return index < result.rows.length;
   }
 }

moor/lib/src/vm/vm_database.dart

@@ -1,96 +1,47 @@
 part of 'package:moor/moor_vm.dart';
 
-class _DbState {
-  final bool logStatements;
-  final File file;
-  final Lock lock = Lock();
+/// A moor database that runs on the Dart VM.
+class VMDatabase extends DelegatedDatabase {
+  VMDatabase._(DatabaseDelegate delegate, bool logStatements)
+      : super(delegate, isSequential: true, logStatements: logStatements);
 
-  Database db;
+  /// Creates a database that will store its result in the [file], creating it
+  /// if it doesn't exist.
+  factory VMDatabase(File file, {bool logStatements = false}) {
+    return VMDatabase._(_VmDelegate(file), logStatements);
+  }
 
-  _DbState(this.logStatements, this.file);
+  /// Creates a database won't persist its changes on disk.
+  factory VMDatabase.memory({bool logStatements = false}) {
+    return VMDatabase._(_VmDelegate(null), logStatements);
+  }
 }
 
-abstract class _DatabaseUser extends QueryExecutor {
-  final _DbState _state;
+class _VmDelegate extends DatabaseDelegate {
+  Database _db;
 
-  bool get _bypassLock => false;
-  Database get _db => _state.db;
+  final File file;
 
-  _DatabaseUser(this._state);
-
-  void _logStmt(String statement, List<dynamic> args) {
-    if (_state.logStatements) {
-      print('Executing $statement with variables $args');
-    }
-  }
-
-  Future<T> _synchronized<T>(FutureOr<T> computation()) async {
-    final lock = _state.lock;
-    if (_bypassLock) {
-      return await computation();
-    }
-
-    return await lock.synchronized(computation);
-  }
+  _VmDelegate(this.file);
 
   @override
-  Future<void> runCustom(String statement) {
-    return _synchronized(() {
-      _logStmt(statement, const []);
-      _db.execute(statement);
-    });
-  }
+  final TransactionDelegate transactionDelegate = const NoTransactionDelegate();
 
-  void _runWithArgs(String statement, List<dynamic> args) {
-    _logStmt(statement, args);
+  @override
+  DbVersionDelegate versionDelegate;
 
-    if (args.isEmpty) {
-      _db.execute(statement);
+  @override
+  Future<bool> get isOpen => Future.value(_db != null);
+
+  @override
+  Future<void> open([GeneratedDatabase db]) {
+    if (file != null) {
+      _db = Database.openFile(file);
     } else {
-      _db.prepare(statement)
-        ..execute(args)
-        ..close();
+      _db = Database.memory();
     }
-  }
-
-  Future<int> _runAndReturnAffected(String statement, List<dynamic> args) {
-    _runWithArgs(statement, args);
-    return Future.value(_db.updatedRows);
-  }
-
-  @override
-  Future<int> runDelete(String statement, List<dynamic> args) {
-    return _synchronized(() {
-      return _runAndReturnAffected(statement, args);
-    });
-  }
-
-  @override
-  Future<int> runUpdate(String statement, List<dynamic> args) {
-    return _synchronized(() {
-      return _runAndReturnAffected(statement, args);
-    });
-  }
-
-  @override
-  Future<int> runInsert(String statement, List<dynamic> args) {
-    return _synchronized(() {
-      _runWithArgs(statement, args);
-      return Future.value(_db.lastInsertId);
-    });
-  }
-
-  @override
-  Future<List<Map<String, dynamic>>> runSelect(
-      String statement, List<dynamic> args) {
-    return _synchronized(() {
-      _logStmt(statement, args);
-      final stmt = _db.prepare(statement);
-      final result = stmt.select(args);
-      stmt.close();
-
-      return Future.value(result.toList());
-    });
+    versionDelegate = _VmVersionDelegate(_db);
+    return Future.value();
   }
 
   @override
@@ -107,103 +58,56 @@ abstract class _DatabaseUser extends QueryExecutor {
 
     return Future.value();
   }
-}
 
-class VMDatabase extends _DatabaseUser {
-  VMDatabase(File file, {bool logStatements = false})
-      : super(_DbState(logStatements, file));
-
-  VMDatabase.memory({bool logStatements = false})
-      : this(null, logStatements: logStatements);
-
-  @override
-  Future<bool> ensureOpen() async {
-    if (_db == null) {
-      _state.db = _openInternal();
-      await _runMigrations();
-    }
-    return true;
-  }
-
-  Database _openInternal() {
-    if (_state.file == null) {
-      return Database.memory();
+  void _runWithArgs(String statement, List<dynamic> args) {
+    if (args.isEmpty) {
+      _db.execute(statement);
     } else {
-      return Database.openFile(_state.file);
+      _db.prepare(statement)
+        ..execute(args)
+        ..close();
     }
   }
 
-  Future _runMigrations() async {
-    final current = _db.userVersion;
-    final target = databaseInfo.schemaVersion;
-
-    if (current == 0) {
-      await databaseInfo.handleDatabaseCreation(executor: runCustom);
-    } else if (current < target) {
-      await databaseInfo.handleDatabaseVersionChange(
-          executor: null, from: current, to: target);
-    }
-
-    _db.userVersion = target;
-
-    await _synchronized(() {
-      databaseInfo.beforeOpenCallback(
-          _BeforeOpenExecutor(_state), OpeningDetails(current, target));
-    });
-  }
-
   @override
-  Future<void> close() {
-    _db?.close();
+  Future<void> runCustom(String statement, List args) {
+    _runWithArgs(statement, args);
     return Future.value();
   }
 
   @override
-  TransactionExecutor beginTransaction() {
-    final transactionReady = Completer<bool>();
-    final executor = _TransactionExecutor(_state, transactionReady.future);
-
-    _synchronized(() async {
-      // we have the lock, so start the transaction
-      transactionReady.complete(true);
-      await executor.completed;
-    });
-
-    return executor;
-  }
-}
-
-class _BeforeOpenExecutor extends _DatabaseUser with BeforeOpenMixin {
-  @override
-  final bool _bypassLock = true;
-  _BeforeOpenExecutor(_DbState state) : super(state);
-}
-
-class _TransactionExecutor extends _DatabaseUser with TransactionExecutor {
-  @override
-  final bool _bypassLock = true;
-  final Future<bool> _openingFuture;
-  bool _sentBeginTransaction = false;
-
-  final Completer<void> _completer = Completer();
-  Future<void> get completed => _completer.future;
-
-  _TransactionExecutor(_DbState state, this._openingFuture) : super(state);
-
-  @override
-  Future<bool> ensureOpen() async {
-    await _openingFuture;
-    if (!_sentBeginTransaction) {
-      _db.execute('BEGIN TRANSACTION');
-      _sentBeginTransaction = true;
-    }
-    return Future.value(true);
+  Future<int> runInsert(String statement, List args) {
+    _runWithArgs(statement, args);
+    return Future.value(_db.lastInsertId);
   }
 
   @override
-  Future<void> send() {
-    _db.execute('COMMIT TRANSACTION;');
-    _completer.complete();
+  Future<int> runUpdate(String statement, List args) {
+    _runWithArgs(statement, args);
+    return Future.value(_db.updatedRows);
+  }
+
+  @override
+  Future<QueryResult> runSelect(String statement, List args) {
+    final stmt = _db.prepare(statement);
+    final result = stmt.select(args);
+    stmt.close();
+
+    return Future.value(QueryResult(result.columnNames, result.rows));
+  }
+}
+
+class _VmVersionDelegate extends DynamicVersionDelegate {
+  final Database database;
+
+  _VmVersionDelegate(this.database);
+
+  @override
+  Future<int> get schemaVersion => Future.value(database.userVersion);
+
+  @override
+  Future<void> setSchemaVersion(int version) {
+    database.userVersion = version;
     return Future.value();
   }
 }

moor/lib/src/web/web_db.dart

@@ -228,14 +228,23 @@ class WebDatabase extends _DatabaseUser {
   }
 }
 
-class _BeforeOpenExecutor extends _DatabaseUser with BeforeOpenMixin {
+class _BeforeOpenExecutor extends _DatabaseUser {
   _BeforeOpenExecutor(_DbState state) : super(state);
 
   @override
   final bool _bypassLock = true;
+
+  @override
+  TransactionExecutor beginTransaction() {
+    throw Error();
+  }
+
+  @override
+  Future<bool> ensureOpen() => Future.value(true);
 }
 
-class _TransactionExecutor extends _DatabaseUser with TransactionExecutor {
+class _TransactionExecutor extends _DatabaseUser
+    implements TransactionExecutor {
   _TransactionExecutor(_DbState state, this._openingFuture) : super(state);
 
   @override
@@ -270,4 +279,9 @@ class _TransactionExecutor extends _DatabaseUser with TransactionExecutor {
     _completer.complete();
     return Future.value();
   }
+
+  @override
+  TransactionExecutor beginTransaction() {
+    throw Error();
+  }
 }

moor/test/vm/integration_test.dart

@@ -1,4 +1,7 @@
+import 'dart:async';
+
 import 'package:moor/moor.dart';
+import 'package:pedantic/pedantic.dart';
 import 'package:test_api/test_api.dart';
 import 'package:moor/moor_vm.dart';
 
@@ -32,6 +35,29 @@ void main() {
     final readUpdated = await db.select(db.todosTable).getSingle();
     expect(readUpdated.content, 'Updated content');
   });
+
+  test('Transactions test', () async {
+    db = TodoDb(VMDatabase.memory(logStatements: false));
+
+    final completedOperations = StreamController<String>();
+
+    unawaited(db.transaction((_) async {
+      await insertCategory();
+      completedOperations.add('transaction');
+      await pumpEventQueue();
+    }));
+
+    unawaited(insertUser().then((_) {
+      completedOperations.add('regular');
+    }));
+
+    await expectLater(
+        completedOperations.stream, emitsInOrder(['transaction', 'regular']));
+
+    // call .getSingle to verify both rows have been written
+    await db.select(db.users).getSingle();
+    await db.select(db.categories).getSingle();
+  });
 }
 
 Future insertCategory() async {