Add DatabaseConnection.delayed constructor

docs/content/en/docs/Advanced Features/isolates.md

@@ -63,6 +63,24 @@ void main() async {
 }
 ```
 
+If you need to construct the database outside of an `async` context, you can use the new 
+`DatabaseConnection.delayed` constructor introduced in moor 3.4. In the example above, you
+could synchronously obtain a `TodoDb` by using:
+
+```dart
+Future<DatabaseConnection> _connectAsync() async {
+  MoorIsolate isolate = await MoorIsolate.spawn(_backgroundConnection);
+  return isolate.connect();
+}
+
+void main() {
+  final db = TodoDb.connect(DatabaseConnection.delayed(_connectAsync()));
+}
+```
+
+This can be helpful when using moor in DI frameworks, since you have the database available
+immediately. Internally, moor will connect when the first query is sent to the database.
+
 ### Initialization on the main thread
 
 Platform channels are not available on background isolates, but sometimes you might want to use

moor/CHANGELOG.md

@@ -1,3 +1,8 @@
+## 3.4.0 (unreleased)
+
+- New `DatabaseConnection.delayed` constructor to synchronously obtain a database connection
+  that requires async setup. This can be useful when connecting to a `MoorIsolate`.
+
 ## 3.3.1
 
 - Support changing `onData` handlers for query streams.

moor/lib/src/runtime/api/connection.dart

@@ -26,6 +26,41 @@ class DatabaseConnection {
       : typeSystem = SqlTypeSystem.defaultInstance,
         streamQueries = StreamQueryStore();
 
+  /// Database connection that is instantly available, but delegates work to a
+  /// connection only available through a `Future`.
+  ///
+  /// This can be useful in scenarios where you need to obtain a database
+  /// instance synchronously, but need an async setup. A prime example here is
+  /// `MoorIsolate`:
+  ///
+  /// ```dart
+  /// @UseMoor(...)
+  /// class MyDatabase extends _$MyDatabase {
+  ///   MyDatabase._connect(DatabaseConnection c): super.connect(c);
+  ///
+  ///   factory MyDatabase.fromIsolate(MoorIsolate isolate) {
+  ///     return MyDatabase._connect(
+  ///       // isolate.connect() returns a future, but we can still return a
+  ///       // database synchronously thanks to DatabaseConnection.delayed!
+  ///       DatabaseConnection.delayed(isolate.connect()),
+  ///     );
+  ///   }
+  /// }
+  /// ```
+  factory DatabaseConnection.delayed(FutureOr<DatabaseConnection> connection) {
+    if (connection is DatabaseConnection) {
+      return connection;
+    }
+
+    final future = connection as Future<DatabaseConnection>;
+
+    return DatabaseConnection(
+      SqlTypeSystem.defaultInstance,
+      LazyDatabase(() async => (await future).executor),
+      DelayedStreamQueryStore(future.then((conn) => conn.streamQueries)),
+    );
+  }
+
   /// Returns a database connection that is identical to this one, except that
   /// it uses the provided [executor].
   DatabaseConnection withExecutor(QueryExecutor executor) {

moor/lib/src/runtime/api/runtime_api.dart

@@ -2,6 +2,7 @@ import 'dart:async';
 
 import 'package:meta/meta.dart';
 import 'package:moor/moor.dart';
+import 'package:moor/src/runtime/executor/delayed_stream_queries.dart';
 import 'package:moor/src/runtime/executor/stream_queries.dart';
 
 part 'batch.dart';

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

@@ -0,0 +1,50 @@
+import 'package:moor/src/runtime/api/runtime_api.dart';
+
+import 'stream_queries.dart';
+
+/// Version of [StreamQueryStore] that delegates work to an asynchronously-
+/// available delegate.
+/// This class is internal and should not be exposed to moor users. It's used
+/// through a delayed database connection.
+class DelayedStreamQueryStore implements StreamQueryStore {
+  Future<StreamQueryStore> _delegate;
+  StreamQueryStore _resolved;
+
+  /// Creates a [StreamQueryStore] that will work after [delegate] is
+  /// available.
+  DelayedStreamQueryStore(Future<StreamQueryStore> delegate) {
+    _delegate = delegate.then((value) => _resolved = value);
+  }
+
+  @override
+  Future<void> close() async => (await _delegate).close();
+
+  @override
+  void handleTableUpdates(Set<TableUpdate> updates) {
+    _resolved?.handleTableUpdates(updates);
+  }
+
+  @override
+  void markAsClosed(QueryStream stream, Function() whenRemoved) {
+    throw UnimplementedError('The stream will call this on the delegate');
+  }
+
+  @override
+  void markAsOpened(QueryStream stream) {
+    throw UnimplementedError('The stream will call this on the delegate');
+  }
+
+  @override
+  Stream<T> registerStream<T>(QueryStreamFetcher<T> fetcher) {
+    return Stream.fromFuture(_delegate)
+        .asyncExpand((resolved) => resolved.registerStream(fetcher))
+        .asBroadcastStream();
+  }
+
+  @override
+  Stream<Null> updatesForSync(TableUpdateQuery query) {
+    return Stream.fromFuture(_delegate)
+        .asyncExpand((resolved) => resolved.updatesForSync(query))
+        .asBroadcastStream();
+  }
+}

moor/lib/src/utils/lazy_database.dart

@@ -66,4 +66,13 @@ class LazyDatabase extends QueryExecutor {
   @override
   Future<int> runUpdate(String statement, List args) =>
       _delegate.runUpdate(statement, args);
+
+  @override
+  Future<void> close() {
+    if (_delegate != null) {
+      return _delegate.close();
+    } else {
+      return Future.value();
+    }
+  }
 }

moor/pubspec.yaml

@@ -1,6 +1,6 @@
 name: moor
 description: Moor is a safe and reactive persistence library for Dart applications
-version: 3.3.1
+version: 3.4.0-dev
 repository: https://github.com/simolus3/moor
 homepage: https://moor.simonbinder.eu/
 issue_tracker: https://github.com/simolus3/moor/issues

moor/test/isolate_test.dart

@@ -83,26 +83,25 @@ void main() {
 void _runTests(
     FutureOr<MoorIsolate> Function() spawner, bool terminateIsolate) {
   MoorIsolate isolate;
-  DatabaseConnection isolateConnection;
+  TodoDb database;
 
   setUp(() async {
     isolate = await spawner();
-    isolateConnection = await isolate.connect(isolateDebugLog: false);
+
+    database = TodoDb.connect(
+      DatabaseConnection.delayed(isolate.connect(isolateDebugLog: false)),
+    );
   });
 
-  tearDown(() {
-    isolateConnection.executor.close();
+  tearDown(() async {
+    await database.close();
 
     if (terminateIsolate) {
-      return isolate.shutdownAll();
-    } else {
-      return Future.value();
+      await isolate.shutdownAll();
     }
   });
 
   test('can open database and send requests', () async {
-    final database = TodoDb.connect(isolateConnection);
-
     final result = await database.select(database.todosTable).get();
     expect(result, isEmpty);
   });
@@ -110,7 +109,6 @@ void _runTests(
   test('can run beforeOpen', () async {
     var beforeOpenCalled = false;
 
-    final database = TodoDb.connect(isolateConnection);
     database.migration = MigrationStrategy(beforeOpen: (details) async {
       await database.customStatement('PRAGMA foreign_keys = ON');
       beforeOpenCalled = true;
@@ -118,26 +116,20 @@ void _runTests(
 
     // run a select statement to verify that the database is open
     await database.customSelect('SELECT 1').get();
-    await database.close();
     expect(beforeOpenCalled, isTrue);
   });
 
   test('stream queries work as expected', () async {
-    final database = TodoDb.connect(isolateConnection);
     final initialCompanion = TodosTableCompanion.insert(content: 'my content');
 
     final stream = database.select(database.todosTable).watchSingle();
-    final expectation = expectLater(
-      stream,
-      emitsInOrder([null, TodoEntry(id: 1, content: 'my content')]),
-    );
 
+    await expectLater(stream, emits(null));
     await database.into(database.todosTable).insert(initialCompanion);
-    await expectation;
+    await expectLater(stream, emits(TodoEntry(id: 1, content: 'my content')));
   });
 
   test('can start transactions', () async {
-    final database = TodoDb.connect(isolateConnection);
     final initialCompanion = TodosTableCompanion.insert(content: 'my content');
 
     await database.transaction(() async {
@@ -149,15 +141,12 @@ void _runTests(
   });
 
   test('supports no-op transactions', () async {
-    final database = TodoDb.connect(isolateConnection);
     await database.transaction(() {
       return Future.value(null);
     });
-    await database.close();
   });
 
   test('supports transactions in migrations', () async {
-    final database = TodoDb.connect(isolateConnection);
     database.migration = MigrationStrategy(beforeOpen: (details) async {
       await database.transaction(() async {
         return await database.customSelect('SELECT 1').get();
@@ -165,15 +154,11 @@ void _runTests(
     });
 
     await database.customSelect('SELECT 2').get();
-
-    await database.close();
   });
 
   test('transactions have an isolated view on data', () async {
     // regression test for https://github.com/simolus3/moor/issues/324
-    final db = TodoDb.connect(isolateConnection);
-
-    await db
+    await database
         .customStatement('create table tbl (id integer primary key not null)');
 
     Future<void> expectRowCount(TodoDb db, int count) async {
@@ -182,74 +167,65 @@ void _runTests(
     }
 
     final rowInserted = Completer<void>();
-    final runTransaction = db.transaction(() async {
-      await db.customInsert('insert into tbl default values');
-      await expectRowCount(db, 1);
+    final runTransaction = database.transaction(() async {
+      await database.customInsert('insert into tbl default values');
+      await expectRowCount(database, 1);
       rowInserted.complete();
       // Hold transaction open for expectRowCount() outside the transaction to
       // finish
       await Future.delayed(const Duration(seconds: 1));
-      await db.customStatement('delete from tbl');
-      await expectRowCount(db, 0);
+      await database.customStatement('delete from tbl');
+      await expectRowCount(database, 0);
     });
 
     await rowInserted.future;
-    await expectRowCount(db, 0);
+    await expectRowCount(database, 0);
     await runTransaction; // wait for the transaction to complete
-
-    await db.close();
   });
 
   test("can't run queries on a closed database", () async {
-    final db = TodoDb.connect(isolateConnection);
-    await db.customSelect('SELECT 1;').getSingle();
+    await database.customSelect('SELECT 1;').getSingle();
 
-    await db.close();
+    await database.close();
 
     await expectLater(
-        () => db.customSelect('SELECT 1;').getSingle(), throwsStateError);
+        () => database.customSelect('SELECT 1;').getSingle(), throwsStateError);
   });
 
   test('can run deletes, updates and batches', () async {
-    final db = TodoDb.connect(isolateConnection);
-
-    await db.into(db.users).insert(
+    await database.into(database.users).insert(
         UsersCompanion.insert(name: 'simon.', profilePicture: Uint8List(0)));
 
-    await db
-        .update(db.users)
+    await database
+        .update(database.users)
         .write(const UsersCompanion(name: Value('changed name')));
-    var result = await db.select(db.users).getSingle();
+    var result = await database.select(database.users).getSingle();
     expect(result.name, 'changed name');
 
-    await db.delete(db.users).go();
+    await database.delete(database.users).go();
 
-    await db.batch((batch) {
+    await database.batch((batch) {
       batch.insert(
-        db.users,
+        database.users,
         UsersCompanion.insert(name: 'not simon', profilePicture: Uint8List(0)),
       );
     });
 
-    result = await db.select(db.users).getSingle();
+    result = await database.select(database.users).getSingle();
     expect(result.name, 'not simon');
-
-    await db.close();
   });
 
   test('transactions can be rolled back', () async {
-    final db = TodoDb.connect(isolateConnection);
-
-    await expectLater(db.transaction(() async {
-      await db.into(db.categories).insert(
+    await expectLater(database.transaction(() async {
+      await database.into(database.categories).insert(
           CategoriesCompanion.insert(description: 'my fancy description'));
       throw Exception('expected');
     }), throwsException);
 
-    final result = await db.select(db.categories).get();
+    final result = await database.select(database.categories).get();
     expect(result, isEmpty);
 
-    await db.close();
+    await database.close();
   });
 }
 

moor/test/utils/lazy_database_test.dart

@@ -79,4 +79,17 @@ void main() {
 
     verify(inner.ensureOpen(user));
   });
+
+  test('can close inner executor', () async {
+    final inner = MockExecutor();
+    final lazy = LazyDatabase(() => inner);
+    final user = _LazyQueryUserForTest();
+
+    await lazy.close(); // Close before opening, expect no effect
+
+    await lazy.ensureOpen(user);
+    await lazy.close();
+
+    verify(inner.close());
+  });
 }