Ensure the database is open before executing transactions

moor/lib/src/runtime/database.dart

@@ -157,6 +157,7 @@ mixin QueryEngine on DatabaseConnectionUser {
   ///     queries and updates must be sent to the [QueryEngine] passed to the
   ///     [action] function.
   Future transaction(Future Function(QueryEngine transaction) action) async {
+    await executor.doWhenOpened((executor) async {
       final transaction = Transaction(this, executor.beginTransaction());
 
       try {
@@ -164,6 +165,7 @@ mixin QueryEngine on DatabaseConnectionUser {
       } finally {
         await transaction.complete();
       }
+    });
   }
 }
 

moor/test/transactions_test.dart

@@ -50,4 +50,10 @@ void main() {
     verify(streamQueries.handleTableUpdates({db.users})).called(1);
     verify(executor.transactions.send());
   });
+
+  test('the database is opened before starting a transaction', () async {
+    await db.transaction((t) async {
+      verify(executor.doWhenOpened(any));
+    });
+  });
 }