Avoid unecessary async in lambda

drift_dev/CHANGELOG.md

@@ -7,7 +7,8 @@
 - Support two different queries using `LIST()` columns having the same result class name.
 - Fix table classes not extending defining Dart classes with modular generation.
 - Fix `@UseDataClass` with `extending` not working with modular generation.
-- Fix `drift_dev` generating invalid code when using a type converter with a nullable JSON type.
+- Fix generating invalid code when using a type converter with a nullable JSON type.
+- Avoid unecessary `async` modifier when mapping queries to existing row classes.
 
 ## 2.4.1
 

drift_dev/lib/src/writer/queries/query_writer.dart

@@ -78,9 +78,10 @@ class QueryWriter {
     final resultSet = query.resultSet!;
     final queryRow = _emitter.drift('QueryRow');
     final existingRowType = resultSet.existingRowType;
+    final asyncModifier = query.needsAsyncMapping ? 'async' : '';
 
     if (existingRowType != null) {
-      _emitter.write('($queryRow row) async => ');
+      _emitter.write('($queryRow row) $asyncModifier => ');
       _writeArgumentExpression(existingRowType, resultSet);
     } else if (resultSet.singleColumn) {
       final column = resultSet.scalarColumns.single;
@@ -97,11 +98,9 @@ class QueryWriter {
         _writeArgumentExpression(match, resultSet);
       }
     } else {
-      _buffer.write('($queryRow row) ');
-      if (query.needsAsyncMapping) {
-        _buffer.write('async ');
-      }
-      _buffer.write('{ return ${query.resultClassName}(');
+      _buffer
+        ..writeln('($queryRow row) $asyncModifier {')
+        ..write('return ${query.resultClassName}(');
 
       if (options.rawResultSetData) {
         _buffer.write('row: row,\n');

drift_dev/test/writer/queries/query_writer_test.dart

@@ -228,4 +228,63 @@ class MyRow {
       result,
     );
   });
+
+  test('can map to existing row class synchronously', () async {
+    // Regression test for https://github.com/simolus3/drift/issues/2282
+    final result = await emulateDriftBuild(
+      inputs: {
+        'a|lib/row.dart': '''
+class TestCustom {
+  final int testId;
+  final String testOneText;
+  final String testTwoText;
+  TestCustom({
+    required this.testId,
+    required this.testOneText,
+    required this.testTwoText,
+  });
+}
+''',
+        'a|lib/a.drift': '''
+import 'row.dart';
+
+CREATE TABLE TestOne (
+  test_id INT NOT NULL,
+  test_one_text TEXT NOT NULL
+);
+
+CREATE TABLE TestTwo (
+  test_id INT NOT NULL,
+  test_two_text TEXT NOT NULL
+);
+
+getTest WITH TestCustom:
+  SELECT
+      one.*,
+      two.test_two_text
+  FROM TestOne one
+  INNER JOIN TestTwo two
+    ON one.test_id = two.test_id;
+''',
+      },
+      modularBuild: true,
+    );
+
+    checkOutputs({
+      'a|lib/a.drift.dart': decodedMatches(contains(
+          '  i0.Selectable<i3.TestCustom> getTest() {\n'
+          '    return customSelect(\n'
+          '        \'SELECT one.*, two.test_two_text FROM TestOne AS one INNER JOIN TestTwo AS two ON one.test_id = two.test_id\',\n'
+          '        variables: [],\n'
+          '        readsFrom: {\n'
+          '          testTwo,\n'
+          '          testOne,\n'
+          '        }).map((i0.QueryRow row) => i3.TestCustom(\n'
+          '          testId: row.read<int>(\'test_id\'),\n'
+          '          testOneText: row.read<String>(\'test_one_text\'),\n'
+          '          testTwoText: row.read<String>(\'test_two_text\'),\n'
+          '        ));\n'
+          '  }')),
+    }, result.dartOutputs, result);
+  });
 }