✅ Add a test to make sure data classes and companion classes are using a const constructor

drift_dev/test/writer/data_class_writer_test.dart

@@ -0,0 +1,111 @@
+import 'package:analyzer/dart/analysis/features.dart';
+import 'package:analyzer/dart/analysis/utilities.dart';
+import 'package:analyzer/dart/ast/ast.dart';
+import 'package:analyzer/file_system/memory_file_system.dart';
+import 'package:build/build.dart';
+import 'package:build_test/build_test.dart';
+import 'package:drift_dev/src/backends/build/drift_builder.dart';
+import 'package:pub_semver/pub_semver.dart';
+import 'package:test/test.dart';
+
+const _testInput = r'''
+import 'package:drift/drift.dart';
+
+part 'main.moor.dart';
+
+class Users extends Table {
+  IntColumn get id => integer().autoIncrement()();
+  TextColumn get name => text()();
+}
+
+@DriftDatabase(
+  tables: [Users],
+)
+class Database extends _$Database {}
+''';
+
+void main() {
+  test(
+    'generates const constructor for data classes can companion classes',
+    () async {
+      await testBuilder(
+        DriftPartBuilder(const BuilderOptions({})),
+        const {'a|lib/main.dart': _testInput},
+        reader: await PackageAssetReader.currentIsolate(),
+        outputs: const {
+          'a|lib/main.moor.dart': _GeneratesConstDataClasses(
+            {'User', 'UsersCompanion'},
+          ),
+        },
+      );
+    },
+    tags: 'analyzer',
+  );
+}
+
+class _GeneratesConstDataClasses extends Matcher {
+  final Set<String> expectedWithConstConstructor;
+
+  const _GeneratesConstDataClasses(this.expectedWithConstConstructor);
+
+  @override
+  Description describe(Description description) {
+    return description.add('generates classes $expectedWithConstConstructor '
+        'const constructor.');
+  }
+
+  @override
+  bool matches(dynamic desc, Map matchState) {
+    // Parse the file, assure we don't have final fields in data classes.
+    final resourceProvider = MemoryResourceProvider();
+    if (desc is List<int>) {
+      resourceProvider.newFileWithBytes('/foo.dart', desc);
+    } else if (desc is String) {
+      resourceProvider.newFile('/foo.dart', desc);
+    } else {
+      desc['desc'] = 'Neither a List<int> or String - cannot be parsed';
+      return false;
+    }
+
+    final parsed = parseFile(
+      path: '/foo.dart',
+      featureSet: FeatureSet.fromEnableFlags2(
+        sdkLanguageVersion: Version(2, 12, 0),
+        flags: const [],
+      ),
+      resourceProvider: resourceProvider,
+      throwIfDiagnostics: true,
+    ).unit;
+
+    final remaining = expectedWithConstConstructor.toSet();
+
+    final definedClasses = parsed.declarations.whereType<ClassDeclaration>();
+    for (final definedClass in definedClasses) {
+      if (expectedWithConstConstructor.contains(definedClass.name.name)) {
+        final constructor = definedClass.getConstructor(null);
+        if (constructor?.constKeyword == null) {
+          matchState['desc'] = 'Constructor ${definedClass.name.name} is not '
+              'const.';
+          return false;
+        }
+
+        remaining.remove(definedClass.name.name);
+      }
+    }
+
+    // Also ensure that all expected classes were generated.
+    if (remaining.isNotEmpty) {
+      matchState['desc'] = 'Did not generate $remaining classes';
+      return false;
+    }
+
+    return true;
+  }
+
+  @override
+  Description describeMismatch(dynamic item, Description mismatchDescription,
+      Map matchState, bool verbose) {
+    return mismatchDescription
+        .add((matchState['desc'] as String?) ?? 'Had syntax errors');
+  }
+}