Verify behavior of the type-extracting builder

moor_generator/test/backends/build/preprocess_builder_tests.dart

@@ -0,0 +1,59 @@
+import 'dart:convert';
+
+import 'package:build/build.dart';
+import 'package:build_test/build_test.dart';
+import 'package:moor_generator/src/backends/build/preprocess_builder.dart';
+import 'package:test/test.dart';
+
+import '../../test_utils.dart';
+
+void main() {
+  test('writes types from expressions in moor files', () async {
+    final writer = InMemoryAssetWriter();
+    final reader = MultiAssetReader([
+      WrittenAssetsReader(writer),
+      await PackageAssetReader.currentIsolate(),
+    ]);
+
+    await testBuilder(
+      PreprocessBuilder(),
+      {
+        'foo|main.moor': '''
+import 'converter.dart';
+--import 'package:moor_converters/converters.dart';
+ 
+CREATE TABLE foo (
+  id INT NOT NULL MAPPED BY `const MyConverter()`
+);
+        ''',
+        'foo|converter.dart': '''
+import 'package:moor/moor.dart';
+
+class MyConverter extends TypeConverter<DateTime, int> {
+  const MyConverter();
+  
+  int mapToSql(DateTime time) => time?.millisecondsSinceEpoch;
+  
+  DateTime mapToDart(int fromSql) {
+    if (fromSql == null) return null;
+    return DateTime.fromMillisecondsSinceEpoch(fromSql);
+  }
+}
+        ''',
+      },
+      writer: writer,
+      reader: reader,
+    );
+
+    final output =
+        await reader.readAsString(AssetId.parse('foo|main.dart_in_moor'));
+    final serialized = json.decode(output);
+
+    expect(serialized['const MyConverter()'], {
+      'type': 'interface',
+      'library': 'asset:foo/converter.dart',
+      'class_name': 'MyConverter',
+      'type_args': [],
+    });
+  });
+}

moor_generator/test/test_utils.dart

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+import 'dart:convert';
+
+import 'package:build/build.dart';
+import 'package:build_test/build_test.dart';
+import 'package:glob/glob.dart';
+
+/// A [MultiPackageAssetReader] able to read assets from a
+/// [RecordingAssetWriter].
+class WrittenAssetsReader extends MultiPackageAssetReader {
+  final RecordingAssetWriter source;
+
+  WrittenAssetsReader(this.source);
+
+  @override
+  Future<bool> canRead(AssetId id) {
+    return Future.value(source.assets.containsKey(id));
+  }
+
+  @override
+  Stream<AssetId> findAssets(Glob glob, {String package}) {
+    return Stream.fromIterable(source.assets.keys).where((id) {
+      final matchesPath = glob.matches(id.path);
+      if (package != null) {
+        return id.package == package && matchesPath;
+      }
+      return matchesPath;
+    });
+  }
+
+  @override
+  Future<List<int>> readAsBytes(AssetId id) {
+    return Future.value(source.assets[id]);
+  }
+
+  @override
+  Future<String> readAsString(AssetId id, {Encoding encoding}) {
+    final actualEncoding = encoding ?? utf8;
+    return Future.value(actualEncoding.decode(source.assets[id]));
+  }
+}