Simplify generation of enum type converters

docs/content/en/docs/Examples/relationships.md

@@ -69,9 +69,9 @@ Future<void> writeShoppingCart(CartWithItems entry) {
         .go();
 
     // And write the new ones
-    await into(shoppingCartEntries).insertAll([
+    for (final item in entry.items) {
-      for (var item in entry.items) ShoppingCartEntry(shoppingCart: cart.id, item: item.id)
+      await into(shoppingCartEntries).insert(ShoppingCartEntry(shoppingCart: cart.id, item: item.id));
-    ]);
+    }
   });
 }
 ```

moor/lib/src/runtime/types/custom_type.dart

@@ -20,3 +20,23 @@ abstract class TypeConverter<D, S> {
   /// nullable.
   D mapToDart(S fromDb);
 }
+
+/// Implementation for an enum to int converter that uses the index of the enum
+/// as the value stored in the database.
+class EnumIndexConverter<T> extends TypeConverter<T, int> {
+  /// All values of the enum.
+  final List<T> values;
+
+  /// Constant default constructor.
+  const EnumIndexConverter(this.values);
+
+  @override
+  T mapToDart(int fromDb) {
+    return fromDb == null ? null : values[fromDb];
+  }
+
+  @override
+  int mapToSql(T value) {
+    return (value as dynamic)?.index as int;
+  }
+}

moor/test/data/tables/todos.g.dart

@@ -7,19 +7,6 @@ part of 'todos.dart';
 // **************************************************************************
 
 // ignore_for_file: unnecessary_brace_in_string_interps, unnecessary_this
-class _$GeneratedConverter$0 extends TypeConverter<CategoryPriority, int> {
-  const _$GeneratedConverter$0();
-  @override
-  CategoryPriority mapToDart(int fromDb) {
-    return fromDb == null ? null : CategoryPriority.values[fromDb];
-  }
-
-  @override
-  int mapToSql(CategoryPriority value) {
-    return value?.index;
-  }
-}
-
 class TodoEntry extends DataClass implements Insertable<TodoEntry> {
   final int id;
   final String title;
@@ -573,7 +560,7 @@ class $CategoriesTable extends Categories
   }
 
   static TypeConverter<CategoryPriority, int> $converter0 =
-      const _$GeneratedConverter$0();
+      const EnumIndexConverter<CategoryPriority>(CategoryPriority.values);
 }
 
 class User extends DataClass implements Insertable<User> {

moor_generator/lib/src/model/used_type_converter.dart

@@ -20,7 +20,7 @@ class UsedTypeConverter {
   /// The expression that will construct the type converter at runtime. The
   /// type converter constructed will map a [mappedType] to the [sqlType] and
   /// vice-versa.
-  String expression;
+  final String expression;
 
   /// The type that will be present at runtime.
   final DartType mappedType;
@@ -54,8 +54,10 @@ class UsedTypeConverter {
       throw InvalidTypeForEnumConverterException('Not an enum', enumType);
     }
 
+    final className = creatingClass.name;
+
     return UsedTypeConverter(
-      expression: 'bogus expression for enum value',
+      expression: 'const EnumIndexConverter<$className>($className.values)',
       mappedType: enumType,
       sqlType: ColumnType.integer,
       isForEnum: true,

moor_generator/lib/src/writer/database_writer.dart

@@ -1,4 +1,3 @@
-import 'package:analyzer/dart/element/type.dart';
 import 'package:moor/moor.dart';
 // ignore: implementation_imports
 import 'package:moor/src/runtime/executor/stream_queries.dart';
@@ -17,44 +16,6 @@ class DatabaseWriter {
   DatabaseWriter(this.db, this.scope);
 
   void write() {
-    // Write generated convertesr
-    final enumConverters =
-        db.tables.expand((t) => t.converters).where((c) => c.isForEnum);
-    final generatedConvertersForType = <DartType, String>{};
-    var amountOfGeneratedConverters = 0;
-
-    for (final converter in enumConverters) {
-      String classForConverter;
-
-      if (generatedConvertersForType.containsKey(converter.mappedType)) {
-        classForConverter = generatedConvertersForType[converter.mappedType];
-      } else {
-        final id = amountOfGeneratedConverters++;
-        classForConverter = '_\$GeneratedConverter\$$id';
-
-        final buffer = scope.leaf();
-        final dartType = converter.mappedType.getDisplayString();
-        final superClass = converter.displayNameOfConverter;
-
-        buffer
-          ..writeln('class $classForConverter extends $superClass {')
-          ..writeln('const $classForConverter();')
-          ..writeln('@override')
-          ..writeln('$dartType mapToDart(int fromDb) {')
-          ..writeln('return fromDb == null ? null : $dartType.values[fromDb];')
-          ..writeln('}')
-          ..writeln('@override')
-          ..writeln('int mapToSql($dartType value) {')
-          ..writeln('return value?.index;')
-          ..writeln('}')
-          ..writeln('}');
-
-        generatedConvertersForType[converter.mappedType] = classForConverter;
-      }
-
-      converter.expression = 'const $classForConverter()';
-    }
-
     // Write referenced tables
     for (final table in db.tables) {
       TableWriter(table, scope.child()).writeInto();

moor_generator/test/writer/database_writer_test.dart

@@ -1,46 +0,0 @@
-import 'package:moor_generator/src/analyzer/options.dart';
-import 'package:moor_generator/src/analyzer/runner/results.dart';
-import 'package:moor_generator/src/writer/database_writer.dart';
-import 'package:moor_generator/src/writer/writer.dart';
-import 'package:test/test.dart';
-
-import '../analyzer/utils.dart';
-
-void main() {
-  test('does not generate multiple converters for the same enum', () async {
-    final state = TestState.withContent({
-      'foo|lib/a.dart': '''
-        import 'package:moor/moor.dart';
-        
-        enum MyEnum { foo, bar, baz }
-        
-        class TableA extends Table {
-          IntColumn get col => intEnum<MyEnum>()();
-        }
-        
-        class TableB extends Table {
-          IntColumn get another => intEnum<MyEnum>()();
-        }
-        
-        @UseMoor(tables: [TableA, TableB])
-        class Database {
-        
-        }
-      ''',
-    });
-
-    final file = await state.analyze('package:foo/a.dart');
-    final db = (file.currentResult as ParsedDartFile).declaredDatabases.single;
-
-    final writer = Writer(const MoorOptions());
-    DatabaseWriter(db, writer.child()).write();
-
-    expect(
-      writer.writeGenerated(),
-      allOf(
-        contains(r'_$GeneratedConverter$0'),
-        isNot(contains(r'_$GeneratedConverter$1')),
-      ),
-    );
-  });
-}