feat: use Dart 3 class modifiers (#40)

lib/src/errors.dart

@@ -1,5 +1,5 @@
 /// Used to notify unexpected errors
-class StockError extends Error {
+final class StockError extends Error {
   /// Constructor
   StockError(this.message);
 

lib/src/fetcher.dart

@@ -12,9 +12,7 @@ import 'package:stock/src/stock_response.dart';
 /// See [ofFuture] for easily translating from a regular `Future` function.
 /// See [ofStream], for easily translating to [StockResponse] (and
 /// automatically transforming exceptions into [StockResponseError]).
-abstract class Fetcher<Key, T> {
-  Fetcher._();
-
+base class Fetcher<Key, T> {
   /// "Creates" a [Fetcher] from a [futureFactory] and translates the results
   /// into a [StockResponse].
   ///

lib/src/implementations/factory_fetcher.dart

@@ -2,17 +2,17 @@
 
 import 'package:stock/src/fetcher.dart';
 
-class FactoryFetcher<Key, Output> implements Fetcher<Key, Output> {
+sealed class FactoryFetcher<Key, Output> extends Fetcher<Key, Output> {
   FactoryFetcher(this.factory);
 
   Stream<Output> Function(Key key) factory;
 }
 
-class FutureFetcher<Key, Output> extends FactoryFetcher<Key, Output> {
+final class FutureFetcher<Key, Output> extends FactoryFetcher<Key, Output> {
   FutureFetcher(Future<Output> Function(Key key) factory)
       : super((key) => Stream.fromFuture(factory(key)));
 }
 
-class StreamFetcher<Key, Output> extends FactoryFetcher<Key, Output> {
+final class StreamFetcher<Key, Output> extends FactoryFetcher<Key, Output> {
   StreamFetcher(super.factory);
 }

lib/src/implementations/source_of_truth_impl.dart

@@ -2,7 +2,7 @@
 
 import 'package:stock/src/source_of_truth.dart';
 
-class SourceOfTruthImpl<Key, T> implements SourceOfTruth<Key, T> {
+final class SourceOfTruthImpl<Key, T> implements SourceOfTruth<Key, T> {
   SourceOfTruthImpl(this._reader, this._writer, this._delete, this._deleteAll);
 
   final Stream<T?> Function(Key key) _reader;
@@ -23,7 +23,8 @@ class SourceOfTruthImpl<Key, T> implements SourceOfTruth<Key, T> {
   Future<void> deleteAll() async => await _deleteAll?.call();
 }
 
-class WriteWrappedSourceOfTruth<Key, T> extends CachedSourceOfTruth<Key, T> {
+final class WriteWrappedSourceOfTruth<Key, T>
+    extends CachedSourceOfTruth<Key, T> {
   WriteWrappedSourceOfTruth(this._realSourceOfTruth);
 
   final SourceOfTruth<Key, T>? _realSourceOfTruth;

lib/src/source_of_truth.dart

@@ -37,7 +37,7 @@ import 'package:stock/src/stock_extensions.dart';
 /// local storage is needed.
 /// For this case you can use the [mapTo] and [mapToUsingMapper] extensions.
 ///
-abstract class SourceOfTruth<Key, T> {
+abstract interface class SourceOfTruth<Key, T> {
   /// Creates a source of truth that is accessed via [reader], [writer],
   /// [delete] and [deleteAll].
   ///

lib/src/stock.dart

@@ -14,7 +14,7 @@ import 'package:stock/src/stock_response.dart';
 /// truth. Its purpose is to eliminate the need for waiting on a network update
 /// before local modifications are available (via [Stock.stream]).
 ///
-abstract class Stock<Key, T> {
+abstract interface class Stock<Key, T> {
   /// Stock constructor
   factory Stock({
     required Fetcher<Key, T> fetcher,

lib/src/stock_request.dart

@@ -10,7 +10,7 @@ import 'package:stock/src/stock.dart';
 /// If it's `false`, [Stock] will try to return the [SourceOfTruth] data, and
 /// if it doesn't exist, [Stock] will request fresh data using the [Fetcher].
 ///
-class StockRequest<Key> {
+final class StockRequest<Key> {
   /// [StockRequest] constructor
   StockRequest({
     required this.key,

lib/src/stock_response.dart

@@ -9,7 +9,7 @@ import 'package:stock/src/stock.dart';
 /// uses this holder class to represent each response. This allows the [Stream]
 /// to keep flowing even if an error happens so that if there is an observable
 /// single source of truth, the application can keep observing it.
-class StockResponse<Output> {
+sealed class StockResponse<Output> {
   const StockResponse._(this.origin);
 
   /// Loading event dispatched by [Stock] to signal the [Fetcher] is currently
@@ -35,7 +35,7 @@ class StockResponse<Output> {
 /// Loading event dispatched by [Stock] to signal the [Fetcher] is currently
 /// running.
 @immutable
-class StockResponseLoading<T> extends StockResponse<T> {
+final class StockResponseLoading<T> extends StockResponse<T> {
   /// StockResponseLoading constructor
   const StockResponseLoading(super.origin) : super._();
 
@@ -56,7 +56,7 @@ class StockResponseLoading<T> extends StockResponse<T> {
 
 /// Data dispatched by [Stock]
 @immutable
-class StockResponseData<T> extends StockResponse<T> {
+final class StockResponseData<T> extends StockResponse<T> {
   /// StockResponseData constructor
   const StockResponseData(super.origin, this.value) : super._();
 
@@ -80,7 +80,7 @@ class StockResponseData<T> extends StockResponse<T> {
 
 /// Error dispatched by a pipeline
 @immutable
-class StockResponseError<T> extends StockResponse<T> {
+final class StockResponseError<T> extends StockResponse<T> {
   /// StockResponseError constructor
   const StockResponseError(super.origin, this.error, [this.stackTrace])
       : super._();

lib/src/stock_response_extensions.dart

@@ -5,25 +5,27 @@ import 'package:stock/src/stock_response.dart';
 /// Useful [StockResponse] extensions.
 extension StockResponseExtensions<T> on StockResponse<T> {
   /// Returns the available data or throws error if there is no data.
-  T requireData() => when(
-        onData: (_, data) => data,
-        onLoading: (_) => throw StockError('There is no data in loading'),
+  T requireData() => switch (this) {
+        StockResponseLoading<T>() =>
+          throw StockError('There is no data in loading'),
+        StockResponseData<T>(value: final value) => value,
         // ignore: only_throw_errors
-        onError: (_, error, __) => throw error,
-      );
+        StockResponseError<T>(error: final error) => throw error,
+      };
 
   /// If there is data available, returns it; otherwise returns null.
-  T? getDataOrNull() => this is StockResponseData<T>
-      ? (this as StockResponseData<T>).value
-      : null;
+  T? getDataOrNull() => switch (this) {
+        StockResponseData<T>(value: final value) => value,
+        _ => null
+      };
 
   /// Returns the available data or throws error if there is no data.
-  Object requireError() => maybeMap(
-        onError: (response) => response.error,
-        orElse: () => throw StockError(
-          'Response is not an StockResponseError. Response: $this',
-        ),
-      );
+  Object requireError() => switch (this) {
+        StockResponseError<T>(error: final error) => error,
+        _ => throw StockError(
+            'Response is not an StockResponseError. Response: $this',
+          ),
+      };
 
   /// If this [StockResponse] is of type [StockResponseError], throws the
   /// exception. Otherwise, does nothing.
@@ -61,17 +63,12 @@ extension StockResponseExtensions<T> on StockResponse<T> {
     required E Function(StockResponseLoading<T> value) onLoading,
     required E Function(StockResponseData<T> value) onData,
     required E Function(StockResponseError<T> value) onError,
-  }) {
-    if (this is StockResponseLoading<T>) {
-      return onLoading(this as StockResponseLoading<T>);
-    } else if (this is StockResponseData<T>) {
-      return onData(this as StockResponseData<T>);
-    } else if (this is StockResponseError<T>) {
-      return onError(this as StockResponseError<T>);
-    } else {
-      throw StockError('Unknown StockResponse type: $this');
-    }
-  }
+  }) =>
+      switch (this) {
+        StockResponseLoading<T>() => onLoading(this as StockResponseLoading<T>),
+        StockResponseData<T>() => onData(this as StockResponseData<T>),
+        StockResponseError<T>() => onError(this as StockResponseError<T>),
+      };
 
   /// Invokes [onData] or [orElse] as fallback if the response is successful,
   /// [onLoading] or [orElse] as fallback if the response is loading, and

lib/src/type_mapper.dart

@@ -1,6 +1,6 @@
 /// Converts the [Input] type to the [Output] and vice versa.
 /// Used to transform DB entity to network entity and vice versa.
-abstract class StockTypeMapper<Input, Output> {
+abstract interface class StockTypeMapper<Input, Output> {
   /// Transform a [Input] into a [Output]
   Output fromInput(Input value);
 

test/clear_and_clear_all_test.dart

@@ -1,18 +1,20 @@
 import 'package:mockito/mockito.dart';
+import 'package:stock/src/implementations/factory_fetcher.dart';
 import 'package:stock/src/stock.dart';
 import 'package:test/test.dart';
 
+import 'common/fetcher_mock.dart';
 import 'common/source_of_truth/cached_and_mocked_source_of_truth.dart';
-import 'common_mocks.mocks.dart';
 
 void main() {
   group('Clear tests', () {
     test('Stock Clear invokes SOT clear', () async {
       final sourceOfTruth = createMockedSourceOfTruth<int, int>();
 
-      final fetcher = MockFutureFetcher<int, int>();
       var timesCalled = 0;
-      when(fetcher.factory).thenReturn((key) => Stream.value(++timesCalled));
+      final mockFetcher =
+          MockFutureFetcher<int, int>((key) => Future.value(++timesCalled));
+      final fetcher = FutureFetcher<int, int>(mockFetcher.factory);
 
       final stock = Stock<int, int>(
         fetcher: fetcher,
@@ -28,9 +30,10 @@ void main() {
     test('Stock ClearAll invokes SOT clearAll', () async {
       final sourceOfTruth = createMockedSourceOfTruth<int, int>();
 
-      final fetcher = MockFutureFetcher<int, int>();
       var timesCalled = 0;
-      when(fetcher.factory).thenReturn((key) => Stream.value(++timesCalled));
+      final mockFetcher =
+          MockFutureFetcher<int, int>((key) => Future.value(++timesCalled));
+      final fetcher = FutureFetcher<int, int>(mockFetcher.factory);
 
       final stock = Stock<int, int>(
         fetcher: fetcher,

test/common/fetcher_mock.dart

@@ -0,0 +1,12 @@
+class MockFutureFetcher<Key, Output> {
+  MockFutureFetcher(Future<Output> Function(Key key) factory) {
+    this.factory = (key) {
+      invocations++;
+      return factory(key);
+    };
+  }
+
+  int invocations = 0;
+
+  late Future<Output> Function(Key key) factory;
+}

test/common_mocks.dart

@@ -1,14 +1,11 @@
 import 'package:mockito/annotations.dart';
-import 'package:stock/src/implementations/factory_fetcher.dart';
 import 'package:stock/src/source_of_truth.dart';
 
 import 'stock_response_extension_test.dart';
 
 @GenerateMocks([
   CallbackVoid,
   CallbackInt,
-  FutureFetcher,
-  StreamFetcher,
   SourceOfTruth,
 ])
 void main() {}