Eliminate MethodCall hashCode and equals (#12277)

Since MethodCall equality checks are limited to test scenarios, this
patch replaces them with an equivalent test matcher. At present
MethodCalls are always used in scenarios where indentity-based
equality/hashing is appropriate.

This change avoids an assertion failure when MethodCall args are
Iterable (possible since args are of type dyanmic), and hashValue() from
dart:ui asserts that its input is not an Iterable.

The alternative of implementing support for deep equality in dart:ui was
rejected on the basis that if we're to encourage performant code,
expensive checks should be obviously-expensive to the author.

packages/flutter/lib/src/services/message_codec.dart

@@ -3,7 +3,6 @@
 // found in the LICENSE file.
 
 import 'dart:typed_data';
-import 'dart:ui' show hashValues;
 
 import 'package:flutter/foundation.dart';
 
@@ -46,48 +45,6 @@ class MethodCall {
   /// Must be a valid value for the [MethodCodec] used.
   final dynamic arguments;
 
-  @override
-  bool operator == (dynamic other) {
-    if (identical(this, other))
-      return true;
-    if (runtimeType != other.runtimeType)
-      return false;
-    return method == other.method && _deepEquals(arguments, other.arguments);
-  }
-
-  @override
-  int get hashCode => hashValues(method, arguments);
-
-  bool _deepEquals(dynamic a, dynamic b) {
-    if (a == b)
-      return true;
-    if (a is List)
-      return b is List && _deepEqualsList(a, b);
-    if (a is Map)
-      return b is Map && _deepEqualsMap(a, b);
-    return false;
-  }
-
-  bool _deepEqualsList(List<dynamic> a, List<dynamic> b) {
-    if (a.length != b.length)
-      return false;
-    for (int i = 0; i < a.length; i++) {
-      if (!_deepEquals(a[i], b[i]))
-        return false;
-    }
-    return true;
-  }
-
-  bool _deepEqualsMap(Map<dynamic, dynamic> a, Map<dynamic, dynamic> b) {
-    if (a.length != b.length)
-      return false;
-    for (dynamic key in a.keys) {
-      if (!b.containsKey(key) || !_deepEquals(a[key], b[key]))
-        return false;
-    }
-    return true;
-  }
-
   @override
   String toString() => '$runtimeType($method, $arguments)';
 }

packages/flutter/test/services/haptic_feedback_test.dart

@@ -5,6 +5,8 @@
 import 'package:flutter/services.dart';
 import 'package:test/test.dart';
 
+import 'message_codecs_utils.dart';
+
 void main() {
   test('Haptic feedback control test', () async {
     final List<MethodCall> log = <MethodCall>[];
@@ -15,6 +17,7 @@ void main() {
 
     await HapticFeedback.vibrate();
 
-    expect(log, equals(<MethodCall>[const MethodCall('HapticFeedback.vibrate')]));
+    expect(log, hasLength(1));
+    expect(log.single, isMethodCall('HapticFeedback.vibrate', arguments: null));
   });
 }

packages/flutter/test/services/message_codecs_utils.dart

@@ -0,0 +1,68 @@
+// Copyright 2017 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+import 'package:flutter/services.dart' show MethodCall;
+import 'package:meta/meta.dart';
+import 'package:test/test.dart';
+
+class _IsMethodCall extends Matcher {
+  const _IsMethodCall(this.name, this.arguments);
+
+  final String name;
+  final dynamic arguments;
+
+  @override
+  bool matches(dynamic item, Map<dynamic, dynamic> matchState) {
+    if (item is! MethodCall)
+      return false;
+    if (item.method != name)
+      return false;
+    return _deepEquals(item.arguments, arguments);
+  }
+
+  bool _deepEquals(dynamic a, dynamic b) {
+    if (a == b)
+      return true;
+    if (a is List)
+      return b is List && _deepEqualsList(a, b);
+    if (a is Map)
+      return b is Map && _deepEqualsMap(a, b);
+    return false;
+  }
+
+  bool _deepEqualsList(List<dynamic> a, List<dynamic> b) {
+    if (a.length != b.length)
+      return false;
+    for (int i = 0; i < a.length; i++) {
+      if (!_deepEquals(a[i], b[i]))
+        return false;
+    }
+    return true;
+  }
+
+  bool _deepEqualsMap(Map<dynamic, dynamic> a, Map<dynamic, dynamic> b) {
+    if (a.length != b.length)
+      return false;
+    for (dynamic key in a.keys) {
+      if (!b.containsKey(key) || !_deepEquals(a[key], b[key]))
+        return false;
+    }
+    return true;
+  }
+
+  @override
+  Description describe(Description description) {
+    return description
+      .add('has method name: ').addDescriptionOf(name)
+      .add(' with arguments: ').addDescriptionOf(arguments);
+  }
+}
+
+/// Returns a matcher that matches [MethodCall] instances with the specified
+/// method name and arguments.
+///
+/// Arguments checking implements deep equality for [List] and [Map] types.
+Matcher isMethodCall(String name, {@required dynamic arguments}) {
+  return new _IsMethodCall(name, arguments);
+}

packages/flutter/test/services/system_chrome_test.dart

@@ -7,6 +7,8 @@ import 'dart:typed_data';
 import 'package:flutter/services.dart';
 import 'package:flutter_test/flutter_test.dart';
 
+import 'message_codecs_utils.dart';
+
 void main() {
   testWidgets('SystemChrome overlay style test', (WidgetTester tester) async {
     // The first call is a cache miss and will queue a microtask
@@ -33,10 +35,11 @@ void main() {
       DeviceOrientation.portraitUp,
     ]);
 
-    expect(log, equals(<MethodCall>[new MethodCall(
+    expect(log, hasLength(1));
+    expect(log.single, isMethodCall(
       'SystemChrome.setPreferredOrientations',
-      <String>['DeviceOrientation.portraitUp'],
+      arguments: <String>['DeviceOrientation.portraitUp'],
-    )]));
+    ));
   });
 
   test('setApplicationSwitcherDescription control test', () async {
@@ -50,10 +53,11 @@ void main() {
       const ApplicationSwitcherDescription(label: 'Example label', primaryColor: 0xFF00FF00)
     );
 
-    expect(log, equals(<MethodCall>[new MethodCall(
+    expect(log, hasLength(1));
+    expect(log.single, isMethodCall(
       'SystemChrome.setApplicationSwitcherDescription',
-      <String, dynamic>{'label':'Example label','primaryColor':4278255360}
+      arguments: <String, dynamic>{'label': 'Example label', 'primaryColor': 4278255360},
-    )]));
+    ));
   });
 
   test('setApplicationSwitcherDescription missing plugin', () async {
@@ -80,9 +84,10 @@ void main() {
 
     await SystemChrome.setEnabledSystemUIOverlays(<SystemUiOverlay>[SystemUiOverlay.top]);
 
-    expect(log, equals(<MethodCall>[new MethodCall(
+    expect(log, hasLength(1));
+    expect(log.single, isMethodCall(
       'SystemChrome.setEnabledSystemUIOverlays',
-      <String>['SystemUiOverlay.top'],
+      arguments: <String>['SystemUiOverlay.top'],
-    )]));
+    ));
   });
 }

packages/flutter/test/services/system_navigator_test.dart

@@ -5,6 +5,8 @@
 import 'package:flutter/services.dart';
 import 'package:test/test.dart';
 
+import 'message_codecs_utils.dart';
+
 void main() {
   test('System navigator control test', () async {
     final List<MethodCall> log = <MethodCall>[];
@@ -15,6 +17,7 @@ void main() {
 
     await SystemNavigator.pop();
 
-    expect(log, equals(<MethodCall>[const MethodCall('SystemNavigator.pop')]));
+    expect(log, hasLength(1));
+    expect(log.single, isMethodCall('SystemNavigator.pop', arguments: null));
   });
 }

packages/flutter/test/services/system_sound_test.dart

@@ -5,6 +5,8 @@
 import 'package:flutter/services.dart';
 import 'package:test/test.dart';
 
+import 'message_codecs_utils.dart';
+
 void main() {
   test('System sound control test', () async {
     final List<MethodCall> log = <MethodCall>[];
@@ -15,6 +17,7 @@ void main() {
 
     await SystemSound.play(SystemSoundType.click);
 
-    expect(log, equals(<MethodCall>[const MethodCall('SystemSound.play', 'SystemSoundType.click')]));
+    expect(log, hasLength(1));
+    expect(log.single, isMethodCall('SystemSound.play', arguments: 'SystemSoundType.click'));
   });
 }

packages/flutter/test/widgets/editable_text_test.dart

@@ -10,6 +10,7 @@ import 'package:flutter/material.dart';
 import 'package:flutter/widgets.dart';
 import 'package:flutter/services.dart';
 
+import '../services/message_codecs_utils.dart';
 import 'semantics_tester.dart';
 
 void main() {
@@ -243,8 +244,10 @@ void main() {
     });
     await tester.pump();
 
-    expect(log, <MethodCall>[
+    expect(log, hasLength(1));
-      const MethodCall('TextInput.setEditingState', const <String, dynamic>{
+    expect(log.single, isMethodCall(
+          'TextInput.setEditingState',
+          arguments: const <String, dynamic>{
             'text': 'Wobble',
             'selectionBase': -1,
             'selectionExtent': -1,
@@ -252,8 +255,8 @@ void main() {
             'selectionIsDirectional': false,
             'composingBase': -1,
             'composingExtent': -1,
-      }),
+          },
-    ]);
+    ));
   });
 
   testWidgets('EditableText identifies as text field (w/ focus) in semantics', (WidgetTester tester) async {

packages/flutter/test/widgets/title_test.dart

@@ -6,6 +6,8 @@ import 'package:flutter_test/flutter_test.dart';
 import 'package:flutter/widgets.dart';
 import 'package:flutter/services.dart';
 
+import '../services/message_codecs_utils.dart';
+
 void main() {
   testWidgets('toString control test', (WidgetTester tester) async {
     final Widget widget = new Title(
@@ -58,9 +60,10 @@ void main() {
       color: const Color(0xFF00FF00),
     ));
 
-    expect(log, equals(<MethodCall>[new MethodCall(
+    expect(log, hasLength(1));
+    expect(log.single, isMethodCall(
       'SystemChrome.setApplicationSwitcherDescription',
-        <String, dynamic>{'label': '', 'primaryColor': 4278255360},
+      arguments: <String, dynamic>{'label': '', 'primaryColor': 4278255360},
-    )]));
+    ));
   });
 }