[pigeon] Dart Class Equality (#8788)

Adds Equality and Hash methods to custom classes in Dart.
I am still working on other languages, but this can be a standalone pr while I complete the others.

fixes flutter/flutter#118087

Author: tarrinneal

packages/pigeon/CHANGELOG.md

@@ -1,3 +1,7 @@
+## 25.1.0
+
+* [dart] Adds equality methods to generated data classes.
+
 ## 25.0.0
 
 * **Breaking Change** Removes `oneLanguage` field from `PigeonOptions`.
@@ -11,8 +15,7 @@
 
 ## 24.2.1
 
-* [dart] Fixes potential race condition caused by a ProxyApi constructor message call being made in
-  an async method.
+* [dart] Fixes potential race condition caused by a ProxyApi constructor message call being made in an async method.
 
 ## 24.2.0
 

packages/pigeon/example/app/lib/src/event_channel_messages.g.dart

@@ -20,18 +20,38 @@ class IntEvent extends PlatformEvent {
 
   int data;
 
-  Object encode() {
+  List<Object?> _toList() {
     return <Object?>[
       data,
     ];
   }
 
+  Object encode() {
+    return _toList();
+  }
+
   static IntEvent decode(Object result) {
     result as List<Object?>;
     return IntEvent(
       data: result[0]! as int,
     );
   }
+
+  @override
+  // ignore: avoid_equals_and_hash_code_on_mutable_classes
+  bool operator ==(Object other) {
+    if (other is! IntEvent || other.runtimeType != runtimeType) {
+      return false;
+    }
+    if (identical(this, other)) {
+      return true;
+    }
+    return data == other.data;
+  }
+
+  @override
+  // ignore: avoid_equals_and_hash_code_on_mutable_classes
+  int get hashCode => Object.hashAll(_toList());
 }
 
 class StringEvent extends PlatformEvent {
@@ -41,18 +61,38 @@ class StringEvent extends PlatformEvent {
 
   String data;
 
-  Object encode() {
+  List<Object?> _toList() {
     return <Object?>[
       data,
     ];
   }
 
+  Object encode() {
+    return _toList();
+  }
+
   static StringEvent decode(Object result) {
     result as List<Object?>;
     return StringEvent(
       data: result[0]! as String,
     );
   }
+
+  @override
+  // ignore: avoid_equals_and_hash_code_on_mutable_classes
+  bool operator ==(Object other) {
+    if (other is! StringEvent || other.runtimeType != runtimeType) {
+      return false;
+    }
+    if (identical(this, other)) {
+      return true;
+    }
+    return data == other.data;
+  }
+
+  @override
+  // ignore: avoid_equals_and_hash_code_on_mutable_classes
+  int get hashCode => Object.hashAll(_toList());
 }
 
 class _PigeonCodec extends StandardMessageCodec {

packages/pigeon/example/app/lib/src/messages.g.dart

@@ -29,6 +29,22 @@ List<Object?> wrapResponse(
   return <Object?>[error.code, error.message, error.details];
 }
 
+bool _deepEquals(Object? a, Object? b) {
+  if (a is List && b is List) {
+    return a.length == b.length &&
+        a.indexed
+            .every(((int, dynamic) item) => _deepEquals(item.$2, b[item.$1]));
+  }
+  if (a is Map && b is Map) {
+    final Iterable<Object?> keys = (a as Map<Object?, Object?>).keys;
+    return a.length == b.length &&
+        keys.every((Object? key) =>
+            (b as Map<Object?, Object?>).containsKey(key) &&
+            _deepEquals(a[key], b[key]));
+  }
+  return a == b;
+}
+
 enum Code {
   one,
   two,
@@ -50,7 +66,7 @@ class MessageData {
 
   Map<String, String> data;
 
-  Object encode() {
+  List<Object?> _toList() {
     return <Object?>[
       name,
       description,
@@ -59,6 +75,10 @@ class MessageData {
     ];
   }
 
+  Object encode() {
+    return _toList();
+  }
+
   static MessageData decode(Object result) {
     result as List<Object?>;
     return MessageData(
@@ -68,6 +88,25 @@ class MessageData {
       data: (result[3] as Map<Object?, Object?>?)!.cast<String, String>(),
     );
   }
+
+  @override
+  // ignore: avoid_equals_and_hash_code_on_mutable_classes
+  bool operator ==(Object other) {
+    if (other is! MessageData || other.runtimeType != runtimeType) {
+      return false;
+    }
+    if (identical(this, other)) {
+      return true;
+    }
+    return name == other.name &&
+        description == other.description &&
+        code == other.code &&
+        _deepEquals(data, other.data);
+  }
+
+  @override
+  // ignore: avoid_equals_and_hash_code_on_mutable_classes
+  int get hashCode => Object.hashAll(_toList());
 }
 
 class _PigeonCodec extends StandardMessageCodec {

packages/pigeon/lib/src/dart/dart_generator.dart

@@ -214,6 +214,8 @@ class DartGenerator extends StructuredGenerator<InternalDartOptions> {
         indent.writeln('$datatype ${field.name};');
         indent.newln();
       }
+      _writeToList(indent, classDefinition);
+      indent.newln();
       writeClassEncode(
         generatorOptions,
         root,
@@ -229,6 +231,14 @@ class DartGenerator extends StructuredGenerator<InternalDartOptions> {
         classDefinition,
         dartPackageName: dartPackageName,
       );
+      indent.newln();
+      writeClassEquality(
+        generatorOptions,
+        root,
+        indent,
+        classDefinition,
+        dartPackageName: dartPackageName,
+      );
     });
   }
 
@@ -248,6 +258,17 @@ class DartGenerator extends StructuredGenerator<InternalDartOptions> {
     });
   }
 
+  void _writeToList(Indent indent, Class classDefinition) {
+    indent.writeScoped('List<Object?> _toList() {', '}', () {
+      indent.writeScoped('return <Object?>[', '];', () {
+        for (final NamedType field
+            in getFieldsInSerializationOrder(classDefinition)) {
+          indent.writeln('${field.name},');
+        }
+      });
+    });
+  }
+
   @override
   void writeClassEncode(
     InternalDartOptions generatorOptions,
@@ -259,14 +280,8 @@ class DartGenerator extends StructuredGenerator<InternalDartOptions> {
     indent.write('Object encode() ');
     indent.addScoped('{', '}', () {
       indent.write(
-        'return <Object?>',
+        'return _toList();',
       );
-      indent.addScoped('[', '];', () {
-        for (final NamedType field
-            in getFieldsInSerializationOrder(classDefinition)) {
-          indent.writeln('${field.name},');
-        }
-      });
     });
   }
 
@@ -317,6 +332,48 @@ class DartGenerator extends StructuredGenerator<InternalDartOptions> {
     });
   }
 
+  @override
+  void writeClassEquality(
+    InternalDartOptions generatorOptions,
+    Root root,
+    Indent indent,
+    Class classDefinition, {
+    required String dartPackageName,
+  }) {
+    indent.writeln('@override');
+    indent.writeln('// ignore: avoid_equals_and_hash_code_on_mutable_classes');
+    indent.writeScoped('bool operator ==(Object other) {', '}', () {
+      indent.writeScoped(
+          'if (other is! ${classDefinition.name} || other.runtimeType != runtimeType) {',
+          '}', () {
+        indent.writeln('return false;');
+      });
+      indent.writeScoped('if (identical(this, other)) {', '}', () {
+        indent.writeln('return true;');
+      });
+      indent.writeScoped('return ', '', () {
+        indent.format(
+            classDefinition.fields
+                .map((NamedType field) => field.type.baseName == 'List' ||
+                        field.type.baseName == 'Float64List' ||
+                        field.type.baseName == 'Int32List' ||
+                        field.type.baseName == 'Int64List' ||
+                        field.type.baseName == 'Uint8List' ||
+                        field.type.baseName == 'Map'
+                    ? '_deepEquals(${field.name}, other.${field.name})'
+                    : '${field.name} == other.${field.name}')
+                .join('\n&& '),
+            trailingNewline: false);
+        indent.addln(';');
+      }, addTrailingNewline: false);
+    });
+    indent.newln();
+    indent.writeln('@override');
+    indent.writeln('// ignore: avoid_equals_and_hash_code_on_mutable_classes');
+    indent.writeln('int get hashCode => Object.hashAll(_toList())');
+    indent.addln(';');
+  }
+
   @override
   void writeGeneralCodec(
     InternalDartOptions generatorOptions,
@@ -1031,6 +1088,13 @@ final BinaryMessenger? ${varNamePrefix}binaryMessenger;
         generatorOptions.testOut != null) {
       _writeWrapResponse(generatorOptions, root, indent);
     }
+    if (root.classes.isNotEmpty &&
+        root.classes.any((Class dataClass) => dataClass.fields.any(
+            (NamedType field) =>
+                field.type.baseName.startsWith('List') ||
+                field.type.baseName.startsWith('Map')))) {
+      _writeDeepEquals(indent);
+    }
   }
 
   /// Writes [wrapResponse] method.
@@ -1050,6 +1114,25 @@ final BinaryMessenger? ${varNamePrefix}binaryMessenger;
     });
   }
 
+  void _writeDeepEquals(Indent indent) {
+    indent.format(r'''
+bool _deepEquals(Object? a, Object? b) {
+  if (a is List && b is List) {
+    return a.length == b.length &&
+        a.indexed
+        .every(((int, dynamic) item) => _deepEquals(item.$2, b[item.$1]));
+  }
+  if (a is Map && b is Map) {
+    final Iterable<Object?> keys = (a as Map<Object?, Object?>).keys;
+    return a.length == b.length && keys.every((Object? key) =>
+        (b as Map<Object?, Object?>).containsKey(key) &&
+        _deepEquals(a[key], b[key]));
+  }
+  return a == b;
+}
+    ''');
+  }
+
   void _writeCreateConnectionError(Indent indent) {
     indent.newln();
     indent.format('''

packages/pigeon/lib/src/generator.dart

@@ -251,6 +251,15 @@ abstract class StructuredGenerator<InternalOptions>
     required String dartPackageName,
   }) {}
 
+  /// Writes a single class decode method to [indent].
+  void writeClassEquality(
+    InternalOptions generatorOptions,
+    Root root,
+    Indent indent,
+    Class classDefinition, {
+    required String dartPackageName,
+  }) {}
+
   /// Writes all apis to [indent].
   ///
   /// Can be overridden to add extra code before/after classes.

packages/pigeon/lib/src/generator_tools.dart

@@ -14,7 +14,7 @@ import 'ast.dart';
 /// The current version of pigeon.
 ///
 /// This must match the version in pubspec.yaml.
-const String pigeonVersion = '25.0.0';
+const String pigeonVersion = '25.1.0';
 
 /// Read all the content from [stdin] to a String.
 String readStdin() {
@@ -119,7 +119,7 @@ class Indent {
       _sink.write(begin + newline);
     }
     nest(nestCount, func);
-    if (end != null) {
+    if (end != null && end.isNotEmpty) {
       _sink.write(str() + end);
       if (addTrailingNewline) {
         _sink.write(newline);
@@ -130,12 +130,18 @@ class Indent {
   /// Like `addScoped` but writes the current indentation level.
   void writeScoped(
     String? begin,
-    String end,
+    String? end,
     Function func, {
+    int nestCount = 1,
     bool addTrailingNewline = true,
   }) {
-    addScoped(str() + (begin ?? ''), end, func,
-        addTrailingNewline: addTrailingNewline);
+    addScoped(
+      str() + (begin ?? ''),
+      end,
+      func,
+      nestCount: nestCount,
+      addTrailingNewline: addTrailingNewline,
+    );
   }
 
   /// Scoped increase of the indent level.